Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270106025108/gd3032sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270106025108/gd3032Isup2.hkl |
CCDC reference: 618642
Compound (I), AZO33, was prepared by diazotization of 4-nitroaniline followed by coupling with N,N-(2-carboxyethyl)aniline. N,N-(2-Carboxyethyl)aniline was obtained by alkylation of aniline with methyl-2-bromopropionate, followed by vacuum distillation of N,N-(2-methoxycarbonylethyl)aniline. Basic hydrolysis of this product gave N,N-(2-carboxyethyl)aniline. The synthesis of N,N-(2-carboxyethyl)aniline was carried out as follows. A mixture of aniline (10 g, 0,107 mol) and methyl-3-bromopropionate (44.6 g, 0.268 mol) was heated under reflux for 5 h. During this time, a 9% w/w aqueous NaOH solution (8.6 g, 0.215 mol) was added in portions. After 5 h, the reaction mixture was cooled to room temperature and the pH was adjusted to 7–8. The organic layer was extracted with chloroform, washed with water (3 ×) and dried over sodium sulfate; the solvent was then removed under reduced pressure. The crude product was purified by vacuum distillation. A dense yellow oil was obtained (yield 55%). Spectroscopic analysis: 1H NMR (CDCl3, δ, p.p.m.): 2.563–2.656 (t, 4H, J = 9.4 Hz), 3.600–3.697 (m, 10H), 6.615–6.800 (m, 3H), 7.138–7.277 (m, 2H). The basic hydrolysis of N,N-(2-carboxyethyl)aniline was carried out as follows. To a boiling mixture of N,N-(2-methoxycarbonylethyl)aniline (3.0 g, 0.0126 mol) and ethanol (20 ml) was added a concentrated aqueous KOH solution (2.84 g, 0.0505 mol in 15 ml water) in portions. Boiling was continued for 1 h, adding water in order to keep the volume constant. After 1 h, the solution was cooled to room temperature and acidified with dilute HCl to pH 5. The resulting solution, containing N,N-(2-carboxyethyl)aniline, was used for the subsequent step of diazo-coupling. The procedure for the diazo-coupling is analogous to that we have already described for the synthesis of similar diazo-chromophores (Beltrani et al., 2001). Purification of AZO33 was achieved by recrystallization from glacial acetic acid. The final yield for the diazotization/coupling step is 90% [m.p. 478 K (decomposition)]. Single crystals were obtained by slow evaporation from an ethanol solution. Spectroscopic analysis: 1H NMR (py-d5, δ, p.p.m.): 2.95 (t, 4H, J = 9 Hz), 4.11 (t, 4H, J = 9 Hz), 7.10 (d, 2H, J = 10 Hz), 8.05 (d, 2H, J = 10 Hz), 8.16 (d, 2H, J = 10 Hz), 8.35 (d, 2H, J = 10 Hz).
H atoms of carboxy groups were located in a difference map, and from comparison of the peak heights they were all assigned occupancy 0.5. A l l other H atoms were generated stereochemically. All H atoms were refined using a riding model, with Uiso(H) = Ueq of the carrier atom. Bond lengths in the carboxy groups clearly indicate that they are disordered, as is frequently observed in carboxylic acids (Leiserowitz, 1976). Coherently, H atoms bonded to both O atoms were found in difference Fourier maps [Repetition of first sentence?].
Data collection: COLLECT (Nonius, 2000); cell refinement: DIRAX/LSQ (Duisenberg et al., 2000); data reduction: EVALCCD (Duisenberg et al., 2003); 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 PLATON (Spek, 2003); software used to prepare material for publication: WinGX (Farrugia, 1999).
