research communications
Hydrogen-bonded L-proline
structure of benzoic acid and zwitterionica764 Natural Sciences Complex, Buffalo, 14260-3000, USA, b730 Natural Sciences Complex, Buffalo, 14260-3000, USA, and c771 Natural Sciences Complex, Buffalo, 14260-3000, USA
*Correspondence e-mail: jbb6@buffalo.edu
The title compound [systematic name: benzoic acid–pyrrolidin-1-ium-2-carboxylate (1/1)], C7H6O2·C5H9NO2, is an example of the application of non-centrosymmetric co-crystallization for the growth of a crystal containing a typically centrosymmetric component in a It co-crystallizes in the P212121 and contains benzoic acid and L-proline in equal proportions. The exhibits chains of L-proline capped by benzoic acid molecules which form a C(5)[R33(11)] hydrogen-bonded network along [100]. The is examined and compared to that of a similar containing L-proline and 4-aminobenzoic acid.
Keywords: crystal structure; co-crystal; benzoic acid; proline; hydrogen bonding.
CCDC reference: 1530619
1. Chemical context
Non-centrosymmetric materials are of particular importance in the field of materials chemistry for the large number of symmetry-dependent properties they can possess, including ; McMillen et al., 2012; Aitken et al., 2009). While purposefully engineering these materials can be difficult, one method for eliminating centrosymmetry in crystalline materials is co-crystallization with an enantiopure chiral compound (Kwon et al., 2006). In this way, provided that the chiral compound is not capable of the potential point groups are limited only to those which are chiral, and therefore non-centrosymmetric. The amino acid proline plays an important role in determining the structure of proteins, due to its structural rigidity. Proline has also been shown to be a good candidate for synthesizing non-centrosymmetric co-crystals. In fact, Timofeeva et al. (2003) reported success co-crystallizing dicyanovinyl aromatic compounds with L-proline while the same compounds would grow neat crystals when co-crystallization with L-tartaric acid was attempted.
and non-linear optical behavior (Halasyamani & Poeppelmeier, 19982. Structural commentary
L-proline zwitterion (LP) and benzoic acid (BA) co-crystallize in the P212121 with one molecule of L-proline and one molecule of benzoic acid in the shown in Fig. 1. The L-proline exists in its zwitterionic form within the lattice while the carboxylic acid group of the benzoic acid molecules remain protonated. Although the could not be used to unambiguously assign the the enantiomer was reliably assigned by reference to an unchanging chiral centre in the synthetic procedure.
3. Supramolecular features
In this structure, each LP hydrogen bonds with four other LP molecules and one BA. The LP hydrogen bonding forms 1D chains along [100] via (carboxylate) O⋯H—N (pyrollium) interactions in a C(5)[(11)] motif (Table 1). The BA molecules act as capping groups and hydrogen bond to each of the LP carboxylates through O—H⋯O (carboxylate) interactions. The complete BA–LP chains, as shown in Fig. 2, propagate along [100] and are approximately contained in (021) and (01). These chains are held together by edge–face-type π–π stacking between adjacent BA molecules approximately along [010], with a ring-centroid to ring-centroid distance of 4.8451 (16) Å.
4. Database survey
Recently, the LP and para-aminobenzoic acid (PABA) was reported (Athimoolam & Natarajan, 2007). While the structure of BA–LP retains some structural similarities with the PABA–LP due to the absence of one hydrogen-bonding moiety, the amino group, the structure of BA–LP (Fig. 3) also exhibits some important differences when compared to that of PABA–LP. The head-to-tail LP chains in PABA–LP are similar to those in BA–LP, though instead of two chains hydrogen-bonded together to form rings, the chains hydrogen bond to form a continuous 2D sheet of LP molecules. Much like BA–LP, the PABA molecules hydrogen bond to the periphery of the LP chains; however, this crystal incorporated water into the lattice and it is to these water molecules that the PABA molecules are bound. The major difference between the two structures is the presence of the hydrogen-bond donating group at the 4-position of the PABA molecules. This moiety allows the PABA molecules to bridge the LP chains in PABA--LP, a supramolecular feature absent in the title compound. The result of the lack of para-substitution and water in the lattice is that BA–LP forms a hydrogen-bonding network which extends in only one dimension, instead of the three-dimensional network of PABA–LP.
