Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270107013832/fa3080sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270107013832/fa3080Isup2.hkl |
CCDC reference: 649084
The title compound (I) was crystallized from a liquid mixture [Solvent?] of 4-aminobenzoic acid and L-proline in the stochiometric ratio of 1:2 at room temperature, by the technique of slow evaporation.
The H atoms of the water molecule were located in a difference Fourier map and refined isotropically [Range of refined O—H distances?]. All other H atoms were positioned geometrically and refined using a riding model, with C—H = 0.93 (aromatic), 0.97 (CH2) or 0.98 Å (CH), O—H = 0.82 Å, and N—H = 0.86 (NH2 in PABA) or 0.90 Å (NH2 in proline), and with Uiso(H) = 1.2Ueq(parent) for CH, CH2, NH2 and aromatic CH, or 1.5Ueq(OH). In one of the proline residues, the Cγ atom (C25) is disordered over two positions with site occupancies of 0.65 and 0.35. In addition to the 1794 unique reflections, 203 Friedel pairs were measured. However, owing to the absence of atoms with significant anomalous dispersion effects, these data were merged.
Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXTL/PC (Bruker, 2000); program(s) used to refine structure: SHELXTL/PC; molecular graphics: ORTEP-3 (Farrugia, 1997), Mercury (Version 1.4.1; Macrae et al., 2006 ) and PLATON (Spek, 2003); software used to prepare material for publication: SHELXTL/PC.
C7H7NO2·2C5H9NO2·H2O | F(000) = 412 |
Mr = 385.42 | Dx = 1.328 Mg m−3 Dm = 1.32 (1) Mg m−3 Dm measured by flotation in a liquid mixture of xylene and carbon tetrachloride |
Monoclinic, P21 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2yb | Cell parameters from 25 reflections |
a = 9.8171 (6) Å | θ = 10.1–14.2° |
b = 10.4167 (11) Å | µ = 0.10 mm−1 |
c = 10.1713 (12) Å | T = 293 K |
β = 112.078 (9)° | Needle, pink |
V = 963.87 (16) Å3 | 0.21 × 0.16 × 0.14 mm |
Z = 2 |
Nonius MACH3 diffractometer | 1573 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.014 |
Graphite monochromator | θmax = 25.0°, θmin = 2.2° |
ω/2θ scans | h = 0→11 |
Absorption correction: ψ scan (North et al., 1968) | k = −1→12 |
Tmin = 0.965, Tmax = 0.981 | l = −12→11 |
2117 measured reflections | 3 standard reflections every 60 min |
1794 independent reflections | intensity decay: none |
Refinement on F2 | Hydrogen site location: inferred from neighbouring sites |
Least-squares matrix: full | H atoms treated by a mixture of independent and constrained refinement |
R[F2 > 2σ(F2)] = 0.044 | w = 1/[σ2(Fo2) + (0.0347P)2 + 0.6713P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.115 | (Δ/σ)max < 0.001 |
S = 1.09 | Δρmax = 0.38 e Å−3 |
1794 reflections | Δρmin = −0.35 e Å−3 |
263 parameters | Extinction correction: SHELXTL/PC (Bruker, 2000), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
