Investigation of hydrogen-bond network in bis(glycinium) oxalate using single-crystal neutron diffraction and spectroscopic studies

Single-crystal neutron diffraction investigation of bis(glycinium) oxalate was undertaken in order to study its hydrogen-bonding network, particularly the very short hydrogen bond between the glycinum and oxalate ions, indicated by the X-ray diffraction study. The non-existence of any phase transition in these crystals was attributed to the fact that the short hydrogen bond in bis(glycinium) oxalate is asymmetric in nature, with no hydrogen disorder. The potential energy landscape for the above-mentioned H atom was found to have a single minimum closer to the glycinium ion. IR and Raman investigations of the title complex supported the above result.

Computing details

Data collection: SCAD; cell refinement: REFINE; data reduction: DATRED; program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP; software used to prepare material for publication: SHELX.

Figures

(miss)

Crystal data

C2H6NO2·0.5(C2O4)	F(000) = 120
Mr = 120.08	Dx = 1.509 Mg m^−3
Monoclinic, P21/n	Neutron radiation, λ = 0.99500 Å
a = 4.934 (3) Å	Cell parameters from 50 reflections
b = 9.955 (6) Å	θ = 7–76°
c = 10.854 (9) Å	µ = 0.18 mm^−1
β = 97.44 (1)°	T = 300 K
V = 528.6 (6) Å^3	Needle with six faces, colourless
Z = 4	6 × 2.12 × 1.06 mm

Data collection

Four circle diffractometer	894 reflections with I > 2σ(I)
Radiation source: Dhruva Reactor	Rint = 0.000
Cu monochromator	θmax = 41.8°, θmin = 3.9°
θ–\2q scans	h = 0→6
Absorption correction: integration datred	k = 0→13
Tmin = 0.409, Tmax = 0.831	l = −14→13
1298 measured reflections	2 standard reflections every 25 reflections
1298 independent reflections	intensity decay: < 3

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)] = 0.057	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.180	w = 1/[σ^2(Fo^2) + (0.0841P)^2 + 3.773P] where P = (Fo^2 + 2Fc^2)/3
S = 1.09	(Δ/σ)max < 0.001
1298 reflections	Δρmax = 1.06 e Å^−3
128 parameters	Δρmin = −0.82 e Å^−3
0 restraints	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.071 (9)

Special details

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
O1	0.1456 (5)	0.3395 (3)	−0.0002 (3)	0.0328 (6)
O2	0.2936 (5)	0.5232 (3)	0.1060 (3)	0.0320 (6)
C1	0.1258 (4)	0.4588 (2)	0.02873 (19)	0.0248 (5)
O3	0.6961 (6)	0.3880 (3)	0.1856 (3)	0.0386 (7)
O4	0.7108 (7)	0.4691 (3)	0.3776 (3)	0.0444 (8)
C2	0.8022 (4)	0.4014 (2)	0.2996 (2)	0.0291 (5)
N1	1.1426 (3)	0.30423 (17)	0.46356 (16)	0.0314 (5)
H1	0.9911 (13)	0.2529 (6)	0.4997 (6)	0.0509 (13)
H2	1.3205 (12)	0.2471 (6)	0.4779 (5)	0.0495 (13)
C3	1.0632 (5)	0.3201 (3)	0.3294 (2)	0.0398 (7)
H4	1.2228 (15)	0.3739 (14)	0.2918 (9)	0.102 (4)
H5	1.039 (2)	0.2237 (10)	0.2889 (7)	0.090 (3)
H3	1.1796 (14)	0.3924 (7)	0.5083 (6)	0.0587 (16)
H6	0.5034 (12)	0.4528 (6)	0.1534 (5)	0.0494 (12)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0306 (12)	0.0237 (12)	0.0413 (14)	0.0022 (9)	−0.0065 (10)	−0.0043 (10)
O2	0.0314 (11)	0.0274 (12)	0.0326 (12)	−0.0003 (9)	−0.0128 (9)	−0.0005 (10)
C1	0.0259 (9)	0.0204 (10)	0.0258 (9)	−0.0005 (7)	−0.0048 (7)	0.0028 (7)
O3	0.0411 (14)	0.0446 (16)	0.0268 (13)	0.0118 (12)	−0.0089 (10)	−0.0017 (11)
O4	0.0493 (16)	0.0446 (17)	0.0348 (14)	0.0163 (13)	−0.0125 (12)	−0.0147 (13)
C2	0.0308 (10)	0.0262 (11)	0.0278 (10)	0.0024 (8)	−0.0058 (8)	0.0036 (8)
N1	0.0350 (9)	0.0271 (9)	0.0292 (8)	0.0021 (6)	−0.0070 (6)	0.0042 (6)
H1	0.061 (3)	0.050 (3)	0.041 (2)	−0.004 (3)	0.004 (2)	0.009 (2)
H2	0.056 (3)	0.044 (3)	0.045 (3)	0.012 (2)	−0.007 (2)	0.005 (2)
C3	0.0373 (12)	0.0547 (18)	0.0268 (11)	0.0167 (11)	0.0019 (9)	0.0122 (11)
H4	0.049 (3)	0.168 (11)	0.091 (6)	0.032 (5)	0.021 (4)	0.083 (7)
H5	0.127 (7)	0.086 (6)	0.048 (3)	0.061 (5)	−0.029 (4)	−0.019 (4)
H3	0.068 (4)	0.041 (3)	0.060 (3)	0.002 (2)	−0.019 (3)	−0.009 (3)
H6	0.056 (3)	0.045 (3)	0.045 (3)	−0.003 (2)	0.002 (2)	−0.006 (2)

