On the temperature dependence of H-U_iso in the riding hydrogen model

The temperature dependence of H-U_iso in N-acetyl-L-4-hydroxyproline monohydrate is investigated. Imposing a constant temperature-independent multiplier of 1.2 or 1.5 for the riding hydrogen model is found to be inaccurate, and severely underestimates H-U_iso below 100 K. Neutron diffraction data at temperatures of 9, 150, 200 and 250 K provide benchmark results for this study. X-ray diffraction data to high resolution, collected at temperatures of 9, 30, 50, 75, 100, 150, 200 and 250 K (synchrotron and home source), reproduce neutron results only when evaluated by aspherical-atom refinement models, since these take into account bonding and lone-pair electron density; both invariom and Hirshfeld-atom refinement models enable a more precise determination of the magnitude of H-atom displacements than independent-atom model refinements. Experimental efforts are complemented by computing displacement parameters following the TLS+ONIOM approach. A satisfactory agreement between all approaches is found.

1. Introduction

The riding hydrogen model is widely used in refining small-molecule X-ray diffraction data. Three positional and one isotropic displacement parameter can be constrained to a `parent atom' that the H atom is `riding' on, improving the data-to-parameter ratio and ensuring a chemically meaningful geometry. Alternatively, a single isotropic displacement parameter per riding H atom can be included in the least-squares refinement model while still constraining hydrogen positional parameters.

Predicted H-atom positions usually lead to comparable figures of merit to a free refinement of H-atom positional parameters. This holds even for high-quality X-ray data, extending far into reciprocal space, since the scattering contribution of hydrogen is small and limited in resolution. Therefore predicted positions, e.g. by SHELXL  (Sheldrick, 2008), have also been used for `invariom' (Dittrich et al., 2004) aspherical-atom refinements (Schürmann et al., 2012; Pröpper et al., 2013). Such H-atom treatment, in combination with elongating X—H vectors to bond distances computed by quantum chemical optimizations of model compounds, provides structures of high quality from conventional diffraction data.

As stated above, the riding hydrogen model can include constraints for isotropic hydrogen displacement parameters. Ratios of 1.2 and 1.5 of H-U_iso with respect to the U_eq of the parent atom are being used in most refinement programs today. These ratios had been empirically derived for use with room-temperature data. However, most of today's data sets are collected at temperatures of 100 K or lower, making full use of reduced thermal motion, e.g. to reduce the bias of anisotropic displacement parameters on bond distances (Busing & Levy, 1964). We will show that the ratio of H-U_iso/X-U_eq is temperature dependent, which indirectly follows from Bürgi & Capelli (2000). Therefore constant H-U_iso multipliers are inaccurate; the simple remedy of using temperature-dependent multipliers is proposed herein.

Taking into account the temperature dependence of riding hydrogen treatments of H-U_iso is a detail of increasing importance in X-ray diffraction, as experimental data quality is improving with modern detectors and X-ray sources. Taking the effect into account allows removal of a resolution-dependent systematic error that would otherwise only affect low-resolution data, which is where the hydrogen scattering contributes. While the effect of underestimating H-U_iso might seem unimportant when only looking at the R factor (which is practically unchanged), the effect can be frequently detected when aspherical scattering factors,¹ which take into account bonding and lone-pair electron-density distribution, are used for least-squares refinement of positional and atomic displacement parameters (ADPs).² For charge-density studies, where the aim is to adjust the scattering factor via multipole parameters to the X-ray data, the anisotropic description of atomic displacements should be used. Hydrogen ADPs are usually estimated in such studies. Munshi et al. (2008) have compared competing approaches for such estimates, and the SHADE (simple hydrogen anisotropic displacement estimator) server (Madsen, 2006) is the approach most frequently used for that purpose today. Since the focus of this work is the most frequently used isotropic treatment of hydrogen displacements, we will not discuss the anisotropic description here.

2. Experimental

Single crystals of the compound N-acetyl-L-4-hydroxyproline monohydrate (NAC·H₂O) were grown by slow evaporation of saturated solutions prepared in hot acetone. Crystals grow to sizes suitable for neutron diffraction. A series of multi-temperature X-ray diffraction data collections³ at 9, 30, 50 and 75 K on the same specimen with dimensions of 0.34 × 0.28 × 0.28 mm (0.5 mm pinhole) were collected at the DORIS beamline D3 at the HASYLAB/DESY synchrotron in Hamburg. The experimental setup consisted of an Oxford Diffraction open-flow helium gas-stream cooling device, a Huber type 512 four-circle diffractometer and a 165 mm MAR CCD detector. A wavelength of 0.5166 Å and a detector distance of 40.3 mm were chosen, allowing a high resolution of d = 0.50 Å or of 1.0 Å⁻¹ to be reached with a single detector setting. The XDS program (Kabsch, 2010) was used for data integration and scaling. Standard deviations of the unit-cell parameters (Fig. 1) were obtained by calculating the variance of intermediate cells during integration.

Figure 1 Temperature dependence of the lattice constants of the X-ray data of N-acetyl-L-hydroxyproline monohydrate. Unit-cell parameters and volume are normalized to the lowest data point at 9 K. E.s.d's are also plotted (but may not be visible when small). Connecting lines are only guidelines for the eye.

A detector correction (Johnas et al., 2006) was applied to properly correct for the effect of oblique incidence (Wu et al., 2002) on the measured intensities. An empirical absorption correction was not performed at this short wavelength; Friedel opposites were merged. The structural model, cell settings but not the atom notation of the original structure determination by Hospital et al. (1979) as given in the CIF file of the Cambridge Structural Database refcode NAHYPL were used as input. Preliminary least-squares refinements were initialized with this model and performed with the program SHELXL (Sheldrick, 2008).

Data sets at 100, 150 and 200 and 250 K were collected on an Xcalibur S diffractometer equipped with an Mo  sealed tube. Here an analytical absorption correction was performed following the method of Clark & Reid (1995) as implemented in the program CRYSALIS RED (Oxford Diffraction Ltd, 2006) employed for data reduction; Friedel mates were not merged. A second specimen was used for these four higher temperatures. High-resolution data () were again measured with the exception of the data set at 250 K.

Neutron diffraction data were collected at the OPAL reactor on the Koala beamline at ANSTO, the Australian Nuclear Science and Technology Organization, in Lucas Heights, Australia. Laue neutron data were collected for a single specimen 1.8 × 1.4 × 0.5 mm using an unmonochromated thermal neutron beam on KOALA (Edwards, 2011) at  9, 150, 200 and 250 K. Each data set comprises 16, 12, 12 and ten images (each exposure = 42 min) accumulated on the image plate and from which intensities were extracted using LaueG (Piltz, 2011) employing unit-cell dimensions from the corresponding X-ray determination. The CRYSTALS program (Betteridge et al., 2003) was used for the refinement of positions and ADPs for all atoms. An isotropic extinction parameter was required at 9 K due to good crystal quality and comparably large specimen size for the neutron data. CCDC 977814–977817 contain the supplementary crystallographic information for the neutron data. These files can be obtained free of charge from the Cambridge Crystallographic Data Centre via https://www.ccdc.cam.ac.uk/data_request/cif . A depiction of the molecule with its atomic numbering scheme and anisotropic ADPs at 9 K from neutron diffraction is shown in Fig. 2.

Figure 2 ADPs of N-acetyl-L-hydroxyproline monohydrate from neutron diffraction at T = 9 K. Ellipsoids at 50% probability (Burnett & Johnson, 1996).

3. Methods

H-U_iso/X-U_eq ratios reported here were derived from four independent methods. Benchmark results for NAC·H₂O were obtained from multi-temperature neutron diffraction. Values for the hydrogen ADPs from multi-temperature single-crystal X-ray diffraction evaluated with the independent-atom model (IAM) cannot reach the accuracy achievable by neutron diffraction. To improve the physical significance of ADPs and their accuracy from X-ray diffraction (Jelsch et al., 1998; Dittrich et al., 2008), we therefore performed aspherical-atom refinements [either Hirshfeld-atom (Jayatilaka & Dittrich, 2008) or invariom refinement (Dittrich et al., 2004), see below]. QM/MM and MO/MO quantum mechanical cluster calculations (for details of how to run such computations see Dittrich et al., 2012) yield normal modes within the `molecular Einstein approximation'. These were combined with a TLS fit in the TLS+ONIOM approach (Whitten & Spackman, 2006) and were subsequently converted to give anisotropic ADPs for H atoms. Such computations were performed to complement the experimental results (see §3.3).

3.1. Aspherical-atom refinements

Two types of aspherical-atom refinements were performed: in invariom refinement (Dittrich et al., 2005, 2006, 2013) the molecular electron-density distribution is reconstructed from Hansen/Coppens' multipole-model parameter values (Hansen & Coppens, 1978) as tabulated in the generalized invariom database (Dittrich et al., 2013). In Hirshfeld-atom refinement (HAR) (Jayatilaka & Dittrich, 2008) the electron density of the asymmetric unit is obtained by a single-point energy calculation.

Invariom refinements. For structure models based on invariom refinements a least-squares refinement of positions and displacement parameters was carried out using the program XDLSM of the XD2006 package (Volkov et al., 2006). The program INVARIOMTOOL (Hübschle et al., 2007) was used to set up XD system files for that purpose. Refinement was against F² with a SHELXL-type weighting scheme, and the R₁ factor was calculated for all reflections with . Crystallographic details are given in Table 1.

Table 1
Crystal data of N-acetyl-L-4-hydroxyproline monohydrate from invariom refinements

GoF = goodness of fit; GoFW = goodness of fit (weighted).

Crystal data
Chemical formula	C7H10NO4·H2O
Formula weight	191.18
Cell setting, space group	Orthorhombic, P212121
Temperature (K)	9	30	50	75	100	150	200	250
a (Å)	9.854 (3)	9.853 (4)	9.866 (7)	9.884 (6)	9.9026 (2)	9.9408 (2)	9.9748 (2)	10.0123 (2)
b (Å)	9.249 (3)	9.251 (5)	9.250 (7)	9.253 (6)	9.2485 (2)	9.2479 (2)	9.2492 (2)	9.2556 (2)
c (Å)	10.144 (2)	10.145 (2)	10.149 (6)	10.155 (3)	10.1662 (2)	10.1875 (2)	10.2103 (2)	10.2441 (2)
V (Å^3)	924.5 (4)	924.7 (7)	926.2 (11)	928.7 (9)	931.06 (3)	936.55 (3)	941.99 (3)	949.32 (3)
Z, F(000)	4, 408
Dx (Mg m^−3)	1.374	1.373	1.371	1.367	1.364	1.356	1.348	1.338
Radiation type	Synchrotron	Synchrotron	Synchrotron	Synchrotron	Mo Kα	Mo Kα	Mo Kα	Mo Kα
μ (mm^−1)	0.070	0.061	0.061	0.061	0.116	0.116	0.115	0.114
Crystal form, colour	Rectangular, colourless				Rectangular, colourless
Crystal size (mm)	0.34 × 0.28× 0.28				0.54 × 0.27 × 0.14
Data collection
Diffractometer	Huber Type 512				Oxford Diffraction Xcalibur S
Data-collection method	φ scans				ω and φ scans
Absorption correction	None				Analytical
Tmin, Tmax	n/a	n/a	n/a	n/a	0.959/0.986	0.954/0.987	0.960/0.989	0.956/0.989
No. of measured reflections	45747	25178	44258	45127	39746	30837	30309	17876
No. of independent reflections	8304	7775	7803	7809	10866	7826	7829	4420
No. of observed reflections	7885	7262	7372	7255	7744	5673	4860	3245
Criterion for observed reflections
Rint (%)	0.040	0.038	0.055	0.051	0.037	0.039	0.039	0.020
(°),	31.90, 1.022	31.88, 1.000	31.90, 1.000	31.87, 1.000	53.28, 1.132	53.32, 1.000	53.31, 1.069	36.25, 0.833
Invariom refinement
Refinement on	F^2
R1	0.026	0.028	0.026	0.028	0.031	0.029	0.029	0.025
No. of reflections	7885	7262	7372	7255	7744	5673	4860	3245
No. of parameters	131
H-atom treatment	Invarioms: calculated H position, bond-length elongated, Uiso refined; HAR: all parameters adjusted
Weighting scheme
1/ + [] (P = + )	[0.06P^2+ 0.04P]	[0.04P^2+ 0.05P]	[0.04P^2+ 0.04P]	[0.05P^2+ 0.02P]	[0.04P^2+ 0.07P]	[0.05P^2+ 0.05P]	[0.06P^2+ 0.04P]	[0.04P^2+ 0.08P]
GoF	1.76	1.44	1.48	2.02	2.81	2.96	2.12	3.84
GoFW	0.96	0.95	0.94	1.00	0.81	0.84	0.82	0.81
, (e Å^−3)	0.36/−0.25	0.32/−0.22	0.27/−0.21	0.30/−0.25	0.36/−0.21	0.25/−0.16	0.20/−0.17	0.16/−0.12

CCDC 990102–990109 contain the supplementary crystallographic data for the X-ray structures. CIF files including intensities are only provided for the invariom refinements, since the same intensities were also used for HAR.

Scattering factors, their local atomic site symmetry and invariom names as well as the model compounds these were derived from are given in Table 2. H-atom positions were initially calculated with SHELXL. In invariom refinement the X—H bond distances were then elongated during initial scale-factor refinement to optimized bond distances of the respective model compound for the invariom assigned to the H atom. This new H-atom position was then constrained to have the same shift as the parent X atom. Only U_iso values were freely refined. This procedure was followed because it is also feasible when conventional data of lower resolution than the data studied here are available. Moreover, idealized H-atom positions provided better input for the MO/MO cluster computations (see §3.3), since idealized positions facilitate reaching convergence. Ratios of hydrogen U_iso to U_eq of the parent atom were then averaged for H atoms sharing the same invariom name using the program APD-TOOLKIT.⁴ For direct comparison with HAR, free refinement of H atoms was also performed and the results obtained (not shown) are very similar.

Table 2
Scattering factor assigned during invariom refinement with atom names, invariom names, local atomic site symmetry and model compounds they were derived from

Atom name	Invariom name	Local atomic site symmetry	Model compound
O1	O2c	mm2	Formaldehyde
O2	O1c1h	mz	Methanol
O3	O1.5c[1.5n1c]	mm2	Acetamide
O4	O1c1h	mz	Methanol
O5	O1h1h	mm2	Water
N1	N1.5c[1.5o1c]1c1c	mz	N,N-Dimethylacetamide
C1	C2o1o1c	mz	Acetic acid
C2	C1n1c1c1h	mz	2-Aminopropane
C3	C1c1c1h1h	mm2	Propane
C4	C1o1c1c1h	mz	2-Propanol
C5	C1n1c1h1h	mz	Ethylamine
C6	C1.5o1.5n[1c1c]1c	mz	N,N-Dimethylacetamide
C7	C1c1h1h1h	3m	Ethane
H1,2	H1o[1c]	6	Methanol
H3	H1c[1n1c1c]	6	2-Aminopropane
H4,5	H1c[1c1c1h]	6	Propane
H6	H1c[1o1c1c]	6	2-Propanol
H7,8	H1c[1n1c1h]	6	Ethylamine
H9,10,11	H1c[1c1h1h]	6	Ethane
H12,13	H1o[1h]	6	Water

Hirshfeld-atom refinement. In Hirshfeld refinement the electron density from single-point energy calculations is used and partitioned into atomic contributions using Hirshfeld's fuzzy boundary partitioning scheme (Hirshfeld, 1977). Fourier transform (Jayatilaka, 1994) then gives aspherical atomic scattering factors. Atomic positions and ADPs are adjusted to best fit the experimental data using these scattering factors. In an improved implementation of HAR in the quantum crystallography program TONTO (Jayatilaka & Grimwood, 2003), cycles of molecular electron-density calculations, aspherical-atom partitioning and least-squares refinement are now iterated to convergence in an automatic manner (Capelli et al., 2014). The Hartree–Fock method was used in combination with the basis set cc-pVTZ (Dunning, 1989). A supermolecule cluster approach was chosen to calculate a wavefunction for both molecules of the asymmetric unit for use in HAR (Woinska et al., 2014). The structural model used in HAR included individual positional parameters and isotropic ADPs for H atoms. Ratios of hydrogen U_iso and U_eq of the parent atom were again averaged for H atoms sharing the same invariom name. As expected and shown before for three urea derivatives (Checińska et al., 2013), both types of aspherical-atom models, the Hansen & Coppens multipole model and HAR, give similar figures of merit and anisotropic ADPs of the non-H atoms with experimental X-ray data.

