L-Argininamidium bis­(hydrogen­squarate)

Cations and anions of the title compound {systematic name: 1-[4-(amino­carbonyl)butyl]guanidinium bis­(hydrogen­squarate)}, C₆H₁₇N₅O²⁺·2C₄HO₄⁻, are connected into a three-dimensional network by inter­molecular N—H...O hydrogen bonds between the L-argininamidium ammonium, amide and guanidinium functions and the hydrogensquarate carbonyl O atoms. The independent hydrogensquarate monoanions are linked into dimers by pairs of O—H...O′ hydrogen bonds.

S1. Comment

The search for new classes of organic compounds with second-order nonlinear optical properties and high laser beam thresholds is directed towards crystalline materials with high dipole moments, asymmetrically conjugated π-electron systems and non-centrosymmetric crystal structures. Three main classes of organic compounds with different dimensionalities are known in the literature: (a) one-dimensional compounds (dipoles), such as 4-nitroaniline and its derivatives, (b) two-dimensional compounds (quadrupoles), such as 4,6-dinitroresorcinole and its derivatives, and (c) three-dimensional compounds (octupoles), such as the guanidinium cation and its derivatives (Nalwa et al. 1997; Wolff & Wortmann, 1999; Chemla & Zyss, 1987). In the course of our spectroscopic and structural studies of optically active derivatives of amino acids, having nonlinear optical and electro-optical properties, the crystal structure of the title compound, (I), has now been determined. Structurally, (I) belongs to the C-amidated amino acids, whose salts and ester amides of squaric acid represent a new class of compounds, having great biological importance. We also publish the IR and Raman assignments of (I) for the first time. A structural study of some C-amidated amino acids, viz. Ile, Val, Thr, Ser, Met, Trp, Gln and Arg, was performed by In et al. (2001) and the results were similar to those for the C-unamidated counterparts.

The asymmetric unit of (I) is depicted in Fig. 1 and a projection perpendicular to [010] in Fig. 2. The independent hydrogensquarate monoanions, HSq⁻, are linked into dimers by O3'—H3'···O8'^viii and O7'—H7'···O4'^ix hydrogen bonds (Table 1). Such dimers have previously been reported for argininium hydrogensquarate (Angelova, Velikova et al., 1996) and 4-phenylpyridinium hydrogensquarate (Kolev et al., 2004), but infinite chains are also known, for instance in phenylglycine hydrogensquarate monohydrate (Angelova, Petrova et al., 1996). In contrast to other amino acid amide derivatives, the L-argininamidium cations of (I) are not connected into helical chains by intermolecular N(amide)—H···O(amide) interactions (Kolev et al., 2006). Translation-related cations of (I) are, however, linked by N(ammonium)—H···O(amide) hydrogen bonds (N2—H22···O1ⁱⁱⁱ; Table 1) into chains in the [100] direction. Additional intermolecular N—H···O hydrogen bonds to hydrogensquarate carbonyl O atoms, in which all possible donor NH atoms participate (Table 1), lead to the construction of a three-dimensional network.

S2. Experimental

The starting compound, L-argininamidium dihydrochloride, is a white powder, which was purchased from Bachem (Switzerland) and recrystallized from methanol. Compound (I) was synthesized by adding a methanol solution (10 ml) of L-argininamidium dihydrochloride (246 mg) to an aqueous solution (28 ml) of squaric acid (228 mg) and leaving the mixture to stand. Colourless crystals that formed after four weeks were filtered off and dried in air at room temperature. Single prismatic and colourless crystals, suitable for X-ray analysis, were grown from a methanol–water solution at room temperature over a period of two months. IR (KBr pellet, cm⁻¹): 3426(s), 3300 (m), 3200 (m) ν(NH₂, guanidyl), 3338 ν_as(NH, aminocarbonyl), 3151 ν_s(NH, aminocarbonyl), 2865, 2790, 2740 ν(NH₃, ammonium), 1804 (w) ν(CO, hydrogensquarate), 1689 (s) ν(C=O), 1655 (NH₂, scissoring), 1619 (amide II), 1386 ν(CN, amide III), 1162, 1136 (w) 1109, 908 δ(NH₂), 788 (amide VII), 722 (amide V). These data are in accordance with known values for other arginine-containing tri- and tetrapeptides (Kolev, 2006) obtained by IR–LD spectroscopy and theoretical (ab initio HF/6–31++G**) calculations (Ivanova, 2005, 2006; Ivanova & Arnaudov, 2005). The results show a charge redistribution in the guanidyl fragment, leading to an observation of a broad IR-absorption maximum in the whole 3400–2700 cm⁻¹ region assigned to stretching NH+ and NH2+ vibrations.