C18H18N4O6 | F(000) = 1616 |
Mr = 386.36 | Dx = 1.474 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -C 2yc | Cell parameters from 211 reflections |
a = 43.062 (9) Å | θ = 4.4–20.5° |
b = 6.877 (2) Å | µ = 0.11 mm−1 |
c = 11.979 (2) Å | T = 173 K |
β = 101.06 (2)° | Plate, red |
V = 3481.5 (14) Å3 | 0.59 × 0.13 × 0.02 mm |
Z = 8 |
Bruker Nonius KappaCCD area-detector diffractometer | 3584 independent reflections |
Radiation source: fine-focus sealed tube | 1587 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.094 |
Detector resolution: 9 pixels mm-1 | θmax = 26.5°, θmin = 1.9° |
CCD rotation images, thick slices scans | h = −49→53 |
Absorption correction: multi-scan (SADABS; Bruker Nonius, 2002) | k = −8→8 |
Tmin = 0.936, Tmax = 0.998 | l = −14→11 |
10530 measured reflections |
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)] = 0.070 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.168 | H-atom parameters constrained |
S = 1.00 | w = 1/[σ2(Fo2) + (0.0577P)2 + 3.8477P] where P = (Fo2 + 2Fc2)/3 |
3584 reflections | (Δ/σ)max < 0.001 |
253 parameters | Δρmax = 0.41 e Å−3 |
0 restraints | Δρmin = −0.32 e Å−3 |
C18H18N4O6 | V = 3481.5 (14) Å3 |
Mr = 386.36 | Z = 8 |
Monoclinic, C2/c | Mo Kα radiation |
a = 43.062 (9) Å | µ = 0.11 mm−1 |
b = 6.877 (2) Å | T = 173 K |
c = 11.979 (2) Å | 0.59 × 0.13 × 0.02 mm |
β = 101.06 (2)° |
Bruker Nonius KappaCCD area-detector diffractometer | 3584 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker Nonius, 2002) | 1587 reflections with I > 2σ(I) |
Tmin = 0.936, Tmax = 0.998 | Rint = 0.094 |
10530 measured reflections |
R[F2 > 2σ(F2)] = 0.070 | 0 restraints |
wR(F2) = 0.168 | H-atom parameters constrained |
S = 1.00 | Δρmax = 0.41 e Å−3 |
3584 reflections | Δρmin = −0.32 e Å−3 |
253 parameters |
Experimental. Synthesis of N,N-(2-carboxyethyl)aniline was carried out as follows. A mixture of aniline (10 g, 0,107 mol) and methyl-3-bromopropionate (44.6 g, 0.268 mol) was heated under reflux for 5 h. During this time, a 9% w/w aqueous NaOH solution (8.6 g, 0.215 mol) was added in portions. After 5 h, the reaction mixture was cooled to room temperature and the pH was adjusted to 7–8. The organic layer was extracted with chloroform, washed with water (3 ×) and dried over sodium sulfate; the solvent was then removed under reduced pressure. The crude product was purified by vacuum distillation. A dense yellow oil was obtained (yield 55%). Spectroscopic analysis: 1H NMR (CDCl3, δ, p.p.m.): 2.563–2.656 (t, 4H, J = 9.4 Hz), 3.600–3.697 (m, 10 H), 6.615–6.800 (m, 3H), 7.138–7.277 (m, 2H). The basic hydrolysis of