The structures of 4-dimethylamino-β-nitrostyrene (DANS), C10H12N2O2, and 4-dimethylamino-β-ethyl-β-nitrostyrene (DAENS), C12H16N2O2, have been solved at T = 100 K. The structure solution for DANS was complicated by the presence of a static disorder, characterized by a misorientation of 17% of the molecules. The molecule of DANS is almost planar, indicating significant conjugation, with a push–pull effect through the styrene skeleton extending up to the terminal substituents and enhancing the dipole moment. As a consequence of this conjugation, the hexagonal ring displays a quinoidal character; the lengths of the C—N [1.3595 (15) Å] and C—C [1.448 (2) Å] bonds adjacent to the benzene ring are shorter than single bonds. The molecules are stacked in dimers with antiparallel dipoles. In contrast, the molecule of DAENS is not planar. The ethyl substituent pushes the nitropropene group out of the benzene plane, with a torsion angle of −21.9 (3). Nevertheless, the molecule remains conjugated, with a shortening of the same bonds as in DANS.
Supporting information
CCDC references: 621286; 621287
The synthesis of both materials consists of the condensation of
4-dimethylaminobenzaldehyde (DABA) with a nitroolefine. To obtain (I), a
mixture of DABA (0.01 mol) with nitromethane (0.03 mol) was used at 373 K,
with a few drops of butylamine. For (II), the synthesis begins with the
condensation of DABA with butylamine to obtain the 4-dimethylaminobenzylidene
butylamine. After separation, this butylamine reacts with nitromethane in the
presence of acetic acid to give the nitrostyrene. Single crystals of (I) were
grown by slow evaporation of solution in toluene. Single crystals of (II) were
obtained from a saturated solution in ethanol prepared at room temparature and
slowly evaporated in a refrigerator [m.p. 390 K for (I) and 361 K for (II)].
The structure of (I) was first refined without consideration of any static
disorder, giving a final R = 0.067 and Δρmax = 1.19 e Å-3.
Fourier difference maps clearly reveal two peaks on both sides of the
ethylenic C71═C81 double bond and approximately equidistant from it. These
two peaks were interpreted as C atoms of the ethylenic double bond belonging
to a second misoriented molecule of (I). The occupancy ratio was initially set
to 0.85:0.15 for both disordered molecules and was refined at each refinement
step. Geometric soft restraints were simultaneously applied on distances and
angles of the disordered moieties, according to values found from density
functional theory quantum chemistry calculations. For the final cycles of
refinement, only the most probable molecule was refined anisotropically, and
an equivalent isotropic displacement parameter was assigned for the atoms of
the misoriented molecule. All H atoms were located geometrically and treated
as riding, with C—H = 1.00 Å, and refined isotropically using equivalence