3.2. Neutron diffraction

As mentioned before, the H-U_eq/X-U_eq ratios from neutron diffraction provide benchmark values for this study. One of the advantages of neutron diffraction is that the scattering lengths of the elements that correspond to atomic scattering factors in X-ray diffraction are constant. Stewart (1976) demonstrated that U_iso and U_eq from single-crystal X-ray and neutron diffraction differ, and that U_eq will be in between the arithmetic and geometric mean of the diagonal elements of the mean-square displacement matrix. Since we are interested in the ratio of hydrogen U_iso and U_eq of the parent atom, conventional least-squares adjustment can nevertheless provide relative reliable experimental estimates of atomic motion at a particular temperature. Equivalent isotropic displacements H-U_eq⁵ (orthorhombic system) were obtained both by geometric and by arithmetric averaging the diagonal elements of the matrix of the anisotropic displacements of H atoms (Fischer & Tillmanns, 1988), and both give the same ratios within the estimated uncertainty. In contrast to the deposited structural model, refinements were evaluated without using split-atom sites to model rotational disorder in the methyl group above 150 K. Structural models are given in the supporting information.⁶

3.3. Theoretical computations

A quantum mechanical cluster computation was performed to complement the experimental results. The computation was initiated using the experimental geometry from invariom refinement at the lowest temperature of 9 K with idealized hydrogen positions and elongated X—H distances. The method/basis set for optimizing these model compounds was B3LYP/D95++(3df,3pd). The utility program BAERLAUCH (Dittrich et al., 2012) was used to generate a cluster of 17 asymmetric units packed around a central unit. The water solvent molecule was optimized together with the main molecule. Preliminary QM/MM calculations [HF/6-31G(d,p):UFF] ensured that this cluster size leads to convergence and is suitable to reproduce experimental ADPs at low temperature. Calculations to obtain final results employed the MO/MO basis-set combination B3LYP/cc-pVTZ:B3LYP/3-21G. Only the central molecule was optimized, whereas the surrounding 16 asymmetric units were kept at fixed positions. Normal modes were calculated and transformed to Cartesian atomic displacements after optimization.

On the basis of the discussion by Dunitz et al. (1988), the temperature dependence of atomic motion can be described in analogy to a Boltzmann-type distribution of the harmonic oscillator. Atomic motion at higher temperatures can therefore be estimated by the formula given by Blessing (1995):

Although the molecular Einstein approach underlying the MO/MO calculations is not able to take into account lattice vibrations with acceptable accuracy, such a cluster calculation can provide a H/parent-atom U_iso/U_eq ratio, which is however dominated by internal atomic motion. Estimates so derived predict a higher ratio than the experimentally observed ratios from neutron and X-ray diffraction and require a U_eq scale factor. To reach agreement between theory and experiment, and to take the temperature dependence into account, it was therefore necessary to go back to the TLS+ONIOM approach (Whitten & Spackman, 2006) and to include the experimental TLS contribution, treating the whole asymmetric unit as a rigid body. In this process the internal atomic relative displacement predicted by the MO/MO computation was subtracted from the experimental ADP data at a given temperature prior to the TLS fit (Schomaker & Trueblood, 1968). Both TLS fit and subtraction were performed by the program APD-TOOLKIT. A more sophisticated (and computationally more demanding) theoretical method based on periodic computations of different-sized unit-cell assemblies was studied by Madsen et al. (2013); for reproducing temperature dependence the TLS+ONIOM approach was sufficient.

4. Results and discussion

4.1. Temperature dependence of U_iso/U_eq of riding hydrogen and parent atom from X-ray data

Prior to further analysis, a way to distinguish H atoms and their chemical environment is required. One choice would be the well established SHELXL AFIX groups. However, this would not distinguish H atoms exhibiting a distinct vibrational behaviour in theoretical calculations, e.g. an OH group in ethyl alcohol and one in phenol. The invariom formalism (Dittrich et al., 2013) allows a finer distinction. Here H atoms that share the same invariom name are in the same covalent bonding environment and have the same number of next-nearest non-H neighbours, so it was used for classification throughout.⁷ Vibrational modes of individual invarioms (as derived from their model compounds) in other molecules will be investigated in a forthcoming study.

We can now consider the ratio of hydrogen U_iso and parent-atom U_eq from X-ray diffraction at different temperatures. Initial observations with invariom refinements on D,L-serine (Dittrich et al., 2005) indicated a temperature dependence at very low temperatures. Subsequent tests using the IAM showed that the IAM does not provide the model precision required to obtain significant results (Thorn, 2012). Our first question was therefore whether the U_iso/U_eq ratios from aspherical-atom refinements on NAC·H₂O are able to reproduce the temperature dependence seen for D,L-serine. Fig. 3 shows such ratios for several hydrogen invarioms. Values were either obtained from invariom refinements with constrained riding hydrogen positions, but adjusted hydrogen U_iso (Fig. 3a), or by free least-squares refinement of positional and isotropic displacement parameters with HAR (Jayatilaka & Dittrich, 2008) (Fig. 3b). As one can see, the programs/methods used, XD (Fig. 3a) (Volkov et al., 2006) and TONTO (Jayatilaka & Grimwood, 2003) (Fig. 3b), give comparable results. Both refinements do indeed show the expected temperature dependence and even distinguish different hydrogen invarioms from X-ray data, although the standard deviation associated with each value is non-negligible (not shown for clarity).⁸ At very low temperatures the relative motion of H atoms relative to their parent atoms is clearly appreciably extended compared to higher temperatures.

Figure 3 Temperature dependence of the Uiso/Ueq ratio from the X-ray data of N-acetyl-L-hydroxyproline monohydrate. (a) Invariom refinement with constrained hydrogen positions and refined Uiso. (b) Hirshfeld-atom refinement with freely refined hydrogen positions/Uiso, both using the same X-ray diffraction data.

This temperature dependence can be understood by looking at the low- and high-temperature limits of equation (1) as well as the transition temperature between both limits. Such dependence can be understood by considering the evolution of ADPs of atoms of different mass with temperature (Bürgi & Capelli, 2000). Division of the mass- and temperature-dependent functions and with masses yields a function with the observed shape. Vibrations of atoms with larger contributions from higher internal frequencies are more prominent at lower temperatures, while at higher temperatures the atomic mass independent external modes dominate the overall amplitudes.

Interestingly, the data set that was an outlier in the expansion of the unit-cell volume at 67–75 K shows further deviations in atomic displacements: hydrogen invarioms of the type H1c[1c1h1h] mainly show a deviating behaviour with respect to the other atoms at higher temperatures. This is due to rotational disorder of the methyl group, and it is easily conceivable that the differences in the lattice constants seen at 67–75 K are due to the rotation becoming more frequent, either starting from this temperature or due to temperature fluctuations at this data point. We have previously studied similar disorder in methylaminobutyric acid hydrochloride by difference electron-density plots and molecular-dynamics simulations (Dittrich et al., 2009). The abnormal temperature dependence of the three H1c[1c1h1h] methyl-hydrogen invarioms is proof that rotational disorder is also present in the acetyl group of NAC·H₂O. We will study rotational disorder in this molecule and its anhydrous form in more detail in a subsequent study.

Since positional and displacement parameters are correlated, limiting model flexibility (constrained hydrogen positions) seems to make the onset of additional rotational motion more apparent in invariom refinement, whereas free refinement of positions and U_iso seems to lead to an over-parameterized model in HAR.

4.2. QM/MM and MO/MO calculations

We were interested in reproducing the temperature dependence of U_iso by using the TLS+ONIOM approach (Whitten & Spackman, 2006). For this purpose the above-mentioned two-layer ONIOM computation using the coordinates from the 9 K X-ray diffraction experiment was combined with a TLS fit at each temperature to provide another set of results that includes information independent from experiment.

Details of the procedure need to be highlighted prior to a discussion of the results. Before performing the TLS fit the computed internal modes were subtracted from the experimental non-H-atom ADPs. Contrary to expectation, this is not accompanied by an improvement of the TLS R factors (not shown) with temperature, since the internal ADPs of heavy atoms are mostly spherical in shape and get almost completely absorbed in the TLS ADPs. Nevertheless, such a correction is physically reasonable and we recommend that it is performed. Furthermore, the agreement of the ratio of U_iso/U_eq seen in the aspherical-atom refinements of the X-ray data improves when this internal TLS contribution is taken into account.

Another detail concerns the low-frequency modes describing the movement of the asymmetric unit in the crystal framework. Low-frequency modes have a very large impact on the overall displacements, which can be derived directly from equation (1). Since the approximations present in the theoretical method do not allow the estimation of these frequencies with sufficient accuracy, low-frequency modes were omitted in the calculation of ADPs. A frequency threshold of 200 cm⁻¹ was found to be adequate (Madsen et al., 2013). The required information on the overall displacement is instead taken from the TLS fit, which yields more reliable values. The TLS+ONIOM approach is hence an attractive computational method to understand the ratio of H-U_iso/parent U_eq when experimental TLS contributions are available. It reproduces the temperature dependence nicely, although rotational disorder cannot be predicted. More work is required for ab initio prediction of the temperature dependence by theoretical computations without any experimental input. So far it can only provide an independent source of information for the internal modes and requires the application of the TLS fit; theoretical methods are nevertheless best suited to provide H-U_iso/X-U_eq ratios since experimental errors are limited to ADPs used in the TLS fit.

We now compare these TLS+ONIOM results to those from neutron diffraction, our experimental benchmark (Fig. 4). Since neutron diffraction data sets were not collected at temperatures of 30, 50, 75 and 100 K, these data points are absent in the comparison with high-resolution X-ray and TLS+ONIOM results. The TLS+ONIOM approach confirms that individual displacements of hydrogen invarioms are distinguishable mainly at temperatures below 100 K. Rotational disorder cannot be predicted from this approach, whereas it is also detectable in the neutron data at higher temperatures. Good agreement of neutron diffraction and the TLS+ONIOM approach is found for the temperature-dependent ratio of hydrogen U_iso or U_eq and the parent atom, which also agrees rather well with the X-ray results in Fig. 3. However, at higher temperatures HAR and neutron diffraction show a trend that deviates from the other methods, with the ratio being higher than 1.5, whereas the ratio is smaller in invariom refinement. This is probably due to the predicted/constrained hydrogen positions in invariom refinement, which impose a beneficial limit on the flexibility of the structural model here. Since the rigid-body fit in the TLS+ONIOM approach is based on the invariom results, a similar temperature dependence to that in invariom refinement is observed.

Figure 4 Temperature dependence of the Uiso/Ueq ratios obtained by TLS+ONIOM and neutron diffraction. (a) Internal vibrations from MO/MO ONIOM calculations and TLS fit against ADPs obtained by invariom refinement. (b) Refinement against neutron diffraction data.

A comparison of Figs. 3 and 4 indicates an overall surprisingly good agreement for each curve of H-U_iso/X-U_eq versus temperature over the whole range, especially when taking into account that different methods/experiments were used. All four methods consistently indicate that at very low temperatures the ratio H-U_iso/X-U_eq can be as high as four, e.g. for H atoms attached to an sp³ C atom with three non-H-atom neighbours (corresponding to AFIX 13 in SHELXL). Moreover, all four methods consistently confirm (or reproduce in the case of TLS+ONIOM) the temperature dependence that is predicted from equation (1). Conventional IAM structure determinations employing riding hydrogen constraints – and likewise models with aspherical scattering factors – should therefore take the temperature-dependent ratio into account.

5. Conclusion and outlook

Four different methods providing the temperature-dependent ratio of H-U_iso to X-U_eq in the riding hydrogen treatment have been evaluated and compared. Neutron diffraction experiments provide benchmark values. `Invariom' and `Hirshfeld-atom' aspherical-atom refinements with high-resolution X-ray diffraction data yield very similar results, with the invariom model using constrained hydrogen positions giving a more consistent result, but the Hirshfeld-atom model being closer to neutron diffraction at higher temperatures. Implementing restraints in the TONTO program would therefore be useful. Furthermore, experimental findings can be well reproduced by the TLS+ONIOM approach. Here a single quantum chemical MO/MO cluster calculation is combined with a temperature-dependent rigid-body fit of the non-hydrogen ADPs from aspherical-atom X-ray refinements. All methods show that the ratio of H-U_iso/eq/X-U_eq, which is usually assumed to be 1.2 or 1.5 independent of temperature, is frequently more than twice as high at lower temperatures. Fixed values of 1.2 or 1.5, as usually used in conventional spherical-atom `IAM' refinements, are therefore underestimating the relative displacement of H atoms at cryogenic temperatures. Since all methods used here consistently show or reproduce that the H-U_iso/eq/X-U_eq ratio is temperature dependent, the effect should be taken into account in low-temperature structure determinations, especially around 100 K and below. We will provide relevant functionality (program APD-TOOLKIT) in subsequent work.

Supporting information

Computing details

Data collection: MAATEL/ANSTO control program for hydroxyproline9K, hydroxyproline150K, hydroxyproline200K, hydroxyproline250K. Data reduction: argonne_boxes (Wilkinson et al., 1988) & LaueG (Piltz, 2011) for hydroxyproline9K, hydroxyproline150K, hydroxyproline200K, hydroxyproline250K. Program(s) used to refine structure: Dittrich et al., (2013) Volkov et al., (2006) for (9K), (30K), (50K), (75K), 100K, 150K, xcalibur, 250K; CRYSTALS (Betteridge et al., 2003) for hydroxyproline9K, hydroxyproline150K, hydroxyproline200K, hydroxyproline250K. Molecular graphics: H"ubschle, (2011) for (9K), (30K), (50K), (75K), 100K, 150K, xcalibur, 250K. Software used to prepare material for publication: L"ubben, (to be published) for (9K), (30K), (50K), (75K), 100K, 150K, xcalibur, 250K.

Figures

(9K)

Crystal data

C7H11NO4·H2O	Z = 4
Mr = 191.18	F(000) = 408
Orthorhombic, P212121	Dx = 1.374 Mg m^−3
a = 9.854 (3) Å	Synchrotron radiation, λ = 0.5166 Å
b = 9.249 (3) Å	µ = 0.07 mm^−1
c = 10.144 (2) Å	T = 9 K
V = 924.5 (4) Å^3	0.34 × 0.28 × 0.28 mm

Data collection

45747 measured reflections	θmax = 31.9°, θmin = 2.1°
8275 independent reflections	h = −20→20
7813 reflections with I > 2σ(I)	k = −18→18
Rint = 0.040	l = −20→20

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	Hydrogen site location: mixed
R[F^2 > 2σ(F^2)] = 0.026	Only H-atom displacement parameters refined
wR(F^2) = 0.063	w2 = q/[s^2(Fo^2) + (0.04 P)^2 + 0.05 P + 0.00 + 0.00 sin(th)] where P = (0.3333 Fo^2 + 0.6667 Fc^2) q = 1.0
S = 1.76	(Δ/σ)max < 0.001
7885 reflections	Δρmax = 0.36 e Å^−3
131 parameters	Δρmin = −0.25 e Å^−3

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O(1)	0.57864 (3)	1.11469 (3)	0.77183 (3)	0.007
O(2)	0.79421 (3)	1.11863 (3)	0.84048 (2)	0.006
O(3)	0.84067 (3)	1.20556 (3)	0.55093 (3)	0.007
O(4)	0.78344 (3)	0.69402 (3)	0.51516 (3)	0.006
O(5)	0.90008 (3)	0.45965 (3)	0.43048 (3)	0.011
N(1)	0.87822 (3)	0.97789 (3)	0.61460 (3)	0.005
C(1)	0.69679 (3)	1.07603 (3)	0.76141 (3)	0.005
C(2)	0.73844 (3)	0.96432 (3)	0.66018 (3)	0.005
C(3)	0.73469 (3)	0.81108 (3)	0.71988 (3)	0.006
C(4)	0.84126 (3)	0.73017 (3)	0.63963 (3)	0.005
C(5)	0.95442 (3)	0.84208 (3)	0.62487 (3)	0.006
C(6)	0.91997 (3)	1.10147 (3)	0.55827 (3)	0.005
C(7)	1.06213 (3)	1.10715 (4)	0.50529 (4)	0.008
H(1)	0.75801	1.18383	0.90527	0.021 (2)*
H(2)	0.83076	0.61270	0.47830	0.018 (2)*
H(3)	0.66921	0.96958	0.57511	0.020 (2)*
H(4)	0.76114	0.81290	0.82458	0.016 (2)*
H(5)	0.63444	0.76200	0.70817	0.018 (2)*
H(6)	0.87703	0.63334	0.69178	0.018 (2)*
H(7)	1.02170	0.84233	0.71132	0.024 (3)*
H(8)	1.01502	0.82209	0.53573	0.017 (2)*
H(9)	1.13257	1.06799	0.58024	0.032 (3)*
H(10)	1.08766	1.21843	0.47949	0.025 (3)*
H(11)	1.06952	1.03909	0.41769	0.030 (3)*
H(12)	0.88155	0.36949	0.47416	0.022 (2)*
H(13)	0.95639	0.43869	0.35544	0.019 (2)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O(1)	0.00481 (8)	0.00970 (9)	0.00751 (9)	0.00191 (7)	−0.00032 (7)	−0.00294 (7)
O(2)	0.00604 (8)	0.00750 (8)	0.00540 (8)	−0.00015 (7)	−0.00057 (6)	−0.00127 (7)
O(3)	0.00694 (8)	0.00476 (8)	0.00870 (9)	0.00130 (6)	0.00109 (7)	0.00188 (7)
O(4)	0.00825 (8)	0.00511 (8)	0.00517 (8)	0.00046 (7)	−0.00060 (7)	−0.00025 (6)
O(5)	0.01306 (10)	0.00620 (9)	0.01266 (10)	0.00112 (8)	0.00575 (9)	0.00002 (8)
N(1)	0.00472 (8)	0.00367 (8)	0.00565 (9)	0.00033 (6)	0.00099 (7)	0.00055 (7)
C(1)	0.00452 (9)	0.00487 (9)	0.00424 (9)	0.00039 (7)	0.00015 (7)	−0.00040 (7)
C(2)	0.00492 (9)	0.00463 (9)	0.00413 (9)	−0.00007 (7)	0.00055 (7)	−0.00041 (8)
C(3)	0.00858 (10)	0.00475 (9)	0.00556 (10)	−0.00022 (8)	0.00226 (8)	0.00021 (8)
C(4)	0.00726 (10)	0.00408 (9)	0.00469 (9)	0.00064 (8)	0.00015 (8)	0.00029 (7)
C(5)	0.00575 (10)	0.00515 (9)	0.00785 (10)	0.00101 (8)	−0.00024 (8)	0.00021 (8)
C(6)	0.00486 (9)	0.00453 (9)	0.00509 (9)	−0.00008 (7)	0.00053 (7)	0.00054 (7)
C(7)	0.00557 (10)	0.00890 (11)	0.00950 (11)	−0.00118 (8)	0.00189 (8)	0.00012 (9)

