Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536803011267/wn6161sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536803011267/wn6161Isup2.hkl |
CCDC reference: 214855
Colourless plate-shaped single crystals of (I) were grown from a saturated aqueous solution containing L-leucine and oxalic acid in a stoichiometric ratio of 1:1.
All the H atoms were positioned geometrically and were allowed to ride on their respective carrier atoms, with C—H = 0.96 Å, N—H = 0.89 Å, O—H = 0.82 Å and Uiso = 0.05 Å2.
Data collection: CAD-4 Software (Enraf-Nonius, 1989; cell refinement: CAD-4 Software; data reduction: CAD-4 Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 1999); 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. Packing of the molecules of (I), viewed down the a axis. |
C6H14NO2+·C2HO4− | Z = 2 |
Mr = 221.21 | F(000) = 236 |
Triclinic, P1 | Dx = 1.375 Mg m−3 Dm = 1.39 (3) Mg m−3 Dm measured by flotation in a mixture of xylene and CCl4 |
Hall symbol: P 1 | Cu Kα radiation, λ = 1.54178 Å |
a = 5.674 (3) Å | Cell parameters from 25 reflections |
b = 9.803 (9) Å | θ = 2.8–72° |
c = 9.906 (8) Å | µ = 1.02 mm−1 |
α = 87.37 (7)° | T = 293 K |
β = 99.64 (5)° | Plate, colourless |
γ = 100.35 (6)° | 0.35 × 0.20 × 0.15 mm |
V = 534.3 (7) Å3 |
Enraf-Nonius CAD-4 diffractometer | 1866 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.045 |
Graphite monochromator | θmax = 72.0°, θmin = 4.6° |
ω–2θ scans | h = −4→6 |
Absorption correction: ψ scan (North et al., 1968) | k = −12→11 |
Tmin = 0.773, Tmax = 0.858 | l = −12→12 |
2223 measured reflections | 2 standard reflections every 60min min |
2003 independent reflections | intensity decay: <2% |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.045 | H-atom parameters constrained |
wR(F2) = 0.117 | w = 1/[σ2(Fo2) + (0.0934P)2 + 0.031P] where P = (Fo2 + 2Fc2)/3 |
S = 1.04 | (Δ/σ)max < 0.001 |
2003 reflections | Δρmax = 0.27 e Å−3 |
272 parameters | Δρmin = −0.26 e Å−3 |
3 restraints | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.024 (5) |
C6H14NO2+·C2HO4− | γ = 100.35 (6)° |
Mr = 221.21 | V = 534.3 (7) Å3 |
Triclinic, P1 | Z = 2 |
a = 5.674 (3) Å | Cu Kα radiation |
b = 9.803 (9) Å | µ = 1.02 mm−1 |
c = 9.906 (8) Å | T = 293 K |
α = 87.37 (7)° | 0.35 × 0.20 × 0.15 mm |
β = 99.64 (5)° |
Enraf-Nonius CAD-4 diffractometer | 1866 reflections with I > 2σ(I) |
Absorption correction: ψ scan (North et al., 1968) | Rint = 0.045 |