structure of5. Synthesis and crystallization
Solid BA (10.1 mg, 9.01 × 10 −2 mmol) and LP (9.3 mg, 8.08 × 10−2 mmol) were added to a 25 ml scintillation vial. To this was added approximately 8 ml of ethanol followed by sonication until all solutes were fully dissolved. The loosely capped vial was then placed on an open shelf. After three weeks, colorless needle-shaped crystals of the title compound suitable for single-crystal X-ray diffraction measurements were obtained.
6. Refinement
The crystal, data collection, and . The positions of the carboxylate and pyrollium hydrogen atoms were determined from the Fourier difference map, and all other hydrogen atoms were placed in idealized positions with C—H bond lengths set to 0.93 and 0.97 Å for aryl and alkyl hydrogen atoms, respectively. These hydrogen atoms were refined using a riding model with Uiso(H) = 1.5Ueq(O) for the carboxylic acid proton on the BA molecules and Uiso(H) = 1.2Ueq in all other cases. No other constraints were applied to the model.
details are listed in Table 2Supporting information
CCDC reference: 1530619
https://doi.org/10.1107/S2056989017001785/lh5828sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989017001785/lh5828Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S2056989017001785/lh5828Isup3.cml
Data collection: APEX2 (Bruker, 2013); cell
SAINT (Bruker, 2013); data reduction: SAINT (Bruker, 2013); program(s) used to solve structure: olex2.solve (Bourhis et al., 2015); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).C5H9NO2·C7H6O2 | Dx = 1.372 Mg m−3 |
Mr = 237.25 | Mo Kα radiation, λ = 0.71073 Å |
Orthorhombic, P212121 | Cell parameters from 2011 reflections |
a = 5.6993 (7) Å | θ = 3.4–24.7° |
b = 12.0762 (13) Å | µ = 0.10 mm−1 |
c = 16.6839 (19) Å | T = 90 K |
V = 1148.3 (2) Å3 | Needle, colourless |
Z = 4 | 0.1 × 0.01 × 0.01 mm |
F(000) = 504 |
Bruker SMART APEXII area detector diffractometer | 2880 independent reflections |
Radiation source: microfocus rotating anode, Incoatec Iµs | 2375 reflections with I > 2σ(I) |
Mirror optics monochromator | Rint = 0.069 |
Detector resolution: 7.9 pixels mm-1 | θmax = 28.4°, θmin = 2.1° |
ω and φ scans | h = −7→7 |
Absorption correction: multi-scan (SADABS; Bruker, 2013) | k = −15→16 |
Tmin = 0.619, Tmax = 0.746 | l = −22→22 |
13711 measured reflections |
Refinement on F2 | Hydrogen site location: inferred from neighbouring sites |
Least-squares matrix: full | H-atom parameters constrained |