Geometric parameters (Å, º)

O(1)—C(1)	1.2226 (4)	C(2)—H(3)	1.1010
O(2)—C(1)	1.3115 (4)	C(3)—C(4)	1.5250 (5)
O(2)—H(1)	0.9607	C(3)—H(4)	1.0937
O(3)—C(6)	1.2423 (4)	C(3)—H(5)	1.0937
O(4)—C(4)	1.4249 (4)	C(4)—C(5)	1.5287 (5)
O(4)—H(2)	0.9607	C(4)—H(6)	1.0982
O(5)—H(12)	0.9618	C(5)—H(7)	1.0993
O(5)—H(13)	0.9618	C(5)—H(8)	1.0993
N(1)—C(2)	1.4583 (4)	C(6)—C(7)	1.5012 (4)
N(1)—C(5)	1.4672 (4)	C(7)—H(9)	1.0914
N(1)—C(6)	1.3425 (4)	C(7)—H(10)	1.0914
C(1)—C(2)	1.5134 (4)	C(7)—H(11)	1.0914
C(2)—N(1)—C(5)	112.78 (3)	O(4)—C(4)—C(3)	108.23 (3)
C(2)—N(1)—C(6)	119.85 (3)	O(4)—C(4)—C(5)	111.33 (3)
C(5)—N(1)—C(6)	127.03 (3)	C(3)—C(4)—C(5)	102.84 (3)
O(1)—C(1)—O(2)	123.80 (3)	N(1)—C(5)—C(4)	102.32 (3)
O(1)—C(1)—C(2)	121.10 (3)	O(3)—C(6)—N(1)	119.51 (3)
O(2)—C(1)—C(2)	114.94 (3)	O(3)—C(6)—C(7)	122.57 (3)
N(1)—C(2)—C(1)	114.36 (3)	N(1)—C(6)—C(7)	117.92 (3)

(30K)

Crystal data

C7H11NO4·H2O	Z = 4
Mr = 191.18	F(000) = 408
Orthorhombic, P212121	Dx = 1.373 Mg m^−3
a = 9.853 (4) Å	Synchrotron radiation, λ = 0.5166 Å
b = 9.251 (5) Å	µ = 0.06 mm^−1
c = 10.145 (2) Å	T = 30 K
V = 924.7 (7) Å^3	0.34 × 0.28 × 0.28 mm

Data collection

25178 measured reflections	θmax = 31.9°, θmin = 2.1°
8245 independent reflections	h = −20→19
7578 reflections with I > 2σ(I)	k = −17→18
Rint = 0.038	l = −20→19

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	Hydrogen site location: mixed
R[F^2 > 2σ(F^2)] = 0.028	Only H-atom displacement parameters refined
wR(F^2) = 0.066	w2 = q/[s^2(Fo^2) + (0.04 P)^2 + 0.03 P + 0.00 + 0.00 sin(th)] where P = (0.3333 Fo^2 + 0.6667 Fc^2) q = 1.0
S = 1.44	(Δ/σ)max < 0.001
7262 reflections	Δρmax = 0.32 e Å^−3
131 parameters	Δρmin = −0.22 e Å^−3

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O(1)	0.57872 (3)	1.11458 (3)	0.77171 (3)	0.008
O(2)	0.79412 (3)	1.11865 (3)	0.84035 (3)	0.007
O(3)	0.84069 (3)	1.20549 (3)	0.55082 (3)	0.007
O(4)	0.78354 (3)	0.69400 (3)	0.51505 (3)	0.007
O(5)	0.90008 (4)	0.45962 (3)	0.43048 (4)	0.012
N(1)	0.87822 (3)	0.97790 (3)	0.61456 (3)	0.005
C(1)	0.69679 (3)	1.07608 (4)	0.76130 (3)	0.005
C(2)	0.73845 (3)	0.96431 (4)	0.66005 (3)	0.005
C(3)	0.73466 (4)	0.81107 (4)	0.71973 (4)	0.007
C(4)	0.84123 (4)	0.73017 (4)	0.63953 (3)	0.006
C(5)	0.95430 (4)	0.84211 (4)	0.62491 (4)	0.007
C(6)	0.91994 (3)	1.10144 (4)	0.55820 (3)	0.005
C(7)	1.06211 (4)	1.10715 (4)	0.50526 (4)	0.009
H(1)	0.75767	1.18278	0.90588	0.023 (3)*
H(2)	0.83095	0.61272	0.47825	0.021 (2)*
H(3)	0.66927	0.96962	0.57496	0.018 (2)*
H(4)	0.76104	0.81281	0.82445	0.017 (2)*
H(5)	0.63438	0.76204	0.70793	0.022 (2)*
H(6)	0.87698	0.63339	0.69172	0.020 (2)*
H(7)	1.02150	0.84234	0.71141	0.024 (3)*
H(8)	1.01502	0.82211	0.53585	0.017 (2)*
H(9)	1.13257	1.06822	0.58030	0.030 (3)*
H(10)	1.08757	1.21837	0.47929	0.030 (3)*
H(11)	1.06959	1.03893	0.41780	0.030 (3)*
H(12)	0.88244	0.36853	0.47285	0.025 (2)*
H(13)	0.95559	0.43947	0.35470	0.023 (2)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O(1)	0.00535 (9)	0.01058 (10)	0.00806 (10)	0.00208 (8)	−0.00033 (7)	−0.00331 (9)
O(2)	0.00682 (9)	0.00808 (10)	0.00575 (9)	−0.00014 (8)	−0.00065 (7)	−0.00120 (8)
O(3)	0.00757 (9)	0.00532 (9)	0.00929 (10)	0.00120 (8)	0.00122 (8)	0.00218 (8)
O(4)	0.00949 (10)	0.00569 (9)	0.00553 (9)	0.00043 (8)	−0.00044 (7)	−0.00017 (7)
O(5)	0.01497 (12)	0.00648 (10)	0.01451 (12)	0.00110 (9)	0.00673 (10)	−0.00002 (9)
N(1)	0.00529 (9)	0.00437 (9)	0.00610 (10)	0.00049 (8)	0.00101 (8)	0.00056 (8)
C(1)	0.00522 (10)	0.00549 (10)	0.00456 (10)	0.00055 (9)	0.00024 (8)	−0.00056 (9)
C(2)	0.00570 (10)	0.00523 (10)	0.00445 (10)	−0.00008 (9)	0.00069 (8)	−0.00029 (9)
C(3)	0.01018 (12)	0.00532 (11)	0.00607 (11)	−0.00019 (10)	0.00246 (9)	0.00039 (9)
C(4)	0.00884 (12)	0.00470 (10)	0.00523 (10)	0.00071 (9)	0.00000 (9)	0.00041 (9)
C(5)	0.00641 (11)	0.00575 (11)	0.00866 (12)	0.00153 (9)	−0.00043 (9)	0.00016 (10)
C(6)	0.00551 (10)	0.00501 (11)	0.00549 (10)	−0.00004 (8)	0.00071 (8)	0.00042 (8)
C(7)	0.00609 (11)	0.00997 (13)	0.01006 (13)	−0.00137 (10)	0.00198 (10)	−0.00009 (11)

Geometric parameters (Å, º)

O(1)—C(1)	1.2213 (4)	C(2)—H(3)	1.1010
O(2)—C(1)	1.3107 (4)	C(3)—C(4)	1.5247 (5)
O(2)—H(1)	0.9607	C(3)—H(4)	1.0937
O(3)—C(6)	1.2418 (4)	C(3)—H(5)	1.0937
O(4)—C(4)	1.4247 (4)	C(4)—C(5)	1.5283 (5)
O(4)—H(2)	0.9607	C(4)—H(6)	1.0982
O(5)—H(12)	0.9618	C(5)—H(7)	1.0993
O(5)—H(13)	0.9618	C(5)—H(8)	1.0993
N(1)—C(2)	1.4578 (4)	C(6)—C(7)	1.5011 (5)
N(1)—C(5)	1.4666 (5)	C(7)—H(9)	1.0914
N(1)—C(6)	1.3424 (5)	C(7)—H(10)	1.0914
C(1)—C(2)	1.5142 (5)	C(7)—H(11)	1.0914
C(2)—N(1)—C(5)	112.73 (3)	O(4)—C(4)—C(3)	108.27 (3)
C(2)—N(1)—C(6)	119.84 (3)	O(4)—C(4)—C(5)	111.35 (3)
C(5)—N(1)—C(6)	127.10 (3)	C(3)—C(4)—C(5)	102.78 (3)
O(1)—C(1)—O(2)	123.81 (3)	N(1)—C(5)—C(4)	102.40 (3)
O(1)—C(1)—C(2)	121.07 (3)	O(3)—C(6)—N(1)	119.54 (3)
O(2)—C(1)—C(2)	114.95 (3)	O(3)—C(6)—C(7)	122.55 (3)
N(1)—C(2)—C(1)	114.33 (3)	N(1)—C(6)—C(7)	117.91 (3)

(50K)

Crystal data

C7H11NO4·H2O	Z = 4
Mr = 191.18	F(000) = 408
Orthorhombic, P212121	Dx = 1.371 Mg m^−3
a = 9.866 (7) Å	Synchrotron radiation, λ = 0.5166 Å
b = 9.250 (7) Å	µ = 0.06 mm^−1
c = 10.149 (6) Å	T = 50 K
V = 926.2 (11) Å^3	0.34 × 0.28 × 0.28 mm

Data collection

44258 measured reflections	θmax = 31.9°, θmin = 2.1°
8284 independent reflections	h = −20→20
7710 reflections with I > 2σ(I)	k = −18→18
Rint = 0.055	l = −20→20

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	Hydrogen site location: mixed
R[F^2 > 2σ(F^2)] = 0.026	Only H-atom displacement parameters refined
wR(F^2) = 0.065	w2 = q/[s^2(Fo^2) + (0.04 P)^2 + 0.04 P + 0.00 + 0.00 sin(th)] where P = (0.3333 Fo^2 + 0.6667 Fc^2) q = 1.0
S = 1.48	(Δ/σ)max < 0.001
7372 reflections	Δρmax = 0.27 e Å^−3
131 parameters	Δρmin = −0.21 e Å^−3

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O(1)	0.57876 (3)	1.11441 (3)	0.77141 (3)	0.01
O(2)	0.79391 (3)	1.11875 (3)	0.84002 (3)	0.008
O(3)	0.84068 (3)	1.20552 (3)	0.55051 (3)	0.009
O(4)	0.78373 (3)	0.69411 (3)	0.51482 (3)	0.009
O(5)	0.90001 (4)	0.45963 (3)	0.43046 (4)	0.015
N(1)	0.87811 (3)	0.97798 (3)	0.61441 (3)	0.007
C(1)	0.69668 (3)	1.07604 (3)	0.76102 (3)	0.006
C(2)	0.73846 (3)	0.96437 (3)	0.65982 (3)	0.006
C(3)	0.73457 (4)	0.81112 (4)	0.71934 (3)	0.009
C(4)	0.84112 (4)	0.73027 (4)	0.63929 (3)	0.008
C(5)	0.95405 (4)	0.84207 (4)	0.62484 (4)	0.009
C(6)	0.91983 (3)	1.10149 (3)	0.55802 (3)	0.007
C(7)	1.06189 (4)	1.10714 (4)	0.50532 (4)	0.011
H(1)	0.75766	1.18374	0.90490	0.023 (2)*
H(2)	0.83126	0.61295	0.47803	0.021 (2)*
H(3)	0.66946	0.96973	0.57469	0.021 (2)*
H(4)	0.76077	0.81279	0.82405	0.019 (2)*
H(5)	0.63444	0.76210	0.70740	0.023 (2)*
H(6)	0.87671	0.63345	0.69150	0.024 (2)*
H(7)	1.02107	0.84220	0.71138	0.027 (3)*
H(8)	1.01476	0.82205	0.53587	0.022 (2)*
H(9)	1.13216	1.06864	0.58060	0.037 (3)*
H(10)	1.08723	1.21829	0.47898	0.032 (3)*
H(11)	1.06959	1.03852	0.41816	0.035 (3)*
H(12)	0.88488	0.36933	0.47506	0.027 (2)*
H(13)	0.95602	0.43768	0.35553	0.026 (2)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O(1)	0.00686 (8)	0.01278 (10)	0.00974 (9)	0.00238 (7)	−0.00035 (7)	−0.00383 (8)
O(2)	0.00810 (9)	0.00987 (9)	0.00719 (8)	−0.00014 (7)	−0.00072 (7)	−0.00135 (7)
O(3)	0.00918 (9)	0.00683 (8)	0.01132 (9)	0.00112 (7)	0.00134 (8)	0.00239 (7)
O(4)	0.01172 (10)	0.00665 (8)	0.00721 (8)	0.00077 (7)	−0.00035 (7)	−0.00018 (7)
O(5)	0.01906 (13)	0.00752 (9)	0.01898 (13)	0.00129 (9)	0.00986 (11)	0.00000 (9)
N(1)	0.00649 (9)	0.00561 (8)	0.00756 (9)	0.00069 (7)	0.00114 (7)	0.00058 (7)
C(1)	0.00639 (9)	0.00678 (9)	0.00572 (9)	0.00054 (8)	0.00035 (8)	−0.00030 (8)
C(2)	0.00699 (9)	0.00627 (9)	0.00554 (10)	−0.00022 (8)	0.00091 (8)	−0.00034 (8)
C(3)	0.01323 (12)	0.00646 (10)	0.00762 (11)	−0.00040 (9)	0.00317 (9)	0.00066 (9)
C(4)	0.01143 (11)	0.00590 (9)	0.00670 (10)	0.00115 (9)	0.00003 (9)	0.00072 (8)
C(5)	0.00838 (11)	0.00751 (10)	0.01054 (12)	0.00203 (9)	−0.00079 (9)	0.00006 (9)
C(6)	0.00659 (10)	0.00660 (10)	0.00687 (10)	−0.00016 (8)	0.00064 (8)	0.00063 (8)
C(7)	0.00726 (11)	0.01252 (12)	0.01224 (12)	−0.00155 (9)	0.00219 (9)	−0.00020 (10)

Geometric parameters (Å, º)

O(1)—C(1)	1.2210 (4)	C(2)—H(3)	1.1010
O(2)—C(1)	1.3111 (4)	C(3)—C(4)	1.5246 (5)
O(2)—H(1)	0.9607	C(3)—H(4)	1.0937
O(3)—C(6)	1.2416 (4)	C(3)—H(5)	1.0937
O(4)—C(4)	1.4242 (4)	C(4)—C(5)	1.5272 (5)
O(4)—H(2)	0.9607	C(4)—H(6)	1.0982
O(5)—H(12)	0.9618	C(5)—H(7)	1.0993
O(5)—H(13)	0.9618	C(5)—H(8)	1.0993
N(1)—C(2)	1.4583 (4)	C(6)—C(7)	1.5010 (5)
N(1)—C(5)	1.4674 (4)	C(7)—H(9)	1.0914
N(1)—C(6)	1.3423 (4)	C(7)—H(10)	1.0914
C(1)—C(2)	1.5139 (4)	C(7)—H(11)	1.0914
C(2)—N(1)—C(5)	112.68 (3)	O(4)—C(4)—C(3)	108.29 (3)
C(2)—N(1)—C(6)	119.86 (3)	O(4)—C(4)—C(5)	111.34 (3)
C(5)—N(1)—C(6)	127.12 (3)	C(3)—C(4)—C(5)	102.83 (3)
O(1)—C(1)—O(2)	123.83 (3)	N(1)—C(5)—C(4)	102.39 (3)
O(1)—C(1)—C(2)	121.09 (3)	O(3)—C(6)—N(1)	119.54 (3)
O(2)—C(1)—C(2)	114.92 (3)	O(3)—C(6)—C(7)	122.57 (3)
N(1)—C(2)—C(1)	114.38 (3)	N(1)—C(6)—C(7)	117.89 (3)