S3. Refinement

The S configuration of the argininamidium Cα atom C2 is known for the natural amino acid and was assigned to C2. As atoms heavier than Si are not present in (I), anomalous scattering contributions are negligible and no Friedel pairs were measured. H atoms were treated as riding, with C—H distances of 0.97 Å for the methylene C atoms and 0.98 Å for atom C2, N—H distances of 0.89 Å for ammonium atom N2 and 0.86 for all other N atoms, and O—H distances of 0.82 Å [U_iso(H) = 1.2 U_eq(C) for the H atoms of C2 and C5; U_iso(H) = 1.35 U_eq(N) for the H atoms of N2 and 1.2 U_eq(N) for the H atoms of N6, N8 and N9; U_iso(H) = 1.2 U_eq(O) for the H atom of O7'; all other U_iso(H) values were refined freely].

Computing details

Data collection: R3m/V (Siemens, 1989); cell refinement: R3m/V; data reduction: XDISK (Siemens, 1989); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL-Plus (Sheldrick, 1995); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The molecular structure of (I), showing the atom-labelling scheme and the N2—H···O hydrogen bonds as dashed lines. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. A projection of (I) perpendicular to [010], showing the construction of a three-dimensional network through intermolecular hydrogen bonds (dashed lines).

1-[4-(Aminocarbonyl)butyl]guanidinium bis(hydrogensquarate)

Crystal data

C6H17N5O^2+·2C4HO4^−	F(000) = 420
Mr = 401.34	Dx = 1.507 Mg m^−3
Monoclinic, P21	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2yb	Cell parameters from 15 reflections
a = 5.185 (1) Å	θ = 8.0–14.4°
b = 16.668 (3) Å	µ = 0.13 mm^−1
c = 10.458 (2) Å	T = 294 K
β = 101.90 (3)°	Prism, colourless
V = 884.5 (3) Å^3	0.54 × 0.24 × 0.22 mm
Z = 2

Data collection

Siemens P4 four-circle diffractometer	1972 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.030
Graphite monochromator	θmax = 30.0°, θmin = 2.3°
Profile fitted ω scans	h = 0→7
Absorption correction: ψ scan (XPREP in SHELXTL; Sheldrick, 1995)	k = 0→23
Tmin = 0.945, Tmax = 0.977	l = −14→14
2919 measured reflections	3 standard reflections every 100 reflections
2659 independent reflections	intensity decay: 2%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.045	H-atom parameters constrained
wR(F^2) = 0.099	w = 1/[σ^2(Fo^2) + (0.046P)^2 + 0.0784P] where P = (Fo^2 + 2Fc^2)/3
S = 1.01	(Δ/σ)max < 0.001
2659 reflections	Δρmax = 0.23 e Å^−3
260 parameters	Δρmin = −0.19 e Å^−3
1 restraint	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.023 (4)

Special details

Experimental. The IR spectrum of (I) (KBr pellet) exhibits no characteristic sharp bands for ν (OH) connected via hydrogen bonds. The bands at 2865 and 1790 and 2740 cm⁻¹ could be assigned to the ν NH₃ vibrations, an assignment that is supported by quantum-chemical calculations. Detailed experimental linear-dichroic infrared spectral analysis and ab initio (UHF/6–31G**) calculations of amino acids, peptides and amides, as well as their Au(III) complexes by Ivanova, have indicated a multiple 3400–2200 cm⁻¹ range for ν NH₃ stretching vibrations. The strong Raman bands at 2998, 2942, 2923 and 2905 cm⁻¹ belong to the C—H stretching vibrations of the methylene groups. Streching vibrations of the aminocarbonyl group generate the following bands in the IR spectrum: the antisymmetric vibration at 3338 cm⁻¹ and the symmetric one at ca 3151 cm⁻¹. The guanidyl group can be characterized by a strong IR band at 3426, and moderate ones at 3300 and 3200 cm⁻¹belonging to ν NH₂ vibrations. A very intensive ν (C=O) (amide I) band of (I) is observed at 1689 cm⁻¹ (IR) with its Raman counterpart lying at 1682 cm⁻¹ and being of intermediate intensity.

