Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536807017217/hb2365sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536807017217/hb2365Isup2.hkl |
CCDC reference: 647600
Equimolecular amounts of 4-phenylpyridine (2.15 mmol, 334 mg) and tartaric acid (324 mg) were mixed in distilled water (20 ml). The reaction mixture was stirred for 6 h at room temperature and monitored by thin-layer chromatography.
After completion of the reaction, the obtained solution was filtered and the filtrate set aside. The deposition of crystals of (I) began after one week. The product was separated by filtration and dried in air.
The water H atoms were located in a difference map. The other H atoms were placed in idealized positions, with O—H = 0.82 Å, C—H = 0.93 Å and N—H = 0.86 Å. All H atoms were refined as riding, with Uiso(H) = 1.2Ueq(C or N) or 1.5Ueq(O).
The synthesis and structure determination of the title compound, (I) [systematic name: 4-phenylpyridinium 3-carboxy-2,3-dihydroxypropanoate dihydrate], were carried out as a part of our project dealing with organic compounds with potential nonlinear-optical, photorefractive and electro-optical properties (Kolev et al., 2005, 2004, 1997).
Compound (I) is attractive from a crystal engineering and supramolecular chemistry point of view because it posseses a non-centrosymmetric structure and large dipole moments (Zyss et al., 1993). Recent theoretical calculations for torsional barriers and nonlinear-optical properties of phenylpyridines (Alyar et al., 2006) revealed that such molecules posses very weak nonlinear optical properties. However, the second-harmonic generation (SHG) of crystalline materials depends on both the magnitude of the molecular hyperpolarizability and the orientation of the molecules in the crystal lattice. Owing to its ability to form multidirectional hydrogen bonds, L-tartaric acid builds acentric crystalline salts with many organic bases (Turkington et al., 2005; Farrell et al., 2002; Guru Row, 1999; Akeroy & Hitchcock, 1993). Moreover, a number of salts of L-tartaric acid and substituted pyridines have been prepared and quantitative measurements showed that those materials are SHG active (Dastidar et al., 1993).
Crystallization from H2O–methanol solutions of an equimolar mixture of 4-phenylpyridine (H4PPN) and L-tartaric acid gives the title compound, (I), in which complete transfer of a single H atom from the acid component to the basic component has occurred. The geometric parameters of both organic molecules are comparable with those reported earlier (Kolev et al., 2004, 2005; Zyss et al., 1993; Turkington et al., 2005). The 4PPN+ cation exhibits an interplanar angle of 34.15 (1)°, comparable with ones found previously in 4PPN-hydrogensquarate and 4PPN-betaine of squaric acid [31.6 (1)° and 28.6 (1)°, respectively].
An extensive hydrogen-bonding network is observed in the structure of (I) (Table 1). The hydrogentartrate (HT) anions are linked by strong bifurcated O41—H41···.(O11, O12) hydrogen bonds to form chains with graph-set symbol C(7)/R21(4) along the a axis. There are two water molecules of crystallization in the structure and both act as bridges between neighbouring HT chains through hydrogen bonding. Each of the water solvent molecules holds three symmetry-related HT molecules to form undulating layers infinite in the a and b directions and stacked along the c direction. The 4PPN cation decorates both sides of the layers taking part in the formation of N21—H21···OW2 hydrogen bond.
The same crystal packing was found for L-tartaric acid 4-dimethilaminopyridine dihydrate, (II) (Dastidar et al., 1993). In (I), similar to the 4-dimethylaminopyridinium cation in (II), the 4PPN anions are superimposed with dipoles in opposite orientations to each other, and consequently no resultant second-order susceptibility Ξ2 could be expected. The only difference is that the cation in (II) is hydrogen-bonded to an HT anion and not to a water molecule as in (I). Nevertheless, both structures crystallize in the orthorhombic P212121 space group with close values for a and b cell parameters [7.305 (2) and 11.850 (2) Å in (I), and 7.321 (1) and 11.846 (1) Å in (II)]. Only the stacking parameter c in (I) is longer, due to the larger cation used [18.165 (3) Å in (I) versus 16.469 (1) Å in (II)]. Taking into consideration the measurements and conclusions made by Dastidar et al., it could be expected that (I) will show similar values for the nonlinear response parameters as (II). It is possible that strong π–π interactions between neighbouring 4PPN anions will improve the SHG activity of (I) [Cg1···Cg2i = 3.668 (2) Å; symmetry code: (i) x - 1/2, -y + 1/2, -z; Cg1 and Cg2 are the centroids of the 4PPN benzyl and pyridine rings, respectively].