constraints.
Data collection: SMART (Bruker, 2001) for (I); COLLECT (Nonius, 2000) for (II). Cell refinement: SMART for (I); DIRAX (Duisenberg et al., 2000) for (II). Data reduction: SAINT (Bruker, 2001) for (I); EVALCCD (Duisenberg et al., 2003) for (II). For both compounds, program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Watkin et al., 2001); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: CRYSTALS.
(I) 4-dimethyamino-
β-nitrostyrene
top
Crystal data top
C10H12N2O2 | Dx = 1.368 Mg m−3 |
Mr = 192.22 | Melting point: 390 K |
OrthorhombicPbca | Mo Kα radiation, λ = 0.71073 Å |
a = 10.1460 (2) Å | Cell parameters from 5978 reflections |
b = 7.3091 (2) Å | θ = 2.6–27.5° |
c = 25.1662 (7) Å | µ = 0.10 mm−1 |
V = 1866.28 (8) Å3 | T = 100 K |
Z = 8 | Plate, dark red |
F(000) = 816.02 | 0.26 × 0.18 × 0.16 mm |
Data collection top
Bruker APEXII diffractometer | 2137 independent reflections |
Radiation source: X-ray tube | 1488 reflections with I > 2σ(I) |
Horizontally mounted graphite crystal monochromator | Rint = 0.032 |
CCD rotation images, thick slices scans | θmax = 27.5°, θmin = 2.6° |
Absorption correction: multi-scan (SADABS; Sheldrick, 2002) | h = −13→9 |
Tmin = 0.975, Tmax = 0.985 | k = −9→9 |
20691 measured reflections | l = −32→30 |
Refinement top
Refinement on F | 60 restraints |
Least-squares matrix: full | H-atom parameters constrained |
R[F2 > 2σ(F2)] = 0.033 | Prince (1982) modified Chebychev polynomial with five
parameters (Watkin, 1994): 1.34 1.99 1.39 0.636 0.244 |
wR(F2) = 0.037 | (Δ/σ)max = 0.001 |
S = 1.17 | Δρmax = 0.22 e Å−3 |
1488 reflections | Δρmin = −0.21 e Å−3 |
161 parameters | |
Crystal data top
C10H12N2O2 | V = 1866.28 (8) Å3 |
Mr = 192.22 | Z = 8 |
OrthorhombicPbca | Mo Kα radiation |
a = 10.1460 (2) Å | µ = 0.10 mm−1 |
b = 7.3091 (2) Å | T = 100 K |
c = 25.1662 (7) Å | 0.26 × 0.18 × 0.16 mm |
Data collection top
Bruker APEXII diffractometer | 2137 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2002) | 1488 reflections with I > 2σ(I) |
Tmin = 0.975, Tmax = 0.985 | Rint = 0.032 |
20691 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.033 | 60 restraints |
wR(F2) = 0.037 | H-atom parameters constrained |
S = 1.17 | Δρmax = 0.22 e Å−3 |
1488 reflections | Δρmin = −0.21 e Å−3 |
161 parameters | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
O11 | 0.30077 (12) | 0.52197 (19) | 0.33507 (6) | 0.0344 | 0.830 (3) |
O12 | 0.3140 (7) | 0.5475 (9) | 0.3566 (3) | 0.0208 (9)* | 0.170 (3) |
O21 | 0.46427 (19) | 0.7099 (3) | 0.34689 (6) | 0.0335 | 0.830 (3) |
O22 | 0.4803 (10) | 0.7212 (14) | 0.3351 (3) | 0.0208 (9)* | 0.170 (3) |
N1 | 0.39672 (10) | 0.73485 (14) | 0.67920 (4) | 0.0208 | |
N21 | 0.37398 (16) | 0.6127 (2) | 0.36439 (5) | 0.0224 | 0.830 (3) |
N22 | 0.4071 (8) | 0.6536 (13) | 0.3677 (3) | 0.0208 (9)* | 0.170 (3) |