R[F2 > 2σ(F2)] = 0.043 | w = 1/[σ2(Fo2) + (0.0344P)2 + 0.0827P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.086 | (Δ/σ)max < 0.001 |
S = 1.06 | Δρmax = 0.20 e Å−3 |
2880 reflections | Δρmin = −0.18 e Å−3 |
155 parameters | Absolute structure: Flack x determined using 824 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013) |
0 restraints | Absolute structure parameter: 0.5 (8) |
Primary atom site location: iterative |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
Refinement. 1. Fixed Uiso At 1.2 times of: All C(H) groups, All C(H,H) groups, All N(H,H) groups At 1.5 times of: All O(H) groups 2.a Ternary CH refined with riding coordinates: C4(H4) 2.b Secondary CH2 refined with riding coordinates: N1(H1A,H1B), C1(H1C,H1D), C2(H2A,H2B), C3(H3A,H3B) 2.c Aromatic/amide H refined with riding coordinates: C7(H7), C8(H8), C9(H9), C10(H10), C11(H11) 2.d Idealised tetrahedral OH refined as rotating group: O4(H4A) |
x | y | z | Uiso*/Ueq | ||
O1 | 0.6846 (3) | 0.69609 (14) | 0.45367 (10) | 0.0186 (4) | |
O2 | 0.8438 (3) | 0.62955 (13) | 0.34146 (9) | 0.0131 (4) | |
N1 | 0.2560 (3) | 0.72586 (15) | 0.39137 (11) | 0.0118 (4) | |
H1A | 0.1317 | 0.6787 | 0.3892 | 0.014* | |
H1B | 0.3091 | 0.7281 | 0.4428 | 0.014* | |
C1 | 0.1825 (5) | 0.8393 (2) | 0.36504 (13) | 0.0161 (5) | |
H1C | 0.2726 | 0.8972 | 0.3936 | 0.019* | |
H1D | 0.0129 | 0.8512 | 0.3745 | 0.019* | |
C2 | 0.2381 (4) | 0.8397 (2) | 0.27615 (13) | 0.0161 (5) | |
H2A | 0.2546 | 0.9162 | 0.2556 | 0.019* | |
H2B | 0.1152 | 0.8008 | 0.2451 | 0.019* | |
C3 | 0.4714 (4) | 0.7775 (2) | 0.27268 (14) | 0.0149 (5) | |
H3A | 0.6039 | 0.8275 | 0.2854 | 0.018* | |
H3B | 0.4968 | 0.7451 | 0.2189 | 0.018* | |
C4 | 0.4481 (4) | 0.68629 (19) | 0.33630 (13) | 0.0110 (5) | |
H4 | 0.3995 | 0.6154 | 0.3101 | 0.013* | |
C5 | 0.6756 (4) | 0.66858 (18) | 0.38222 (14) | 0.0119 (5) | |
O3 | 0.2945 (3) | 0.46855 (14) | 0.70526 (9) | 0.0174 (4) | |
O4 | 0.6289 (3) | 0.37449 (14) | 0.68623 (9) | 0.0173 (4) | |
H4A | 0.6367 | 0.3789 | 0.7364 | 0.026* | |
C6 | 0.3977 (4) | 0.41409 (19) | 0.57268 (14) | 0.0125 (5) | |
C7 | 0.1924 (5) | 0.4564 (2) | 0.54035 (14) | 0.0183 (5) | |
H7 | 0.0767 | 0.4870 | 0.5749 | 0.022* | |
C8 | 0.1538 (5) | 0.4548 (2) | 0.45852 (14) | 0.0201 (6) | |
H8 | 0.0124 | 0.4839 | 0.4369 | 0.024* | |
C9 | 0.3232 (5) | 0.41022 (19) | 0.40809 (14) | 0.0196 (6) | |
H9 | 0.2987 | 0.4095 | 0.3518 | 0.024* | |
C10 | 0.5282 (5) | 0.3668 (2) | 0.44000 (15) | 0.0200 (6) | |