N,N-(2-carboxyethyl)aniline was carried out as follows. To a boiling mixture of N,N-(2-methoxycarbonylethyl)aniline (3.0 g, 0.0126 mol) and ethanol (20 ml) was added a concentrated aqueous KOH solution (2.84 g, 0.0505 mol in 15 ml water) in portions. Boiling was continued for 1 h, adding water in order to keep the volume constant. After 1 h, the solution was cooled to room temperature and acidified with dilute HCl to pH 5. The resulting solution, containing N,N-(2-carboxyethyl)aniline, was used for the subsequent step of diazo-coupling. Reflections corresponding to lattice centring were not collected. |
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. The two carboxy groups show positional disorder, as frequently observed in carboxylic acids. Coherently, H atoms bonded to both O atoms of each carboxy group were found in difmaps. These H atoms were given 0.5 occupation factors. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
O1 | 0.01007 (7) | −0.0894 (4) | 0.1182 (2) | 0.0390 (8) | |
H1 | −0.0088 | −0.1274 | 0.0696 | 0.039* | 0.50 |
O2 | 0.03182 (6) | −0.3683 (4) | 0.1889 (2) | 0.0297 (7) | |
H2 | 0.0165 | −0.4329 | 0.1505 | 0.030* | 0.50 |
O3 | 0.01969 (6) | 0.4341 (4) | 0.4066 (2) | 0.0278 (7) | |
H3 | 0.0241 | 0.7953 | 0.4540 | 0.028* | 0.50 |
O4 | 0.04194 (6) | 0.7170 (4) | 0.4715 (2) | 0.0290 (7) | |
H4 | 0.0008 | 0.5076 | 0.3738 | 0.029* | 0.50 |
O5 | 0.35384 (7) | 0.3396 (4) | 0.1195 (3) | 0.0394 (8) | |
O6 | 0.36873 (6) | 0.2595 (4) | 0.2972 (3) | 0.0364 (8) | |
N1 | 0.08170 (7) | 0.2331 (5) | 0.3295 (3) | 0.0217 (8) | |
N2 | 0.20142 (8) | 0.3235 (5) | 0.2152 (3) | 0.0345 (10) | |
N3 | 0.22341 (8) | 0.3437 (5) | 0.2990 (3) | 0.0328 (9) | |
N4 | 0.34840 (8) | 0.3069 (5) | 0.2144 (3) | 0.0276 (9) | |
C1 | 0.03202 (9) | −0.1835 (6) | 0.1786 (3) | 0.0222 (9) | |
C2 | 0.06040 (8) | −0.0771 (5) | 0.2420 (3) | 0.0231 (10) | |
H2A | 0.0786 | −0.1028 | 0.2044 | 0.023* | |
H2B | 0.0658 | −0.1300 | 0.3202 | 0.023* | |
C3 | 0.05593 (8) | 0.1424 (6) | 0.2490 (3) | 0.0240 (10) | |
H3A | 0.0549 | 0.2002 | 0.1727 | 0.024* | |
H3B | 0.0356 | 0.1694 | 0.2729 | 0.024* | |
C4 | 0.04342 (9) | 0.5348 (6) | 0.4536 (3) | 0.0216 (10) | |
C5 | 0.07482 (8) | 0.4407 (6) | 0.4929 (3) | 0.0227 (10) | |
H5A | 0.0791 | 0.4362 | 0.5770 | 0.023* | |
H5B | 0.0913 | 0.5239 | 0.4698 | 0.023* | |
C6 | 0.07828 (8) | 0.2362 (5) | 0.4487 (3) | 0.0206 (9) | |
H6A | 0.0971 | 0.1739 | 0.4958 | 0.021* | |
H6B | 0.0595 | 0.1588 | 0.4568 | 0.021* | |
C7 | 0.11077 (8) | 0.2644 (6) | 0.3023 (3) | 0.0220 (10) | |
C8 | 0.13664 (9) | 0.3289 (5) | 0.3850 (4) | 0.0245 (10) | |
H8 | 0.1336 | 0.3562 | 0.4599 | 0.025* | |
