Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536802023334/ci6191sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536802023334/ci6191Isup2.hkl |
CCDC reference: 204668
Colorless needle-shaped single crystals of (I) were grown from a saturated aqueous solution containing DL-aspartic acid and oxalic acid in a 1:1 stoichiometric ratio.
All H atoms were generated geometrically and were allowed to ride on their respective parent atoms with SHELXL97 (Sheldrick, 1997) defaults for bond lengths and displacement parameters. Rotating-group refinement was used for the –OH groups.
Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1996); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: TEXSAN for Windows (Molecular Structure Corporation, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97.
Fig. 1. The molecular structure of (I), with the atom-numbering scheme and 50% probability displacement ellipsoids. | |
Fig. 2. The packing of the molecules of (I), viewed down the b axis. |
C4H8NO4+·0.5C2O42− | F(000) = 372 |
Mr = 178.12 | Dx = 1.600 Mg m−3 Dm = 1.61 Mg m−3 Dm measured by flotation in a mixture of xylene and bromoform |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2yn | Cell parameters from 25 reflections |
a = 7.387 (1) Å | θ = 39.3–39.8° |
b = 5.477 (1) Å | µ = 0.15 mm−1 |
c = 18.522 (3) Å | T = 293 K |
β = 99.36 (1)° | Needle, colourless |
V = 739.4 (2) Å3 | 0.24 × 0.22 × 0.12 mm |
Z = 4 |
Rigaku AFC-5R diffractometer | 1191 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.050 |
Graphite monochromator | θmax = 30.1°, θmin = 2.8° |
ω–2θ scans | h = 0→10 |
Absorption correction: ψ scan (North et al., 1968) | k = 0→7 |
Tmin = 0.89, Tmax = 0.99 | l = −26→25 |
2321 measured reflections | 3 standard reflections every 150 reflections |
2171 independent reflections | intensity decay: none |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.047 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.193 | H-atom parameters constrained |
S = 1.04 | w = 1/[σ2(Fo2) + (0.0959P)2 + 0.3684P] where P = (Fo2 + 2Fc2)/3 |
2171 reflections | (Δ/σ)max < 0.001 |
111 parameters | Δρmax = 0.38 e Å−3 |
0 restraints | Δρmin = −0.36 e Å−3 |
C4H8NO4+·0.5C2O42− | V = 739.4 (2) Å3 |
Mr = 178.12 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 7.387 (1) Å | µ = 0.15 mm−1 |
b = 5.477 (1) Å | T = 293 K |
c = 18.522 (3) Å | 0.24 × 0.22 × 0.12 mm |
β = 99.36 (1)° |
Rigaku AFC-5R diffractometer | 1191 reflections with I > 2σ(I) |
Absorption correction: ψ scan (North et al., 1968) | Rint = 0.050 |
Tmin = 0.89, Tmax = 0.99 | 3 standard reflections every 150 reflections |
2321 measured reflections | intensity decay: none |
2171 independent reflections |
R[F2 > 2σ(F2)] = 0.047 | 0 restraints |
wR(F2) = 0.193 | H-atom parameters constrained |
S = 1.04 | Δρmax = 0.38 e Å−3 |
2171 reflections | Δρmin = −0.36 e Å−3 |
111 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
O1 | 0.2183 (3) | 0.8831 (4) | 0.93073 (11) | 0.0458 (5) | |
H1 | 0.2570 | 1.0079 | 0.9523 | 0.069* | |
O2 | −0.0508 (3) | 1.0786 (3) | 0.91478 (11) | 0.0442 (5) | |
O3 | 0.0634 (4) | 0.5955 (4) | 0.69742 (10) | 0.0547 (6) | |
H3 | 0.0421 | 0.6843 | 0.6614 | 0.082* | |
O4 | −0.0869 (3) | 0.8853 (4) | 0.74711 (10) | 0.0480 (5) | |
O5 | 0.4943 (3) | 0.6218 (4) | 0.08590 (9) | 0.0431 (5) | |
O6 | 0.6566 (3) | 0.7363 (4) | 0.00140 (10) | 0.0489 (6) | |
N1 | −0.2429 (3) | 0.6923 (5) | 0.86635 (11) | 0.0426 (6) | |
H1A | −0.2961 | 0.5525 | 0.8502 | 0.064* | |
H1B | −0.2676 | 0.8062 | 0.8319 | 0.064* | |
H1C | −0.2859 | 0.7397 | 0.9063 | 0.064* | |
C1 | 0.0416 (3) | 0.8988 (4) | 0.91156 (12) | 0.0313 (5) | |