Geometric parameters (Å, º)

O1—C1	1.236 (4)	C2—C3	1.520 (4)
O2—C1	1.272 (3)	N1—C3	1.467 (3)
O2—H6	1.300 (7)	N1—H1	1.025 (7)
C1—C1^i	1.550 (4)	N1—H2	1.040 (6)
O3—C2	1.286 (4)	N1—H3	1.009 (6)
O3—H6	1.165 (7)	C3—H4	1.075 (9)
O4—C2	1.214 (4)	C3—H5	1.056 (10)
C1—O2—H6	114.0 (4)	H1—N1—H2	108.3 (6)
O1—C1—O2	125.8 (2)	C3—N1—H3	113.1 (4)
O1—C1—C1^i	119.5 (2)	H1—N1—H3	110.2 (6)
O2—C1—C1^i	114.7 (3)	H2—N1—H3	107.9 (5)
C2—O3—H6	116.5 (4)	N1—C3—C2	112.3 (2)
O4—C2—O3	125.9 (3)	N1—C3—H4	108.4 (6)
O4—C2—C3	121.9 (2)	C2—C3—H4	107.2 (5)
O3—C2—C3	112.2 (2)	N1—C3—H5	108.4 (5)
C3—N1—H1	108.6 (4)	C2—C3—H5	110.4 (5)
C3—N1—H2	108.6 (4)	H4—C3—H5	110.1 (10)

Symmetry code: (i) −x, −y+1, −z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O1^ii	1.025 (7)	1.937 (7)	2.910 (5)	157.3 (5)
N1—H1···O3^ii	1.025 (7)	2.556 (7)	3.062 (5)	110.0 (5)
N1—H2···O1^iii	1.040 (6)	1.810 (7)	2.848 (5)	175.1 (6)
N1—H2···O2^iv	1.040 (6)	2.445 (7)	2.925 (5)	107.1 (4)
N1—H3···O4^v	1.009 (6)	1.885 (7)	2.874 (5)	166.3 (6)
O3—H6···O2	1.165 (7)	1.300 (7)	2.461 (5)	174.2 (6)
O3—H6···O1	1.165 (7)	2.531 (7)	3.203 (6)	115.0 (4)
C3—H4···O2^vi	1.075 (9)	2.566 (8)	3.460 (5)	140.2 (6)
C3—H5···O2^iv	1.056 (10)	2.392 (9)	3.099 (6)	123.1 (5)

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