H10 | 0.6438 | 0.3363 | 0.4054 | 0.024* | |
C11 | 0.5651 (5) | 0.3678 (2) | 0.52216 (14) | 0.0162 (5) | |
H11 | 0.7046 | 0.3369 | 0.5439 | 0.019* | |
C12 | 0.4324 (4) | 0.42155 (19) | 0.66114 (14) | 0.0132 (5) |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0133 (9) | 0.0308 (10) | 0.0117 (8) | 0.0002 (8) | −0.0019 (7) | −0.0037 (7) |
O2 | 0.0085 (9) | 0.0172 (8) | 0.0135 (8) | 0.0008 (7) | −0.0004 (7) | −0.0001 (7) |
N1 | 0.0101 (11) | 0.0146 (9) | 0.0106 (9) | −0.0001 (8) | −0.0006 (8) | 0.0010 (8) |
C1 | 0.0155 (13) | 0.0137 (11) | 0.0191 (12) | 0.0018 (12) | 0.0015 (10) | −0.0011 (9) |
C2 | 0.0186 (14) | 0.0141 (11) | 0.0155 (12) | 0.0045 (11) | −0.0008 (10) | 0.0015 (9) |
C3 | 0.0139 (13) | 0.0181 (12) | 0.0127 (12) | 0.0029 (11) | 0.0020 (10) | 0.0016 (10) |
C4 | 0.0108 (12) | 0.0128 (11) | 0.0094 (11) | 0.0004 (10) | 0.0011 (9) | −0.0010 (9) |
C5 | 0.0112 (12) | 0.0116 (10) | 0.0129 (11) | −0.0026 (11) | −0.0005 (10) | 0.0022 (9) |
O3 | 0.0169 (10) | 0.0200 (9) | 0.0152 (8) | 0.0022 (8) | 0.0045 (7) | 0.0013 (7) |
O4 | 0.0186 (10) | 0.0231 (9) | 0.0101 (8) | 0.0053 (8) | −0.0017 (7) | 0.0015 (7) |
C6 | 0.0116 (12) | 0.0116 (11) | 0.0142 (11) | −0.0024 (10) | 0.0007 (9) | 0.0017 (9) |
C7 | 0.0157 (13) | 0.0174 (12) | 0.0216 (13) | 0.0029 (11) | 0.0018 (11) | 0.0008 (10) |
C8 | 0.0196 (14) | 0.0169 (12) | 0.0237 (13) | 0.0018 (11) | −0.0068 (12) | 0.0044 (11) |
C9 | 0.0272 (15) | 0.0168 (12) | 0.0147 (12) | −0.0033 (12) | −0.0059 (11) | 0.0017 (9) |
C10 | 0.0241 (14) | 0.0197 (13) | 0.0164 (12) | −0.0006 (12) | 0.0005 (11) | −0.0027 (11) |
C11 | 0.0160 (13) | 0.0153 (11) | 0.0172 (12) | 0.0028 (11) | −0.0010 (10) | 0.0011 (10) |
C12 | 0.0138 (13) | 0.0111 (11) | 0.0146 (11) | −0.0032 (10) | 0.0026 (10) | 0.0027 (9) |
O1—C5 | 1.239 (3) | C4—C5 | 1.521 (3) |
O2—C5 | 1.266 (3) | O3—C12 | 1.217 (3) |
N1—H1A | 0.9100 | O4—H4A | 0.8400 |
N1—H1B | 0.9100 | O4—C12 | 1.324 (3) |
N1—C1 | 1.498 (3) | C6—C7 | 1.386 (3) |
N1—C4 | 1.507 (3) | C6—C11 | 1.391 (3) |
C1—H1C | 0.9900 | C6—C12 | 1.492 (3) |
C1—H1D | 0.9900 | C7—H7 | 0.9500 |
C1—C2 | 1.517 (3) | C7—C8 | 1.383 (3) |
C2—H2A | 0.9900 | C8—H8 | 0.9500 |
C2—H2B | 0.9900 | C8—C9 | 1.389 (4) |
C2—C3 | 1.528 (3) | C9—H9 | 0.9500 |
C3—H3A | 0.9900 | C9—C10 | 1.386 (4) |
C3—H3B | 0.9900 | C10—H10 | 0.9500 |
C3—C4 | 1.536 (3) | C10—C11 | 1.387 (3) |
C4—H4 | 1.0000 | C11—H11 | 0.9500 |
H1A—N1—H1B | 108.4 | C5—C4—C3 | 112.05 (19) |
C1—N1—H1A | 110.0 | C5—C4—H4 | 109.6 |
C1—N1—H1B | 110.0 | O1—C5—O2 | 125.8 (2) |