For related literature, see: Akeroy & Hitchcock (1993); Alyar et al. (2006); Dastidar et al. (1993); Farrell et al. (2002); Guru Row (1999); Kolev et al. (1997, 2004, 2005); Turkington et al. (2005); Zyss et al. (1993).
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: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Macrae et al., 2006); software used to prepare material for publication: WinGX (Farrugia, 1999).
C11H10N+·C4H5O6−·2H2O | F(000) = 720 |
Mr = 341.31 | Dx = 1.442 Mg m−3 Dm = not meaured Mg m−3 Dm measured by none |
Orthorhombic, P212121 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2ac 2ab | Cell parameters from 22 reflections |
a = 7.3051 (16) Å | θ = 18.1–19.5° |
b = 11.850 (2) Å | µ = 0.12 mm−1 |
c = 18.165 (3) Å | T = 290 K |
V = 1572.5 (5) Å3 | Prism, brown |
Z = 4 | 0.20 × 0.13 × 0.13 mm |
Enraf–Nonius CAD-4 diffractometer | Rint = 0.048 |
Radiation source: fine-focus sealed tube | θmax = 28.0°, θmin = 2.1° |
Graphite monochromator | h = 0→9 |
nonprofiled ω/2θ scans | k = 0→15 |
4241 measured reflections | l = −23→23 |
2180 independent reflections | 3 standard reflections every 120 min |
1406 reflections with I > 2σ(I) | 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)] = 0.045 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.119 | H-atom parameters constrained |
S = 0.94 | w = 1/[σ2(Fo2) + (0.0534P)2 + 0.3826P] where P = (Fo2 + 2Fc2)/3 |
2180 reflections | (Δ/σ)max < 0.001 |
217 parameters | Δρmax = 0.18 e Å−3 |
0 restraints | Δρmin = −0.20 e Å−3 |
C11H10N+·C4H5O6−·2H2O | V = 1572.5 (5) Å3 |
Mr = 341.31 | Z = 4 |
Orthorhombic, P212121 | Mo Kα radiation |
a = 7.3051 (16) Å | µ = 0.12 mm−1 |
b = 11.850 (2) Å | T = 290 K |
c = 18.165 (3) Å | 0.20 × 0.13 × 0.13 mm |
Enraf–Nonius CAD-4 diffractometer | Rint = 0.048 |
4241 measured reflections | 3 standard reflections every 120 min |
2180 independent reflections | intensity decay: none |
1406 reflections with I > 2σ(I) |
R[F2 > 2σ(F2)] = 0.045 | 0 restraints |
wR(F2) = 0.119 | H-atom parameters constrained |
S = 0.94 | Δρmax = 0.18 e Å−3 |
2180 reflections | Δρmin = −0.20 e Å−3 |
217 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 | ||
C1 | −0.0051 (4) | 0.2771 (3) | 0.86282 (19) | 0.0299 (7) | |
C2 | 0.2041 (4) | 0.2727 (3) | 0.86494 (19) | 0.0316 (7) | |
H2 | 0.2412 | 0.2212 | 0.9044 | 0.038* | |
C3 | 0.2900 (4) | 0.3865 (3) | 0.87922 (19) | 0.0321 (8) | |
H3 | 0.2611 | 0.4094 | 0.9297 | 0.039* | |