(75K)

Crystal data

C7H11NO4·H2O	Z = 4
Mr = 191.18	F(000) = 408
Orthorhombic, P212121	Dx = 1.367 Mg m^−3
a = 9.884 (6) Å	Synchrotron radiation, λ = 0.5166 Å
b = 9.253 (6) Å	µ = 0.06 mm^−1
c = 10.155 (3) Å	T = 75 K
V = 928.7 (9) Å^3	0.34 × 0.28 × 0.28 mm

Data collection

45127 measured reflections	θmax = 31.9°, θmin = 2.1°
8293 independent reflections	h = −20→20
7571 reflections with I > 2σ(I)	k = −18→18
Rint = 0.051	l = −20→20

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	Hydrogen site location: mixed
R[F^2 > 2σ(F^2)] = 0.028	Only H-atom displacement parameters refined
wR(F^2) = 0.074	w2 = q/[s^2(Fo^2) + (0.05 P)^2 + 0.02 P + 0.00 + 0.00 sin(th)] where P = (0.3333 Fo^2 + 0.6667 Fc^2) q = 1.0
S = 2.02	(Δ/σ)max < 0.001
7255 reflections	Δρmax = 0.30 e Å^−3
131 parameters	Δρmin = −0.25 e Å^−3

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O(1)	0.57882 (3)	1.11436 (4)	0.77113 (3)	0.012
O(2)	0.79370 (3)	1.11880 (4)	0.83960 (3)	0.01
O(3)	0.84060 (3)	1.20546 (3)	0.55017 (3)	0.011
O(4)	0.78380 (3)	0.69417 (3)	0.51449 (3)	0.01
O(5)	0.89986 (4)	0.45959 (4)	0.43035 (4)	0.018
N(1)	0.87789 (3)	0.97800 (4)	0.61424 (3)	0.008
C(1)	0.69669 (4)	1.07606 (4)	0.76063 (4)	0.008
C(2)	0.73845 (4)	0.96448 (4)	0.65936 (3)	0.007
C(3)	0.73434 (5)	0.81115 (4)	0.71877 (4)	0.011
C(4)	0.84092 (4)	0.73030 (4)	0.63901 (4)	0.01
C(5)	0.95379 (4)	0.84216 (4)	0.62478 (4)	0.011
C(6)	0.91971 (4)	1.10136 (4)	0.55780 (4)	0.008
C(7)	1.06163 (4)	1.10715 (5)	0.50536 (5)	0.013
H(1)	0.75730	1.18286	0.90508	0.022 (2)*
H(2)	0.83044	0.61217	0.47834	0.022 (2)*
H(3)	0.66973	0.97000	0.57418	0.025 (3)*
H(4)	0.76017	0.81273	0.82349	0.022 (2)*
H(5)	0.63441	0.76220	0.70652	0.026 (3)*
H(6)	0.87631	0.63351	0.69126	0.026 (3)*
H(7)	1.02055	0.84228	0.71137	0.031 (3)*
H(8)	1.01454	0.82222	0.53594	0.027 (3)*
H(9)	1.13171	1.06923	0.58088	0.041 (3)*
H(10)	1.08670	1.21822	0.47864	0.037 (3)*
H(11)	1.06968	1.03817	0.41854	0.039 (3)*
H(12)	0.88021	0.36999	0.47438	0.024 (2)*
H(13)	0.95670	0.43933	0.35573	0.028 (3)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O(1)	0.00813 (10)	0.01544 (12)	0.01197 (11)	0.00289 (9)	−0.00036 (9)	−0.00458 (10)
O(2)	0.00983 (10)	0.01153 (11)	0.00854 (10)	−0.00010 (9)	−0.00075 (8)	−0.00157 (8)
O(3)	0.01107 (11)	0.00825 (10)	0.01347 (11)	0.00136 (8)	0.00166 (9)	0.00303 (9)
O(4)	0.01442 (12)	0.00767 (10)	0.00881 (10)	0.00095 (9)	−0.00009 (9)	0.00009 (8)
O(5)	0.02317 (16)	0.00856 (11)	0.02333 (16)	0.00144 (11)	0.01253 (14)	0.00006 (11)
N(1)	0.00775 (10)	0.00695 (10)	0.00905 (11)	0.00091 (8)	0.00125 (8)	0.00059 (9)
C(1)	0.00770 (11)	0.00812 (11)	0.00693 (11)	0.00066 (9)	0.00040 (9)	−0.00052 (9)
C(2)	0.00828 (11)	0.00749 (11)	0.00665 (11)	−0.00026 (9)	0.00118 (9)	−0.00042 (9)
C(3)	0.01619 (14)	0.00788 (12)	0.00903 (13)	−0.00052 (11)	0.00382 (11)	0.00080 (10)
C(4)	0.01434 (14)	0.00695 (11)	0.00815 (11)	0.00175 (10)	0.00016 (10)	0.00079 (10)
C(5)	0.00999 (13)	0.00893 (12)	0.01291 (14)	0.00250 (10)	−0.00093 (11)	0.00000 (11)
C(6)	0.00794 (11)	0.00808 (12)	0.00839 (11)	−0.00025 (9)	0.00072 (9)	0.00051 (9)
C(7)	0.00860 (12)	0.01526 (15)	0.01490 (15)	−0.00222 (11)	0.00253 (11)	−0.00031 (12)

Geometric parameters (Å, º)

O(1)—C(1)	1.2224 (5)	C(2)—H(3)	1.1010
O(2)—C(1)	1.3111 (5)	C(3)—C(4)	1.5249 (6)
O(2)—H(1)	0.9607	C(3)—H(4)	1.0937
O(3)—C(6)	1.2431 (5)	C(3)—H(5)	1.0937
O(4)—C(4)	1.4246 (5)	C(4)—C(5)	1.5287 (6)
O(4)—H(2)	0.9607	C(4)—H(6)	1.0982
O(5)—H(12)	0.9618	C(5)—H(7)	1.0993
O(5)—H(13)	0.9618	C(5)—H(8)	1.0993
N(1)—C(2)	1.4578 (5)	C(6)—C(7)	1.5013 (5)
N(1)—C(5)	1.4677 (5)	C(7)—H(9)	1.0914
N(1)—C(6)	1.3425 (5)	C(7)—H(10)	1.0914
C(1)—C(2)	1.5145 (5)	C(7)—H(11)	1.0914
C(2)—N(1)—C(5)	112.76 (3)	O(4)—C(4)—C(3)	108.23 (3)
C(2)—N(1)—C(6)	119.88 (3)	O(4)—C(4)—C(5)	111.36 (3)
C(5)—N(1)—C(6)	127.01 (3)	C(3)—C(4)—C(5)	102.84 (3)
O(1)—C(1)—O(2)	123.80 (4)	N(1)—C(5)—C(4)	102.34 (3)
O(1)—C(1)—C(2)	121.10 (3)	O(3)—C(6)—N(1)	119.46 (3)
O(2)—C(1)—C(2)	114.94 (3)	O(3)—C(6)—C(7)	122.54 (4)
N(1)—C(2)—C(1)	114.37 (3)	N(1)—C(6)—C(7)	118.00 (3)

(100K)

Crystal data

C7H11NO4·H2O	F(000) = 408.0
Mr = 191.18	Dx = 1.364 Mg m^−3
Orthorhombic, P212121	Mo Kα radiation, λ = 0.7107 Å
a = 9.9026 (2) Å	Cell parameters from 18260 reflections
b = 9.2485 (2) Å	θ = 3.0–53.3°
c = 10.1662 (2) Å	µ = 0.12 mm^−1
V = 931.06 (3) Å^3	T = 100 K
Z = 4	0.54 × 0.28 × 0.14 mm

Data collection

Radiation source: Enhance (Mo) X-ray Source	7744 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.037
Detector resolution: 16.0009 pixels mm^-1	θmax = 53.3°, θmin = 3.0°
Absorption correction: analytical CrysAlis RED, Oxford Diffraction Ltd., Version 1.171.32.5 (release 08-05-2007 CrysAlis171 .NET) (compiled May 8 2007,13:10:02) Analytical numeric absorption correction using a multifaceted crystal model based on expressions derived by R.C. Clark & J.S. Reid. (Clark, R. C. & Reid, J. S. (1995). Acta Cryst. A51, 887-897)	h = −22→19
Tmin = 0.959, Tmax = 0.986	k = −19→20
39746 measured reflections	l = −22→21
10866 independent reflections

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	Only H-atom displacement parameters refined
R[F^2 > 2σ(F^2)] = 0.031	w2 = q/[s^2(Fo^2) + (0.04 P)^2 + 0.07 P + 0.00 + 0.00 sin(th)] where P = (0.3333 Fo^2 + 0.6667 Fc^2) q = 1.0
wR(F^2) = 0.066	(Δ/σ)max < 0.001
S = 2.81	Δρmax = 0.36 e Å^−3
7744 reflections	Δρmin = −0.21 e Å^−3
131 parameters

Special details

Refinement. An invariom refinement was performed. For details see Dittrich, et al. (2013).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O(1)	0.57902 (3)	1.11424 (4)	0.77061 (4)	0.016
O(2)	0.79339 (3)	1.11890 (4)	0.83896 (3)	0.014
O(3)	0.84048 (4)	1.20534 (4)	0.54958 (4)	0.015
O(4)	0.78382 (4)	0.69428 (4)	0.51396 (3)	0.014
O(5)	0.89990 (5)	0.45972 (4)	0.43023 (5)	0.025
N(1)	0.87773 (4)	0.97799 (4)	0.61382 (4)	0.011
C(1)	0.69647 (4)	1.07606 (4)	0.76009 (4)	0.011
C(2)	0.73829 (4)	0.96472 (4)	0.65881 (4)	0.01
C(3)	0.73381 (5)	0.81136 (5)	0.71798 (4)	0.015
C(4)	0.84028 (5)	0.73037 (5)	0.63867 (4)	0.013
C(5)	0.95318 (5)	0.84210 (5)	0.62474 (5)	0.015
C(6)	0.91953 (4)	1.10123 (4)	0.55739 (4)	0.011
C(7)	1.06118 (5)	1.10711 (6)	0.50536 (5)	0.017
H(1)	0.75761	1.18504	0.90295	0.027 (3)*
H(2)	0.83028	0.61205	0.47809	0.026 (2)*
H(3)	0.66980	0.97043	0.57365	0.022 (2)*
H(4)	0.75935	0.81285	0.82264	0.031 (3)*
H(5)	0.63404	0.76252	0.70547	0.029 (3)*
H(6)	0.87539	0.63344	0.69088	0.024 (2)*
H(7)	1.01959	0.84216	0.71139	0.031 (3)*
H(8)	1.01401	0.82196	0.53615	0.029 (3)*
H(9)	1.13059	1.06501	0.57944	0.043 (3)*
H(10)	1.08768	1.21886	0.48251	0.049 (4)*
H(11)	1.06836	1.04162	0.41632	0.054 (4)*
H(12)	0.88063	0.36964	0.47360	0.032 (3)*
H(13)	0.95927	0.44440	0.35667	0.033 (3)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O(1)	0.01123 (11)	0.02079 (14)	0.01632 (13)	0.00352 (10)	−0.00041 (10)	−0.00618 (11)
O(2)	0.01341 (11)	0.01563 (12)	0.01187 (10)	0.00032 (10)	−0.00120 (9)	−0.00226 (9)
O(3)	0.01483 (12)	0.01196 (12)	0.01856 (13)	0.00141 (10)	0.00222 (10)	0.00385 (10)
O(4)	0.01948 (13)	0.01028 (11)	0.01238 (10)	0.00117 (10)	0.00002 (10)	0.00001 (9)
O(5)	0.0305 (2)	0.01130 (13)	0.03167 (19)	0.00155 (12)	0.01698 (17)	−0.00003 (13)
N(1)	0.01062 (11)	0.01020 (12)	0.01282 (12)	0.00080 (9)	0.00186 (9)	0.00083 (9)
C(1)	0.01060 (12)	0.01177 (13)	0.01041 (12)	0.00082 (10)	0.00070 (10)	−0.00106 (10)
C(2)	0.01066 (12)	0.01014 (13)	0.01004 (12)	−0.00008 (10)	0.00120 (10)	−0.00037 (10)
C(3)	0.02136 (17)	0.01138 (14)	0.01240 (14)	−0.00101 (13)	0.00496 (12)	0.00103 (11)
C(4)	0.01885 (16)	0.00958 (13)	0.01185 (13)	0.00184 (12)	0.00015 (12)	0.00165 (10)
C(5)	0.01347 (14)	0.01254 (15)	0.01783 (16)	0.00314 (12)	−0.00163 (13)	−0.00040 (12)
C(6)	0.01063 (12)	0.01150 (14)	0.01165 (12)	−0.00046 (10)	0.00083 (10)	0.00079 (10)
C(7)	0.01194 (14)	0.02032 (18)	0.01903 (17)	−0.00321 (13)	0.00337 (13)	−0.00046 (14)

Geometric parameters (Å, º)

O(1)—C(1)	1.2201 (5)	C(2)—H(3)	1.1010
O(2)—C(1)	1.3119 (5)	C(3)—C(4)	1.5241 (6)
O(2)—H(1)	0.9607	C(3)—H(4)	1.0937
O(3)—C(6)	1.2435 (5)	C(3)—H(5)	1.0937
O(4)—C(4)	1.4253 (5)	C(4)—C(5)	1.5290 (7)
O(4)—H(2)	0.9607	C(4)—H(6)	1.0982
O(5)—H(12)	0.9618	C(5)—H(7)	1.0993
O(5)—H(13)	0.9618	C(5)—H(8)	1.0993
N(1)—C(2)	1.4597 (5)	C(6)—C(7)	1.5001 (6)
N(1)—C(5)	1.4663 (6)	C(7)—H(9)	1.0914
N(1)—C(6)	1.3415 (5)	C(7)—H(10)	1.0914
C(1)—C(2)	1.5140 (5)	C(7)—H(11)	1.0914
C(2)—N(1)—C(5)	112.72 (3)	O(4)—C(4)—C(3)	108.32 (4)
C(2)—N(1)—C(6)	119.82 (3)	O(4)—C(4)—C(5)	111.26 (4)
C(5)—N(1)—C(6)	127.11 (4)	C(3)—C(4)—C(5)	102.87 (3)
O(1)—C(1)—O(2)	123.81 (4)	N(1)—C(5)—C(4)	102.34 (4)
O(1)—C(1)—C(2)	121.14 (4)	O(3)—C(6)—N(1)	119.40 (4)
O(2)—C(1)—C(2)	114.89 (4)	O(3)—C(6)—C(7)	122.55 (4)
N(1)—C(2)—C(1)	114.50 (3)	N(1)—C(6)—C(7)	118.05 (4)

(150K)

Crystal data

C7H11NO4·H2O	F(000) = 408.0
Mr = 191.18	Dx = 1.356 Mg m^−3
Orthorhombic, P212121	Mo Kα radiation, λ = 0.7107 Å
a = 9.9408 (2) Å	Cell parameters from 11294 reflections
b = 9.2479 (2) Å	θ = 3.0–53.3°
c = 10.1875 (2) Å	µ = 0.12 mm^−1
V = 936.55 (3) Å^3	T = 150 K
Z = 4	0.54 × 0.28 × 0.14 mm

Data collection

Radiation source: Enhance (Mo) X-ray Source	5673 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.039
Detector resolution: 16.0009 pixels mm^-1	θmax = 53.3°, θmin = 3.0°
Absorption correction: analytical CrysAlis RED, Oxford Diffraction Ltd., Version 1.171.32.5 (release 08-05-2007 CrysAlis171 .NET) (compiled May 8 2007,13:10:02) Analytical numeric absorption correction using a multifaceted crystal model based on expressions derived by R.C. Clark & J.S. Reid. (Clark, R. C. & Reid, J. S. (1995). Acta Cryst. A51, 887-897)	h = −22→16
Tmin = 0.954, Tmax = 0.987	k = −19→20
30837 measured reflections	l = −22→21
7826 independent reflections

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	Only H-atom displacement parameters refined
R[F^2 > 2σ(F^2)] = 0.029	w2 = q/[s^2(Fo^2) + (0.05 P)^2 + 0.05 P + 0.00 + 0.00 sin(th)] where P = (0.3333 Fo^2 + 0.6667 Fc^2) q = 1.0
wR(F^2) = 0.069	(Δ/σ)max < 0.001
S = 2.96	Δρmax = 0.25 e Å^−3
5673 reflections	Δρmin = −0.16 e Å^−3
131 parameters