Tmin = 0.773, Tmax = 0.858 | 2 standard reflections every 60min min |
2223 measured reflections | intensity decay: <2% |
2003 independent reflections |
R[F2 > 2σ(F2)] = 0.045 | 3 restraints |
wR(F2) = 0.117 | H-atom parameters constrained |
S = 1.04 | Δρmax = 0.27 e Å−3 |
2003 reflections | Δρmin = −0.26 e Å−3 |
272 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. |
x | y | z | Uiso*/Ueq | ||
O11 | 0.6308 (5) | 0.2550 (2) | 0.5904 (3) | 0.0628 (7) | |
H11 | 0.6659 | 0.3331 | 0.5580 | 0.094* | |
O12 | 0.3846 (4) | 0.2159 (2) | 0.3905 (2) | 0.0502 (6) | |
O21 | 0.6788 (6) | 0.1131 (2) | 0.1400 (3) | 0.0658 (8) | |
H21 | 0.5955 | 0.0528 | 0.1802 | 0.099* | |
O22 | 0.8599 (4) | 0.1733 (2) | 0.3515 (2) | 0.0473 (5) | |
O31 | 0.7642 (4) | 0.8191 (2) | 0.2095 (3) | 0.0508 (6) | |
H31 | 0.8783 | 0.7786 | 0.2082 | 0.076* | |
O32 | 0.5463 (5) | 0.6055 (2) | 0.1970 (3) | 0.0584 (7) | |
O33 | 0.3719 (4) | 0.92160 (19) | 0.2395 (2) | 0.0445 (5) | |
O34 | 0.1472 (4) | 0.7104 (2) | 0.2157 (2) | 0.0460 (5) | |
O41 | 0.4537 (4) | 0.5704 (2) | 0.5233 (2) | 0.0483 (5) | |
H41 | 0.3380 | 0.6090 | 0.5267 | 0.072* | |
O42 | 0.6609 (4) | 0.7870 (2) | 0.5320 (3) | 0.0520 (6) | |
O43 | 0.8545 (4) | 0.4770 (2) | 0.4831 (3) | 0.0501 (6) | |
O44 | 1.0744 (4) | 0.6853 (2) | 0.5317 (2) | 0.0445 (5) | |
N11 | 0.1556 (5) | −0.0283 (2) | 0.4688 (3) | 0.0444 (6) | |
H11A | 0.0906 | −0.1084 | 0.5046 | 0.067* | |
H11B | 0.2202 | −0.0448 | 0.3966 | 0.067* | |
H11C | 0.0408 | 0.0229 | 0.4427 | 0.067* | |
N21 | 1.1085 (5) | 0.4117 (2) | 0.2699 (3) | 0.0442 (6) | |
H21A | 1.1960 | 0.4836 | 0.2325 | 0.066* | |
H21B | 1.2064 | 0.3684 | 0.3297 | 0.066* | |
H21C | 1.0020 | 0.4416 | 0.3128 | 0.066* | |
C11 | 0.4550 (6) | 0.1830 (3) | 0.5069 (3) | 0.0424 (6) | |
C12 | 0.3478 (6) | 0.0474 (3) | 0.5730 (3) | 0.0419 (7) | |
H12 | 0.4755 | −0.0086 | 0.5996 | 0.050* | |
C13 | 0.2465 (6) | 0.0767 (3) | 0.7010 (3) | 0.0485 (7) | |
H13A | 0.3721 | 0.1374 | 0.7596 | 0.058* | |
H13B | 0.1128 | 0.1264 | 0.6727 | 0.058* | |
C14 | 0.1571 (6) | −0.0505 (3) | 0.7853 (3) | 0.0510 (8) | |
H14 | 0.0281 | −0.1107 | 0.7263 | 0.061* | |
C15 | 0.0470 (9) | −0.0023 (5) | 0.9027 (4) | 0.0748 (12) | |
H15A | −0.0113 | −0.0813 | 0.9565 | 0.112* | |
H15B | −0.0854 | 0.0440 | 0.8653 | 0.112* | |
H15C | 0.1688 | 0.0604 | 0.9595 | 0.112* | |
C16 | 0.3528 (8) | −0.1329 (4) | 0.8400 (4) | 0.0687 (10) | |
H16A | 0.2860 | −0.2120 | 0.8909 | 0.103* | |