3 restraints | Extinction coefficient: 0.143 (8) |
Primary atom site location: structure-invariant direct methods | Absolute structure: by known absolute configuration of a chiral reference molecule |
Secondary atom site location: difference Fourier map |
C7H7NO2·2C5H9NO2·H2O | V = 963.87 (16) Å3 |
Mr = 385.42 | Z = 2 |
Monoclinic, P21 | Mo Kα radiation |
a = 9.8171 (6) Å | µ = 0.10 mm−1 |
b = 10.4167 (11) Å | T = 293 K |
c = 10.1713 (12) Å | 0.21 × 0.16 × 0.14 mm |
β = 112.078 (9)° |
Nonius MACH3 diffractometer | 1573 reflections with I > 2σ(I) |
Absorption correction: ψ scan (North et al., 1968) | Rint = 0.014 |
Tmin = 0.965, Tmax = 0.981 | 3 standard reflections every 60 min |
2117 measured reflections | intensity decay: none |
1794 independent reflections |
R[F2 > 2σ(F2)] = 0.044 | 3 restraints |
wR(F2) = 0.115 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.09 | Δρmax = 0.38 e Å−3 |
1794 reflections | Δρmin = −0.35 e Å−3 |
263 parameters | Absolute structure: by known absolute configuration of a chiral reference molecule |
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 | Occ. (<1) | |
C1 | −0.0133 (6) | 1.0327 (5) | 0.2419 (6) | 0.0679 (14) | |
C11 | −0.0812 (11) | 1.1360 (8) | 0.2882 (15) | 0.135 (4) | |
O1A | −0.1836 (7) | 1.1973 (6) | 0.1827 (8) | 0.126 (2) | |
H1A | −0.2283 | 1.2465 | 0.2150 | 0.189* | |
O1B | −0.0574 (8) | 1.1697 (7) | 0.4098 (7) | 0.155 (3) | |
C2 | −0.0594 (5) | 0.9871 (5) | 0.1043 (6) | 0.0632 (13) | |
H2 | −0.1431 | 1.0221 | 0.0357 | 0.076* | |
C3 | 0.0147 (5) | 0.8919 (4) | 0.0665 (5) | 0.0539 (11) | |
H3 | −0.0197 | 0.8626 | −0.0267 | 0.065* | |
C4 | 0.1416 (5) | 0.8387 (5) | 0.1668 (5) | 0.0551 (11) | |
N41 | 0.2199 (5) | 0.7487 (4) | 0.1290 (6) | 0.0822 (14) | |
H41A | 0.2967 | 0.7151 | 0.1921 | 0.099* | |
H41B | 0.1927 | 0.7252 | 0.0418 | 0.099* | |
C5 | 0.1832 (6) | 0.8785 (6) | 0.3074 (5) | 0.0753 (16) | |
H5 | 0.2632 | 0.8404 | 0.3778 | 0.090* | |
C6 | 0.1075 (8) | 0.9724 (7) | 0.3414 (6) | 0.0848 (18) | |
H6 | 0.1377 | 0.9978 | 0.4357 | 0.102* | |
C21 | 0.4682 (4) | 0.6140 (4) | 0.4686 (4) | 0.0438 (10) | |
O2A | 0.4992 (3) | 0.6700 (3) | 0.3732 (3) | 0.0513 (7) | |
O2B | 0.4695 (4) | 0.6626 (3) | 0.5804 (3) | 0.0664 (10) | |
C22 | 0.4270 (5) | 0.4734 (4) | 0.4419 (4) | 0.0465 (10) | |
H22 | 0.5089 | 0.4264 | 0.4316 | 0.056* | |
N23 | 0.3932 (4) | 0.4163 (3) | 0.5606 (3) | 0.0440 (8) | |
H23A | 0.4372 | 0.3393 | 0.5842 | 0.053* | |
H23B | 0.4273 | 0.4677 | 0.6372 | 0.053* | |
C24 | 0.2314 (5) | 0.4015 (6) | 0.5144 (5) | 0.0677 (14) | |
C25 | 0.1723 (9) | 0.4633 (10) | 0.3721 (8) | 0.066 (2) | 0.65 |
H25A | 0.0827 | 0.4211 | 0.3113 | 0.079* | 0.65 |
H25B | 0.1514 | 0.5533 | 0.3802 | 0.079* | 0.65 |
C25' | 0.183 (2) | 0.368 (2) | 0.3481 (19) | 0.079 (5) | 0.35 |