Special details

Refinement. An invariom refinement was performed. For details see Dittrich, et al. (2013).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O(1)	0.57947 (4)	1.11407 (6)	0.76947 (5)	0.023
O(2)	0.79288 (4)	1.11890 (5)	0.83745 (4)	0.019
O(3)	0.84020 (5)	1.20508 (5)	0.54824 (5)	0.021
O(4)	0.78374 (5)	0.69446 (5)	0.51284 (4)	0.02
O(5)	0.89928 (7)	0.45993 (6)	0.42971 (7)	0.035
N(1)	0.87691 (5)	0.97802 (5)	0.61298 (5)	0.016
C(1)	0.69642 (5)	1.07620 (6)	0.75871 (5)	0.015
C(2)	0.73793 (5)	0.96502 (5)	0.65751 (5)	0.014
C(3)	0.73258 (7)	0.81157 (6)	0.71585 (6)	0.021
C(4)	0.83894 (7)	0.73033 (6)	0.63748 (6)	0.019
C(5)	0.95169 (6)	0.84209 (6)	0.62438 (7)	0.021
C(6)	0.91895 (5)	1.10117 (6)	0.55636 (5)	0.016
C(7)	1.06010 (6)	1.10733 (8)	0.50517 (7)	0.024
H(1)	0.75689	1.18390	0.90209	0.031 (3)*
H(2)	0.82952	0.61154	0.47776	0.031 (3)*
H(3)	0.66997	0.97150	0.57237	0.025 (3)*
H(4)	0.75688	0.81243	0.82056	0.038 (3)*
H(5)	0.63314	0.76322	0.70221	0.039 (3)*
H(6)	0.87332	0.63336	0.68990	0.031 (3)*
H(7)	1.01710	0.84208	0.71138	0.038 (3)*
H(8)	1.01301	0.82180	0.53650	0.039 (3)*
H(9)	1.12848	1.06282	0.57860	0.051 (4)*
H(10)	1.08744	1.21940	0.48481	0.069 (6)*
H(11)	1.06732	1.04401	0.41504	0.071 (5)*
H(12)	0.88008	0.37051	0.47411	0.043 (3)*
H(13)	0.95857	0.44361	0.35659	0.041 (3)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O(1)	0.01598 (16)	0.0297 (2)	0.02322 (19)	0.00522 (15)	−0.00084 (15)	−0.00880 (17)
O(2)	0.01839 (17)	0.02252 (17)	0.01697 (16)	0.00023 (14)	−0.00110 (13)	−0.00404 (14)
O(3)	0.02124 (18)	0.01664 (16)	0.0266 (2)	0.00149 (14)	0.00346 (16)	0.00622 (15)
O(4)	0.0270 (2)	0.01460 (14)	0.01759 (16)	0.00220 (14)	0.00014 (15)	0.00047 (13)
O(5)	0.0431 (3)	0.01558 (17)	0.0450 (3)	0.00218 (18)	0.0241 (3)	0.00047 (18)
N(1)	0.01471 (16)	0.01434 (16)	0.01761 (18)	0.00159 (13)	0.00230 (14)	0.00102 (14)
C(1)	0.01481 (18)	0.01644 (17)	0.01481 (19)	0.00105 (14)	0.00084 (15)	−0.00089 (15)
C(2)	0.01553 (18)	0.01432 (17)	0.01349 (18)	−0.00010 (14)	0.00225 (14)	−0.00028 (14)
C(3)	0.0306 (3)	0.01521 (19)	0.0179 (2)	−0.00132 (18)	0.00720 (19)	0.00196 (16)
C(4)	0.0276 (2)	0.01342 (18)	0.0170 (2)	0.00316 (17)	0.00004 (18)	0.00212 (16)
C(5)	0.0192 (2)	0.0174 (2)	0.0251 (3)	0.00509 (17)	−0.00201 (19)	0.00035 (18)
C(6)	0.01505 (18)	0.01636 (18)	0.01640 (18)	−0.00081 (14)	0.00148 (15)	0.00068 (15)
C(7)	0.0164 (2)	0.0283 (3)	0.0283 (3)	−0.00455 (19)	0.0046 (2)	−0.0008 (2)

Geometric parameters (Å, º)

O(1)—C(1)	1.2192 (7)	C(2)—H(3)	1.1010
O(2)—C(1)	1.3111 (7)	C(3)—C(4)	1.5231 (9)
O(2)—H(1)	0.9607	C(3)—H(4)	1.0937
O(3)—C(6)	1.2422 (7)	C(3)—H(5)	1.0937
O(4)—C(4)	1.4226 (7)	C(4)—C(5)	1.5304 (9)
O(4)—H(2)	0.9607	C(4)—H(6)	1.0982
O(5)—H(12)	0.9618	C(5)—H(7)	1.0993
O(5)—H(13)	0.9618	C(5)—H(8)	1.0993
N(1)—C(2)	1.4591 (7)	C(6)—C(7)	1.4981 (8)
N(1)—C(5)	1.4650 (7)	C(7)—H(9)	1.0914
N(1)—C(6)	1.3433 (7)	C(7)—H(10)	1.0914
C(1)—C(2)	1.5134 (7)	C(7)—H(11)	1.0914
C(2)—C(3)	1.5394 (8)
C(2)—N(1)—C(5)	112.65 (4)	C(2)—C(3)—C(4)	103.20 (4)
C(2)—N(1)—C(6)	119.86 (4)	O(4)—C(4)—C(3)	108.37 (5)
C(5)—N(1)—C(6)	127.13 (5)	O(4)—C(4)—C(5)	111.23 (5)
O(1)—C(1)—O(2)	123.77 (5)	C(3)—C(4)—C(5)	102.77 (5)
O(1)—C(1)—C(2)	121.09 (5)	N(1)—C(5)—C(4)	102.40 (5)
O(2)—C(1)—C(2)	114.97 (5)	O(3)—C(6)—N(1)	119.24 (5)
N(1)—C(2)—C(1)	114.45 (4)	O(3)—C(6)—C(7)	122.53 (5)
N(1)—C(2)—C(3)	103.22 (4)	N(1)—C(6)—C(7)	118.24 (5)
C(1)—C(2)—C(3)	110.72 (4)

(xcalibur)

Crystal data

C7H11NO4·H2O	F(000) = 408.0
Mr = 191.18	Dx = 1.348 Mg m^−3
Orthorhombic, P212121	Mo Kα radiation, λ = 0.7107 Å
a = 9.9748 (2) Å	Cell parameters from 9686 reflections
b = 9.2492 (2) Å	θ = 3.0–53.3°
c = 10.2103 (2) Å	µ = 0.11 mm^−1
V = 941.99 (3) Å^3	T = 200 K
Z = 4	0.54 × 0.28 × 0.14 mm

Data collection

Radiation source: Enhance (Mo) X-ray Source	4860 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.039
Detector resolution: 16.0009 pixels mm^-1	θmax = 53.3°, θmin = 3.0°
Absorption correction: analytical CrysAlis RED, Oxford Diffraction Ltd., Version 1.171.32.5 (release 08-05-2007 CrysAlis171 .NET) (compiled May 8 2007,13:10:02) Analytical numeric absorption correction using a multifaceted crystal model based on expressions derived by R.C. Clark & J.S. Reid. (Clark, R. C. & Reid, J. S. (1995). Acta Cryst. A51, 887-897)	h = −22→16
Tmin = 0.960, Tmax = 0.989	k = −19→20
30309 measured reflections	l = −22→21
7829 independent reflections

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	Only H-atom displacement parameters refined
R[F^2 > 2σ(F^2)] = 0.029	w2 = q/[s^2(Fo^2) + (0.06 P)^2 + 0.04 P + 0.00 + 0.00 sin(th)] where P = (0.3333 Fo^2 + 0.6667 Fc^2) q = 1.0
wR(F^2) = 0.074	(Δ/σ)max < 0.001
S = 2.12	Δρmax = 0.20 e Å^−3
4860 reflections	Δρmin = −0.17 e Å^−3
131 parameters

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O(1)	0.57995 (5)	1.11413 (7)	0.76832 (6)	0.03
O(2)	0.79246 (5)	1.11887 (6)	0.83585 (5)	0.025
O(3)	0.83997 (6)	1.20478 (6)	0.54676 (6)	0.028
O(4)	0.78359 (6)	0.69501 (5)	0.51184 (5)	0.026
O(5)	0.89880 (8)	0.45994 (7)	0.42911 (8)	0.045
N(1)	0.87621 (5)	0.97809 (6)	0.61221 (6)	0.02
C(1)	0.69624 (6)	1.07643 (6)	0.75744 (6)	0.02
C(2)	0.73763 (6)	0.96568 (6)	0.65609 (6)	0.019
C(3)	0.73162 (8)	0.81193 (7)	0.71378 (7)	0.028
C(4)	0.83821 (8)	0.73081 (7)	0.63649 (7)	0.025
C(5)	0.95022 (8)	0.84203 (7)	0.62394 (8)	0.027
C(6)	0.91842 (6)	1.10108 (7)	0.55554 (6)	0.021
C(7)	1.05895 (7)	1.10742 (9)	0.50501 (9)	0.032
H(1)	0.75636	1.18161	0.90203	0.034 (3)*
H(2)	0.83218	0.61511	0.47493	0.041 (3)*
H(3)	0.67015	0.97270	0.57099	0.030 (3)*
H(4)	0.75512	0.81251	0.81842	0.050 (4)*
H(5)	0.63256	0.76376	0.69943	0.043 (3)*
H(6)	0.87204	0.63371	0.68884	0.044 (4)*
H(7)	1.01470	0.84193	0.71127	0.052 (4)*
H(8)	1.01207	0.82147	0.53679	0.042 (4)*
H(9)	1.12712	1.06611	0.57978	0.064 (5)*
H(10)	1.08514	1.21912	0.48193	0.078 (6)*
H(11)	1.06735	1.04138	0.41681	0.108 (8)*
H(12)	0.87799	0.37108	0.47362	0.046 (4)*
H(13)	0.95949	0.44271	0.35760	0.061 (4)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O(1)	0.0215 (2)	0.0391 (3)	0.0306 (3)	0.00705 (19)	−0.00148 (18)	−0.0117 (2)
O(2)	0.0241 (2)	0.0300 (2)	0.0223 (2)	0.00049 (18)	−0.00145 (17)	−0.00453 (18)
O(3)	0.0283 (2)	0.0219 (2)	0.0346 (3)	0.00163 (18)	0.0047 (2)	0.00810 (18)
O(4)	0.0367 (3)	0.01832 (17)	0.0234 (2)	0.00300 (17)	0.00035 (19)	0.00064 (16)
O(5)	0.0555 (4)	0.0199 (2)	0.0594 (4)	0.0029 (2)	0.0314 (4)	0.0002 (2)
N(1)	0.0196 (2)	0.01855 (19)	0.0230 (2)	0.00216 (16)	0.00257 (17)	0.00094 (17)
C(1)	0.0195 (2)	0.0211 (2)	0.0184 (2)	0.00103 (17)	0.00132 (18)	−0.00176 (18)
C(2)	0.0205 (2)	0.0184 (2)	0.0178 (2)	−0.00004 (17)	0.00251 (17)	−0.00053 (18)
C(3)	0.0405 (4)	0.0201 (2)	0.0235 (3)	−0.0019 (2)	0.0095 (3)	0.0024 (2)
C(4)	0.0370 (3)	0.0175 (2)	0.0216 (3)	0.0049 (2)	−0.0003 (2)	0.00274 (19)
C(5)	0.0252 (3)	0.0231 (3)	0.0340 (3)	0.0074 (2)	−0.0031 (3)	−0.0004 (2)
C(6)	0.0198 (2)	0.0213 (2)	0.0217 (2)	−0.00105 (18)	0.00225 (19)	0.00095 (19)
C(7)	0.0209 (3)	0.0378 (3)	0.0366 (4)	−0.0062 (3)	0.0064 (3)	−0.0010 (3)

Geometric parameters (Å, º)

O(1)—C(1)	1.2164 (8)	C(2)—H(3)	1.1010
O(2)—C(1)	1.3100 (8)	C(3)—C(4)	1.5219 (10)
O(2)—H(1)	0.9607	C(3)—H(4)	1.0937
O(3)—C(6)	1.2411 (8)	C(3)—H(5)	1.0937
O(4)—C(4)	1.4234 (9)	C(4)—C(5)	1.5242 (11)
O(4)—H(2)	0.9607	C(4)—H(6)	1.0982
O(5)—H(12)	0.9618	C(5)—H(7)	1.0993
O(5)—H(13)	0.9618	C(5)—H(8)	1.0993
N(1)—C(2)	1.4576 (8)	C(6)—C(7)	1.4948 (9)
N(1)—C(5)	1.4639 (8)	C(7)—H(9)	1.0914
N(1)—C(6)	1.3439 (8)	C(7)—H(10)	1.0914
C(1)—C(2)	1.5135 (8)	C(7)—H(11)	1.0914
C(2)—N(1)—C(5)	112.67 (5)	O(4)—C(4)—C(3)	108.12 (6)
C(2)—N(1)—C(6)	119.74 (5)	O(4)—C(4)—C(5)	111.25 (6)
C(5)—N(1)—C(6)	127.22 (6)	C(3)—C(4)—C(5)	102.88 (5)
O(1)—C(1)—O(2)	123.85 (6)	N(1)—C(5)—C(4)	102.56 (6)
O(1)—C(1)—C(2)	121.11 (6)	O(3)—C(6)—N(1)	119.19 (6)
O(2)—C(1)—C(2)	114.88 (5)	O(3)—C(6)—C(7)	122.41 (6)
N(1)—C(2)—C(1)	114.56 (5)	N(1)—C(6)—C(7)	118.40 (6)

(250K)

Crystal data

C7H11NO4·H2O	F(000) = 408.0
Mr = 191.18	Dx = 1.338 Mg m^−3
Orthorhombic, P212121	Mo Kα radiation, λ = 0.7107 Å
a = 10.0123 (2) Å	Cell parameters from 9593 reflections
b = 9.2556 (2) Å	θ = 2.8–36.3°
c = 10.2441 (2) Å	µ = 0.11 mm^−1
V = 949.32 (3) Å^3	T = 250 K
Z = 4	0.54 × 0.28 × 0.14 mm

Data collection

Radiation source: Enhance (Mo) X-ray Source	3245 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.020
Detector resolution: 16.0009 pixels mm^-1	θmax = 36.3°, θmin = 2.8°
Absorption correction: analytical CrysAlis RED, Oxford Diffraction Ltd., Version 1.171.32.5 (release 08-05-2007 CrysAlis171 .NET) (compiled May 8 2007,13:10:02) Analytical numeric absorption correction using a multifaceted crystal model based on expressions derived by R.C. Clark & J.S. Reid. (Clark, R. C. & Reid, J. S. (1995). Acta Cryst. A51, 887-897)	h = −15→15
Tmin = 0.956, Tmax = 0.989	k = −16→16
17876 measured reflections	l = −15→16
4420 independent reflections

Refinement

Refinement on F^2	131 parameters
Least-squares matrix: full	0 restraints
R[F^2 > 2σ(F^2)] = 0.025	w2 = q/[s^2(Fo^2) + (0.04 P)^2 + 0.08 P + 0.00 + 0.00 sin(th)] where P = (0.3333 Fo^2 + 0.6667 Fc^2) q = 1.0
wR(F^2) = 0.063	(Δ/σ)max < 0.001
S = 3.84	Δρmax = 0.16 e Å^−3
3245 reflections	Δρmin = −0.12 e Å^−3