C1 | 0.40288 (10) | 0.71801 (15) | 0.62546 (5) | 0.0176 | |
C9 | 0.49764 (12) | 0.83659 (19) | 0.70776 (5) | 0.0251 | |
C10 | 0.30262 (13) | 0.62660 (19) | 0.70947 (5) | 0.0290 | |
C21 | 0.4998 (3) | 0.8158 (4) | 0.59644 (7) | 0.0170 | 0.830 (3) |
C22 | 0.4936 (15) | 0.796 (3) | 0.5895 (4) | 0.0208 (9)* | 0.170 (3) |
C31 | 0.50576 (15) | 0.8036 (2) | 0.54137 (6) | 0.0169 | 0.830 (3) |
C32 | 0.4733 (9) | 0.7724 (14) | 0.5363 (3) | 0.0208 (9)* | 0.170 (3) |
C41 | 0.41664 (14) | 0.6977 (2) | 0.51173 (5) | 0.0164 | 0.830 (3) |
C42 | 0.3747 (8) | 0.6570 (12) | 0.5184 (2) | 0.0208 (9)* | 0.170 (3) |
C51 | 0.32284 (15) | 0.5975 (2) | 0.54076 (6) | 0.0181 | 0.830 (3) |
C52 | 0.2905 (8) | 0.5712 (12) | 0.5539 (3) | 0.0208 (9)* | 0.170 (3) |
C61 | 0.31540 (19) | 0.6071 (3) | 0.59517 (6) | 0.0190 | 0.830 (3) |
C62 | 0.3010 (12) | 0.600 (2) | 0.6069 (3) | 0.0208 (9)* | 0.170 (3) |
C71 | 0.42780 (13) | 0.69515 (19) | 0.45437 (6) | 0.0185 | 0.830 (3) |
C72 | 0.3606 (7) | 0.6261 (9) | 0.4620 (2) | 0.0208 (9)* | 0.170 (3) |
C81 | 0.35170 (14) | 0.6022 (2) | 0.42047 (5) | 0.0209 | 0.830 (3) |
C82 | 0.4317 (6) | 0.7008 (9) | 0.4228 (3) | 0.0208 (9)* | 0.170 (3) |
H91 | 0.4775 | 0.8344 | 0.7467 | 0.0336 (13)* | |
H92 | 0.4988 | 0.9661 | 0.6949 | 0.0336 (13)* | |
H93 | 0.5857 | 0.7793 | 0.7014 | 0.0336 (13)* | |
H101 | 0.3117 | 0.6558 | 0.7481 | 0.0336 (13)* | |
H102 | 0.3204 | 0.4935 | 0.7037 | 0.0336 (13)* | |
H103 | 0.2111 | 0.6562 | 0.6974 | 0.0336 (13)* | |
H211 | 0.5664 | 0.8932 | 0.6152 | 0.0336 (13)* | 0.830 (3) |
H221 | 0.5676 | 0.8740 | 0.6030 | 0.0336 (13)* | 0.170 (3) |
H311 | 0.5746 | 0.8736 | 0.5215 | 0.0336 (13)* | 0.830 (3) |
H321 | 0.5337 | 0.8341 | 0.5104 | 0.0336 (13)* | 0.170 (3) |
H511 | 0.2596 | 0.5161 | 0.5215 | 0.0336 (13)* | 0.830 (3) |
H521 | 0.2223 | 0.4843 | 0.5403 | 0.0336 (13)* | 0.170 (3) |
H611 | 0.2467 | 0.5356 | 0.6147 | 0.0336 (13)* | 0.830 (3) |
H621 | 0.2381 | 0.5417 | 0.6324 | 0.0336 (13)* | 0.170 (3) |
H710 | 0.5000 | 0.7717 | 0.4389 | 0.0336 (13)* | 0.830 (3) |
H720 | 0.2860 | 0.5379 | 0.4577 | 0.0336 (13)* | 0.170 (3) |
H810 | 0.2784 | 0.5243 | 0.4345 | 0.0341 (13)* | 0.830 (3) |
H820 | 0.5017 | 0.7921 | 0.4316 | 0.0341 (13)* | 0.170 (3) |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O11 | 0.0339 (6) | 0.0466 (8) | 0.0226 (6) | 0.0082 (6) | −0.0108 (5) | −0.0140 (6) |
O21 | 0.0434 (9) | 0.0364 (7) | 0.0208 (8) | 0.0020 (7) | 0.0042 (7) | 0.0038 (7) |
N1 | 0.0201 (5) | 0.0233 (5) | 0.0190 (5) | −0.0020 (4) | 0.0023 (4) | 0.0010 (4) |
N21 | 0.0250 (9) | 0.0241 (9) | 0.0180 (6) | 0.0082 (7) | −0.0032 (5) | −0.0010 (5) |
C1 | 0.0167 (5) | 0.0149 (5) | 0.0211 (5) | 0.0042 (4) | −0.0023 (4) | −0.0004 (4) |
C9 | 0.0262 (6) | 0.0323 (7) | 0.0167 (6) | −0.0011 (5) | −0.0023 (4) | −0.0019 (5) |
C10 | 0.0277 (6) | 0.0286 (6) | 0.0307 (7) | 0.0006 (6) | 0.0085 (5) | 0.0090 (6) |
C21 | 0.0193 (7) | 0.0159 (10) | 0.0159 (8) | −0.0002 (6) | −0.0023 (7) | −0.0027 (7) |