H25C | 0.1947 | 0.2780 | 0.3326 | 0.095* | 0.35 |
H25D | 0.0821 | 0.3941 | 0.2942 | 0.095* | 0.35 |
C26 | 0.2894 (7) | 0.4488 (6) | 0.3138 (5) | 0.0732 (16) | |
H24A | 0.2025 | 0.3103 | 0.5083 | 0.088* | 0.65 |
H24B | 0.1934 | 0.4431 | 0.5798 | 0.088* | 0.65 |
H24C | 0.1837 | 0.4788 | 0.5288 | 0.088* | 0.35 |
H24D | 0.2052 | 0.3307 | 0.5652 | 0.088* | 0.35 |
H26A | 0.2794 | 0.5099 | 0.2377 | 0.088* | 0.65 |
H26B | 0.2904 | 0.3619 | 0.2753 | 0.088* | 0.65 |
H26C | 0.2449 | 0.5290 | 0.2724 | 0.088* | 0.35 |
H26D | 0.3170 | 0.4043 | 0.2410 | 0.088* | 0.35 |
C31 | 0.4939 (4) | 0.4931 (4) | −0.0269 (4) | 0.0410 (9) | |
O3A | 0.4613 (4) | 0.4349 (3) | −0.1423 (3) | 0.0576 (9) | |
O3B | 0.4777 (4) | 0.4519 (3) | 0.0812 (3) | 0.0615 (9) | |
C32 | 0.5589 (4) | 0.6276 (4) | −0.0208 (4) | 0.0395 (9) | |
H32 | 0.4869 | 0.6845 | −0.0887 | 0.047* | |
N33 | 0.6026 (4) | 0.6800 (3) | 0.1273 (3) | 0.0420 (8) | |
H33A | 0.5582 | 0.6349 | 0.1754 | 0.050* | |
H33B | 0.5745 | 0.7626 | 0.1240 | 0.050* | |
C34 | 0.7684 (5) | 0.6699 (5) | 0.2016 (5) | 0.0569 (11) | |
H34A | 0.8136 | 0.7542 | 0.2185 | 0.068* | |
H34B | 0.7948 | 0.6251 | 0.2914 | 0.068* | |
C35 | 0.8148 (5) | 0.5941 (5) | 0.0984 (5) | 0.0553 (11) | |
H35A | 0.9128 | 0.6185 | 0.1058 | 0.066* | |
H35B | 0.8132 | 0.5027 | 0.1156 | 0.066* | |
C36 | 0.7020 (5) | 0.6293 (5) | −0.0451 (4) | 0.0521 (11) | |
H36A | 0.7005 | 0.5670 | −0.1165 | 0.062* | |
H36B | 0.7212 | 0.7138 | −0.0744 | 0.062* | |
O1W | 0.6771 (5) | 0.3414 (4) | 0.3208 (5) | 0.0756 (11) | |
H1W | 0.641 (6) | 0.288 (5) | 0.354 (6) | 0.08 (2)* | |
H2W | 0.627 (13) | 0.387 (11) | 0.252 (10) | 0.26 (7)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.079 (4) | 0.057 (3) | 0.084 (4) | −0.015 (3) | 0.050 (3) | −0.013 (3) |
C11 | 0.129 (7) | 0.062 (4) | 0.281 (14) | −0.019 (5) | 0.152 (9) | −0.024 (7) |
O1A | 0.118 (4) | 0.081 (4) | 0.229 (7) | 0.004 (3) | 0.123 (5) | −0.023 (4) |
O1B | 0.223 (7) | 0.117 (5) | 0.201 (6) | −0.036 (5) | 0.166 (6) | −0.073 (5) |
C2 | 0.048 (2) | 0.059 (3) | 0.081 (3) | 0.006 (2) | 0.022 (2) | 0.016 (3) |
C3 | 0.060 (3) | 0.046 (2) | 0.052 (2) | −0.002 (2) | 0.017 (2) | 0.007 (2) |
C4 | 0.053 (2) | 0.042 (2) | 0.065 (3) | −0.003 (2) | 0.016 (2) | 0.010 (2) |
N41 | 0.069 (3) | 0.058 (3) | 0.104 (4) | 0.016 (2) | 0.015 (3) | −0.002 (3) |
C5 | 0.078 (4) | 0.076 (4) | 0.051 (3) | 0.006 (3) | 0.000 (3) | 0.010 (3) |
C6 | 0.107 (5) | 0.091 (5) | 0.051 (3) | −0.020 (4) | 0.024 (3) | −0.012 (3) |
C21 | 0.048 (2) | 0.033 (2) | 0.049 (3) | 0.0013 (18) | 0.0159 (19) | −0.0017 (19) |
O2A | 0.0635 (18) | 0.0393 (16) | 0.0531 (17) | −0.0050 (15) | 0.0243 (14) | 0.0037 (14) |
O2B | 0.108 (3) | 0.0422 (18) | 0.0498 (18) | −0.0087 (19) | 0.0308 (18) | −0.0109 (16) |
C22 | 0.068 (3) | 0.035 (2) | 0.047 (2) | −0.003 (2) | 0.033 (2) | −0.0038 (18) |