Special details

Refinement. An invariom refinement was performed. For details see Dittrich, et al. (2013).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O(1)	0.58066 (6)	1.11426 (7)	0.76704 (6)	0.038
O(2)	0.79194 (6)	1.11883 (7)	0.83443 (6)	0.031
O(3)	0.84014 (6)	1.20456 (7)	0.54572 (6)	0.035
O(4)	0.78372 (7)	0.69571 (6)	0.51116 (6)	0.032
O(5)	0.89806 (9)	0.46008 (7)	0.42897 (9)	0.055
N(1)	0.87566 (6)	0.97841 (7)	0.61151 (6)	0.025
C(1)	0.69641 (7)	1.07661 (8)	0.75633 (7)	0.025
C(2)	0.73784 (7)	0.96612 (8)	0.65492 (7)	0.023
C(3)	0.73091 (10)	0.81237 (9)	0.71204 (8)	0.034
C(4)	0.83730 (10)	0.73126 (9)	0.63539 (8)	0.032
C(5)	0.94910 (9)	0.84218 (9)	0.62370 (9)	0.034
C(6)	0.91761 (7)	1.10078 (8)	0.55487 (8)	0.026
C(7)	1.05839 (8)	1.10739 (11)	0.50476 (11)	0.04
H(1)	0.75708	1.18614	0.89717	0.049 (4)*
H(2)	0.82994	0.61333	0.47629	0.045 (3)*
H(3)	0.67084	0.97374	0.56997	0.026 (2)*
H(4)	0.75341	0.81240	0.81652	0.054 (4)*
H(5)	0.63226	0.76452	0.69677	0.060 (4)*
H(6)	0.87052	0.63421	0.68784	0.042 (3)*
H(7)	1.01305	0.84189	0.71094	0.060 (4)*
H(8)	1.01093	0.82145	0.53702	0.052 (4)*
H(9)	1.12588	1.06287	0.57812	0.088 (5)*
H(10)	1.08548	1.21946	0.48490	0.100 (6)*
H(11)	1.06623	1.04434	0.41506	0.108 (7)*
H(12)	0.87933	0.37091	0.47356	0.065 (4)*
H(13)	0.95712	0.44217	0.35672	0.061 (4)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O(1)	0.0267 (3)	0.0484 (4)	0.0379 (3)	0.0093 (3)	−0.0011 (2)	−0.0149 (3)
O(2)	0.0298 (3)	0.0366 (3)	0.0277 (3)	0.0005 (2)	−0.0015 (2)	−0.0059 (2)
O(3)	0.0352 (3)	0.0280 (3)	0.0429 (3)	0.0028 (2)	0.0061 (3)	0.0098 (2)
O(4)	0.0457 (3)	0.0225 (2)	0.0292 (3)	0.0040 (2)	0.0004 (2)	0.0002 (2)
O(5)	0.0685 (5)	0.0244 (3)	0.0723 (5)	0.0040 (3)	0.0380 (4)	−0.0007 (3)
N(1)	0.0242 (3)	0.0232 (3)	0.0272 (3)	0.0022 (2)	0.0033 (2)	0.0002 (2)
C(1)	0.0245 (3)	0.0263 (3)	0.0229 (3)	0.0021 (3)	0.0011 (2)	−0.0009 (3)
C(2)	0.0256 (3)	0.0226 (3)	0.0215 (3)	−0.0008 (2)	0.0028 (2)	−0.0005 (2)
C(3)	0.0497 (4)	0.0244 (3)	0.0282 (4)	−0.0026 (3)	0.0112 (3)	0.0025 (3)
C(4)	0.0458 (4)	0.0228 (3)	0.0273 (4)	0.0061 (3)	0.0004 (3)	0.0040 (3)
C(5)	0.0315 (4)	0.0302 (4)	0.0408 (4)	0.0091 (3)	−0.0034 (3)	−0.0004 (3)
C(6)	0.0243 (3)	0.0270 (3)	0.0268 (3)	−0.0005 (3)	0.0027 (3)	0.0007 (3)
C(7)	0.0257 (3)	0.0478 (5)	0.0478 (5)	−0.0081 (4)	0.0081 (4)	−0.0015 (4)

Geometric parameters (Å, º)

O(1)—C(1)	1.2152 (9)	C(2)—H(3)	1.1010
O(2)—C(1)	1.3068 (10)	C(3)—C(4)	1.5214 (12)
O(2)—H(1)	0.9607	C(3)—H(4)	1.0937
O(3)—C(6)	1.2382 (10)	C(3)—H(5)	1.0937
O(4)—C(4)	1.4197 (10)	C(4)—C(5)	1.5236 (13)
O(4)—H(2)	0.9607	C(4)—H(6)	1.0982
O(5)—H(12)	0.9618	C(5)—H(7)	1.0993
O(5)—H(13)	0.9618	C(5)—H(8)	1.0993
N(1)—C(2)	1.4543 (9)	C(6)—C(7)	1.5013 (11)
N(1)—C(5)	1.4650 (10)	C(7)—H(9)	1.0914
N(1)—C(6)	1.3401 (10)	C(7)—H(10)	1.0914
C(1)—C(2)	1.5156 (10)	C(7)—H(11)	1.0914
C(2)—N(1)—C(5)	112.51 (6)	O(4)—C(4)—C(3)	108.21 (7)
C(2)—N(1)—C(6)	119.73 (6)	O(4)—C(4)—C(5)	111.30 (7)
C(5)—N(1)—C(6)	127.37 (6)	C(3)—C(4)—C(5)	102.85 (7)
O(1)—C(1)—O(2)	123.85 (7)	N(1)—C(5)—C(4)	102.58 (6)
O(1)—C(1)—C(2)	121.09 (7)	O(3)—C(6)—N(1)	119.48 (7)
O(2)—C(1)—C(2)	114.90 (6)	O(3)—C(6)—C(7)	122.05 (8)
N(1)—C(2)—C(1)	114.61 (6)	N(1)—C(6)—C(7)	118.47 (7)

(hydroxyproline9K)

Crystal data

C7H11NO4·H2O	F(000) = 144
Mr = 191.18	Dx = 1.373 Mg m^−3
Orthorhombic, P212121	Neutron radiation, λ = 0.85 Å
Hall symbol: P 2ac 2ab	Cell parameters from not applicable reflections
a = 9.854 (3) Å	θ = not applicable–not applicable°
b = 9.249 (3) Å	µ = 0.0 mm^−1
c = 10.144 (2) Å	T = 9 K
V = 924.5 (4) Å^3	Block, colorless
Z = 4	1.8 × 1.4 × 0.5 mm

Data collection

KOALA diffractometer	Rint = 0.068
Radiation source: nuclear reactor, OPAL reactor, ANSTO, Lucas Heights, Australia	θmax = 70.9°
Laue scans	h = −15→15
21579 measured reflections	k = −15→15
1355 independent reflections	l = −15→15
1243 reflections with I > 3.0σ(I)

Refinement

Refinement on F	Hydrogen site location: difference Fourier map
Least-squares matrix: full	All H-atom parameters refined
R[F^2 > 2σ(F^2)] = 0.027	Method, part 1, Chebychev polynomial, (Watkin, 1994, Prince, 1982) [weight] = 1.0/[A0*T0(x) + A1*T1(x) ··· + An-1]*Tn-1(x)] where Ai are the Chebychev coefficients listed below and x = F /Fmax Method = Robust Weighting (Prince, 1982) W = [weight] * [1-(deltaF/6*sigmaF)^2]^2 Ai are: -1.70 6.60 -5.09 3.23 -0.829
wR(F^2) = 0.025	(Δ/σ)max = 0.0004256
S = 0.99	Δρmax = 0.67 e Å^−3
1243 reflections	Δρmin = −0.64 e Å^−3
236 parameters	Extinction correction: Larson (1970), Equation 22
0 restraints	Extinction coefficient: 7.8 (7)
Primary atom site location: isomorphous structure methods

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.57863 (11)	1.11458 (19)	0.77209 (11)	0.0082
C1	0.69652 (10)	1.07608 (16)	0.76162 (9)	0.0050
O2	0.79426 (11)	1.11850 (18)	0.84052 (11)	0.0068
H1	0.7569 (2)	1.1900 (4)	0.9077 (2)	0.0179
C2	0.73840 (9)	0.96392 (16)	0.66045 (9)	0.0049
N1	0.87824 (7)	0.97794 (11)	0.61475 (7)	0.0061
C5	0.95464 (10)	0.84244 (16)	0.62478 (11)	0.0069
C4	0.84135 (11)	0.73007 (16)	0.63979 (9)	0.0065
C3	0.73460 (10)	0.81134 (16)	0.72019 (10)	0.0070
H4	0.7650 (3)	0.8145 (4)	0.8237 (2)	0.0219
H5	0.6341 (3)	0.7603 (4)	0.7126 (3)	0.0226
O4	0.78331 (12)	0.69404 (19)	0.51517 (11)	0.0066
H2	0.8326 (3)	0.6095 (4)	0.4775 (2)	0.0185
H6	0.8774 (3)	0.6313 (4)	0.6885 (2)	0.0195
H7	1.0200 (3)	0.8425 (4)	0.7124 (3)	0.0196
H8	1.0162 (3)	0.8232 (4)	0.5367 (3)	0.0212
C6	0.92001 (9)	1.10170 (15)	0.55818 (9)	0.0058
O3	0.84071 (12)	1.20518 (19)	0.55102 (12)	0.0080
C7	1.06233 (10)	1.10733 (17)	0.50527 (10)	0.0080
H9	1.1357 (3)	1.0659 (5)	0.5759 (3)	0.0293
H10	1.0894 (3)	1.2169 (5)	0.4793 (4)	0.0298
H11	1.0698 (3)	1.0408 (5)	0.4175 (3)	0.0341
H3	0.6681 (2)	0.9754 (4)	0.5767 (2)	0.0161
O5	0.90038 (14)	0.4600 (2)	0.43079 (13)	0.0111
H13	0.9593 (3)	0.4391 (4)	0.3571 (3)	0.0201
H12	0.8821 (3)	0.3676 (4)	0.4746 (3)	0.0212

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0049 (4)	0.0121 (9)	0.0076 (4)	0.0001 (4)	−0.0002 (3)	−0.0034 (5)
C1	0.0040 (3)	0.0070 (8)	0.0040 (3)	−0.0004 (3)	0.0003 (2)	−0.0002 (4)
O2	0.0049 (4)	0.0098 (9)	0.0056 (4)	0.0005 (4)	−0.0012 (3)	−0.0022 (5)
H1	0.0186 (9)	0.021 (2)	0.0139 (8)	0.0019 (10)	0.0006 (7)	−0.0051 (9)
C2	0.0044 (3)	0.0054 (7)	0.0050 (3)	0.0001 (3)	0.0004 (3)	−0.0001 (4)
N1	0.0042 (2)	0.0075 (6)	0.0065 (2)	−0.0004 (3)	0.00116 (19)	0.0006 (3)
C5	0.0047 (3)	0.0078 (8)	0.0082 (4)	0.0009 (3)	−0.0004 (3)	0.0000 (4)
C4	0.0066 (3)	0.0075 (8)	0.0054 (4)	0.0002 (3)	−0.0002 (3)	0.0010 (4)
C3	0.0068 (4)	0.0078 (8)	0.0064 (4)	−0.0006 (4)	0.0021 (3)	−0.0003 (4)
H4	0.0329 (12)	0.022 (2)	0.0111 (8)	0.0024 (12)	−0.0008 (8)	−0.0002 (9)
H5	0.0151 (9)	0.022 (2)	0.0306 (12)	−0.0077 (9)	0.0025 (9)	0.0001 (11)
O4	0.0072 (4)	0.0062 (10)	0.0062 (4)	−0.0001 (4)	−0.0006 (3)	0.0003 (4)
H2	0.0221 (9)	0.0162 (18)	0.0172 (8)	0.0040 (11)	−0.0009 (7)	−0.0024 (10)
H6	0.0239 (10)	0.0155 (19)	0.0193 (9)	0.0041 (10)	−0.0028 (8)	0.0041 (10)
H7	0.0204 (9)	0.0155 (19)	0.0228 (10)	−0.0017 (9)	−0.0106 (9)	0.0006 (10)
H8	0.0193 (9)	0.022 (2)	0.0225 (11)	0.0027 (10)	0.0096 (8)	−0.0015 (11)
C6	0.0043 (3)	0.0070 (8)	0.0060 (3)	−0.0005 (4)	0.0008 (3)	−0.0002 (4)
O3	0.0058 (4)	0.0092 (9)	0.0089 (4)	0.0011 (4)	0.0006 (3)	0.0021 (5)
C7	0.0054 (4)	0.0085 (9)	0.0100 (4)	−0.0011 (4)	0.0025 (3)	0.0003 (4)
H9	0.0171 (10)	0.042 (3)	0.0292 (12)	0.0031 (11)	−0.0039 (9)	0.0094 (13)
H10	0.0230 (11)	0.016 (2)	0.0499 (17)	−0.0032 (12)	0.0110 (12)	0.0097 (15)
H11	0.0263 (12)	0.049 (3)	0.0274 (13)	−0.0097 (14)	0.0090 (10)	−0.0177 (15)
H3	0.0143 (8)	0.0209 (18)	0.0132 (8)	0.0009 (8)	−0.0030 (7)	0.0011 (9)
O5	0.0121 (5)	0.0091 (11)	0.0121 (5)	0.0013 (5)	0.0059 (4)	−0.0005 (6)
H13	0.0238 (10)	0.0168 (19)	0.0196 (10)	0.0003 (9)	0.0102 (8)	−0.0019 (10)
H12	0.0243 (10)	0.015 (2)	0.0242 (10)	−0.0028 (10)	0.0032 (9)	0.0046 (11)

Geometric parameters (Å, º)

O1—C1	1.2197 (15)	C4—O4	1.4270 (15)
C1—O2	1.3122 (15)	C4—H6	1.098 (3)
C1—C2	1.5165 (17)	C3—H4	1.092 (3)
O2—H1	1.019 (3)	C3—H5	1.099 (3)
C2—N1	1.4597 (12)	O4—H2	0.996 (4)
C2—C3	1.536 (2)	C6—O3	1.238 (2)
C2—H3	1.101 (2)	C6—C7	1.5025 (14)
N1—C5	1.4655 (17)	C7—H9	1.088 (3)
N1—C6	1.3450 (16)	C7—H10	1.080 (4)
C5—C4	1.5328 (18)	C7—H11	1.085 (3)
C5—H7	1.098 (3)	O5—H13	0.967 (3)
C5—H8	1.094 (3)	O5—H12	0.980 (4)
C4—C3	1.5285 (16)
O1—C1—O2	123.96 (13)	C3—C4—O4	108.16 (9)
O1—C1—C2	121.18 (11)	C5—C4—H6	111.91 (18)
O2—C1—C2	114.68 (10)	C3—C4—H6	113.08 (17)
C1—O2—H1	109.69 (17)	O4—C4—H6	109.5 (2)
C1—C2—N1	114.27 (10)	C2—C3—C4	102.97 (9)
C1—C2—C3	110.78 (9)	C2—C3—H4	110.3 (2)
N1—C2—C3	103.29 (9)	C4—C3—H4	109.72 (18)
C1—C2—H3	106.56 (17)	C2—C3—H5	112.9 (2)
N1—C2—H3	109.86 (14)	C4—C3—H5	111.8 (2)
C3—C2—H3	112.21 (19)	H4—C3—H5	109.0 (3)
C2—N1—C5	112.77 (9)	C4—O4—H2	109.10 (18)
C2—N1—C6	120.00 (9)	N1—C6—O3	119.33 (10)
C5—N1—C6	126.88 (8)	N1—C6—C7	117.88 (11)
N1—C5—C4	102.27 (9)	O3—C6—C7	122.79 (13)
N1—C5—H7	110.9 (2)	C6—C7—H9	111.86 (18)
C4—C5—H7	110.33 (19)	C6—C7—H10	110.5 (2)
N1—C5—H8	111.5 (2)	H9—C7—H10	109.1 (3)
C4—C5—H8	112.0 (2)	C6—C7—H11	109.70 (19)
H7—C5—H8	109.7 (2)	H9—C7—H11	107.2 (3)
C5—C4—C3	102.76 (11)	H10—C7—H11	108.4 (3)
C5—C4—O4	111.24 (9)	H13—O5—H12	106.7 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H1···O4^i	1.019	1.579	2.5940 (16)	173.3 (2)
C3—H4···O3^i	1.092	2.537	3.4405 (16)	139.4 (2)
C3—H5···O1^ii	1.099	2.497	3.5839 (16)	169.5 (3)
O4—H2···O5	0.996	1.607	2.5980 (16)	172.2 (3)
C7—H10···O3^iii	1.080	2.598	3.2952 (16)	121.6 (3)
C7—H11···O1^iv	1.085	2.526	3.4259 (16)	139.7 (2)
C2—H3···O2^iv	1.101	2.575	3.3492 (16)	126.50 (18)
O5—H13···O1^v	0.967	1.829	2.7922 (16)	174.2 (3)
O5—H12···O3^vi	0.980	1.739	2.7180 (16)	177.1 (3)

Symmetry codes: (i) −x+3/2, −y+2, z+1/2; (ii) −x+1, y−1/2, −z+3/2; (iii) x+1/2, −y+5/2, −z+1; (iv) −x+3/2, −y+2, z−1/2; (v) x+1/2, −y+3/2, −z+1; (vi) x, y−1, z.