H16B | 0.4806 | −0.0759 | 0.8989 | 0.103* | |
H16C | 0.4168 | −0.1635 | 0.7651 | 0.103* | |
C21 | 0.8314 (6) | 0.1932 (3) | 0.2297 (3) | 0.0417 (6) | |
C22 | 0.9758 (6) | 0.3135 (3) | 0.1601 (3) | 0.0405 (6) | |
H22 | 1.0966 | 0.2773 | 0.1185 | 0.049* | |
C23 | 0.8240 (6) | 0.3867 (3) | 0.0483 (3) | 0.0463 (7) | |
H23A | 0.7263 | 0.4380 | 0.0912 | 0.056* | |
H23B | 0.7136 | 0.3168 | −0.0084 | 0.056* | |
C24 | 0.9670 (7) | 0.4868 (3) | −0.0449 (3) | 0.0518 (8) | |
H24 | 1.0874 | 0.5533 | 0.0126 | 0.062* | |
C25 | 0.7928 (10) | 0.5656 (5) | −0.1354 (4) | 0.0753 (12) | |
H25A | 0.7118 | 0.6129 | −0.0793 | 0.113* | |
H25B | 0.6749 | 0.5019 | −0.1933 | 0.113* | |
H25C | 0.8813 | 0.6320 | −0.1910 | 0.113* | |
C26 | 1.0985 (9) | 0.4118 (5) | −0.1313 (5) | 0.0764 (12) | |
H26A | 1.1868 | 0.4779 | −0.1872 | 0.115* | |
H26B | 0.9825 | 0.3467 | −0.1888 | 0.115* | |
H26C | 1.2095 | 0.3633 | −0.0725 | 0.115* | |
C31 | 0.5642 (5) | 0.7285 (3) | 0.2061 (3) | 0.0366 (6) | |
C32 | 0.3423 (5) | 0.7946 (3) | 0.2207 (3) | 0.0357 (6) | |
C41 | 0.6513 (5) | 0.6642 (3) | 0.5247 (3) | 0.0362 (6) | |
C42 | 0.8774 (5) | 0.6016 (3) | 0.5124 (3) | 0.0360 (6) |
U11 | U22 | U33 | U12 | U13 | U23 | |
O11 | 0.0683 (16) | 0.0460 (13) | 0.0585 (13) | −0.0266 (11) | 0.0061 (12) | 0.0024 (10) |
O12 | 0.0443 (13) | 0.0377 (11) | 0.0622 (14) | −0.0047 (10) | 0.0066 (10) | 0.0113 (10) |
O21 | 0.0841 (19) | 0.0412 (12) | 0.0564 (13) | −0.0303 (12) | 0.0111 (12) | −0.0005 (10) |
O22 | 0.0452 (12) | 0.0398 (11) | 0.0521 (12) | −0.0046 (9) | 0.0093 (9) | 0.0072 (9) |
O31 | 0.0326 (11) | 0.0369 (11) | 0.0805 (16) | −0.0050 (9) | 0.0140 (10) | −0.0018 (10) |
O32 | 0.0457 (13) | 0.0322 (12) | 0.0991 (19) | −0.0014 (10) | 0.0247 (13) | −0.0055 (11) |
O33 | 0.0448 (13) | 0.0276 (9) | 0.0591 (12) | −0.0038 (9) | 0.0130 (10) | −0.0033 (8) |
O34 | 0.0332 (11) | 0.0321 (10) | 0.0695 (13) | −0.0077 (8) | 0.0133 (9) | −0.0021 (9) |
O41 | 0.0314 (11) | 0.0366 (11) | 0.0732 (15) | −0.0054 (9) | 0.0096 (10) | −0.0031 (9) |
O42 | 0.0441 (13) | 0.0324 (11) | 0.0783 (15) | 0.0007 (9) | 0.0126 (11) | −0.0012 (9) |
O43 | 0.0426 (12) | 0.0281 (10) | 0.0788 (15) | −0.0054 (9) | 0.0188 (10) | −0.0043 (9) |
O44 | 0.0320 (11) | 0.0315 (10) | 0.0666 (12) | −0.0064 (8) | 0.0107 (9) | −0.0003 (8) |
N11 | 0.0543 (16) | 0.0271 (11) | 0.0479 (13) | −0.0068 (10) | 0.0123 (11) | −0.0002 (9) |