C4 | 0.4989 (4) | 0.3800 (3) | 0.8712 (2) | 0.0314 (8) | |
C212 | 0.4524 (5) | 0.1070 (3) | 0.4994 (2) | 0.0425 (9) | |
H212 | 0.4797 | 0.0937 | 0.5487 | 0.051* | |
C211 | 0.4563 (6) | 0.0194 (3) | 0.4502 (2) | 0.0475 (10) | |
H211 | 0.4901 | −0.0523 | 0.4658 | 0.057* | |
C210 | 0.4095 (6) | 0.0378 (4) | 0.3768 (2) | 0.0513 (10) | |
H210 | 0.4093 | −0.0218 | 0.3435 | 0.062* | |
C29 | 0.3640 (6) | 0.1439 (3) | 0.3542 (2) | 0.0495 (11) | |
H29 | 0.3332 | 0.1561 | 0.3052 | 0.059* | |
C28 | 0.3629 (5) | 0.2332 (3) | 0.4027 (2) | 0.0422 (9) | |
H28 | 0.3321 | 0.3052 | 0.3864 | 0.051* | |
C27 | 0.4084 (5) | 0.2152 (3) | 0.47646 (18) | 0.0372 (8) | |
C24 | 0.4095 (5) | 0.3097 (3) | 0.52912 (18) | 0.0361 (8) | |
C23 | 0.4631 (5) | 0.4188 (3) | 0.5084 (2) | 0.0415 (9) | |
H23 | 0.5000 | 0.4327 | 0.4603 | 0.050* | |
C22 | 0.4616 (5) | 0.5052 (3) | 0.5587 (2) | 0.0469 (10) | |
H22 | 0.4957 | 0.5777 | 0.5447 | 0.056* | |
C26 | 0.3556 (6) | 0.3821 (4) | 0.6505 (2) | 0.0497 (10) | |
H26 | 0.3179 | 0.3716 | 0.6989 | 0.060* | |
C25 | 0.3547 (5) | 0.2934 (4) | 0.6024 (2) | 0.0453 (10) | |
H25 | 0.3178 | 0.2223 | 0.6182 | 0.054* | |
N21 | 0.4108 (5) | 0.4841 (3) | 0.62782 (18) | 0.0476 (8) | |
H21N | 0.4137 | 0.5384 | 0.6592 | 0.057* | |
O11 | −0.0810 (3) | 0.2321 (2) | 0.81114 (14) | 0.0473 (7) | |
O12 | −0.0837 (3) | 0.3244 (2) | 0.91785 (12) | 0.0418 (6) | |
O21 | 0.2725 (3) | 0.2304 (2) | 0.79728 (14) | 0.0447 (7) | |
H21 | 0.1936 | 0.1919 | 0.7773 | 0.067* | |
O31 | 0.2197 (3) | 0.4688 (2) | 0.83042 (15) | 0.0454 (7) | |
H31 | 0.2690 | 0.5297 | 0.8386 | 0.068* | |
O41 | 0.5784 (3) | 0.3136 (2) | 0.91606 (13) | 0.0426 (6) | |
H41 | 0.6889 | 0.3138 | 0.9080 | 0.064* | |
O42 | 0.5708 (3) | 0.4383 (2) | 0.82451 (16) | 0.0525 (7) | |
OW1 | 0.1312 (4) | 0.0776 (2) | 0.69310 (15) | 0.0504 (7) | |
HW1A | 0.2112 | 0.0176 | 0.6874 | 0.060* | |
HW1B | 0.0527 | 0.0275 | 0.7042 | 0.060* | |
OW2 | 0.3906 (3) | 0.63832 (19) | 0.73677 (14) | 0.0460 (7) | |
HW2A | 0.4742 | 0.6829 | 0.7300 | 0.055* | |
HW2B | 0.3184 | 0.6762 | 0.7245 | 0.055* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0153 (14) | 0.0318 (17) | 0.0427 (19) | −0.0011 (13) | −0.0001 (13) | 0.0067 (16) |
C2 | 0.0168 (14) | 0.0358 (18) | 0.0424 (19) | 0.0002 (14) | 0.0010 (14) | 0.0014 (16) |
C3 | 0.0159 (15) | 0.0396 (18) | 0.0408 (18) | −0.0001 (14) | −0.0007 (14) | −0.0035 (17) |
C4 | 0.0161 (14) | 0.0349 (18) | 0.0433 (19) | −0.0030 (14) | 0.0006 (14) | −0.0080 (17) |