The –NH₂ deformation (amide II) is expected in the region 1580–1640 cm⁻¹ and we assign the bands at 1619 cm⁻¹ (IR) and 1620 cm⁻¹ (Raman) to amide II modes. In this region, absorbtion of the amino groups of the guanidyl function is also expected, and the scissoring vibrations of this group could not be satifactorily assigned because they overlap with the –NH₃-group. The C—N stretching vibration (amide III) is presumalty at 1386 cm⁻¹ but this attribution is not certain. The –NH₂ rocking mode absorbs at 1136 cm⁻¹ and is weak in the IR but strong in the Raman spectrum. An amide VII band absorbing at 788 ^1–1 in the IR has a very weak Raman counterpart at nearly 790 cm⁻¹. A mixed vibration atributed to the –NH₂ wag with a contribition from the C=O out-of-plane deformation is responsible for the amide V band at 722 cm⁻¹. The band belonging to the asymetric scissoring vibration of the –NH₂ group is observed at 1655 cm⁻¹(IR) and at 1650 cm⁻¹ (Raman). Other prominent bands are those at 1596 and 1498 cm⁻¹ (IR) belonging to the symmetric deformation vibrations of the –NH₂ group. Assignment of the band at 1498 cm⁻¹ is not unambiguous because this band overlaps with the band attributed to the mixed C=O and C=C vibration of the hydrogensquarate anion. For the –NH₂ rocks, three bands can be taken into account at 1168, 1109 and 908 cm⁻¹, respectively. Characteristic bands for hydrogensquarate anions are recorded at 1804 (w) cm⁻¹ (IR) and 1810 (m) cm⁻¹ (Raman) and can be assigned to a mixed C—O and C=O vibration. The strong Raman bands at 1123 and 629 cm⁻¹ as well as an intermediate one at 1082 cm⁻¹ are attributed to the in and out-of-plane vibrations of the aforementioned anion. CH₂ deformation vibrations are found at 1442 and 1344 cm⁻¹.