N21 | 0.0478 (14) | 0.0271 (11) | 0.0507 (13) | −0.0093 (10) | 0.0063 (11) | 0.0037 (9) |
C11 | 0.0386 (16) | 0.0296 (13) | 0.0559 (16) | −0.0067 (11) | 0.0121 (12) | −0.0004 (11) |
C12 | 0.0446 (17) | 0.0257 (12) | 0.0518 (15) | −0.0048 (11) | 0.0101 (12) | −0.0001 (11) |
C13 | 0.0530 (19) | 0.0387 (15) | 0.0516 (16) | −0.0050 (13) | 0.0152 (13) | −0.0047 (12) |
C14 | 0.053 (2) | 0.0463 (16) | 0.0460 (15) | −0.0133 (14) | 0.0099 (13) | 0.0013 (12) |
C15 | 0.073 (3) | 0.088 (3) | 0.062 (2) | −0.005 (2) | 0.0296 (19) | 0.0040 (19) |
C16 | 0.077 (3) | 0.063 (2) | 0.059 (2) | 0.000 (2) | 0.0081 (18) | 0.0150 (16) |
C21 | 0.0427 (16) | 0.0273 (12) | 0.0516 (15) | −0.0035 (11) | 0.0086 (12) | 0.0016 (10) |
C22 | 0.0441 (16) | 0.0271 (12) | 0.0470 (14) | −0.0059 (11) | 0.0115 (12) | −0.0001 (10) |
C23 | 0.0455 (17) | 0.0377 (14) | 0.0496 (15) | −0.0043 (12) | 0.0050 (12) | 0.0058 (11) |
C24 | 0.060 (2) | 0.0411 (15) | 0.0444 (15) | −0.0122 (14) | 0.0032 (14) | 0.0035 (11) |
C25 | 0.096 (3) | 0.061 (2) | 0.061 (2) | 0.006 (2) | 0.005 (2) | 0.0207 (17) |
C26 | 0.073 (3) | 0.092 (3) | 0.065 (2) | 0.008 (2) | 0.024 (2) | 0.016 (2) |
C31 | 0.0331 (14) | 0.0313 (12) | 0.0415 (13) | −0.0043 (10) | 0.0064 (10) | 0.0019 (10) |
C32 | 0.0356 (15) | 0.0302 (13) | 0.0379 (13) | −0.0046 (11) | 0.0076 (10) | 0.0000 (10) |
C41 | 0.0369 (15) | 0.0305 (13) | 0.0376 (12) | −0.0031 (11) | 0.0055 (10) | 0.0000 (10) |
C42 | 0.0325 (14) | 0.0285 (12) | 0.0427 (13) | −0.0062 (11) | 0.0074 (10) | 0.0029 (10) |
O11—C11 | 1.304 (4) | C13—H13A | 0.9700 |
O11—H11 | 0.8200 | C13—H13B | 0.9700 |
O12—C11 | 1.205 (4) | C14—C16 | 1.504 (6) |
O21—C21 | 1.311 (4) | C14—C15 | 1.537 (6) |
O21—H21 | 0.8200 | C14—H14 | 0.9800 |
O22—C21 | 1.202 (4) | C15—H15A | 0.9600 |
O31—C31 | 1.306 (4) | C15—H15B | 0.9600 |
O31—H31 | 0.8200 | C15—H15C | 0.9600 |
O32—C31 | 1.198 (4) | C16—H16A | 0.9600 |
O33—C32 | 1.244 (4) | C16—H16B | 0.9600 |
O34—C32 | 1.251 (4) | C16—H16C | 0.9600 |
O41—C41 | 1.315 (3) | C21—C22 | 1.518 (4) |
O41—H41 | 0.8200 | C22—C23 | 1.521 (4) |
O42—C41 | 1.200 (4) | C22—H22 | 0.9800 |
O43—C42 | 1.247 (4) | C23—C24 | 1.535 (4) |
O44—C42 | 1.254 (3) | C23—H23A | 0.9700 |
N11—C12 | 1.486 (4) | C23—H23B | 0.9700 |
N11—H11A | 0.8900 | C24—C25 | 1.513 (6) |
N11—H11B | 0.8900 | C24—C26 | 1.516 (6) |
N11—H11C | 0.8900 | C24—H24 | 0.9800 |
N21—C22 | 1.497 (4) | C25—H25A | 0.9600 |
N21—H21A | 0.8900 | C25—H25B | 0.9600 |
N21—H21B | 0.8900 | C25—H25C | 0.9600 |