C212 | 0.041 (2) | 0.0417 (19) | 0.045 (2) | −0.0032 (17) | −0.0082 (17) | 0.0096 (17) |
C211 | 0.045 (2) | 0.041 (2) | 0.057 (2) | 0.0001 (19) | −0.0054 (19) | 0.0081 (19) |
C210 | 0.052 (2) | 0.052 (2) | 0.050 (2) | −0.007 (2) | 0.002 (2) | −0.0044 (19) |
C29 | 0.056 (3) | 0.055 (2) | 0.038 (2) | −0.001 (2) | −0.0018 (19) | 0.0077 (19) |
C28 | 0.039 (2) | 0.044 (2) | 0.044 (2) | 0.0032 (18) | −0.0016 (16) | 0.0094 (18) |
C27 | 0.0274 (17) | 0.0424 (19) | 0.0417 (19) | −0.0042 (17) | 0.0001 (16) | 0.0105 (16) |
C24 | 0.0255 (17) | 0.0429 (19) | 0.0398 (18) | 0.0030 (17) | −0.0019 (17) | 0.0047 (16) |
C23 | 0.034 (2) | 0.048 (2) | 0.042 (2) | −0.0019 (17) | 0.0020 (16) | 0.0096 (18) |
C22 | 0.036 (2) | 0.048 (2) | 0.056 (2) | −0.0040 (19) | −0.0011 (18) | 0.004 (2) |
C26 | 0.044 (2) | 0.061 (3) | 0.044 (2) | −0.001 (2) | 0.0032 (18) | 0.004 (2) |
C25 | 0.041 (2) | 0.050 (2) | 0.045 (2) | −0.0041 (18) | 0.0029 (17) | 0.0106 (19) |
N21 | 0.0381 (17) | 0.0514 (19) | 0.053 (2) | −0.0016 (17) | −0.0016 (17) | −0.0049 (16) |
O11 | 0.0208 (12) | 0.0649 (17) | 0.0562 (15) | −0.0020 (13) | −0.0027 (12) | −0.0196 (14) |
O12 | 0.0170 (12) | 0.0671 (17) | 0.0412 (13) | −0.0001 (12) | 0.0002 (11) | −0.0073 (13) |
O21 | 0.0234 (12) | 0.0513 (15) | 0.0594 (15) | −0.0046 (12) | 0.0067 (12) | −0.0217 (14) |
O31 | 0.0244 (13) | 0.0331 (13) | 0.0786 (19) | 0.0017 (11) | −0.0014 (13) | 0.0088 (13) |
O41 | 0.0146 (11) | 0.0641 (16) | 0.0491 (14) | 0.0010 (12) | 0.0007 (11) | 0.0057 (13) |
O42 | 0.0233 (13) | 0.0605 (17) | 0.0738 (19) | −0.0047 (13) | 0.0049 (13) | 0.0210 (15) |
OW1 | 0.0327 (14) | 0.0416 (14) | 0.0770 (18) | 0.0004 (12) | 0.0008 (13) | −0.0104 (14) |
OW2 | 0.0281 (12) | 0.0384 (13) | 0.0716 (17) | −0.0010 (11) | −0.0035 (13) | 0.0132 (12) |
C1—O11 | 1.213 (4) | C28—H28 | 0.9300 |
C1—O12 | 1.282 (4) | C27—C24 | 1.473 (5) |
C1—C2 | 1.530 (4) | C24—C23 | 1.402 (5) |
C2—O21 | 1.419 (4) | C24—C25 | 1.403 (5) |
C2—C3 | 1.510 (5) | C23—C22 | 1.372 (5) |
C2—H2 | 0.9800 | C23—H23 | 0.9300 |
C3—O31 | 1.415 (4) | C22—N21 | 1.333 (5) |
C3—C4 | 1.535 (4) | C22—H22 | 0.9300 |
C3—H3 | 0.9800 | C26—N21 | 1.339 (5) |
C4—O42 | 1.213 (4) | C26—C25 | 1.367 (5) |
C4—O41 | 1.273 (4) | C26—H26 | 0.9300 |
C212—C211 | 1.370 (6) | C25—H25 | 0.9300 |
C212—C27 | 1.386 (5) | N21—H21N | 0.8600 |
C212—H212 | 0.9300 | O21—H21 | 0.8200 |
C211—C210 | 1.394 (6) | O31—H31 | 0.8200 |
C211—H211 | 0.9300 | O41—H41 | 0.8200 |
C210—C29 | 1.363 (6) | OW1—HW1A | 0.9258 |
C210—H210 | 0.9300 | OW1—HW1B | 0.8495 |