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

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

	x	y	z	Uiso*/Ueq
C1'	0.6409 (6)	0.32405 (19)	0.2642 (3)	0.0369 (7)
O1'	0.7821 (5)	0.37009 (17)	0.3405 (2)	0.0555 (7)
C2'	0.6141 (6)	0.30259 (19)	0.1239 (3)	0.0356 (6)
O2'	0.7203 (5)	0.32579 (16)	0.0350 (2)	0.0528 (6)
C3'	0.4086 (6)	0.24732 (19)	0.1383 (3)	0.0347 (6)
O3'	0.2690 (5)	0.19802 (15)	0.0537 (2)	0.0478 (6)
H3'	0.1569	0.1762	0.0868	0.059 (12)*
C4'	0.4284 (6)	0.26614 (19)	0.2734 (3)	0.0350 (6)
O4'	0.3218 (5)	0.24522 (15)	0.3652 (2)	0.0474 (6)
C5'	0.4129 (6)	0.53035 (18)	0.7961 (3)	0.0310 (6)
O5'	0.5537 (4)	0.48650 (14)	0.8744 (2)	0.0426 (5)
C6'	0.3731 (6)	0.54673 (18)	0.6522 (3)	0.0316 (6)
O6'	0.4717 (4)	0.51994 (13)	0.56320 (19)	0.0396 (5)
C7'	0.1743 (6)	0.60470 (17)	0.6659 (3)	0.0324 (6)
O7'	0.0293 (5)	0.65092 (15)	0.5784 (2)	0.0481 (6)
H7'	−0.0551	0.6820	0.6146	0.058*
C8'	0.2037 (5)	0.58970 (18)	0.8027 (3)	0.0322 (6)
O8'	0.1007 (5)	0.61370 (14)	0.8947 (2)	0.0437 (6)
C1	1.0043 (5)	0.35767 (17)	0.7428 (3)	0.0289 (5)
O1	1.1166 (4)	0.37749 (14)	0.6554 (2)	0.0409 (5)
N1	1.1117 (5)	0.36099 (17)	0.8694 (2)	0.0391 (6)
H11	1.2706	0.3780	0.8947	0.047*
H12	1.0223	0.3462	0.9260	0.047*
C2	0.7251 (5)	0.32405 (16)	0.7102 (3)	0.0268 (5)
H2	0.6258	0.3446	0.7734	0.032*
N2	0.6032 (4)	0.35426 (15)	0.5779 (2)	0.0329 (5)
H21	0.5479	0.4044	0.5839	0.044*
H22	0.4669	0.3233	0.5431	0.044*
H23	0.7217	0.3532	0.5273	0.044*
C3	0.7263 (5)	0.23211 (17)	0.7149 (3)	0.0324 (6)
H31	0.7747	0.2114	0.6364	0.042 (9)*
H32	0.8584	0.2144	0.7892	0.052 (10)*
C4	0.4599 (5)	0.19779 (16)	0.7259 (3)	0.0305 (6)
H41	0.3258	0.2191	0.6555	0.036 (8)*
H42	0.4182	0.2152	0.8078	0.047 (10)*
C5	0.4518 (6)	0.10630 (17)	0.7200 (3)	0.0374 (7)
H51	0.2789	0.0879	0.7289	0.045*
H52	0.4801	0.0887	0.6355	0.045*
N6	0.6516 (5)	0.07069 (15)	0.8228 (2)	0.0394 (6)
H6	0.6643	0.0894	0.9005	0.047*
C7	0.8163 (6)	0.01196 (17)	0.8076 (3)	0.0329 (6)
N8	0.8127 (5)	−0.02190 (18)	0.6928 (2)	0.0447 (7)
H81	0.7013	−0.0060	0.6248	0.054*
H82	0.9218	−0.0598	0.6861	0.054*
N9	0.9916 (6)	−0.01320 (19)	0.9115 (3)	0.0518 (7)
H91	1.1003	−0.0509	0.9033	0.062*