N21—H21C | 0.8900 | C26—H26A | 0.9600 |
C11—C12 | 1.526 (4) | C26—H26B | 0.9600 |
C12—C13 | 1.535 (4) | C26—H26C | 0.9600 |
C12—H12 | 0.9800 | C31—C32 | 1.546 (4) |
C13—C14 | 1.525 (4) | C41—C42 | 1.543 (4) |
C11—O11—H11 | 109.5 | H16A—C16—H16C | 109.5 |
C21—O21—H21 | 109.5 | H16B—C16—H16C | 109.5 |
C31—O31—H31 | 109.5 | O22—C21—O21 | 125.0 (3) |
C41—O41—H41 | 109.5 | O22—C21—C22 | 123.6 (3) |
C12—N11—H11A | 109.5 | O21—C21—C22 | 111.4 (3) |
C12—N11—H11B | 109.5 | N21—C22—C21 | 107.1 (2) |
H11A—N11—H11B | 109.5 | N21—C22—C23 | 111.3 (2) |
C12—N11—H11C | 109.5 | C21—C22—C23 | 114.3 (3) |
H11A—N11—H11C | 109.5 | N21—C22—H22 | 108.0 |
H11B—N11—H11C | 109.5 | C21—C22—H22 | 108.0 |
C22—N21—H21A | 109.5 | C23—C22—H22 | 108.0 |
C22—N21—H21B | 109.5 | C22—C23—C24 | 115.7 (3) |
H21A—N21—H21B | 109.5 | C22—C23—H23A | 108.4 |
C22—N21—H21C | 109.5 | C24—C23—H23A | 108.4 |
H21A—N21—H21C | 109.5 | C22—C23—H23B | 108.4 |
H21B—N21—H21C | 109.5 | C24—C23—H23B | 108.4 |
O12—C11—O11 | 125.3 (3) | H23A—C23—H23B | 107.4 |
O12—C11—C12 | 122.7 (3) | C25—C24—C26 | 110.5 (3) |
O11—C11—C12 | 111.9 (3) | C25—C24—C23 | 108.6 (3) |
N11—C12—C11 | 107.7 (2) | C26—C24—C23 | 112.0 (3) |
N11—C12—C13 | 111.6 (3) | C25—C24—H24 | 108.5 |
C11—C12—C13 | 110.4 (2) | C26—C24—H24 | 108.5 |
N11—C12—H12 | 109.1 | C23—C24—H24 | 108.5 |
C11—C12—H12 | 109.1 | C24—C25—H25A | 109.5 |
C13—C12—H12 | 109.1 | C24—C25—H25B | 109.5 |
C14—C13—C12 | 115.7 (3) | H25A—C25—H25B | 109.5 |
C14—C13—H13A | 108.3 | C24—C25—H25C | 109.5 |
C12—C13—H13A | 108.3 | H25A—C25—H25C | 109.5 |
C14—C13—H13B | 108.3 | H25B—C25—H25C | 109.5 |
C12—C13—H13B | 108.3 | C24—C26—H26A | 109.5 |
H13A—C13—H13B | 107.4 | C24—C26—H26B | 109.5 |
C16—C14—C13 | 113.1 (3) | H26A—C26—H26B | 109.5 |
C16—C14—C15 | 110.8 (3) | C24—C26—H26C | 109.5 |
C13—C14—C15 | 108.4 (3) | H26A—C26—H26C | 109.5 |
C16—C14—H14 | 108.1 | H26B—C26—H26C | 109.5 |
C13—C14—H14 | 108.1 | O32—C31—O31 | 125.8 (3) |
C15—C14—H14 | 108.1 | O32—C31—C32 | 121.1 (3) |
C14—C15—H15A | 109.5 | O31—C31—C32 | 113.1 (2) |
C14—C15—H15B | 109.5 | O33—C32—O34 | 126.4 (3) |
H15A—C15—H15B | 109.5 | O33—C32—C31 | 119.0 (2) |
C14—C15—H15C | 109.5 | O34—C32—C31 | 114.5 (2) |
H15A—C15—H15C | 109.5 | O42—C41—O41 | 125.1 (3) |
H15B—C15—H15C | 109.5 | O42—C41—C42 | 121.7 (3) |
C14—C16—H16A | 109.5 | O41—C41—C42 | 113.2 (2) |
C14—C16—H16B | 109.5 | O43—C42—O44 | 125.2 (3) |
H16A—C16—H16B | 109.5 | O43—C42—C41 | 120.0 (2) |