N23 | 0.063 (2) | 0.0321 (17) | 0.0376 (16) | 0.0034 (16) | 0.0204 (15) | 0.0017 (14) |
C24 | 0.061 (3) | 0.080 (4) | 0.071 (3) | 0.004 (3) | 0.035 (2) | 0.013 (3) |
C25 | 0.057 (4) | 0.068 (6) | 0.052 (4) | −0.002 (5) | −0.004 (3) | 0.008 (4) |
C25' | 0.075 (11) | 0.067 (12) | 0.084 (12) | −0.023 (10) | 0.018 (9) | −0.002 (10) |
C26 | 0.105 (4) | 0.066 (3) | 0.047 (2) | −0.033 (3) | 0.027 (3) | −0.009 (3) |
C31 | 0.051 (2) | 0.034 (2) | 0.036 (2) | 0.0013 (18) | 0.0147 (17) | 0.0036 (17) |
O3A | 0.092 (2) | 0.0383 (17) | 0.0433 (16) | −0.0151 (17) | 0.0263 (15) | −0.0067 (14) |
O3B | 0.092 (2) | 0.051 (2) | 0.0462 (16) | −0.0168 (18) | 0.0316 (16) | 0.0023 (15) |
C32 | 0.051 (2) | 0.0308 (19) | 0.0350 (18) | 0.0011 (18) | 0.0146 (16) | 0.0011 (16) |
N33 | 0.0566 (19) | 0.0316 (17) | 0.0427 (17) | 0.0023 (16) | 0.0243 (15) | −0.0015 (15) |
C34 | 0.061 (3) | 0.059 (3) | 0.046 (2) | 0.000 (2) | 0.014 (2) | 0.000 (2) |
C35 | 0.051 (2) | 0.054 (3) | 0.061 (3) | 0.003 (2) | 0.022 (2) | −0.003 (2) |
C36 | 0.067 (3) | 0.048 (3) | 0.051 (2) | −0.010 (2) | 0.033 (2) | −0.006 (2) |
O1W | 0.089 (3) | 0.059 (2) | 0.092 (3) | 0.011 (2) | 0.049 (2) | 0.006 (2) |
C1—C2 | 1.383 (7) | C24—H24D | 0.989 (5) |
C1—C6 | 1.386 (9) | C25—C26 | 1.486 (10) |
C1—C11 | 1.436 (10) | C25—H25A | 0.9700 |
C11—O1B | 1.220 (13) | C25—H25B | 0.9700 |
C11—O1A | 1.326 (13) | C25'—C26 | 1.481 (18) |
O1A—H1A | 0.8200 | C25'—H25C | 0.9700 |
C2—C3 | 1.367 (7) | C25'—H25D | 0.9700 |
C2—H2 | 0.9300 | C26—H26A | 0.978 (5) |
C3—C4 | 1.395 (6) | C26—H26B | 0.988 (6) |
C3—H3 | 0.9300 | C26—H26C | 0.964 (6) |
C4—N41 | 1.357 (7) | C26—H26D | 0.994 (5) |
C4—C5 | 1.395 (7) | C31—O3B | 1.245 (5) |
N41—H41A | 0.8600 | C31—O3A | 1.251 (5) |
N41—H41B | 0.8600 | C31—C32 | 1.532 (5) |
C5—C6 | 1.349 (9) | C32—N33 | 1.505 (5) |
C5—H5 | 0.9300 | C32—C36 | 1.515 (5) |
C6—H6 | 0.9300 | C32—H32 | 0.9800 |
C21—O2B | 1.241 (5) | N33—C34 | 1.519 (6) |
C21—O2A | 1.263 (5) | N33—H33A | 0.9000 |
C21—C22 | 1.516 (6) | N33—H33B | 0.9000 |
C22—N23 | 1.491 (5) | C34—C35 | 1.513 (6) |
C22—C26 | 1.505 (7) | C34—H34A | 0.9700 |
C22—H22 | 0.9800 | C34—H34B | 0.9700 |
N23—C24 | 1.486 (6) | C35—C36 | 1.509 (6) |
N23—H23A | 0.9000 | C35—H35A | 0.9700 |
N23—H23B | 0.9000 | C35—H35B | 0.9700 |
C24—C25 | 1.488 (9) | C36—H36A | 0.9700 |
C24—C25' | 1.612 (19) | C36—H36B | 0.9700 |
C24—H24A | 0.986 (6) | O1W—H1W | 0.80 (4) |
C24—H24B | 0.977 (5) | O1W—H2W | 0.84 (5) |
C24—H24C | 0.969 (6) | ||
C2—C1—C6 | 116.6 (5) | C26—C25—H25B | 110.6 |
C2—C1—C11 | 125.0 (8) | C24—C25—H25B | 110.6 |
C6—C1—C11 | 118.4 (8) | H25A—C25—H25B | 108.8 |
O1B—C11—O1A | 118.7 (8) | C26—C25'—C24 | 99.8 (10) |
O1B—C11—C1 | 127.7 (12) | C26—C25'—H25C | 111.8 |
O1A—C11—C1 | 113.6 (10) | C24—C25'—H25C | 111.8 |