C9 | 0.16615 (9) | 0.3528 (5) | 0.3588 (4) | 0.0268 (11) | |
H9 | 0.1833 | 0.3944 | 0.4159 | 0.027* | |
C10 | 0.17103 (9) | 0.3164 (6) | 0.2489 (4) | 0.0273 (11) | |
C11 | 0.14567 (9) | 0.2621 (6) | 0.1659 (4) | 0.0287 (10) | |
H11 | 0.1487 | 0.2436 | 0.0901 | 0.029* | |
C12 | 0.11621 (9) | 0.2344 (6) | 0.1906 (3) | 0.0244 (10) | |
H12 | 0.0992 | 0.1946 | 0.1321 | 0.024* | |
C13 | 0.25448 (10) | 0.3417 (6) | 0.2683 (4) | 0.0310 (11) | |
C14 | 0.27939 (9) | 0.3313 (6) | 0.3582 (4) | 0.0342 (11) | |
H14 | 0.2755 | 0.3315 | 0.4335 | 0.034* | |
C15 | 0.30993 (9) | 0.3205 (6) | 0.3413 (4) | 0.0294 (11) | |
H15 | 0.3271 | 0.3111 | 0.4042 | 0.029* | |
C16 | 0.31542 (9) | 0.3234 (6) | 0.2310 (4) | 0.0251 (10) | |
C17 | 0.29115 (9) | 0.3401 (6) | 0.1380 (4) | 0.0311 (11) | |
H17 | 0.2953 | 0.3452 | 0.0630 | 0.031* | |
C18 | 0.26007 (9) | 0.3494 (6) | 0.1575 (4) | 0.0342 (12) | |
H18 | 0.2428 | 0.3609 | 0.0952 | 0.034* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0315 (17) | 0.0371 (18) | 0.0409 (19) | 0.0002 (16) | −0.0121 (15) | −0.0025 (16) |
O2 | 0.0267 (15) | 0.0260 (18) | 0.0358 (19) | −0.0071 (13) | 0.0045 (13) | −0.0014 (14) |
O3 | 0.0213 (15) | 0.0325 (17) | 0.0291 (17) | 0.0021 (15) | 0.0036 (13) | 0.0004 (14) |
O4 | 0.0288 (16) | 0.0240 (17) | 0.0339 (18) | 0.0060 (13) | 0.0050 (13) | −0.0021 (14) |
O5 | 0.0414 (19) | 0.046 (2) | 0.035 (2) | −0.0041 (15) | 0.0187 (16) | −0.0017 (16) |
O6 | 0.0220 (15) | 0.0404 (19) | 0.044 (2) | 0.0005 (15) | 0.0000 (15) | 0.0062 (16) |
N1 | 0.0167 (17) | 0.0266 (19) | 0.021 (2) | 0.0001 (16) | 0.0025 (15) | −0.0027 (16) |
N2 | 0.040 (2) | 0.021 (2) | 0.040 (2) | 0.0042 (18) | 0.000 (2) | 0.0060 (17) |
N3 | 0.038 (2) | 0.026 (2) | 0.034 (2) | 0.0001 (18) | 0.0059 (19) | 0.0002 (17) |
N4 | 0.024 (2) | 0.021 (2) | 0.039 (2) | −0.0037 (16) | 0.0092 (19) | −0.0007 (18) |
C1 | 0.022 (2) | 0.025 (2) | 0.022 (2) | −0.001 (2) | 0.0088 (18) | −0.001 (2) |
C2 | 0.014 (2) | 0.028 (2) | 0.027 (2) | −0.0050 (19) | 0.0041 (18) | 0.000 (2) |
C3 | 0.017 (2) | 0.032 (2) | 0.024 (2) | −0.0023 (19) | 0.0057 (18) | 0.001 (2) |
C4 | 0.026 (2) | 0.031 (3) | 0.010 (2) | −0.003 (2) | 0.0093 (18) | 0.0003 (19) |
C5 | 0.015 (2) | 0.031 (2) | 0.022 (2) | 0.0011 (19) | 0.0020 (17) | 0.001 (2) |
C6 | 0.0144 (19) | 0.023 (2) | 0.025 (2) | −0.0026 (18) | 0.0041 (17) | −0.0028 (19) |
C7 | 0.017 (2) | 0.018 (2) | 0.031 (3) | 0.0065 (18) | 0.0050 (19) | 0.005 (2) |
C8 | 0.021 (2) | 0.022 (2) | 0.031 (3) | 0.0027 (19) | 0.0057 (19) | 0.002 (2) |
C9 | 0.018 (2) | 0.019 (2) | 0.042 (3) | −0.0013 (18) | 0.002 (2) | 0.001 (2) |