H92	0.9962	0.0083	0.9867	0.062*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1'	0.0361 (15)	0.0415 (17)	0.0358 (15)	−0.0083 (14)	0.0134 (12)	−0.0004 (13)
O1'	0.0566 (14)	0.0678 (17)	0.0462 (13)	−0.0313 (14)	0.0204 (11)	−0.0132 (12)
C2'	0.0355 (15)	0.0362 (15)	0.0363 (15)	−0.0027 (13)	0.0101 (12)	0.0037 (13)
O2'	0.0561 (14)	0.0659 (17)	0.0406 (12)	−0.0165 (12)	0.0200 (11)	0.0075 (11)
C3'	0.0359 (14)	0.0385 (16)	0.0304 (13)	−0.0048 (13)	0.0085 (11)	0.0026 (12)
O3'	0.0545 (14)	0.0566 (15)	0.0344 (11)	−0.0252 (12)	0.0143 (10)	−0.0056 (10)
C4'	0.0327 (14)	0.0397 (17)	0.0351 (15)	−0.0068 (12)	0.0127 (12)	−0.0017 (13)
O4'	0.0514 (13)	0.0590 (15)	0.0371 (11)	−0.0245 (12)	0.0214 (10)	−0.0080 (11)
C5'	0.0321 (14)	0.0290 (14)	0.0303 (13)	−0.0005 (12)	0.0028 (11)	−0.0014 (11)
O5'	0.0443 (12)	0.0413 (12)	0.0370 (11)	0.0074 (11)	−0.0039 (9)	0.0045 (10)
C6'	0.0328 (14)	0.0306 (14)	0.0314 (14)	0.0011 (11)	0.0064 (11)	0.0018 (12)
O6'	0.0459 (12)	0.0433 (13)	0.0314 (10)	0.0126 (10)	0.0117 (9)	0.0024 (9)
C7'	0.0362 (15)	0.0318 (15)	0.0292 (13)	0.0067 (12)	0.0069 (11)	0.0051 (12)
O7'	0.0540 (13)	0.0613 (15)	0.0311 (10)	0.0297 (12)	0.0135 (10)	0.0105 (11)
C8'	0.0347 (14)	0.0340 (15)	0.0277 (13)	0.0011 (12)	0.0063 (11)	0.0030 (11)
O8'	0.0556 (14)	0.0494 (14)	0.0295 (10)	0.0162 (11)	0.0165 (10)	0.0056 (10)
C1	0.0257 (12)	0.0290 (13)	0.0333 (13)	0.0034 (11)	0.0092 (10)	−0.0017 (11)
O1	0.0315 (10)	0.0567 (14)	0.0378 (11)	−0.0097 (10)	0.0153 (9)	0.0016 (10)
N1	0.0313 (12)	0.0547 (16)	0.0319 (12)	−0.0095 (13)	0.0077 (10)	−0.0009 (12)
C2	0.0225 (12)	0.0308 (13)	0.0280 (13)	0.0018 (10)	0.0077 (10)	0.0005 (10)
N2	0.0287 (11)	0.0352 (12)	0.0361 (12)	0.0004 (10)	0.0096 (9)	0.0052 (11)
C3	0.0275 (13)	0.0295 (13)	0.0419 (15)	0.0017 (11)	0.0112 (11)	−0.0015 (12)
C4	0.0280 (13)	0.0273 (13)	0.0383 (15)	0.0025 (11)	0.0115 (11)	0.0012 (12)
C5	0.0393 (16)	0.0269 (14)	0.0443 (16)	0.0020 (13)	0.0048 (13)	−0.0013 (13)
N6	0.0579 (16)	0.0320 (13)	0.0278 (11)	0.0091 (12)	0.0079 (11)	−0.0034 (10)
C7	0.0357 (14)	0.0314 (14)	0.0314 (14)	−0.0035 (12)	0.0063 (11)	−0.0008 (12)
N8	0.0444 (15)	0.0524 (17)	0.0345 (14)	0.0170 (13)	0.0016 (11)	−0.0070 (13)
N9	0.0631 (18)	0.0531 (17)	0.0335 (13)	0.0162 (16)	−0.0031 (12)	0.0025 (13)