C14—C16—H16C | 109.5 | O44—C42—C41 | 114.8 (2) |
O12—C11—C12—N11 | 0.6 (4) | O22—C21—C22—N21 | −12.2 (4) |
O11—C11—C12—N11 | −178.3 (3) | O21—C21—C22—N21 | 169.6 (3) |
O12—C11—C12—C13 | −121.4 (3) | O22—C21—C22—C23 | −135.9 (3) |
O11—C11—C12—C13 | 59.7 (4) | O21—C21—C22—C23 | 45.9 (4) |
N11—C12—C13—C14 | 66.4 (4) | N21—C22—C23—C24 | 71.3 (4) |
C11—C12—C13—C14 | −174.0 (3) | C21—C22—C23—C24 | −167.2 (3) |
C12—C13—C14—C16 | 60.5 (4) | C22—C23—C24—C25 | −171.7 (3) |
C12—C13—C14—C15 | −176.2 (3) | C22—C23—C24—C26 | 66.0 (4) |
O32—C31—C32—O33 | 175.0 (3) | O42—C41—C42—O43 | −168.5 (3) |
O31—C31—C32—O33 | −3.0 (4) | O41—C41—C42—O43 | 10.1 (4) |
O32—C31—C32—O34 | −3.0 (4) | O42—C41—C42—O44 | 10.4 (4) |
O31—C31—C32—O34 | 179.0 (3) | O41—C41—C42—O44 | −170.9 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
O11—H11···O43 | 0.82 | 1.82 | 2.593 (4) | 157 |
O21—H21···O33i | 0.82 | 1.79 | 2.600 (4) | 169 |
O31—H31···O34ii | 0.82 | 1.76 | 2.578 (3) | 173 |
O41—H41···O44iii | 0.82 | 1.80 | 2.616 (3) | 177 |
N11—H11A···O44iv | 0.89 | 2.02 | 2.820 (4) | 150 |
N11—H11B···O33i | 0.89 | 1.97 | 2.856 (4) | 178 |
N11—H11C···O22iii | 0.89 | 2.04 | 2.898 (4) | 162 |
N21—H21A···O32ii | 0.89 | 2.20 | 3.013 (4) | 152 |
N21—H21B···O12ii | 0.89 | 1.97 | 2.795 (4) | 154 |
N21—H21C···O43 | 0.89 | 2.07 | 2.902 (4) | 155 |
Symmetry codes: (i) x, y−1, z; (ii) x+1, y, z; (iii) x−1, y, z; (iv) x−1, y−1, z. |
Experimental details
Crystal data | |
Chemical formula | C6H14NO2+·C2HO4− |
Mr | 221.21 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 293 |
a, b, c (Å) | 5.674 (3), 9.803 (9), 9.906 (8) |
α, β, γ (°) | 87.37 (7), 99.64 (5), 100.35 (6) |
V (Å3) | 534.3 (7) |
Z | 2 |
Radiation type | Cu Kα |
µ (mm−1) | 1.02 |
Crystal size (mm) | 0.35 × 0.20 × 0.15 |
Data collection | |
Diffractometer | Enraf-Nonius CAD-4 diffractometer |
Absorption correction | ψ scan (North et al., 1968) |
Tmin, Tmax | 0.773, 0.858 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2223, 2003, 1866 |
Rint | 0.045 |
(sin θ/λ)max (Å−1) | 0.617 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.045, 0.117, 1.04 |
No. of reflections | 2003 |
No. of parameters | 272 |
No. of restraints | 3 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.27, −0.26 |
Computer programs: CAD-4 Software (Enraf-Nonius, 1989, CAD-4 Software, SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), PLATON (Spek, 1999), SHELXL97.