C31 | 0.0176 (8) | 0.0167 (8) | 0.0163 (7) | −0.0006 (5) | −0.0038 (5) | −0.0014 (5) |
C41 | 0.0176 (7) | 0.0144 (7) | 0.0173 (7) | 0.0035 (5) | −0.0037 (5) | −0.0016 (5) |
C51 | 0.0164 (7) | 0.0159 (7) | 0.0219 (8) | −0.0005 (6) | −0.0047 (6) | −0.0020 (6) |
C61 | 0.0160 (8) | 0.0165 (7) | 0.0245 (9) | 0.0002 (6) | −0.0015 (7) | 0.0007 (8) |
C71 | 0.0195 (7) | 0.0174 (6) | 0.0187 (8) | 0.0040 (5) | −0.0012 (5) | 0.0006 (5) |
C81 | 0.0206 (7) | 0.0242 (7) | 0.0178 (7) | 0.0057 (6) | −0.0017 (5) | −0.0012 (5) |
Geometric parameters (Å, º) top
O11—N21 | 1.2394 (19) | C22—H221 | 1.000 |
O12—N22 | 1.254 (7) | C31—C41 | 1.4045 (17) |
O21—N21 | 1.240 (2) | C31—H311 | 1.000 |
O22—N22 | 1.213 (7) | C32—C42 | 1.383 (8) |
N1—C1 | 1.3595 (15) | C32—H321 | 1.000 |
N1—C9 | 1.4554 (15) | C41—C51 | 1.4057 (19) |
N1—C10 | 1.4554 (15) | C41—C71 | 1.448 (2) |
N21—C81 | 1.4313 (19) | C42—C52 | 1.386 (7) |
N22—C82 | 1.449 (8) | C42—C72 | 1.446 (7) |
C1—C21 | 1.418 (2) | C51—C61 | 1.373 (2) |
C1—C22 | 1.413 (8) | C51—H511 | 1.000 |
C1—C61 | 1.423 (2) | C52—C62 | 1.353 (8) |
C1—C62 | 1.425 (8) | C52—H521 | 1.000 |
C9—H91 | 1.000 | C61—H611 | 1.000 |
C9—H92 | 1.000 | C62—H621 | 1.000 |
C9—H93 | 1.000 | C71—C81 | 1.336 (2) |
C10—H101 | 1.000 | C71—H710 | 1.000 |
C10—H102 | 1.000 | C72—C82 | 1.338 (7) |
C10—H103 | 1.000 | C72—H720 | 1.000 |
C21—C31 | 1.390 (2) | C81—H810 | 1.000 |
C21—H211 | 1.000 | C82—H820 | 1.000 |
C22—C32 | 1.367 (9) | | |
| | | |
C1—N1—C9 | 120.35 (10) | C22—C32—C42 | 120.4 (5) |
C1—N1—C10 | 120.11 (10) | C22—C32—H321 | 119.118 |
C9—N1—C10 | 118.73 (10) | C42—C32—H321 | 120.437 |
O21—N21—O11 | 122.53 (15) | C31—C41—C51 | 116.55 (12) |
O21—N21—C81 | 119.86 (16) | C31—C41—C71 | 119.10 (13) |
O11—N21—C81 | 117.61 (16) | C51—C41—C71 | 124.35 (13) |
O12—N22—O22 | 124.1 (7) | C32—C42—C52 | 120.8 (5) |
O12—N22—C82 | 119.4 (6) | C32—C42—C72 | 119.1 (5) |
O22—N22—C82 | 116.5 (6) | C52—C42—C72 | 120.1 (6) |
N1—C1—C21 | 119.90 (11) | C41—C51—C61 | 121.93 (13) |
N1—C1—C61 | 123.75 (11) | C41—C51—H511 | 119.521 |
C21—C1—C61 | 116.34 (12) | C61—C51—H511 | 118.547 |
N1—C9—H91 | 109.359 | C42—C52—C62 | 121.1 (5) |
N1—C9—H92 | 109.436 | C42—C52—H521 | 119.452 |
H91—C9—H92 | 109.476 | C62—C52—H521 | 119.447 |
N1—C9—H93 | 109.603 | C1—C61—C51 | 121.91 (13) |
H91—C9—H93 | 109.477 | C1—C61—H611 | 118.025 |
H92—C9—H93 | 109.476 | C51—C61—H611 | 120.059 |
N1—C10—H101 | 109.432 | C1—C62—H621 | 120.637 |
N1—C10—H102 | 109.509 | C52—C62—H621 | 121.063 |
H101—C10—H102 | 109.476 | C41—C71—C81 | 126.72 (14) |
N1—C10—H103 | 109.459 | C41—C71—H710 | 115.910 |
H101—C10—H103 | 109.475 | C81—C71—H710 | 117.371 |
H102—C10—H103 | 109.476 | C42—C72—C82 | 127.4 (5) |
C1—C21—C31 | 120.75 (13) | C42—C72—H720 | 106.341 |
C1—C21—H211 | 120.733 | C82—C72—H720 | 126.283 |
C31—C21—H211 | 118.502 | N21—C81—C71 | 120.71 (14) |