C10 | 0.023 (2) | 0.022 (2) | 0.042 (3) | 0.0057 (19) | 0.018 (2) | 0.004 (2) |
C11 | 0.028 (2) | 0.028 (2) | 0.031 (3) | 0.003 (2) | 0.007 (2) | 0.005 (2) |
C12 | 0.022 (2) | 0.022 (2) | 0.030 (3) | 0.0050 (19) | 0.0065 (19) | 0.005 (2) |
C13 | 0.030 (3) | 0.019 (2) | 0.049 (3) | −0.003 (2) | 0.020 (2) | −0.003 (2) |
C14 | 0.024 (2) | 0.034 (3) | 0.046 (3) | 0.001 (2) | 0.010 (2) | −0.001 (2) |
C15 | 0.023 (2) | 0.028 (3) | 0.038 (3) | −0.001 (2) | 0.006 (2) | 0.002 (2) |
C16 | 0.012 (2) | 0.020 (2) | 0.042 (3) | −0.0004 (18) | 0.0023 (19) | −0.004 (2) |
C17 | 0.025 (2) | 0.028 (3) | 0.038 (3) | −0.002 (2) | 0.002 (2) | −0.002 (2) |
C18 | 0.023 (2) | 0.026 (3) | 0.047 (3) | −0.003 (2) | −0.009 (2) | −0.001 (2) |
O1—C1 | 1.254 (4) | C5—H5A | 0.9900 |
O1—H1 | 0.9421 | C5—H5B | 0.9900 |
O2—C1 | 1.278 (5) | C6—H6A | 0.9900 |
O2—H2 | 0.8543 | C6—H6B | 0.9900 |
O3—C4 | 1.273 (4) | C7—C8 | 1.413 (5) |
O3—H4 | 0.9750 | C7—C12 | 1.418 (5) |
O4—C4 | 1.275 (5) | C8—C9 | 1.376 (5) |
O4—H3 | 0.9275 | C8—H8 | 0.9500 |
O5—N4 | 1.224 (4) | C9—C10 | 1.395 (6) |
O6—N4 | 1.234 (4) | C9—H9 | 0.9500 |
N1—C7 | 1.370 (5) | C10—C11 | 1.380 (5) |
N1—C3 | 1.463 (4) | C11—C12 | 1.370 (5) |
N1—C6 | 1.464 (5) | C11—H11 | 0.9500 |
N2—N3 | 1.248 (4) | C12—H12 | 0.9500 |
N2—C10 | 1.442 (5) | C13—C14 | 1.368 (6) |
N3—C13 | 1.454 (5) | C13—C18 | 1.394 (6) |
N4—C16 | 1.476 (5) | C14—C15 | 1.370 (5) |
C1—C2 | 1.500 (5) | C14—H14 | 0.9500 |
C2—C3 | 1.526 (5) | C15—C16 | 1.386 (6) |
C2—H2A | 0.9900 | C15—H15 | 0.9500 |
C2—H2B | 0.9900 | C16—C17 | 1.379 (5) |
C3—H3A | 0.9900 | C17—C18 | 1.404 (6) |
C3—H3B | 0.9900 | C17—H17 | 0.9500 |
C4—C5 | 1.491 (5) | C18—H18 | 0.9500 |
C5—C6 | 1.520 (5) | ||
C1—O1—H1 | 132.8 | N1—C6—H6B | 109.0 |
C1—O2—H2 | 118.9 | C5—C6—H6B | 109.0 |
C4—O3—H4 | 115.8 | H6A—C6—H6B | 107.8 |
C4—O4—H3 | 126.7 | N1—C7—C8 | 121.1 (4) |
C7—N1—C3 | 121.5 (3) | N1—C7—C12 | 121.7 (3) |
C7—N1—C6 | 119.8 (3) | C8—C7—C12 | 117.2 (3) |
C3—N1—C6 | 116.3 (3) | C9—C8—C7 | 121.1 (4) |
N3—N2—C10 | 111.6 (4) | C9—C8—H8 | 119.5 |
N2—N3—C13 | 112.9 (4) | C7—C8—H8 | 119.5 |
O5—N4—O6 | 124.2 (3) | C8—C9—C10 | 120.4 (4) |
O5—N4—C16 | 118.1 (4) | C8—C9—H9 | 119.8 |
O6—N4—C16 | 117.7 (4) | C10—C9—H9 | 119.8 |
O1—C1—O2 | 123.4 (4) | C11—C10—C9 | 119.1 (4) |
O1—C1—C2 | 119.4 (3) | C11—C10—N2 | 116.3 (4) |
O2—C1—C2 | 117.1 (4) | C9—C10—N2 | 124.5 (4) |
C1—C2—C3 | 114.3 (3) | C12—C11—C10 | 121.3 (4) |
C1—C2—H2A | 108.7 | C12—C11—H11 | 119.3 |
C3—C2—H2A | 108.7 | C10—C11—H11 | 119.3 |
C1—C2—H2B | 108.7 | C11—C12—C7 | 120.7 (4) |
C3—C2—H2B | 108.7 | C11—C12—H12 | 119.6 |
H2A—C2—H2B | 107.6 | C7—C12—H12 | 119.6 |