C11—O1A—H1A | 109.5 | C26—C25'—H25D | 111.8 |
C3—C2—C1 | 121.8 (5) | C24—C25'—H25D | 111.8 |
C3—C2—H2 | 119.1 | H25C—C25'—H25D | 109.5 |
C1—C2—H2 | 119.1 | C25'—C26—C22 | 112.1 (8) |
C2—C3—C4 | 120.4 (5) | C25—C26—C22 | 102.4 (4) |
C2—C3—H3 | 119.8 | C25—C26—H26A | 112.7 (7) |
C4—C3—H3 | 119.8 | C22—C26—H26A | 111.4 (5) |
N41—C4—C5 | 121.2 (5) | C25—C26—H26B | 112.0 (6) |
N41—C4—C3 | 120.9 (5) | C22—C26—H26B | 111.1 (5) |
C5—C4—C3 | 117.9 (5) | H26A—C26—H26B | 107.2 (4) |
C4—N41—H41A | 120.0 | C25'—C26—H26C | 110.4 (10) |
C4—N41—H41B | 120.0 | C22—C26—H26C | 110.0 (5) |
H41A—N41—H41B | 120.0 | C25'—C26—H26D | 109.1 (9) |
C6—C5—C4 | 120.1 (5) | C22—C26—H26D | 108.5 (5) |
C6—C5—H5 | 120.0 | H26C—C26—H26D | 106.6 (4) |
C4—C5—H5 | 120.0 | O3B—C31—O3A | 126.1 (4) |
C5—C6—C1 | 122.9 (5) | O3B—C31—C32 | 117.9 (3) |
C5—C6—H6 | 118.5 | O3A—C31—C32 | 115.9 (3) |
C1—C6—H6 | 118.5 | N33—C32—C36 | 103.1 (3) |
O2B—C21—O2A | 126.4 (4) | N33—C32—C31 | 109.3 (3) |
O2B—C21—C22 | 118.0 (4) | C36—C32—C31 | 113.7 (3) |
O2A—C21—C22 | 115.6 (4) | N33—C32—H32 | 110.2 |
N23—C22—C26 | 103.5 (3) | C36—C32—H32 | 110.2 |
N23—C22—C21 | 111.4 (3) | C31—C32—H32 | 110.2 |
C26—C22—C21 | 114.3 (4) | C32—N33—C34 | 108.8 (3) |
N23—C22—H22 | 109.1 | C32—N33—H33A | 109.9 |
C26—C22—H22 | 109.1 | C34—N33—H33A | 109.9 |
C21—C22—H22 | 109.1 | C32—N33—H33B | 109.9 |
C24—N23—C22 | 108.8 (3) | C34—N33—H33B | 109.9 |
C24—N23—H23A | 109.9 | H33A—N33—H33B | 108.3 |
C22—N23—H23A | 109.9 | C35—C34—N33 | 103.7 (3) |
C24—N23—H23B | 109.9 | C35—C34—H34A | 111.0 |
C22—N23—H23B | 109.9 | N33—C34—H34A | 111.0 |
H23A—N23—H23B | 108.3 | C35—C34—H34B | 111.0 |
N23—C24—C25 | 104.0 (5) | N33—C34—H34B | 111.0 |
N23—C24—C25' | 102.3 (7) | H34A—C34—H34B | 109.0 |
N23—C24—H24A | 111.6 (5) | C36—C35—C34 | 104.0 (4) |
C25—C24—H24A | 111.0 (6) | C36—C35—H35A | 111.0 |
N23—C24—H24B | 112.0 (5) | C34—C35—H35A | 111.0 |
C25—C24—H24B | 111.2 (6) | C36—C35—H35B | 111.0 |
H24A—C24—H24B | 107.2 (4) | C34—C35—H35B | 111.0 |
N23—C24—H24C | 112.7 (5) | H35A—C35—H35B | 109.0 |
C25'—C24—H24C | 111.5 (9) | C35—C36—C32 | 103.2 (3) |
N23—C24—H24D | 111.7 (4) | C35—C36—H36A | 111.1 |
C25'—C24—H24D | 110.9 (8) | C32—C36—H36A | 111.1 |
H24C—C24—H24D | 107.8 (4) | C35—C36—H36B | 111.1 |
C26—C25—C24 | 105.5 (6) | C32—C36—H36B | 111.1 |
C26—C25—H25A | 110.6 | H36A—C36—H36B | 109.1 |
C24—C25—H25A | 110.6 | H1W—O1W—H2W | 123 (10) |
C2—C1—C11—O1B | 170.1 (7) | C25'—C24—C25—C26 | −64.1 (12) |
C6—C1—C11—O1B | −9.6 (10) | N23—C24—C25'—C26 | −35.1 (12) |
C2—C1—C11—O1A | −8.2 (9) | C25—C24—C25'—C26 | 61.9 (11) |
C6—C1—C11—O1A | 172.1 (6) | C24—C25'—C26—C25 | −57.7 (10) |
C6—C1—C2—C3 | −3.3 (7) | C24—C25'—C26—C22 | 25.5 (14) |
C11—C1—C2—C3 | 177.0 (5) | C24—C25—C26—C25' | 69.5 (12) |
C1—C2—C3—C4 | −0.8 (7) | C24—C25—C26—C22 | −40.1 (8) |