C1—C22—C32 | 118.5 (6) | N21—C81—H810 | 119.680 |
C1—C22—H221 | 120.062 | C71—C81—H810 | 119.605 |
C32—C22—H221 | 121.316 | N22—C82—C72 | 121.0 (4) |
C21—C31—C41 | 122.46 (13) | N22—C82—H820 | 119.649 |
C21—C31—H311 | 119.781 | C72—C82—H820 | 119.384 |
C41—C31—H311 | 117.752 | | |
| | | |
C51—C41—C71—C81 | 1.148 | C71—C81—N21—O21 | −0.427 |
C31—C41—C71—C81 | −179.887 | C21—C1—N1—C9 | −6.750 |
C41—C71—C81—N21 | 179.863 | C61—C1—N1—C10 | 4.305 |
C71—C81—N21—O11 | 179.363 | | |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
C9—H91···O21i | 1.00 | 2.55 | 3.534 (2) | 169 |
C9—H93···O11ii | 1.00 | 2.78 | 3.419 (2) | 122 |
C10—H101···O11iii | 1.00 | 2.79 | 3.503 (2) | 129 |
Symmetry codes: (i) x, −y+3/2, z+1/2; (ii) x+1/2, −y+3/2, −z+1; (iii) −x+1/2, −y+1, z+1/2. |
(II) 4-dimethyamino-
β-ethyl-
β-nitrostyrene
top
Crystal data top
C12H16N2O2 | Dx = 1.255 Mg m−3 |
Mr = 220.27 | Melting point: 385 K |
OrthorhombicP212121 | Mo Kα radiation, λ = 0.71073 Å |
a = 5.9641 (1) Å | Cell parameters from 5243 reflections |
b = 8.4492 (1) Å | θ = 2.9–35.0° |
c = 23.1400 (4) Å | µ = 0.09 mm−1 |
V = 1166.07 (3) Å3 | T = 100 K |
Z = 4 | Plate, yellow |
F(000) = 472.00 | 0.45 × 0.34 × 0.28 mm |
Data collection top
Nonius KappaCCD area-detector diffractometer | 5077 independent reflections |
Radiation source: X-ray tube | 2017 reflections with I > 3σ(I) |
Horizontally mounted graphite crystal monochromator | Rint = 0.04 |
CCD scans | θmax = 35.0°, θmin = 3.5° |
Absorption correction: multi-scan (SADABS; Sheldrick, 2002) | h = −5→9 |
Tmin = 0.962, Tmax = 0.976 | k = −13→12 |
14807 measured reflections | l = −32→37 |
Refinement top
Refinement on F | H-atom parameters constrained |
Least-squares matrix: full | Prince (1982) modified Chebychev polynomial with three
parameters (Watkin, 1994): 3.54 -1.10 3.21 |
R[F2 > 2σ(F2)] = 0.038 | (Δ/σ)max = 0.001 |
wR(F2) = 0.039 | Δρmax = 0.28 e Å−3 |
S = 1.14 | Δρmin = −0.22 e Å−3 |
2017 reflections | Absolute structure: Flack (1983), with 3060 Friedel pairs |
148 parameters | Absolute structure parameter: 0.7 (14) |
0 restraints | |
Crystal data top
C12H16N2O2 | V = 1166.07 (3) Å3 |
Mr = 220.27 | Z = 4 |
OrthorhombicP212121 | Mo Kα radiation |
a = 5.9641 (1) Å | µ = 0.09 mm−1 |
b = 8.4492 (1) Å | T = 100 K |
c = 23.1400 (4) Å | 0.45 × 0.34 × 0.28 mm |
Data collection top
Nonius KappaCCD area-detector diffractometer | 5077 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2002) | 2017 reflections with I > 3σ(I) |
Tmin = 0.962, Tmax = 0.976 | Rint = 0.04 |
14807 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.038 | H-atom parameters constrained |
wR(F2) = 0.039 | Δρmax = 0.28 e Å−3 |
S = 1.14 | Δρmin = −0.22 e Å−3 |
2017 reflections | Absolute structure: Flack (1983), with 3060 Friedel pairs |
148 parameters | Absolute structure parameter: 0.7 (14) |
0 restraints | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