(hydroxyproline150K)

Crystal data

C7H11NO4·H2O	F(000) = 144
Mr = 191.18	Dx = 1.356 Mg m^−3
Orthorhombic, P212121	Neutron radiation, λ = 0.85 Å
Hall symbol: P 2ac 2ab	Cell parameters from not applicable reflections
a = 9.9408 (2) Å	θ = not applicable–not applicable°
b = 9.2479 (2) Å	µ = 0.0 mm^−1
c = 10.1875 (2) Å	T = 150 K
V = 936.55 (3) Å^3	Block, colorless
Z = 4	1.8 × 1.4 × 0.5 mm

Data collection

KOALA diffractometer	Rint = 0.092
Radiation source: nuclear reactor, OPAL reactor, ANSTO, Lucas Heights, Australia	θmax = 70.8°
Laue scans	h = −15→14
16001 measured reflections	k = −15→14
1331 independent reflections	l = −15→14
1092 reflections with I > 3.0σ(I)

Refinement

Refinement on F	Primary atom site location: isomorphous structure methods
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.039	All H-atom parameters refined
wR(F^2) = 0.034	Method, part 1, Chebychev polynomial, (Watkin, 1994, Prince, 1982) [weight] = 1.0/[A0*T0(x) + A1*T1(x) ··· + An-1]*Tn-1(x)] where Ai are the Chebychev coefficients listed below and x = F /Fmax Method = Robust Weighting (Prince, 1982) W = [weight] * [1-(deltaF/6*sigmaF)^2]^2 Ai are: 0.661 -0.306 0.427E-01
S = 1.00	(Δ/σ)max = 0.0002363
1092 reflections	Δρmax = 0.71 e Å^−3
235 parameters	Δρmin = −0.81 e Å^−3
0 restraints

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.5797 (2)	1.1141 (4)	0.7699 (2)	0.0233
C1	0.69597 (18)	1.0771 (3)	0.75893 (16)	0.0154
O2	0.7928 (2)	1.1189 (3)	0.8371 (2)	0.0192
H1	0.7568 (5)	1.1889 (7)	0.9048 (4)	0.0298
C2	0.73788 (17)	0.9652 (3)	0.65729 (18)	0.0149
N1	0.87699 (12)	0.97883 (19)	0.61308 (12)	0.0156
C5	0.9517 (2)	0.8425 (3)	0.6239 (2)	0.0217
C4	0.8393 (2)	0.7301 (3)	0.63734 (17)	0.0191
C3	0.7327 (2)	0.8118 (3)	0.7161 (2)	0.0214
H4	0.7610 (7)	0.8137 (7)	0.8190 (4)	0.0407
H5	0.6317 (6)	0.7636 (7)	0.7066 (6)	0.0436
O4	0.7835 (2)	0.6947 (4)	0.5130 (2)	0.0195
H2	0.8321 (5)	0.6090 (7)	0.4755 (4)	0.0308
H6	0.8741 (6)	0.6325 (7)	0.6874 (5)	0.0392
H7	1.0148 (6)	0.8433 (8)	0.7131 (6)	0.0440
H8	1.0147 (5)	0.8229 (8)	0.5380 (6)	0.0416
C6	0.91879 (18)	1.1017 (3)	0.55664 (17)	0.0172
O3	0.8403 (2)	1.2056 (4)	0.5481 (2)	0.0221
C7	1.06006 (19)	1.1067 (4)	0.5052 (2)	0.0250
H9	1.1307 (6)	1.0634 (11)	0.5768 (7)	0.0611
H10	1.0877 (7)	1.2161 (10)	0.4830 (10)	0.0675
H11	1.0688 (7)	1.0429 (12)	0.4183 (7)	0.0748
H3	0.6689 (4)	0.9769 (6)	0.5736 (4)	0.0273
O5	0.8988 (3)	0.4604 (4)	0.4294 (3)	0.0349
H13	0.9573 (5)	0.4405 (7)	0.3577 (5)	0.0370
H12	0.8800 (5)	0.3694 (7)	0.4734 (5)	0.0352

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0165 (8)	0.0323 (19)	0.0210 (8)	0.0051 (10)	−0.0003 (7)	−0.0088 (10)
C1	0.0167 (6)	0.0174 (15)	0.0121 (6)	0.0004 (7)	0.0008 (5)	−0.0008 (7)
O2	0.0178 (8)	0.0232 (18)	0.0165 (8)	0.0042 (9)	−0.0021 (7)	−0.0045 (10)
H1	0.0355 (19)	0.033 (3)	0.0211 (14)	−0.002 (2)	−0.0023 (14)	−0.0050 (17)
C2	0.0151 (6)	0.0152 (14)	0.0145 (6)	0.0002 (6)	0.0013 (5)	−0.0009 (7)
N1	0.0133 (4)	0.0166 (11)	0.0170 (5)	0.0016 (5)	0.0025 (4)	0.0010 (5)
C5	0.0184 (7)	0.0234 (17)	0.0233 (8)	0.0053 (7)	−0.0026 (6)	−0.0003 (9)
C4	0.0275 (8)	0.0153 (16)	0.0145 (7)	0.0039 (8)	−0.0003 (6)	0.0023 (7)
C3	0.0290 (9)	0.0180 (16)	0.0174 (7)	−0.0030 (9)	0.0053 (7)	0.0023 (8)
H4	0.070 (3)	0.032 (4)	0.0200 (16)	0.006 (3)	0.0033 (19)	0.0038 (18)
H5	0.041 (2)	0.039 (4)	0.051 (3)	−0.010 (2)	0.012 (2)	0.001 (3)
O4	0.0260 (10)	0.0147 (19)	0.0179 (8)	0.0017 (10)	0.0009 (7)	0.0001 (9)
H2	0.040 (2)	0.025 (3)	0.0278 (16)	0.009 (2)	0.0027 (16)	−0.0024 (19)
H6	0.061 (3)	0.024 (3)	0.033 (2)	0.009 (2)	−0.005 (2)	0.013 (2)
H7	0.047 (3)	0.040 (4)	0.045 (3)	0.007 (2)	−0.020 (2)	0.000 (3)
H8	0.036 (2)	0.047 (5)	0.042 (3)	0.004 (2)	0.0144 (19)	−0.005 (3)
C6	0.0138 (6)	0.0217 (15)	0.0160 (6)	−0.0006 (7)	0.0006 (5)	0.0010 (8)
O3	0.0226 (9)	0.0178 (18)	0.0260 (10)	0.0014 (10)	0.0046 (8)	0.0064 (10)
C7	0.0147 (7)	0.0328 (19)	0.0276 (9)	−0.0036 (9)	0.0055 (7)	−0.0016 (10)
H9	0.030 (2)	0.090 (6)	0.063 (4)	0.002 (3)	−0.007 (2)	0.012 (4)
H10	0.041 (3)	0.047 (5)	0.114 (6)	−0.006 (3)	0.027 (4)	0.024 (5)
H11	0.048 (3)	0.124 (8)	0.052 (3)	−0.024 (4)	0.021 (3)	−0.046 (4)
H3	0.0269 (16)	0.029 (3)	0.0256 (15)	−0.0016 (17)	−0.0004 (13)	−0.0002 (18)
O5	0.0421 (15)	0.020 (2)	0.0422 (15)	0.0057 (13)	0.0239 (13)	0.0021 (15)
H13	0.039 (2)	0.037 (4)	0.035 (2)	−0.003 (2)	0.0125 (18)	−0.003 (2)
H12	0.0346 (19)	0.031 (4)	0.040 (2)	0.000 (2)	0.0095 (18)	0.003 (2)

Geometric parameters (Å, º)

O1—C1	1.211 (3)	C4—O4	1.421 (3)
C1—O2	1.308 (3)	C4—H6	1.093 (6)
C1—C2	1.522 (3)	C3—H4	1.085 (5)
O2—H1	1.011 (5)	C3—H5	1.102 (6)
C2—N1	1.460 (2)	O4—H2	1.003 (6)
C2—C3	1.541 (4)	C6—O3	1.241 (4)
C2—H3	1.099 (4)	C6—C7	1.500 (3)
N1—C5	1.468 (3)	C7—H9	1.089 (7)
N1—C6	1.339 (3)	C7—H10	1.072 (9)
C5—C4	1.532 (3)	C7—H11	1.068 (7)
C5—H7	1.105 (6)	O5—H13	0.952 (5)
C5—H8	1.091 (6)	O5—H12	0.971 (8)
C4—C3	1.529 (3)
O1—C1—O2	124.3 (2)	C3—C4—O4	108.13 (18)
O1—C1—C2	121.1 (2)	C5—C4—H6	111.8 (4)
O2—C1—C2	114.44 (18)	C3—C4—H6	112.5 (3)
C1—O2—H1	110.1 (3)	O4—C4—H6	110.4 (4)
C1—C2—N1	114.21 (17)	C2—C3—C4	103.16 (16)
C1—C2—C3	110.64 (16)	C2—C3—H4	110.6 (4)
N1—C2—C3	103.37 (17)	C4—C3—H4	109.6 (4)
C1—C2—H3	106.8 (3)	C2—C3—H5	111.6 (4)
N1—C2—H3	110.1 (3)	C4—C3—H5	112.7 (4)
C3—C2—H3	111.8 (3)	H4—C3—H5	109.1 (5)
C2—N1—C5	112.46 (17)	C4—O4—H2	109.5 (3)
C2—N1—C6	119.98 (17)	N1—C6—O3	119.49 (19)
C5—N1—C6	127.15 (15)	N1—C6—C7	117.8 (2)
N1—C5—C4	102.73 (16)	O3—C6—C7	122.7 (2)
N1—C5—H7	110.1 (4)	C6—C7—H9	111.0 (4)
C4—C5—H7	110.2 (4)	C6—C7—H10	110.1 (5)
N1—C5—H8	111.9 (4)	H9—C7—H10	108.9 (7)
C4—C5—H8	112.2 (4)	C6—C7—H11	110.4 (4)
H7—C5—H8	109.6 (5)	H9—C7—H11	107.4 (8)
C5—C4—C3	102.5 (2)	H10—C7—H11	109.0 (9)
C5—C4—O4	111.17 (18)	H13—O5—H12	107.7 (6)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H1···O4^i	1.011	1.592	2.600 (3)	173.8 (5)
C3—H4···O3^i	1.085	2.549	3.463 (3)	141.3 (5)
C3—H5···O1^ii	1.102	2.527	3.606 (3)	165.9 (5)
O4—H2···O5	1.003	1.597	2.595 (3)	172.6 (5)
C7—H11···O1^iii	1.068	2.564	3.442 (3)	139.1 (5)
C2—H3···O2^iii	1.099	2.596	3.367 (3)	126.5 (3)
O5—H13···O1^iv	0.952	1.850	2.798 (3)	173.6 (6)
O5—H12···O3^v	0.971	1.741	2.711 (3)	177.6 (6)

Symmetry codes: (i) −x+3/2, −y+2, z+1/2; (ii) −x+1, y−1/2, −z+3/2; (iii) −x+3/2, −y+2, z−1/2; (iv) x+1/2, −y+3/2, −z+1; (v) x, y−1, z.

(hydroxyproline200K)

Crystal data

C7H11NO4·H2O	F(000) = 144
Mr = 191.18	Dx = 1.348 Mg m^−3
Orthorhombic, P212121	Neutron radiation, λ = 0.85 Å
Hall symbol: P 2ac 2ab	Cell parameters from not applicable reflections
a = 9.9748 (2) Å	θ = not applicable–not applicable°
b = 9.2492 (2) Å	µ = 0.0 mm^−1
c = 10.2103 (2) Å	T = 200 K
V = 941.99 (3) Å^3	Block, colorless
Z = 4	1.8 × 1.4 × 0.5 mm

Data collection

KOALA diffractometer	Rint = 0.088
Radiation source: nuclear reactor, OPAL reactor, ANSTO, Lucas Heights, Australia	θmax = 70.9°
Laue scans	h = −14→15
15826 measured reflections	k = −14→15
1315 independent reflections	l = −14→15
1065 reflections with I > 3.0σ(I)

Refinement

Refinement on F	Primary atom site location: isomorphous structure methods
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.045	All H-atom parameters refined
wR(F^2) = 0.045	Method, part 1, Chebychev polynomial, (Watkin, 1994, Prince, 1982) [weight] = 1.0/[A0*T0(x) + A1*T1(x) ··· + An-1]*Tn-1(x)] where Ai are the Chebychev coefficients listed below and x = F /Fmax Method = Robust Weighting (Prince, 1982) W = [weight] * [1-(deltaF/6*sigmaF)^2]^2 Ai are: 1.49 -0.682 1.01
S = 1.00	(Δ/σ)max = 0.0001787
1065 reflections	Δρmax = 0.76 e Å^−3
232 parameters	Δρmin = −0.89 e Å^−3
0 restraints

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
O1	0.5800 (2)	1.1141 (4)	0.7682 (2)	0.0301
C1	0.69631 (18)	1.0771 (3)	0.75768 (17)	0.0182
O2	0.7927 (2)	1.1192 (4)	0.8354 (2)	0.0233
H1	0.7562 (5)	1.1883 (7)	0.9034 (4)	0.0323
C2	0.73750 (18)	0.9655 (3)	0.65604 (18)	0.0170
N1	0.87619 (13)	0.9782 (2)	0.61209 (13)	0.0188
C5	0.9508 (2)	0.8423 (3)	0.6240 (2)	0.0262
C4	0.8378 (3)	0.7305 (3)	0.63651 (19)	0.0250
C3	0.7319 (2)	0.8124 (3)	0.7138 (2)	0.0267
H4	0.7586 (8)	0.8150 (9)	0.8181 (5)	0.0520
H5	0.6321 (7)	0.7652 (8)	0.7042 (7)	0.0508
O4	0.7838 (3)	0.6944 (4)	0.5124 (2)	0.0246
H2	0.8314 (5)	0.6097 (8)	0.4759 (5)	0.0365
H6	0.8715 (7)	0.6328 (8)	0.6854 (6)	0.0470
H7	1.0119 (7)	0.8439 (9)	0.7134 (8)	0.0515
H8	1.0129 (6)	0.8236 (8)	0.5381 (7)	0.0446
C6	0.91787 (19)	1.1012 (3)	0.55540 (18)	0.0205
O3	0.8402 (3)	1.2042 (4)	0.5465 (3)	0.0266
C7	1.0591 (2)	1.1073 (4)	0.5054 (2)	0.0342
H3	0.6687 (4)	0.9782 (6)	0.5726 (4)	0.0302
O5	0.8991 (4)	0.4604 (5)	0.4294 (4)	0.0438
H13	0.9576 (5)	0.4417 (8)	0.3581 (6)	0.0419
H12	0.8816 (6)	0.3697 (9)	0.4721 (6)	0.0424
H110	1.0575 (14)	1.077 (2)	0.4042 (15)	0.052 (3)*	0.5000
H111	1.0761 (11)	1.0170 (18)	0.4294 (11)	0.037 (2)*	0.5000
H100	1.0944 (14)	1.2165 (19)	0.5069 (15)	0.046 (3)*	0.5000
H101	1.0805 (16)	1.211 (2)	0.4617 (17)	0.052 (3)*	0.5000
H90	1.1285 (14)	1.090 (2)	0.5828 (14)	0.048 (3)*	0.5000
H91	1.1301 (15)	1.037 (2)	0.5664 (16)	0.052 (4)*	0.5000

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0181 (9)	0.045 (2)	0.0272 (10)	0.0056 (11)	−0.0013 (7)	−0.0085 (12)
C1	0.0177 (7)	0.0209 (15)	0.0158 (7)	0.0000 (7)	0.0008 (5)	−0.0006 (8)
O2	0.0215 (8)	0.027 (2)	0.0213 (8)	0.0022 (9)	−0.0016 (7)	−0.0060 (10)
H1	0.042 (2)	0.030 (4)	0.0257 (16)	−0.003 (2)	−0.0001 (15)	−0.0006 (17)
C2	0.0203 (7)	0.0137 (15)	0.0170 (6)	0.0001 (6)	0.0026 (5)	0.0009 (7)
N1	0.0176 (5)	0.0172 (12)	0.0215 (5)	0.0033 (5)	0.0026 (4)	0.0013 (6)
C5	0.0233 (8)	0.0231 (18)	0.0323 (10)	0.0095 (8)	−0.0030 (7)	−0.0016 (10)
C4	0.0380 (10)	0.0164 (19)	0.0204 (8)	0.0029 (9)	0.0025 (7)	0.0036 (8)
C3	0.0378 (10)	0.0192 (19)	0.0229 (8)	−0.0039 (10)	0.0079 (8)	0.0008 (9)
H4	0.084 (5)	0.046 (5)	0.0263 (19)	0.008 (4)	0.005 (2)	0.006 (2)
H5	0.051 (3)	0.042 (5)	0.059 (3)	−0.010 (3)	0.022 (3)	−0.002 (3)
O4	0.0346 (11)	0.017 (2)	0.0222 (9)	0.0050 (11)	0.0003 (8)	0.0009 (10)
H2	0.044 (2)	0.030 (4)	0.0352 (19)	0.003 (2)	0.0047 (17)	−0.001 (2)
H6	0.067 (3)	0.029 (4)	0.045 (3)	0.013 (3)	−0.008 (2)	0.009 (3)
H7	0.054 (3)	0.040 (5)	0.061 (4)	−0.001 (3)	−0.024 (3)	0.005 (3)
H8	0.039 (2)	0.040 (5)	0.055 (3)	0.011 (2)	0.012 (2)	−0.003 (3)
C6	0.0190 (7)	0.0227 (17)	0.0197 (7)	−0.0023 (8)	0.0011 (6)	0.0023 (8)
O3	0.0264 (10)	0.023 (2)	0.0309 (11)	0.0030 (10)	0.0039 (8)	0.0106 (11)
C7	0.0165 (8)	0.049 (2)	0.0373 (11)	−0.0050 (10)	0.0073 (7)	−0.0007 (12)
H3	0.0278 (15)	0.033 (4)	0.0299 (16)	−0.0003 (17)	−0.0005 (13)	−0.0036 (19)
O5	0.0533 (19)	0.023 (3)	0.0550 (19)	0.0036 (15)	0.0322 (16)	−0.0015 (19)
H13	0.038 (2)	0.044 (4)	0.044 (2)	−0.002 (2)	0.0149 (19)	−0.002 (2)
H12	0.047 (3)	0.033 (4)	0.047 (3)	0.007 (3)	0.012 (2)	0.007 (3)