C2—C3—C4—N41 | −176.8 (4) | N23—C22—C26—C25' | −6.0 (11) |
C2—C3—C4—C5 | 4.7 (7) | C21—C22—C26—C25' | −127.4 (10) |
N41—C4—C5—C6 | 176.9 (6) | N23—C22—C26—C25 | 35.5 (6) |
C3—C4—C5—C6 | −4.6 (8) | C21—C22—C26—C25 | −85.9 (6) |
C4—C5—C6—C1 | 0.4 (9) | O3B—C31—C32—N33 | 4.6 (5) |
C2—C1—C6—C5 | 3.5 (9) | O3A—C31—C32—N33 | −175.7 (4) |
C11—C1—C6—C5 | −176.8 (6) | O3B—C31—C32—C36 | 119.1 (4) |
O2B—C21—C22—N23 | 0.2 (6) | O3A—C31—C32—C36 | −61.2 (5) |
O2A—C21—C22—N23 | 179.7 (3) | C36—C32—N33—C34 | −18.1 (4) |
O2B—C21—C22—C26 | 117.1 (4) | C31—C32—N33—C34 | 103.1 (4) |
O2A—C21—C22—C26 | −63.4 (5) | C32—N33—C34—C35 | −7.4 (5) |
C26—C22—N23—C24 | −18.8 (5) | N33—C34—C35—C36 | 30.2 (5) |
C21—C22—N23—C24 | 104.5 (4) | C34—C35—C36—C32 | −42.1 (5) |
C22—N23—C24—C25 | −5.5 (6) | N33—C32—C36—C35 | 36.6 (4) |
C22—N23—C24—C25' | 34.2 (9) | C31—C32—C36—C35 | −81.5 (4) |
N23—C24—C25—C26 | 28.3 (8) |
D—H···A | D—H | H···A | D···A | D—H···A |
O1A—H1A···O1Wi | 0.82 | 1.94 | 2.746 (6) | 170 |
N41—H41B···O1Aii | 0.86 | 2.27 | 3.100 (9) | 162 |
N41—H41A···O2A | 0.86 | 2.19 | 3.040 (6) | 168 |
N23—H23A···O2Aiii | 0.90 | 1.87 | 2.761 (5) | 172 |
N23—H23B···O3Aiv | 0.90 | 2.17 | 2.846 (4) | 132 |
N23—H23B···O2B | 0.90 | 2.19 | 2.659 (5) | 112 |
N33—H33A···O3B | 0.90 | 2.15 | 2.633 (5) | 113 |
N33—H33A···O2A | 0.90 | 2.32 | 3.035 (4) | 136 |
N33—H33B···O3Av | 0.90 | 1.85 | 2.746 (4) | 172 |
O1W—H1W···O2Biii | 0.80 (4) | 1.97 (4) | 2.762 (6) | 173 (6) |
O1W—H2W···O3B | 0.84 (5) | 1.92 (6) | 2.740 (6) | 164 (14) |
Symmetry codes: (i) x−1, y+1, z; (ii) −x, y−1/2, −z; (iii) −x+1, y−1/2, −z+1; (iv) x, y, z+1; (v) −x+1, y+1/2, −z. |
Experimental details
Crystal data | |
Chemical formula | C7H7NO2·2C5H9NO2·H2O |
Mr | 385.42 |
Crystal system, space group | Monoclinic, P21 |
Temperature (K) | 293 |
a, b, c (Å) | 9.8171 (6), 10.4167 (11), 10.1713 (12) |
β (°) | 112.078 (9) |
V (Å3) | 963.87 (16) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.10 |
Crystal size (mm) | 0.21 × 0.16 × 0.14 |
Data collection | |
Diffractometer | Nonius MACH3 diffractometer |
Absorption correction | ψ scan (North et al., 1968) |
Tmin, Tmax | 0.965, 0.981 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2117, 1794, 1573 |
Rint | 0.014 |
(sin θ/λ)max (Å−1) | 0.594 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.044, 0.115, 1.09 |
No. of reflections | 1794 |
No. of parameters | 263 |
No. of restraints | 3 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.38, −0.35 |
Absolute structure | By known absolute configuration of a chiral reference molecule |
Computer programs: CAD-4 EXPRESS (Enraf–Nonius, 1994), CAD-4 EXPRESS, XCAD4 (Harms & Wocadlo, 1995), SHELXTL/PC (Bruker, 2000), SHELXTL/PC, ORTEP-3 (Farrugia, 1997), Mercury (Version 1.4.1; Macrae et al., 2006 ) and PLATON (Spek, 2003).