O1 | 0.3599 (3) | 0.32618 (17) | 0.74674 (6) | 0.0325 | |
O2 | 0.5309 (3) | 0.44741 (16) | 0.81591 (6) | 0.0338 | |
N1 | 0.3426 (3) | −0.15522 (17) | 1.09331 (7) | 0.0223 | |
N2 | 0.4204 (3) | 0.33512 (18) | 0.79755 (7) | 0.0217 | |
C1 | 0.3607 (3) | −0.06704 (19) | 1.04390 (8) | 0.0179 | |
C2 | 0.5465 (3) | 0.03552 (19) | 1.03515 (8) | 0.0196 | |
C3 | 0.5630 (3) | 0.1231 (2) | 0.98484 (8) | 0.0185 | |
C4 | 0.4058 (3) | 0.11429 (19) | 0.94029 (7) | 0.0168 | |
C5 | 0.2202 (3) | 0.01411 (19) | 0.94958 (8) | 0.0182 | |
C6 | 0.1980 (3) | −0.0745 (2) | 0.99990 (7) | 0.0194 | |
C7 | 0.4393 (3) | 0.21535 (19) | 0.89041 (8) | 0.0177 | |
C8 | 0.3523 (3) | 0.20757 (19) | 0.83686 (8) | 0.0194 | |
C9 | 0.4905 (3) | −0.1280 (2) | 1.14227 (8) | 0.0251 | |
C10 | 0.1492 (3) | −0.2571 (2) | 1.10196 (9) | 0.0277 | |
C11 | 0.1994 (3) | 0.08604 (19) | 0.81058 (8) | 0.0207 | |
C12 | −0.0449 (3) | 0.1401 (2) | 0.80929 (9) | 0.0296 | |
H21 | 0.6648 | 0.0449 | 1.0656 | 0.021 (2)* | |
H31 | 0.6940 | 0.1958 | 0.9802 | 0.021 (2)* | |
H51 | 0.1012 | 0.0069 | 0.9192 | 0.021 (2)* | |
H61 | 0.0643 | −0.1445 | 1.0049 | 0.021 (2)* | |
H71 | 0.5447 | 0.3057 | 0.8968 | 0.021 (2)* | |
H91 | 0.4517 | −0.2030 | 1.1742 | 0.0401 (19)* | |
H92 | 0.4723 | −0.0167 | 1.1562 | 0.0401 (19)* | |
H93 | 0.6494 | −0.1455 | 1.1301 | 0.0401 (19)* | |
H101 | 0.1631 | −0.3121 | 1.1401 | 0.0401 (19)* | |
H102 | 0.0092 | −0.1920 | 1.1015 | 0.0401 (19)* | |
H103 | 0.1425 | −0.3376 | 1.0703 | 0.0401 (19)* | |
H111 | 0.2096 | −0.0136 | 0.8338 | 0.0401 (19)* | |
H112 | 0.2498 | 0.0648 | 0.7701 | 0.0401 (19)* | |
H121 | −0.1393 | 0.0554 | 0.7914 | 0.0401 (19)* | |
H122 | −0.0978 | 0.1609 | 0.8496 | 0.0401 (19)* | |
H123 | −0.0577 | 0.2392 | 0.7859 | 0.0401 (19)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O1 | 0.0423 (9) | 0.0309 (7) | 0.0245 (7) | −0.0051 (6) | −0.0048 (6) | 0.0038 (6) |
O2 | 0.0408 (8) | 0.0281 (7) | 0.0324 (8) | −0.0149 (6) | 0.0015 (6) | 0.0018 (6) |
N1 | 0.0219 (7) | 0.0261 (7) | 0.0190 (8) | −0.0076 (6) | −0.0008 (6) | −0.0015 (6) |
N2 | 0.0202 (7) | 0.0224 (7) | 0.0226 (8) | 0.0014 (6) | 0.0030 (6) | 0.0002 (6) |
C1 | 0.0172 (8) | 0.0163 (7) | 0.0201 (9) | −0.0002 (6) | 0.0019 (6) | −0.0052 (6) |
C2 | 0.0157 (8) | 0.0233 (8) | 0.0197 (9) | −0.0031 (6) | −0.0025 (6) | −0.0051 (6) |
C3 | 0.0143 (7) | 0.0183 (7) | 0.0230 (9) | −0.0024 (6) | 0.0029 (6) | −0.0036 (6) |
C4 | 0.0154 (7) | 0.0167 (6) | 0.0183 (9) | 0.0006 (6) | 0.0048 (6) | −0.0044 (6) |
C5 | 0.0157 (7) | 0.0198 (7) | 0.0190 (9) | −0.0023 (6) | −0.0006 (6) | −0.0042 (6) |
C6 | 0.0169 (7) | 0.0193 (7) | 0.0219 (9) | −0.0048 (6) | 0.0024 (6) | −0.0046 (6) |
C7 | 0.0128 (7) | 0.0168 (7) | 0.0236 (9) | −0.0003 (6) | 0.0024 (6) | −0.0037 (6) |
C8 | 0.0158 (7) | 0.0170 (7) | 0.0255 (10) | 0.0033 (6) | 0.0050 (7) | −0.0025 (6) |
C9 | 0.0254 (9) | 0.0313 (9) | 0.0187 (9) | −0.0023 (8) | −0.0022 (7) | 0.0008 (7) |