C2 | −0.0412 (4) | 0.6565 (4) | 0.88420 (12) | 0.0314 (5) | |
H2 | −0.0180 | 0.5403 | 0.9249 | 0.038* | |
C3 | 0.0402 (4) | 0.5495 (4) | 0.82089 (12) | 0.0344 (5) | |
H3A | 0.1722 | 0.5380 | 0.8351 | 0.041* | |
H3B | −0.0069 | 0.3853 | 0.8114 | 0.041* | |
C4 | −0.0010 (3) | 0.6954 (4) | 0.75167 (12) | 0.0324 (5) | |
C5 | 0.5432 (3) | 0.6033 (4) | 0.02542 (12) | 0.0301 (5) |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0421 (10) | 0.0444 (11) | 0.0502 (11) | −0.0088 (8) | 0.0051 (9) | −0.0195 (9) |
O2 | 0.0526 (11) | 0.0283 (9) | 0.0518 (11) | −0.0028 (8) | 0.0087 (9) | −0.0013 (8) |
O3 | 0.0939 (17) | 0.0446 (11) | 0.0312 (10) | 0.0182 (11) | 0.0269 (10) | 0.0083 (8) |
O4 | 0.0622 (13) | 0.0525 (12) | 0.0327 (10) | 0.0206 (10) | 0.0173 (9) | 0.0153 (8) |
O5 | 0.0590 (12) | 0.0467 (11) | 0.0282 (8) | −0.0185 (9) | 0.0206 (8) | −0.0161 (8) |
O6 | 0.0573 (12) | 0.0558 (13) | 0.0393 (10) | −0.0347 (10) | 0.0246 (9) | −0.0213 (9) |
N1 | 0.0475 (13) | 0.0549 (14) | 0.0278 (10) | −0.0213 (11) | 0.0135 (9) | −0.0079 (9) |
C1 | 0.0426 (13) | 0.0273 (11) | 0.0250 (10) | −0.0091 (10) | 0.0083 (9) | −0.0008 (8) |
C2 | 0.0457 (13) | 0.0274 (11) | 0.0207 (9) | −0.0107 (10) | 0.0047 (9) | 0.0011 (8) |
C3 | 0.0548 (14) | 0.0260 (11) | 0.0219 (10) | −0.0016 (10) | 0.0051 (9) | 0.0023 (8) |
C4 | 0.0401 (13) | 0.0331 (12) | 0.0253 (10) | −0.0040 (10) | 0.0089 (9) | 0.0035 (9) |
C5 | 0.0299 (11) | 0.0346 (12) | 0.0267 (10) | −0.0072 (9) | 0.0077 (8) | −0.0080 (9) |
O1—C1 | 1.299 (3) | N1—H1B | 0.89 |
O1—H1 | 0.82 | N1—H1C | 0.89 |
O2—C1 | 1.205 (3) | C1—C2 | 1.514 (3) |
O3—C4 | 1.300 (3) | C2—C3 | 1.520 (3) |
O3—H3 | 0.82 | C2—H2 | 0.98 |
O4—C4 | 1.214 (3) | C3—C4 | 1.499 (3) |
O5—C5 | 1.236 (3) | C3—H3A | 0.97 |
O6—C5 | 1.246 (3) | C3—H3B | 0.97 |
N1—C2 | 1.486 (3) | C5—C5i | 1.542 (4) |
N1—H1A | 0.89 | ||
C1—O1—H1 | 109.5 | C1—C2—H2 | 107.5 |
C4—O3—H3 | 109.5 | C3—C2—H2 | 107.5 |
C2—N1—H1A | 109.5 | C4—C3—C2 | 113.8 (2) |
C2—N1—H1B | 109.5 | C4—C3—H3A | 108.8 |
H1A—N1—H1B | 109.5 | C2—C3—H3A | 108.8 |
C2—N1—H1C | 109.5 | C4—C3—H3B | 108.8 |
H1A—N1—H1C | 109.5 | C2—C3—H3B | 108.8 |
H1B—N1—H1C | 109.5 | H3A—C3—H3B | 107.7 |
O2—C1—O1 | 126.4 (2) | O4—C4—O3 | 124.0 (2) |
O2—C1—C2 | 122.1 (2) | O4—C4—C3 | 123.2 (2) |
O1—C1—C2 | 111.5 (2) | O3—C4—C3 | 112.8 (2) |
N1—C2—C1 | 107.1 (2) | O5—C5—O6 | 126.0 (2) |
N1—C2—C3 | 112.81 (19) | O5—C5—C5i | 117.4 (2) |
C1—C2—C3 | 114.0 (2) | O6—C5—C5i | 116.5 (2) |
N1—C2—H2 | 107.5 | ||
O2—C1—C2—N1 | −1.3 (3) | N1—C2—C3—C4 | 55.8 (3) |
O1—C1—C2—N1 | 178.05 (19) | C1—C2—C3—C4 | −66.7 (3) |
O2—C1—C2—C3 | 124.2 (3) | C2—C3—C4—O4 | 2.0 (4) |
O1—C1—C2—C3 | −56.4 (3) | C2—C3—C4—O3 | −177.3 (2) |
Symmetry code: (i) −x+1, −y+1, −z. |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O6ii | 0.82 | 1.71 | 2.530 (3) | 178 |
O3—H3···O5iii | 0.82 | 1.75 | 2.565 (2) | 179 |
N1—H1A···O4iv | 0.89 | 2.08 | 2.822 (3) | 140 |
N1—H1B···O4 | 0.89 | 2.26 | 2.855 (3) | 124 |
N1—H1C···O6v | 0.89 | 1.88 | 2.733 (3) | 160 |
Symmetry codes: (ii) −x+1, −y+2, −z+1; (iii) x−1/2, −y+3/2, z+1/2; (iv) −x−1/2, y−1/2, −z+3/2; (v) x−1, y, z+1. |
Experimental details
Crystal data | |
Chemical formula | C4H8NO4+·0.5C2O42− |
Mr | 178.12 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 293 |
a, b, c (Å) | 7.387 (1), 5.477 (1), 18.522 (3) |
β (°) | 99.36 (1) |
V (Å3) | 739.4 (2) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.15 |
Crystal size (mm) | 0.24 × 0.22 × 0.12 |
Data collection | |
Diffractometer | Rigaku AFC-5R diffractometer |
Absorption correction | ψ scan (North et al., 1968) |
Tmin, Tmax | 0.89, 0.99 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2321, 2171, 1191 |