C11—O1B | 1.220 (13) | C22—N23 | 1.491 (5) |
C11—O1A | 1.326 (13) | C31—O3B | 1.245 (5) |
C4—N41 | 1.357 (7) | C31—O3A | 1.251 (5) |
C21—O2B | 1.241 (5) | C32—N33 | 1.505 (5) |
C21—O2A | 1.263 (5) | ||
O2B—C21—C22—N23 | 0.2 (6) | N23—C22—C26—C25' | −6.0 (11) |
O2A—C21—C22—N23 | 179.7 (3) | N23—C22—C26—C25 | 35.5 (6) |
C26—C22—N23—C24 | −18.8 (5) | O3B—C31—C32—N33 | 4.6 (5) |
C22—N23—C24—C25 | −5.5 (6) | O3A—C31—C32—N33 | −175.7 (4) |
C22—N23—C24—C25' | 34.2 (9) | C36—C32—N33—C34 | −18.1 (4) |
N23—C24—C25—C26 | 28.3 (8) | C32—N33—C34—C35 | −7.4 (5) |
N23—C24—C25'—C26 | −35.1 (12) | N33—C34—C35—C36 | 30.2 (5) |
C24—C25'—C26—C22 | 25.5 (14) | C34—C35—C36—C32 | −42.1 (5) |
C24—C25—C26—C22 | −40.1 (8) | N33—C32—C36—C35 | 36.6 (4) |
D—H···A | D—H | H···A | D···A | D—H···A |
O1A—H1A···O1Wi | 0.82 | 1.94 | 2.746 (6) | 170 |
N41—H41B···O1Aii | 0.86 | 2.27 | 3.100 (9) | 162 |
N41—H41A···O2A | 0.86 | 2.19 | 3.040 (6) | 168 |
N23—H23A···O2Aiii | 0.90 | 1.87 | 2.761 (5) | 172 |
N23—H23B···O3Aiv | 0.90 | 2.17 | 2.846 (4) | 132 |
N23—H23B···O2B | 0.90 | 2.19 | 2.659 (5) | 112 |
N33—H33A···O3B | 0.90 | 2.15 | 2.633 (5) | 113 |
N33—H33A···O2A | 0.90 | 2.32 | 3.035 (4) | 136 |
N33—H33B···O3Av | 0.90 | 1.85 | 2.746 (4) | 172 |
O1W—H1W···O2Biii | 0.80 (4) | 1.97 (4) | 2.762 (6) | 173 (6) |
O1W—H2W···O3B | 0.84 (5) | 1.92 (6) | 2.740 (6) | 164 (14) |
Symmetry codes: (i) x−1, y+1, z; (ii) −x, y−1/2, −z; (iii) −x+1, y−1/2, −z+1; (iv) x, y, z+1; (v) −x+1, y+1/2, −z. |
4-Aminobenzoic acid (PABA), a member of the vitamin B family, is a starting material in the manufacture of target esters, salts, folic acid, azo dyes and other organic compounds. It acts as a bacterial cofactor involved in the synthesis of folic acid (Robinson, 1966) and as antagonist to the action of the drug sulfonilamide in competition for essential growth metabolites (Pauling & Hayward, 1964). PABA has proved to be a versatile reagent for structure extension by linear and cyclic hydrogen-bonding associations, through both its carboxylic acid and amine functional groups. As a simple organic molecule which promotes the extension of hydrogen-bonded network structures it has no equal, forming associations with neutral molecules such as 4-nitropyridine N-oxide (Moreno Fuquen et al., 1996), 1,3-dimethyl-2-imidazolidinone (Ueda et al., 1986) and urea (Smith, Baldry et al., 1997), with Lewis bases such as 4-(4-nitrobenzyl)pyridine (Smith, Lynch et al., 1997), and with carboxylic acids such as 2,4,6-trinitrobenzoic acid (Lynch et al., 1992a), (2,4-dichlorophenoxy)acetic acid (Lynch et al., 1992b), 2-(carboxyphenoxy)acetic acid (Byriel et al., 1991) and 3,5-dinitrosalicylic acid (Smith et al., 1995). This property of extension was recognized as a possible tool for promoting co-crystallization, with the aim of designing noncentrosymmetric organic materials (Etter & Frankenbach, 1989). However, among the many reported co-crystals of PABA, only a few have been found to crystallize in noncentrosymmetric space groups (Allen, 2002), the title adduct, (I), being another such case.