C10 | 0.0276 (9) | 0.0280 (9) | 0.0273 (11) | −0.0117 (8) | 0.0015 (8) | −0.0027 (7) |
C11 | 0.0204 (8) | 0.0213 (7) | 0.0206 (9) | −0.0005 (6) | −0.0008 (7) | −0.0055 (6) |
C12 | 0.0196 (8) | 0.0359 (10) | 0.0334 (11) | −0.0010 (7) | −0.0033 (8) | −0.0066 (8) |
Geometric parameters (Å, º) top
O1—N2 | 1.232 (2) | C6—H61 | 1.000 |
O2—N2 | 1.231 (2) | C7—C8 | 1.345 (3) |
N1—C1 | 1.369 (2) | C7—H71 | 1.000 |
N1—C9 | 1.454 (2) | C8—C11 | 1.502 (2) |
N1—C10 | 1.453 (2) | C9—H91 | 1.000 |
N2—C8 | 1.468 (2) | C9—H92 | 1.000 |
C1—C2 | 1.421 (2) | C9—H93 | 1.000 |
C1—C6 | 1.408 (2) | C10—H101 | 1.000 |
C2—C3 | 1.383 (2) | C10—H102 | 1.000 |
C2—H21 | 1.000 | C10—H103 | 1.000 |
C3—C4 | 1.395 (2) | C11—C12 | 1.527 (3) |
C3—H31 | 1.000 | C11—H111 | 1.000 |
C4—C5 | 1.410 (2) | C11—H112 | 1.000 |
C4—C7 | 1.450 (2) | C12—H121 | 1.000 |
C5—C6 | 1.391 (3) | C12—H122 | 1.000 |
C5—H51 | 1.000 | C12—H123 | 1.000 |
| | | |
C1—N1—C9 | 121.12 (15) | N2—C8—C7 | 115.37 (16) |
C1—N1—C10 | 120.01 (15) | N2—C8—C11 | 114.77 (16) |
C9—N1—C10 | 117.89 (15) | C7—C8—C11 | 129.85 (16) |
O1—N2—O2 | 122.23 (16) | N1—C9—H91 | 109.552 |
O1—N2—C8 | 117.74 (15) | N1—C9—H92 | 109.511 |
O2—N2—C8 | 120.01 (15) | H91—C9—H92 | 109.476 |
N1—C1—C2 | 120.82 (15) | N1—C9—H93 | 109.336 |
N1—C1—C6 | 121.69 (15) | H91—C9—H93 | 109.476 |
C2—C1—C6 | 117.50 (15) | H92—C9—H93 | 109.476 |
C1—C2—C3 | 120.11 (16) | N1—C10—H101 | 109.339 |
C1—C2—H21 | 119.900 | N1—C10—H102 | 109.584 |
C3—C2—H21 | 119.988 | H101—C10—H102 | 109.476 |
C2—C3—C4 | 123.06 (15) | N1—C10—H103 | 109.476 |
C2—C3—H31 | 118.385 | H101—C10—H103 | 109.476 |
C4—C3—H31 | 118.552 | H102—C10—H103 | 109.476 |
C3—C4—C5 | 116.54 (16) | C8—C11—C12 | 112.52 (14) |
C3—C4—C7 | 117.66 (15) | C8—C11—H111 | 108.722 |
C5—C4—C7 | 125.68 (16) | C12—C11—H111 | 108.685 |
C4—C5—C6 | 121.70 (16) | C8—C11—H112 | 108.623 |
C4—C5—H51 | 119.126 | C12—C11—H112 | 108.790 |
C6—C5—H51 | 119.171 | H111—C11—H112 | 109.466 |
C1—C6—C5 | 121.05 (15) | C11—C12—H121 | 109.328 |
C1—C6—H61 | 119.551 | C11—C12—H122 | 109.590 |
C5—C6—H61 | 119.396 | H121—C12—H122 | 109.476 |
C4—C7—C8 | 130.66 (16) | C11—C12—H123 | 109.482 |
C4—C7—H71 | 114.692 | H121—C12—H123 | 109.475 |
C8—C7—H71 | 114.643 | H122—C12—H123 | 109.476 |
| | | |
C5—C4—C7—C8 | −21.9 (3) | C7—C8—N2—O2 | −7.0 (3) |
C3—C4—C7—C8 | 162.26 (19) | C2—C1—N1—C9 | 10.4 (3) |
C4—C7—C8—N2 | 178.23 (17) | C6—C1—N1—C10 | −1.4 (3) |
C7—C8—N2—O1 | 174.21 (17) | C4—C7—C8—C11 | −3.3 (3) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
C10—H101···O1i | 1.00 | 2.472 | 3.401 (2) | 153.78 |
C12—H121···O1ii | 1.00 | 2.502 | 3.499 (2) | 174.75 |
C9—H92···O2iii | 1.00 | 2.773 | 3.283 (2) | 112.12 |
C10—H102···O2iii | 1.00 | 2.817 | 3.310 (2) | 111.01 |
C11—H112···O2iv | 1.00 | 2.580 | 3.539 (2) | 160.74 |
Symmetry codes: (i) −x+1/2, −y, z+1/2; (ii) −x, y−1/2, −z+3/2; (iii) x−1/2, −y+1/2, −z+2; (iv) −x+1, y−1/2, −z+3/2. |