O12—C11—C12—N11 | 0.6 (4) | O22—C21—C22—N21 | −12.2 (4) |
O11—C11—C12—N11 | −178.3 (3) | O21—C21—C22—N21 | 169.6 (3) |
O12—C11—C12—C13 | −121.4 (3) | O22—C21—C22—C23 | −135.9 (3) |
O11—C11—C12—C13 | 59.7 (4) | O21—C21—C22—C23 | 45.9 (4) |
N11—C12—C13—C14 | 66.4 (4) | N21—C22—C23—C24 | 71.3 (4) |
C11—C12—C13—C14 | −174.0 (3) | C21—C22—C23—C24 | −167.2 (3) |
C12—C13—C14—C16 | 60.5 (4) | C22—C23—C24—C25 | −171.7 (3) |
C12—C13—C14—C15 | −176.2 (3) | C22—C23—C24—C26 | 66.0 (4) |
O32—C31—C32—O33 | 175.0 (3) | O42—C41—C42—O43 | −168.5 (3) |
O31—C31—C32—O33 | −3.0 (4) | O41—C41—C42—O43 | 10.1 (4) |
O32—C31—C32—O34 | −3.0 (4) | O42—C41—C42—O44 | 10.4 (4) |
O31—C31—C32—O34 | 179.0 (3) | O41—C41—C42—O44 | −170.9 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
O11—H11···O43 | 0.82 | 1.82 | 2.593 (4) | 157 |
O21—H21···O33i | 0.82 | 1.79 | 2.600 (4) | 169 |
O31—H31···O34ii | 0.82 | 1.76 | 2.578 (3) | 173 |
O41—H41···O44iii | 0.82 | 1.80 | 2.616 (3) | 177 |
N11—H11A···O44iv | 0.89 | 2.02 | 2.820 (4) | 150 |
N11—H11B···O33i | 0.89 | 1.97 | 2.856 (4) | 178 |
N11—H11C···O22iii | 0.89 | 2.04 | 2.898 (4) | 162 |
N21—H21A···O32ii | 0.89 | 2.20 | 3.013 (4) | 152 |
N21—H21B···O12ii | 0.89 | 1.97 | 2.795 (4) | 154 |
N21—H21C···O43 | 0.89 | 2.07 | 2.902 (4) | 155 |
Symmetry codes: (i) x, y−1, z; (ii) x+1, y, z; (iii) x−1, y, z; (iv) x−1, y−1, z. |
Leucine is one of the most important amino acids, essential for the growth and maintenance of living organisms. Simple carboxylic acids, which are believed to have existed in the prebiotic earth (Miller & Orgel, 1974; Kvenvolden et al., 1971), form crystalline complexes with amino acids. The structure elucidation of the title compound, (I), was undertaken as part of a programme of research on complexes of amino acids with dicarboxylic acids. This research in our laboratory aims to study the nature of intermolecular interactions and characteristic aggregation patterns, at atomic resolution. Recently, the crystal structures of sarcosinium oxalate monohydrate (Krishnakumar et al., 1999), 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), bis(DL-serinium) oxalate dihydrate (Alagar et al., 2002) and bis(DL-aspartic acid) oxalate (Alagar et al., 2003) have been reported from our laboratory.
Fig. 1 shows the molecular structure with the atom-numbering scheme. The asymmetric unit contains two leucinium cations and two semi-oxalate anions; the former have protonated amino groups and uncharged carboxylic acid groups, the latter each have a neutral carboxylic acid group and a negatively charged carboxylate group. The two cations exibit significant differences in conformation, as do the two anions (Table 1; corresponding angles are listed side-by-side). The semi-oxalate ions are related to each other through a psuedo-inversion centre. Interestingly, the two leucinium cations are also related by a psuedo-inversion centre, ignoring the side chain C atoms. A feature common to the crystal structures of glycinium oxalate, L-alaninium oxalate and (I) is that the shortest cell dimensions are similar, viz. 5.650 (2), 5.630 (1) and 5.674 (3) Å, respectively.
Fig. 2 shows the packing of the molecules of (I), viewed down the a axis. The leucinium and semi-oxalate ions are linked to each other through N—H···O and O—H···O hydrogen bonds. Head-to-tail hydrogen bonds, of type S2, with O12 and O22 of the carboxylic groups as acceptors are present in the structure. The semi-oxalate ions are interconnected by direct O—H···O interactions, forming hydrogen-bonded strings along the shorter cell axis, as observed in many other amino acid–oxalic acid complexes. The leucinium and semi-oxalate ions form hydrogen-bonded double layers. The leucinium cations are arranged in these double layers on opposite sides, leading to alternating hydrophobic and hydrophilic layers. These layers are held together, in addition to van der Waals interactions, by a few short contacts O12···O22 (x + 1, y, z) = 2.893 (4) Å; a carbonyl–carbonyl contact O22···C11 (x − 1, y, z) = 2.989 (5) Å (Allen et al., 1998) and C31···C41 = 3.164 (5) Å. The C—C bond lengths of the semi-oxalate anions, C31—C32 = 1.546 (4) Å and C41—C42 = 1.543 (4) Å, are slightly larger and may be justified by intramolecular O···O steric hindrance. Similar large deviations from normally expected values in C—C bond lengths are also observed in the case of oxalic acid dihydrate (1.537 Å; Ahmed & Cruickshank, 1953) and in the crystal structures of anhydrous α- and β-oxalic acids [1.537 (1) and 1.537 (1) Å, respectively; Derrissen & Smith, 1974].