Rint | 0.050 |
(sin θ/λ)max (Å−1) | 0.705 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.047, 0.193, 1.04 |
No. of reflections | 2171 |
No. of parameters | 111 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.38, −0.36 |
Computer programs: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1996), MSC/AFC Diffractometer Control Software, TEXSAN for Windows (Molecular Structure Corporation, 1997), SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), PLATON (Spek, 2003), SHELXL97.
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O6i | 0.82 | 1.71 | 2.530 (3) | 178 |
O3—H3···O5ii | 0.82 | 1.75 | 2.565 (2) | 179 |
N1—H1A···O4iii | 0.89 | 2.08 | 2.822 (3) | 140 |
N1—H1B···O4 | 0.89 | 2.26 | 2.855 (3) | 124 |
N1—H1C···O6iv | 0.89 | 1.88 | 2.733 (3) | 160 |
Symmetry codes: (i) −x+1, −y+2, −z+1; (ii) x−1/2, −y+3/2, z+1/2; (iii) −x−1/2, y−1/2, −z+3/2; (iv) x−1, y, z+1. |
Aspartic acid, considered a non-essential amino acid, plays a paramount role in metabolism during construction of other amino acids and biochemicals in the citric acid cycle. The present study, which reports the crystal structure of a complex of DL-aspartic acid with oxalic acid, (I), forms part of a series of X-ray investigations being carried out in our laboratory on amino–carboxylic acid complexes. Precise X-ray investigations on these complexes have revealed interesting and useful data regarding the ionization states of individual molecules, their stoichiometry and intermolecular aggregation patterns. Recently, the crystal structures of glycinium oxalate (Subha Nandhini et al., 2001a), L-and DL-alaninium oxalate (Subha Nandhini et al., 2001b,c), DL-threoninium oxalate (Subha Nandhini et al., 2001), β-alaninium oxalate (Krishnakumar et al., 2002) and bis(serinium) oxalate dihydrate (Alagar et al., 2002) were reported from our laboratory.
Fig. 1 shows the molecular structure of (I) with the atom-numbering scheme. The amino acid molecule exists in the expected cationic form with a positively charged amino group and protonated carboxylic acid groups. Interestingly, the complexes of racemic (DL–) amino acids with oxalic acids reported so far have crystallized in monoclinic space group P21/c, with the exception of the DL-lysine complex (Venkatraman et al., 1997) in P1 and the β-alanine complex in C2/c, and the values of their shortest cell dimensions lie around 5.5 Å. The main chain torsion angle (C1—C2—C3—C4) has a value of −66.7 (3)° and is significantly different from the value of 174.2 (2)° observed in the neutron diffraction study of DL-aspartic acid (Sequeira et al., 1989). The oxalic acid molecule exists as a double negatively charged oxalate anion (uncommon in similar crystal structures) and lies across the inversion centre in the crystal and its charge contribution to the asymmetric unit is −1. Thus, one amino acid cation and half an oxalate anion are present in the asymmetric unit, leading to a 2:1 stoichiometry.
Fig. 2 shows the packing of the molecules of (I), viewed down the b axis. Each of the carboxylate O atoms of the oxalate anion participates in the hydrogen bonding as an acceptor of two hydrogen bonds. The screw-related aspartic acid cations are linked by N—H···O hydrogen bonds to form infinite column-like structures parallel to the b axis. These molecular columns are interlinked by oxalate anions through O—H···O and N—H···O hydrogen bonds, forming a three-dimensional network (Fig. 2). The aggregation of individual molecules observed in the present structure differs distinctly from other amino—carboxylic acid structures and has some resemblance to oxalic acid complex with serine.