C29—C28 | 1.377 (5) | OW2—HW2A | 0.8170 |
C29—H29 | 0.9300 | OW2—HW2B | 0.7278 |
C28—C27 | 1.398 (5) | ||
O11—C1—O12 | 126.2 (3) | C29—C28—C27 | 119.6 (4) |
O11—C1—C2 | 117.4 (3) | C29—C28—H28 | 120.2 |
O12—C1—C2 | 116.3 (3) | C27—C28—H28 | 120.2 |
O21—C2—C3 | 108.6 (3) | C212—C27—C28 | 119.0 (4) |
O21—C2—C1 | 110.0 (3) | C212—C27—C24 | 120.5 (3) |
C3—C2—C1 | 112.9 (3) | C28—C27—C24 | 120.5 (3) |
O21—C2—H2 | 108.4 | C23—C24—C25 | 117.5 (3) |
C3—C2—H2 | 108.4 | C23—C24—C27 | 121.9 (3) |
C1—C2—H2 | 108.4 | C25—C24—C27 | 120.6 (3) |
O31—C3—C2 | 110.9 (3) | C22—C23—C24 | 120.5 (3) |
O31—C3—C4 | 109.6 (3) | C22—C23—H23 | 119.7 |
C2—C3—C4 | 110.6 (3) | C24—C23—H23 | 119.7 |
O31—C3—H3 | 108.5 | N21—C22—C23 | 119.3 (4) |
C2—C3—H3 | 108.5 | N21—C22—H22 | 120.4 |
C4—C3—H3 | 108.5 | C23—C22—H22 | 120.4 |
O42—C4—O41 | 127.0 (3) | N21—C26—C25 | 119.9 (4) |
O42—C4—C3 | 118.0 (3) | N21—C26—H26 | 120.1 |
O41—C4—C3 | 115.0 (3) | C25—C26—H26 | 120.1 |
C211—C212—C27 | 120.6 (3) | C26—C25—C24 | 120.0 (4) |
C211—C212—H212 | 119.7 | C26—C25—H25 | 120.0 |
C27—C212—H212 | 119.7 | C24—C25—H25 | 120.0 |
C212—C211—C210 | 120.1 (4) | C22—N21—C26 | 122.9 (4) |
C212—C211—H211 | 120.0 | C22—N21—H21N | 118.6 |
C210—C211—H211 | 120.0 | C26—N21—H21N | 118.6 |
C29—C210—C211 | 119.4 (4) | C2—O21—H21 | 109.5 |
C29—C210—H210 | 120.3 | C3—O31—H31 | 109.5 |
C211—C210—H210 | 120.3 | C4—O41—H41 | 109.5 |
C210—C29—C28 | 121.3 (4) | HW1A—OW1—HW1B | 85.2 |
C210—C29—H29 | 119.4 | HW2A—OW2—HW2B | 95.5 |
C28—C29—H29 | 119.4 | ||
C23—C22—N21—C26 | −1.9 (6) | C29—C210—C211—C212 | 1.5 (7) |
N21—C22—C23—C24 | 0.9 (6) | C210—C211—C212—C27 | −2.2 (6) |
C22—C23—C24—C25 | 0.1 (5) | C211—C212—C27—C24 | −178.3 (3) |
C22—C23—C24—C27 | 179.6 (3) | C211—C212—C27—C28 | 1.7 (6) |
C23—C24—C25—C26 | −0.2 (5) | O11—C1—C2—O21 | 9.5 (5) |
C27—C24—C25—C26 | −179.7 (4) | O11—C1—C2—C3 | 130.9 (3) |
C23—C24—C27—C28 | −34.9 (6) | O12—C1—C2—O21 | −173.3 (3) |
C23—C24—C27—C212 | 145.1 (4) | O12—C1—C2—C3 | −51.8 (4) |
C25—C24—C27—C28 | 144.6 (4) | O21—C2—C3—O31 | 71.2 (3) |
C25—C24—C27—C212 | −35.4 (6) | O21—C2—C3—C4 | −50.6 (4) |
C24—C25—C26—N21 | −0.8 (6) | C1—C2—C3—O31 | −51.0 (4) |
C25—C26—N21—C22 | 1.9 (6) | C1—C2—C3—C4 | −172.9 (3) |
C24—C27—C28—C29 | 179.5 (4) | O31—C3—C4—O41 | 175.6 (3) |
C212—C27—C28—C29 | −0.5 (6) | O31—C3—C4—O42 | −3.4 (5) |
C27—C28—C29—C210 | −0.3 (6) | C2—C3—C4—O41 | −61.8 (4) |
C211—C210—C29—C28 | −0.2 (7) | C2—C3—C4—O42 | 119.2 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