Geometric parameters (Å, º)

C1'—O1'	1.233 (4)	C2—N2	1.486 (3)
C1'—C4'	1.483 (4)	C2—C3	1.533 (4)
C1'—C2'	1.489 (4)	C2—H2	0.9800
C2'—O2'	1.236 (3)	N2—H21	0.8900
C2'—C3'	1.440 (4)	N2—H22	0.8900
C3'—O3'	1.311 (4)	N2—H23	0.8900
C3'—C4'	1.431 (4)	C3—C4	1.521 (4)
O3'—H3'	0.8200	C3—H31	0.9700
C4'—O4'	1.252 (3)	C3—H32	0.9700
C5'—O5'	1.221 (4)	C4—C5	1.526 (4)
C5'—C8'	1.480 (4)	C4—H41	0.9700
C5'—C6'	1.501 (4)	C4—H42	0.9700
C6'—O6'	1.235 (3)	C5—N6	1.457 (4)
C6'—C7'	1.441 (4)	C5—H51	0.9700
C7'—O7'	1.309 (4)	C5—H52	0.9700
C7'—C8'	1.429 (4)	N6—C7	1.330 (4)
O7'—H7'	0.8200	N6—H6	0.8600
C8'—O8'	1.259 (3)	C7—N8	1.324 (4)
C1—O1	1.226 (3)	C7—N9	1.332 (4)
C1—N1	1.327 (4)	N8—H81	0.8600
C1—C2	1.524 (4)	N8—H82	0.8600
N1—H11	0.8600	N9—H91	0.8600
N1—H12	0.8600	N9—H92	0.8600
O1'—C1'—C4'	135.4 (3)	C3—C2—H2	109.1
O1'—C1'—C2'	135.2 (3)	C2—N2—H21	109.5
C4'—C1'—C2'	89.3 (2)	C2—N2—H22	109.5
O2'—C2'—C3'	137.2 (3)	H21—N2—H22	109.5
O2'—C2'—C1'	134.4 (3)	C2—N2—H23	109.5
C3'—C2'—C1'	88.4 (2)	H21—N2—H23	109.5
O3'—C3'—C4'	136.2 (3)	H22—N2—H23	109.5
O3'—C3'—C2'	130.4 (3)	C4—C3—C2	112.4 (2)
C4'—C3'—C2'	93.4 (2)	C4—C3—H31	109.1
C3'—O3'—H3'	109.5	C2—C3—H31	109.1
O4'—C4'—C3'	138.0 (3)	C4—C3—H32	109.1
O4'—C4'—C1'	133.1 (3)	C2—C3—H32	109.1
C3'—C4'—C1'	88.9 (2)	H31—C3—H32	107.9
O5'—C5'—C8'	135.4 (3)	C3—C4—C5	113.0 (2)
O5'—C5'—C6'	136.1 (3)	C3—C4—H41	109.0
C8'—C5'—C6'	88.5 (2)	C5—C4—H41	109.0
O6'—C6'—C7'	137.1 (3)	C3—C4—H42	109.0
O6'—C6'—C5'	134.2 (3)	C5—C4—H42	109.0
C7'—C6'—C5'	88.6 (2)	H41—C4—H42	107.8
O7'—C7'—C8'	136.9 (3)	N6—C5—C4	111.6 (3)
O7'—C7'—C6'	130.2 (3)	N6—C5—H51	109.3
C8'—C7'—C6'	92.9 (2)	C4—C5—H51	109.3
C7'—O7'—H7'	109.5	N6—C5—H52	109.3
O8'—C8'—C7'	137.4 (3)	C4—C5—H52	109.3
O8'—C8'—C5'	132.7 (3)	H51—C5—H52	108.0
C7'—C8'—C5'	89.9 (2)	C7—N6—C5	126.1 (2)
O1—C1—N1	124.5 (3)	C7—N6—H6	117.0
O1—C1—C2	120.5 (2)	C5—N6—H6	117.0
N1—C1—C2	115.0 (2)	N8—C7—N6	122.2 (3)
C1—N1—H11	120.0	N8—C7—N9	119.0 (3)
C1—N1—H12	120.0	N6—C7—N9	118.8 (3)
H11—N1—H12	120.0	C7—N8—H81	120.0
N2—C2—C1	106.6 (2)	C7—N8—H82	120.0
N2—C2—C3	111.5 (2)	H81—N8—H82	120.0
C1—C2—C3	111.3 (2)	C7—N9—H91	120.0
N2—C2—H2	109.1	C7—N9—H92	120.0
C1—C2—H2	109.1	H91—N9—H92	120.0

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H11···O5′^i	0.86	2.37	3.095 (3)	143
N1—H12···O2′^ii	0.86	2.15	2.986 (3)	165
N2—H23···O1	0.89	2.24	2.646 (3)	107
N2—H22···O1^iii	0.89	2.52	2.831 (3)	101
N2—H23···O1′	0.89	2.06	2.836 (3)	145
N2—H22···O4′	0.89	2.27	3.007 (3)	140
N2—H21···O6′	0.89	1.97	2.841 (3)	166
N6—H6···O8′^iv	0.86	2.27	3.054 (3)	151
N8—H82···O1′^v	0.86	1.99	2.842 (3)	168
N8—H81···O6′^vi	0.86	2.03	2.863 (3)	162
N9—H91···O2′^v	0.86	2.29	3.066 (4)	150
N9—H92···O5′^vii	0.86	2.51	2.898 (3)	108
N9—H92···O8′^iv	0.86	2.27	3.035 (4)	149
O3′—H3′···O8′^viii	0.82	1.74	2.523 (3)	160
O7′—H7′···O4′^ix	0.82	1.79	2.564 (3)	158

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