C1—N1—C4 | 108.32 (18) | O1—C5—C4 | 118.9 (2) |
C4—N1—H1A | 110.0 | O2—C5—C4 | 115.28 (19) |
C4—N1—H1B | 110.0 | C12—O4—H4A | 109.5 |
N1—C1—H1C | 111.1 | C7—C6—C11 | 119.5 (2) |
N1—C1—H1D | 111.1 | C7—C6—C12 | 118.3 (2) |
N1—C1—C2 | 103.39 (18) | C11—C6—C12 | 122.2 (2) |
H1C—C1—H1D | 109.0 | C6—C7—H7 | 119.6 |
C2—C1—H1C | 111.1 | C8—C7—C6 | 120.8 (2) |
C2—C1—H1D | 111.1 | C8—C7—H7 | 119.6 |
C1—C2—H2A | 111.3 | C7—C8—H8 | 120.2 |
C1—C2—H2B | 111.3 | C7—C8—C9 | 119.6 (3) |
C1—C2—C3 | 102.53 (19) | C9—C8—H8 | 120.2 |
H2A—C2—H2B | 109.2 | C8—C9—H9 | 120.0 |
C3—C2—H2A | 111.3 | C10—C9—C8 | 120.0 (2) |
C3—C2—H2B | 111.3 | C10—C9—H9 | 120.0 |
C2—C3—H3A | 110.8 | C9—C10—H10 | 119.9 |
C2—C3—H3B | 110.8 | C9—C10—C11 | 120.3 (2) |
C2—C3—C4 | 104.55 (19) | C11—C10—H10 | 119.9 |
H3A—C3—H3B | 108.9 | C6—C11—H11 | 120.1 |
C4—C3—H3A | 110.8 | C10—C11—C6 | 119.9 (2) |
C4—C3—H3B | 110.8 | C10—C11—H11 | 120.1 |
N1—C4—C3 | 104.87 (18) | O3—C12—O4 | 123.7 (2) |
N1—C4—H4 | 109.6 | O3—C12—C6 | 122.7 (2) |
N1—C4—C5 | 110.90 (18) | O4—C12—C6 | 113.5 (2) |
C3—C4—H4 | 109.6 | ||
N1—C1—C2—C3 | −39.6 (2) | C7—C6—C11—C10 | 1.6 (4) |
N1—C4—C5—O1 | −6.0 (3) | C7—C6—C12—O3 | −4.2 (3) |
N1—C4—C5—O2 | 176.36 (18) | C7—C6—C12—O4 | 177.2 (2) |
C1—N1—C4—C3 | −4.2 (2) | C7—C8—C9—C10 | 0.7 (4) |
C1—N1—C4—C5 | 117.0 (2) | C8—C9—C10—C11 | −0.1 (4) |
C1—C2—C3—C4 | 37.3 (2) | C9—C10—C11—C6 | −1.0 (4) |
C2—C3—C4—N1 | −20.6 (2) | C11—C6—C7—C8 | −1.0 (4) |
C2—C3—C4—C5 | −141.01 (19) | C11—C6—C12—O3 | 174.9 (2) |
C3—C4—C5—O1 | 110.8 (2) | C11—C6—C12—O4 | −3.7 (3) |
C3—C4—C5—O2 | −66.8 (3) | C12—C6—C7—C8 | 178.1 (2) |
C4—N1—C1—C2 | 27.4 (2) | C12—C6—C11—C10 | −177.5 (2) |
C6—C7—C8—C9 | −0.1 (4) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O2i | 0.91 | 1.92 | 2.751 (3) | 151 |
N1—H1B···O1 | 0.91 | 2.18 | 2.679 (3) | 114 |
N1—H1B···O1ii | 0.91 | 2.08 | 2.782 (2) | 133 |
C4—H4···O3iii | 1.00 | 2.30 | 3.192 (3) | 147 |
O4—H4A···O2iv | 0.84 | 1.76 | 2.595 (2) | 173 |
Symmetry codes: (i) x−1, y, z; (ii) x−1/2, −y+3/2, −z+1; (iii) −x+1/2, −y+1, z−1/2; (iv) −x+3/2, −y+1, z+1/2. |
Footnotes
‡Both authors contributed equally to this report.
Acknowledgements
This material is based upon work supported by the National Science Foundation under grant No. DMR-1455039.
Funding information
Funding for this research was provided by: National Science Foundationhttps://doi.org/10.13039/100000001 (award No. DMR-1455039).
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