N21—H21N···OW2 | 0.86 | 1.85 | 2.698 (4) | 169 |
O21—H21···O11 | 0.82 | 2.15 | 2.595 (3) | 114 |
O21—H21···OW1 | 0.82 | 2.09 | 2.815 (3) | 147 |
O31—H31···OW2 | 0.82 | 2.42 | 2.913 (3) | 119 |
O41—H41···O12i | 0.82 | 1.68 | 2.472 (3) | 163 |
OW1—HW1B···O31ii | 0.85 | 2.20 | 2.901 (3) | 140 |
OW1—HW1A···O42iii | 0.93 | 1.86 | 2.750 (4) | 160 |
OW2—HW2A···O21iv | 0.82 | 2.00 | 2.762 (3) | 156 |
OW2—HW2B···O11v | 0.73 | 1.97 | 2.666 (3) | 161 |
Symmetry codes: (i) x+1, y, z; (ii) −x, y−1/2, −z+3/2; (iii) −x+1, y−1/2, −z+3/2; (iv) −x+1, y+1/2, −z+3/2; (v) −x, y+1/2, −z+3/2. |
Experimental details
Crystal data | |
Chemical formula | C11H10N+·C4H5O6−·2H2O |
Mr | 341.31 |
Crystal system, space group | Orthorhombic, P212121 |
Temperature (K) | 290 |
a, b, c (Å) | 7.3051 (16), 11.850 (2), 18.165 (3) |
V (Å3) | 1572.5 (5) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.12 |
Crystal size (mm) | 0.20 × 0.13 × 0.13 |
Data collection | |
Diffractometer | Enraf–Nonius CAD-4 |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 4241, 2180, 1406 |
Rint | 0.048 |
(sin θ/λ)max (Å−1) | 0.660 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.045, 0.119, 0.94 |
No. of reflections | 2180 |
No. of parameters | 217 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.18, −0.20 |
Computer programs: CAD-4 EXPRESS (Enraf–Nonius, 1994), CAD-4 EXPRESS, XCAD4 (Harms & Wocadlo, 1995), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Macrae et al., 2006), WinGX (Farrugia, 1999).
D—H···A | D—H | H···A | D···A | D—H···A |
N21—H21N···OW2 | 0.86 | 1.85 | 2.698 (4) | 169 |
O21—H21···O11 | 0.82 | 2.15 | 2.595 (3) | 114 |
O21—H21···OW1 | 0.82 | 2.09 | 2.815 (3) | 147 |
O31—H31···OW2 | 0.82 | 2.42 | 2.913 (3) | 119 |
O41—H41···O12i | 0.82 | 1.68 | 2.472 (3) | 163 |
OW1—HW1B···O31ii | 0.85 | 2.20 | 2.901 (3) | 140 |
OW1—HW1A···O42iii | 0.93 | 1.86 | 2.750 (4) | 160 |
OW2—HW2A···O21iv | 0.82 | 2.00 | 2.762 (3) | 156 |
OW2—HW2B···O11v | 0.73 | 1.97 | 2.666 (3) | 161 |
Symmetry codes: (i) x+1, y, z; (ii) −x, y−1/2, −z+3/2; (iii) −x+1, y−1/2, −z+3/2; (iv) −x+1, y+1/2, −z+3/2; (v) −x, y+1/2, −z+3/2. |
The synthesis and structure determination of the title compound, (I) [systematic name: 4-phenylpyridinium 3-carboxy-2,3-dihydroxypropanoate dihydrate], were carried out as a part of our project dealing with organic compounds with potential nonlinear-optical, photorefractive and electro-optical properties (Kolev et al., 2005, 2004, 1997).