Geometric parameters (Å, º)

O1—C1	1.214 (3)	C4—H6	1.085 (7)
C1—O2	1.307 (3)	C3—H4	1.098 (6)
C1—C2	1.520 (3)	C3—H5	1.092 (7)
O2—H1	1.011 (6)	O4—H2	0.989 (7)
C2—N1	1.459 (2)	C6—O3	1.232 (4)
C2—C3	1.535 (4)	C6—C7	1.499 (3)
C2—H3	1.101 (4)	C7—H110	1.071 (15)
N1—C5	1.466 (3)	C7—H111	1.153 (14)
N1—C6	1.342 (3)	C7—H100	1.070 (19)
C5—C4	1.535 (4)	C7—H101	1.076 (19)
C5—H7	1.097 (7)	C7—H90	1.062 (14)
C5—H8	1.087 (6)	C7—H91	1.147 (18)
C4—C3	1.520 (4)	O5—H13	0.949 (6)
C4—O4	1.417 (3)	O5—H12	0.962 (10)
O1—C1—O2	124.4 (3)	C2—C3—H4	110.1 (5)
O1—C1—C2	120.7 (2)	C4—C3—H4	110.3 (4)
O2—C1—C2	114.72 (19)	C2—C3—H5	111.5 (5)
C1—O2—H1	109.9 (3)	C4—C3—H5	112.8 (4)
C1—C2—N1	114.30 (18)	H4—C3—H5	108.5 (6)
C1—C2—C3	110.75 (17)	C4—O4—H2	109.9 (4)
N1—C2—C3	103.10 (17)	N1—C6—O3	119.5 (2)
C1—C2—H3	106.7 (3)	N1—C6—C7	118.0 (2)
N1—C2—H3	110.2 (3)	O3—C6—C7	122.5 (3)
C3—C2—H3	111.9 (4)	C6—C7—H110	107.8 (8)
C2—N1—C5	112.76 (18)	C6—C7—H111	109.9 (6)
C2—N1—C6	119.65 (17)	C6—C7—H100	109.9 (8)
C5—N1—C6	127.22 (16)	C6—C7—H101	111.2 (9)
N1—C5—C4	102.23 (17)	H110—C7—H101	80.6 (15)
N1—C5—H7	109.8 (5)	H111—C7—H101	109.6 (12)
C4—C5—H7	110.3 (5)	C6—C7—H90	110.7 (8)
N1—C5—H8	111.0 (4)	H110—C7—H90	133.5 (14)
C4—C5—H8	112.2 (5)	H111—C7—H90	107.3 (13)
H7—C5—H8	110.9 (6)	H100—C7—H90	85.1 (14)
C5—C4—C3	102.6 (2)	H101—C7—H90	108.1 (14)
C5—C4—O4	111.3 (2)	C6—C7—H91	112.0 (8)
C3—C4—O4	108.5 (2)	H110—C7—H91	112.6 (15)
C5—C4—H6	111.9 (5)	H111—C7—H91	82.1 (13)
C3—C4—H6	113.0 (4)	H100—C7—H91	109.0 (14)
O4—C4—H6	109.4 (5)	H101—C7—H91	127.4 (13)
C2—C3—C4	103.58 (18)	H13—O5—H12	107.5 (7)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H1···O4^i	1.011	1.605	2.612 (3)	173.1 (5)
C3—H4···O3^i	1.098	2.538	3.475 (3)	142.7 (6)
C3—H5···O1^ii	1.092	2.551	3.617 (3)	164.9 (6)
O4—H2···O5	0.989	1.609	2.594 (3)	173.0 (6)
O5—H13···O1^iii	0.949	1.849	2.793 (3)	172.7 (7)
O5—H12···O3^iv	0.962	1.758	2.719 (3)	176.7 (6)
C7—H111···O1^v	1.153	2.570	3.461 (3)	133.1 (8)

Symmetry codes: (i) −x+3/2, −y+2, z+1/2; (ii) −x+1, y−1/2, −z+3/2; (iii) x+1/2, −y+3/2, −z+1; (iv) x, y−1, z; (v) −x+3/2, −y+2, z−1/2.

(hydroxyproline250K)

Crystal data

C7H11NO4·H2O	F(000) = 144
Mr = 191.18	Dx = 1.338 Mg m^−3
Orthorhombic, P212121	Neutron radiation, λ = 0.85 Å
Hall symbol: P 2ac 2ab	Cell parameters from not applicable reflections
a = 10.0123 (2) Å	θ = not applicable–not applicable°
b = 9.2556 (2) Å	µ = 0.0 mm^−1
c = 10.2441 (2) Å	T = 250 K
V = 949.32 (3) Å^3	Block, colorless
Z = 4	1.8 × 1.4 × 0.5 mm

Data collection

KOALA diffractometer	Rint = 0.098
Radiation source: nuclear reactor, OPAL reactor, ANSTO, Lucas Heights, Australia	θmax = 70.9°
Laue scans	h = −9→15
13174 measured reflections	k = −9→15
1307 independent reflections	l = −9→15
967 reflections with I > 3.0σ(I)

Refinement

Refinement on F	Primary atom site location: isomorphous structure methods
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.051	All H-atom parameters refined
wR(F^2) = 0.050	Method, part 1, Chebychev polynomial, (Watkin, 1994, Prince, 1982) [weight] = 1.0/[A0*T0(x) + A1*T1(x) ··· + An-1]*Tn-1(x)] where Ai are the Chebychev coefficients listed below and x = F /Fmax Method = Robust Weighting (Prince, 1982) W = [weight] * [1-(deltaF/6*sigmaF)^2]^2 Ai are: 1.19 -0.518 0.521
S = 1.00	(Δ/σ)max = 0.0001605
9675 reflections	Δρmax = 0.70 e Å^−3
232 parameters	Δρmin = −0.88 e Å^−3
0 restraints

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
O1	0.5808 (3)	1.1136 (6)	0.7671 (4)	0.0366
C1	0.6961 (3)	1.0769 (4)	0.7562 (2)	0.0239
O2	0.7918 (3)	1.1189 (5)	0.8343 (3)	0.0300
H1	0.7556 (7)	1.1897 (10)	0.9020 (6)	0.0419
C2	0.7371 (3)	0.9663 (4)	0.6549 (3)	0.0221
N1	0.87562 (19)	0.9790 (3)	0.61179 (19)	0.0241
C5	0.9496 (3)	0.8424 (5)	0.6232 (3)	0.0328
C4	0.8369 (4)	0.7304 (4)	0.6355 (3)	0.0297
C3	0.7305 (4)	0.8125 (5)	0.7124 (3)	0.0345
H4	0.7551 (11)	0.8148 (11)	0.8151 (7)	0.0588
H5	0.6312 (10)	0.7643 (11)	0.7023 (10)	0.0621
O4	0.7836 (4)	0.6951 (6)	0.5110 (3)	0.0314
H2	0.8316 (8)	0.6113 (10)	0.4752 (7)	0.0448
H6	0.8703 (11)	0.6340 (11)	0.6842 (8)	0.0570
H7	1.0109 (10)	0.8434 (14)	0.7117 (11)	0.0711
H8	1.0117 (8)	0.8242 (12)	0.5379 (11)	0.0563
C6	0.9179 (3)	1.1016 (4)	0.5552 (3)	0.0263
O3	0.8401 (4)	1.2037 (5)	0.5454 (4)	0.0348
C7	1.0576 (3)	1.1070 (6)	0.5042 (4)	0.0416
H3	0.6699 (5)	0.9801 (9)	0.5717 (5)	0.0358
O5	0.8980 (6)	0.4618 (7)	0.4292 (6)	0.0547
H13	0.9566 (8)	0.4419 (11)	0.3574 (8)	0.0529
H12	0.8804 (9)	0.3688 (12)	0.4714 (8)	0.0509
H90	1.128 (2)	1.097 (4)	0.583 (2)	0.069 (7)*	0.5000
H91	1.128 (2)	1.041 (3)	0.568 (2)	0.053 (5)*	0.5000
H110	1.057 (3)	1.087 (3)	0.401 (3)	0.075 (6)*	0.5000
H111	1.0761 (16)	1.024 (2)	0.4315 (17)	0.047 (3)*	0.5000
H100	1.097 (2)	1.218 (3)	0.512 (3)	0.065 (5)*	0.5000
H101	1.081 (2)	1.202 (3)	0.461 (3)	0.065 (5)*	0.5000

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0251 (13)	0.049 (3)	0.0356 (16)	0.0076 (16)	0.0000 (12)	−0.0111 (18)
C1	0.0231 (10)	0.029 (2)	0.0192 (10)	0.0013 (11)	0.0017 (8)	0.0011 (11)
O2	0.0269 (12)	0.037 (3)	0.0262 (14)	0.0045 (15)	−0.0052 (11)	−0.0064 (16)
H1	0.046 (3)	0.047 (5)	0.033 (3)	−0.007 (3)	0.002 (2)	−0.002 (3)
C2	0.0272 (11)	0.018 (2)	0.0206 (9)	0.0000 (10)	0.0033 (8)	0.0016 (10)
N1	0.0226 (7)	0.0246 (17)	0.0251 (8)	0.0025 (8)	0.0021 (6)	0.0011 (8)
C5	0.0289 (12)	0.031 (3)	0.0384 (15)	0.0109 (12)	−0.0056 (11)	−0.0003 (14)
C4	0.0453 (15)	0.018 (2)	0.0254 (12)	0.0053 (13)	0.0015 (11)	0.0055 (13)
C3	0.0490 (17)	0.027 (3)	0.0277 (13)	−0.0040 (16)	0.0121 (13)	0.0021 (14)
H4	0.102 (7)	0.040 (6)	0.035 (3)	0.011 (5)	0.014 (4)	0.011 (3)
H5	0.063 (5)	0.055 (7)	0.068 (5)	−0.016 (4)	0.024 (4)	−0.002 (4)
O4	0.0476 (19)	0.019 (3)	0.0279 (15)	0.0058 (18)	0.0001 (14)	0.0015 (15)
H2	0.053 (4)	0.038 (6)	0.043 (3)	0.006 (4)	0.007 (3)	−0.003 (3)
H6	0.082 (5)	0.039 (6)	0.049 (4)	0.019 (5)	−0.007 (4)	0.013 (4)
H7	0.062 (5)	0.073 (9)	0.079 (6)	0.005 (5)	−0.036 (5)	0.007 (6)
H8	0.043 (3)	0.051 (8)	0.075 (5)	0.014 (4)	0.016 (3)	0.002 (5)
C6	0.0236 (10)	0.029 (2)	0.0264 (11)	−0.0040 (12)	0.0017 (9)	0.0033 (13)
O3	0.0345 (15)	0.030 (3)	0.0401 (18)	0.0051 (17)	0.0077 (13)	0.0104 (18)
C7	0.0231 (12)	0.053 (3)	0.0482 (19)	−0.0061 (16)	0.0092 (12)	−0.0034 (19)
H3	0.029 (2)	0.047 (5)	0.032 (2)	0.000 (2)	0.0024 (19)	−0.002 (3)
O5	0.072 (3)	0.024 (4)	0.068 (3)	0.006 (2)	0.040 (3)	−0.001 (3)
H13	0.053 (4)	0.056 (6)	0.050 (4)	−0.006 (4)	0.017 (3)	−0.002 (4)
H12	0.052 (4)	0.046 (6)	0.054 (4)	0.000 (4)	0.016 (3)	0.010 (4)

Geometric parameters (Å, º)

O1—C1	1.208 (4)	C4—H6	1.076 (9)
C1—O2	1.308 (4)	C3—H4	1.080 (8)
C1—C2	1.514 (4)	C3—H5	1.095 (10)
O2—H1	1.020 (9)	O4—H2	0.984 (11)
C2—N1	1.460 (3)	C6—O3	1.229 (5)
C2—C3	1.542 (5)	C6—C7	1.494 (4)
C2—H3	1.094 (6)	C7—H90	1.08 (3)
N1—C5	1.470 (4)	C7—H91	1.13 (2)
N1—C6	1.343 (4)	C7—H110	1.07 (3)
C5—C4	1.537 (5)	C7—H111	1.087 (19)
C5—H7	1.095 (9)	C7—H100	1.10 (3)
C5—H8	1.086 (10)	C7—H101	1.01 (3)
C4—C3	1.528 (5)	O5—H13	0.959 (9)
C4—O4	1.421 (5)	O5—H12	0.980 (14)
O1—C1—O2	124.1 (4)	C2—C3—H4	110.1 (7)
O1—C1—C2	120.8 (3)	C4—C3—H4	110.7 (6)
O2—C1—C2	114.9 (3)	C2—C3—H5	112.3 (7)
C1—O2—H1	110.2 (5)	C4—C3—H5	112.4 (6)
C1—C2—N1	114.3 (2)	H4—C3—H5	107.9 (8)
C1—C2—C3	110.5 (2)	C4—O4—H2	109.4 (6)
N1—C2—C3	103.3 (3)	N1—C6—O3	119.0 (3)
C1—C2—H3	106.7 (4)	N1—C6—C7	118.3 (3)
N1—C2—H3	109.8 (4)	O3—C6—C7	122.6 (4)
C3—C2—H3	112.3 (5)	C6—C7—H90	110.3 (13)
C2—N1—C5	112.7 (3)	C6—C7—H91	111.1 (11)
C2—N1—C6	119.9 (2)	C6—C7—H110	109.6 (14)
C5—N1—C6	127.0 (2)	H90—C7—H110	137 (2)
N1—C5—C4	102.5 (2)	H91—C7—H110	118 (2)
N1—C5—H7	109.9 (7)	C6—C7—H111	112.0 (9)
C4—C5—H7	110.4 (7)	H90—C7—H111	110 (2)
N1—C5—H8	111.0 (6)	C6—C7—H100	109.7 (13)
C4—C5—H8	112.4 (7)	H91—C7—H100	104.1 (19)
H7—C5—H8	110.3 (9)	H110—C7—H100	103 (2)
C5—C4—C3	102.6 (3)	H111—C7—H100	130.4 (17)
C5—C4—O4	110.9 (3)	C6—C7—H101	113.2 (14)
C3—C4—O4	108.4 (3)	H90—C7—H101	105 (2)
C5—C4—H6	111.7 (7)	H91—C7—H101	125.4 (19)
C3—C4—H6	112.9 (6)	H111—C7—H101	106.2 (19)
O4—C4—H6	110.0 (7)	H13—O5—H12	106.3 (10)
C2—C3—C4	103.4 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H1···O4^i	1.020	1.593	2.609 (5)	173.4 (7)
C3—H4···O3^i	1.080	2.550	3.487 (5)	144.5 (8)
C3—H5···O1^ii	1.095	2.559	3.626 (5)	164.5 (9)
O4—H2···O5	0.984	1.605	2.583 (5)	172.5 (8)
O5—H13···O1^iii	0.959	1.854	2.807 (5)	172.5 (10)
O5—H12···O3^iv	0.980	1.753	2.732 (5)	177.1 (9)

Symmetry codes: (i) −x+3/2, −y+2, z+1/2; (ii) −x+1, y−1/2, −z+3/2; (iii) x+1/2, −y+3/2, −z+1; (iv) x, y−1, z.

 

Footnotes

¹This was only tested for scattering factors from the generalized invariom database (Dittrich et al., 2013), not for those from the UBDB2011  (Jarzembska & Dominiak, 2012), the ELMAM2  (Domagala et al., 2012) nor the SBFA (Hathwar et al., 2011) libraries. For modelling hydrogen scattering, theoretically derived databases have the advantage of higher precision, since experimental scattering factors for hydrogen can only be reliably determined to the dipolar level of the multipole expansion.

²Since displacement parameters used in this work are either isotropic or anisotropic, we use the abbreviation ADPs, which was recommended to be used only for anisotropic displacement parameters (Trueblood et al., 1996), in a different manner here.

³Post-analysis of the temperature and volume dependence of unit-cell parameters showed that the data point at 67 K (as indicated on the low-T device) was an outlier, probably due to inaccuracies caused by heating the cold stream of He gas to higher temperatures. We have corrected this temperature to 75 K, as derived from a plot of the increase of the unit-cell volume with temperature. Another reason for the deviating behaviour might be rotational disorder and this is discussed later on.

⁴This new segmented-body TLS refinement program and its functionality will be described in a forthcoming paper.

⁵We have also refined isotropic ADPs for H atoms using the neutron data instead of the anisotropic description. Results show the same trends within the standard deviations of our experiments, but since the figures of merit are worse we chose to use H-U_eq for neutron data and H-U_isofor the X-ray data.

⁶Supporting information is available from the IUCr electronic archives (Reference: KX5033 ).

⁷It should be noted that differences due to hydrogen bonding are not taken into account in the invariom approach. However, such influences are an order of magnitude smaller than electron-density redistributions due to covalent bonding, which are not taken into account in the IAM model.

⁸For the most common invariom H1c[1c1h1h], which is used three times, the standard deviation of HU_iso/XU_eq varies from 0.03 to 0.3 across all temperatures and experiments.