Crystallographic studies of the non-proton transfer adducts of amino acids are scarce in the literature (Allen, 2002). Proline is a very important amino acid due to its unique conformation, which may affect the structure of proteins, in particular collagen. Investigations have shown that proline extracted and pulverized from the dehydrated fruit skin of Lonsium domesticum possesses antiplasmodal and antimalarial activity (Yapp et al., 2002). The structure of proline differs sharply from that of the other amino acids, as its side chain is bonded back to the N atom as well as to the Cα atom. Because of the bond to N, proline is technically called an imino (–NH–) acid rather than an amino (–NH2–) acid. This secondary amino acid containing a cyclic structure markedly influences protein architecture. Proline has already been investigated in our laboratory in order to understand conformation and hydrogen-bonding interactions in inorganic or organic acid environments (Anitha et al., 2006; Pandiarajan et al., 2002). Disorder in one of the side-chain C atoms is very common in proline complexes and is also found in the present structure. In continuation of our investigations of proline-containing structures, PABA was crystallized with the amino acid L-proline to give the title monohydrate adduct, (I), and its structural features are presented here.
The molecular structure of (I), which contains one 4-aminobenzoic acid molecule, two L-proline zwitterions and one lattice water molecule in the asymmetric unit, is shown in Fig. 1. The carboxyl plane of the vitamin is twisted from the plane of the aromatic ring through an angle of 8.9 (1)°, which is a characteristic feature found in almost all PABA complexes. The zwitterionic nature of the proline residues is confirmed by the C—O and C—N bond lengths (Table 1). The backbone conformation angles about the C'—Cα bond, Ψ1 and Ψ2, reveal that, in contrast with the observation of Lakshminarayanan et al. (1967), twisting of the carboxyl plane away from the C—N bond is not observed in the present structure. The side-chain conformation angles χ1, χ2, χ3, χ4 and θ of the pyrrolidine ring (Prasad & Vijayan, 1993) in the disordered proline are 35.2 (6) [-6.1 (10)], -39.9 (8) [25.6 (13)], 28.2 (8) [-6.1 (10)], -5.4 (6) [34.1 (9)] and -18.6 (5)°, respectively, for the disordered proline (values in square brackets are for the minor component), and 36.6 (4), -42.1 (4), 30.4 (5), -7.7 (5) and -17.9 (4)°, respectively, for the non-disordered proline residue. The major and minor conformers of the pyrrolidine ring in the disordered proline residue adopt a near-envelope conformation, as indicated by puckering analysis [q2 = 0.378 (7)/0.361 (1) Å and ϕ2 = 80.1 (8)/315.8 (17)°; Cremer & Pople, 1975]. For the non-disordered proline residue, the pyrrolidine ring adopts a twisted conformation, as indicated by puckering analysis [q2 = 0.404 (5) Å and ϕ2 = 82.6 (6)°].
As discussed above, PABA is widely known as a structure extension synthon in supramolecular systems. The most elegant aspect of the present work is found not in the molecular structure but in the crystal packing via hydrogen bonds (Fig. 2). The imino groups (NH2+) of each proline residue are involved in one two-centred and one three-centred hydrogen-bonded interaction (Table 2). Both the amino acid zwitterions form Z2 head-to-tail chains (Suresh & Vijayan, 1983) or a C(5) hydrogen-bonding motif (Etter et al., 1990; Bernstein et al., 1995) parallel to the b axis of the unit cell. Interestingly, these ribbons (zigzag chains) are interconnected through another weak N—H···O hydrogen bond between the two different zwitterions, forming a straight S1 head-to-tail chain (Suresh & Vijayan, 1983) or another C(5) hydrogen-bonding motif along the c axis. The combination of these two primary motifs results in two secondary ring motifs, R42(8) and R44(20) (Fig. 3). This forms an aggregation of prolines parallel to the ac plane of the unit cell. The water O atom acts as acceptor for the carboxyl O atom of the PABA and as donor for the carboxylate O atom of the amino acid, thus connecting PABA and L-proline. Generally, the structure extension of PABA is classified into two types, a `head-to-tail' interaction (head = NH2 and tail = COOH) and a carboxyl dimerization. The latter is not observed here, whereas the former feature is observed in the present structure, leading to the formation of a C(8) graph-set motif extending along the b axis of the unit cell through the weak N—H···O hydrogen bond (Fig. 4).
Fig. 5 shows an overlay of the two proline residues (only the major component of the disordered moiety is shown) in the asymmetric unit, indicating the consistency between the conformations, except for the small deviation in the Cγ atom of the side chain.