Compound (I) is attractive from a crystal engineering and supramolecular chemistry point of view because it posseses a non-centrosymmetric structure and large dipole moments (Zyss et al., 1993). Recent theoretical calculations for torsional barriers and nonlinear-optical properties of phenylpyridines (Alyar et al., 2006) revealed that such molecules posses very weak nonlinear optical properties. However, the second-harmonic generation (SHG) of crystalline materials depends on both the magnitude of the molecular hyperpolarizability and the orientation of the molecules in the crystal lattice. Owing to its ability to form multidirectional hydrogen bonds, L-tartaric acid builds acentric crystalline salts with many organic bases (Turkington et al., 2005; Farrell et al., 2002; Guru Row, 1999; Akeroy & Hitchcock, 1993). Moreover, a number of salts of L-tartaric acid and substituted pyridines have been prepared and quantitative measurements showed that those materials are SHG active (Dastidar et al., 1993).
Crystallization from H2O–methanol solutions of an equimolar mixture of 4-phenylpyridine (H4PPN) and L-tartaric acid gives the title compound, (I), in which complete transfer of a single H atom from the acid component to the basic component has occurred. The geometric parameters of both organic molecules are comparable with those reported earlier (Kolev et al., 2004, 2005; Zyss et al., 1993; Turkington et al., 2005). The 4PPN+ cation exhibits an interplanar angle of 34.15 (1)°, comparable with ones found previously in 4PPN-hydrogensquarate and 4PPN-betaine of squaric acid [31.6 (1)° and 28.6 (1)°, respectively].
An extensive hydrogen-bonding network is observed in the structure of (I) (Table 1). The hydrogentartrate (HT) anions are linked by strong bifurcated O41—H41···.(O11, O12) hydrogen bonds to form chains with graph-set symbol C(7)/R21(4) along the a axis. There are two water molecules of crystallization in the structure and both act as bridges between neighbouring HT chains through hydrogen bonding. Each of the water solvent molecules holds three symmetry-related HT molecules to form undulating layers infinite in the a and b directions and stacked along the c direction. The 4PPN cation decorates both sides of the layers taking part in the formation of N21—H21···OW2 hydrogen bond.
The same crystal packing was found for L-tartaric acid 4-dimethilaminopyridine dihydrate, (II) (Dastidar et al., 1993). In (I), similar to the 4-dimethylaminopyridinium cation in (II), the 4PPN anions are superimposed with dipoles in opposite orientations to each other, and consequently no resultant second-order susceptibility Ξ2 could be expected. The only difference is that the cation in (II) is hydrogen-bonded to an HT anion and not to a water molecule as in (I). Nevertheless, both structures crystallize in the orthorhombic P212121 space group with close values for a and b cell parameters [7.305 (2) and 11.850 (2) Å in (I), and 7.321 (1) and 11.846 (1) Å in (II)]. Only the stacking parameter c in (I) is longer, due to the larger cation used [18.165 (3) Å in (I) versus 16.469 (1) Å in (II)]. Taking into consideration the measurements and conclusions made by Dastidar et al., it could be expected that (I) will show similar values for the nonlinear response parameters as (II). It is possible that strong π–π interactions between neighbouring 4PPN anions will improve the SHG activity of (I) [Cg1···Cg2i = 3.668 (2) Å; symmetry code: (i) x - 1/2, -y + 1/2, -z; Cg1 and Cg2 are the centroids of the 4PPN benzyl and pyridine rings, respectively].