N1—C3—C2 | 111.7 (3) | C14—C13—C18 | 119.9 (4) |
N1—C3—H3A | 109.3 | C14—C13—N3 | 115.0 (4) |
C2—C3—H3A | 109.3 | C18—C13—N3 | 125.1 (4) |
N1—C3—H3B | 109.3 | C13—C14—C15 | 121.1 (5) |
C2—C3—H3B | 109.3 | C13—C14—H14 | 119.5 |
H3A—C3—H3B | 107.9 | C15—C14—H14 | 119.5 |
O3—C4—O4 | 123.2 (3) | C14—C15—C16 | 118.9 (4) |
O3—C4—C5 | 120.4 (4) | C14—C15—H15 | 120.5 |
O4—C4—C5 | 116.4 (3) | C16—C15—H15 | 120.5 |
C4—C5—C6 | 115.8 (3) | C17—C16—C15 | 122.0 (4) |
C4—C5—H5A | 108.3 | C17—C16—N4 | 119.8 (4) |
C6—C5—H5A | 108.3 | C15—C16—N4 | 118.2 (4) |
C4—C5—H5B | 108.3 | C16—C17—C18 | 117.9 (4) |
C6—C5—H5B | 108.3 | C16—C17—H17 | 121.0 |
H5A—C5—H5B | 107.4 | C18—C17—H17 | 121.0 |
N1—C6—C5 | 112.8 (3) | C13—C18—C17 | 120.1 (4) |
N1—C6—H6A | 109.0 | C13—C18—H18 | 120.0 |
C5—C6—H6A | 109.0 | C17—C18—H18 | 120.0 |
C10—N2—N3—C13 | 177.2 (3) | C9—C10—C11—C12 | −3.1 (6) |
O1—C1—C2—C3 | 14.2 (5) | N2—C10—C11—C12 | 174.4 (4) |
O2—C1—C2—C3 | −166.3 (3) | C10—C11—C12—C7 | 1.2 (6) |
C7—N1—C3—C2 | 76.7 (4) | N1—C7—C12—C11 | −178.5 (4) |
C6—N1—C3—C2 | −85.9 (4) | C8—C7—C12—C11 | 1.8 (5) |
C1—C2—C3—N1 | 168.9 (3) | N2—N3—C13—C14 | −169.8 (4) |
O3—C4—C5—C6 | 14.0 (5) | N2—N3—C13—C18 | 10.2 (5) |
O4—C4—C5—C6 | −167.0 (3) | C18—C13—C14—C15 | −2.6 (6) |
C7—N1—C6—C5 | 82.8 (4) | N3—C13—C14—C15 | 177.4 (4) |
C3—N1—C6—C5 | −114.3 (3) | C13—C14—C15—C16 | 1.0 (6) |
C4—C5—C6—N1 | 74.9 (4) | C14—C15—C16—C17 | 1.1 (6) |
C3—N1—C7—C8 | −171.8 (3) | C14—C15—C16—N4 | −178.5 (4) |
C6—N1—C7—C8 | −9.8 (5) | O5—N4—C16—C17 | 11.5 (5) |
C3—N1—C7—C12 | 8.4 (5) | O6—N4—C16—C17 | −168.0 (4) |
C6—N1—C7—C12 | 170.4 (3) | O5—N4—C16—C15 | −168.9 (3) |
N1—C7—C8—C9 | 177.4 (3) | O6—N4—C16—C15 | 11.7 (5) |
C12—C7—C8—C9 | −2.9 (5) | C15—C16—C17—C18 | −1.6 (6) |
C7—C8—C9—C10 | 1.0 (6) | N4—C16—C17—C18 | 178.1 (3) |
C8—C9—C10—C11 | 2.0 (6) | C14—C13—C18—C17 | 2.0 (6) |
C8—C9—C10—N2 | −175.2 (4) | N3—C13—C18—C17 | −177.9 (4) |
N3—N2—C10—C11 | −169.5 (4) | C16—C17—C18—C13 | 0.0 (6) |
N3—N2—C10—C9 | 7.8 (5) |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O4i | 0.94 | 1.78 | 2.650 (4) | 153 |
O2—H2···O3i | 0.85 | 1.82 | 2.665 (4) | 169 |
O4—H3···O1ii | 0.93 | 1.75 | 2.650 (4) | 163 |
O3—H4···O2ii | 0.98 | 1.69 | 2.665 (4) | 177 |
Symmetry codes: (i) −x, y−1, −z+1/2; (ii) −x, y+1, −z+1/2. |
Experimental details
Crystal data | |
Chemical formula | C18H18N4O6 |
Mr | 386.36 |
Crystal system, space group | Monoclinic, C2/c |
Temperature (K) | 173 |
a, b, c (Å) | 43.062 (9), 6.877 (2), 11.979 (2) |
β (°) | 101.06 (2) |
V (Å3) | 3481.5 (14) |
Z | 8 |
Radiation type | Mo Kα |
µ (mm−1) | 0.11 |
Crystal size (mm) | 0.59 × 0.13 × 0.02 |
Data collection | |
Diffractometer | Bruker Nonius KappaCCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker Nonius, 2002) |
Tmin, Tmax | 0.936, 0.998 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 10530, 3584, 1587 |
Rint | 0.094 |
(sin θ/λ)max (Å−1) | 0.628 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.070, 0.168, 1.00 |
No. of reflections | 3584 |
No. of parameters | 253 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.41, −0.32 |
Computer programs: COLLECT (Nonius, 2000), DIRAX/LSQ (Duisenberg et al., 2000), EVALCCD (Duisenberg et al., 2003), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 2003), WinGX (Farrugia, 1999).
O1—C1 | 1.254 (4) | N1—C3 | 1.463 (4) |
O2—C1 | 1.278 (5) | N1—C6 | 1.464 (5) |
O3—C4 | 1.273 (4) | N2—N3 | 1.248 (4) |
O4—C4 | 1.275 (5) | N2—C10 | 1.442 (5) |
N1—C7 | 1.370 (5) | N3—C13 | 1.454 (5) |
C7—N1—C3 | 121.5 (3) | N2—N3—C13 | 112.9 (4) |
C7—N1—C6 | 119.8 (3) | O1—C1—O2 | 123.4 (4) |
C3—N1—C6 | 116.3 (3) | O3—C4—O4 | 123.2 (3) |
N3—N2—C10 | 111.6 (4) | ||
C10—N2—N3—C13 | 177.2 (3) | O3—C4—C5—C6 | 14.0 (5) |
O1—C1—C2—C3 | 14.2 (5) | C7—N1—C6—C5 | 82.8 (4) |
C7—N1—C3—C2 | 76.7 (4) | C4—C5—C6—N1 | 74.9 (4) |
C1—C2—C3—N1 | 168.9 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O4i | 0.94 | 1.78 | 2.650 (4) | 153.0 |
O2—H2···O3i | 0.85 | 1.82 | 2.665 (4) | 168.8 |
O4—H3···O1ii | 0.93 | 1.75 | 2.650 (4) | 163.0 |
O3—H4···O2ii | 0.98 | 1.69 | 2.665 (4) | 177.4 |
Symmetry codes: (i) −x, y−1, −z+1/2; (ii) −x, y+1, −z+1/2. |
Organic polymers containing push–pull chromophores covalently attached to the polymer chain as side groups are currently of interest in the field of second-order non-linear optics (NLO) (Prasad & Williams, 1991; Dalton et al., 1999; Dalton, 2002). The noncentrosymmetry of the medium, a necessary condition for second-order NLO activity, is achieved in NLO organic polymers by applying a strong electric field above the glass transition temperature of the polymer (poling procedure). The poling procedure, both for the degree of polar order that can be achieved and for its time stability, is one of the most critical issues for the production of efficient NLO polymer materials (Dalton, 2002). Increasing the performance of poling procedures of NLO polymers would require a detailed preliminary knowledge of the local packing modes of the chromophore units. Although the crystal structures of several chromophores have been reported (Eaton et al., 1987; Marder et al., 1989, 1994; Coe et al., 2000; Thallapally et al., 2002), no structural determination of NLO polymeric systems has been reported to date.
Dicarboxylic acids have been studied as model compounds of stereoregular polyolefins (Corradini et al., 1967) and main-chain liquid-crystalline polymers (Centore et al., 1989; Centore & Tuzi, 1998) because of their possible ability to form, in the crystal phase, extended polymer-like rows via hydrogen bonds between carboxy groups. Here, we report the synthesis and crystal structure of the diacid, (I), AZO33, which can be considered a realistic model for the packing of the relevant class of side-chain NLO polymers. It contains the same chromophore group as DR-1, which is one of the standard reference compounds in the field of organic NLO materials (Ricci et al., 2000; Pliška et al., 2000).
The molecular structure of (I) is shown in Fig. 1. The dihedral angle between the mean planes of the phenyl rings is 21.17 (8)°); the geometry around atom N1 is substantially planar. These features are in accordance with the expected π-conjugation of the chromophore group.
In the crystal structure of (I), molecules form extended chains via hydrogen bonds between carboxy groups, thus simulating the covalent chains of a true polymer (Fig. 2). The hydrogen bonding is formed via the hydrogen-bonded dimer, which is typical for carboxylic acids (Leiserowitz, 1976; Steiner, 2002). The rows have geometric (though non-crystallographic) binary screw symmetry with pitch length 2b. In fact, each molecule is hydrogen bonded to two others obtained by C2 rotation coupled with b or −b translation. As can be seen from Fig. 2, consecutive chromophore units along the chain are arranged approximately perpendicular to the chain axis, on opposite sides. Pairs of helices translated by b with respect to each other are wrapped around the twofold crystallographic axes, giving rise to a double-helix pattern (Fig. 3). Within the helix topology, which is of current interest in crystal engineering (Desiraju, 2000; Vishweshwar et al., 2002), the present report is a rare example of an all-organic solvent-free double helix formed by non-covalent aggregates of small molecules (Coupar et al., 1997; Lavender et al., 1999; Glidewell et al., 2005; Mehta et al., 2005).
A projection of the lateral packing is shown in Fig. 4. Owing to the crystallographic binary screw axes halfway between the binary axes along a, double helices identical to that of Fig. 3 and shifted by b/2 are generated. These are packed laterally along a in interdigitated fashion, i.e. in such a way that each lateral group of a double helix fits well into the space between two consecutive chromophore groups of an adjacent double helix. The resulting packing of chromophore groups is rigorously antiparallel, with optimum mean distances of b/2 = 3.439 (1) Å. The double helix does not seem to be stabilized by specific interactions between the atoms of the two wrapped chains, but by the packing mode of the lateral chromophore units.
Some structural aspects found in model compound (I) may be viewed as general features of side-chain NLO polymers. In fact, the perpendicularity of the side chromophore groups with respect to the main chain, and the interdigitated antiparallel packing of Fig. 4, can also optimize excluded-volume effects and dipolar interactions in polymers.