Experimental details
| (I) | (II) |
Crystal data |
Chemical formula | C10H12N2O2 | C12H16N2O2 |
Mr | 192.22 | 220.27 |
Crystal system, space group | OrthorhombicPbca | OrthorhombicP212121 |
Temperature (K) | 100 | 100 |
a, b, c (Å) | 10.1460 (2), 7.3091 (2), 25.1662 (7) | 5.9641 (1), 8.4492 (1), 23.1400 (4) |
V (Å3) | 1866.28 (8) | 1166.07 (3) |
Z | 8 | 4 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 0.10 | 0.09 |
Crystal size (mm) | 0.26 × 0.18 × 0.16 | 0.45 × 0.34 × 0.28 |
|
Data collection |
Diffractometer | Bruker APEXII diffractometer | Nonius KappaCCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 2002) | Multi-scan (SADABS; Sheldrick, 2002) |
Tmin, Tmax | 0.975, 0.985 | 0.962, 0.976 |
No. of measured, independent and observed reflections | 20691, 2137, 1488 [I > 2σ(I)] | 14807, 5077, 2017 [I > 3σ(I)] |
Rint | 0.032 | 0.04 |
(sin θ/λ)max (Å−1) | 0.649 | 0.808 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.033, 0.037, 1.17 | 0.038, 0.039, 1.14 |
No. of reflections | 1488 | 2017 |
No. of parameters | 161 | 148 |
No. of restraints | 60 | 0 |
H-atom treatment | H-atom parameters constrained | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.22, −0.21 | 0.28, −0.22 |
Absolute structure | ? | Flack (1983), with 3060 Friedel pairs |
Absolute structure parameter | ? | 0.7 (14) |
Selected geometric parameters (Å, º) for (I) topO11—N21 | 1.2394 (19) | C1—C61 | 1.423 (2) |
O21—N21 | 1.240 (2) | C21—C31 | 1.390 (2) |
N1—C1 | 1.3595 (15) | C31—C41 | 1.4045 (17) |
N1—C9 | 1.4554 (15) | C41—C51 | 1.4057 (19) |
N1—C10 | 1.4554 (15) | C41—C71 | 1.448 (2) |
N21—C81 | 1.4313 (19) | C51—C61 | 1.373 (2) |
C1—C21 | 1.418 (2) | C71—C81 | 1.336 (2) |
| | | |
C1—N1—C9 | 120.35 (10) | C1—C21—C31 | 120.75 (13) |
C1—N1—C10 | 120.11 (10) | C21—C31—C41 | 122.46 (13) |
C9—N1—C10 | 118.73 (10) | C31—C41—C51 | 116.55 (12) |
O21—N21—O11 | 122.53 (15) | C31—C41—C71 | 119.10 (13) |
O21—N21—C81 | 119.86 (16) | C51—C41—C71 | 124.35 (13) |
O11—N21—C81 | 117.61 (16) | C41—C51—C61 | 121.93 (13) |
N1—C1—C21 | 119.90 (11) | C1—C61—C51 | 121.91 (13) |
N1—C1—C61 | 123.75 (11) | C41—C71—C81 | 126.72 (14) |
C21—C1—C61 | 116.34 (12) | N21—C81—C71 | 120.71 (14) |
| | | |
C51—C41—C71—C81 | 1.148 | C71—C81—N21—O21 | −0.427 |
C31—C41—C71—C81 | −179.887 | C21—C1—N1—C9 | −6.750 |
C41—C71—C81—N21 | 179.863 | C61—C1—N1—C10 | 4.305 |
C71—C81—N21—O11 | 179.363 | | |
Hydrogen-bond geometry (Å, º) for (I) top
D—H···A | D—H | H···A | D···A | D—H···A |
C9—H91···O21i | 1.00 | 2.547 | 3.534 (2) | 169.19 |
C9—H93···O11ii | 1.00 | 2.777 | 3.419 (2) | 122.24 |
C10—H101···O11iii | 1.00 | 2.789 | 3.503 (2) | 128.75 |
Symmetry codes: (i) x, −y+3/2, z+1/2; (ii) x+1/2, −y+3/2, −z+1; (iii) −x+1/2, −y+1, z+1/2. |
Selected geometric parameters (Å, º) for (II) topO1—N2 | 1.232 (2) | C2—C3 | 1.383 (2) |
O2—N2 | 1.231 (2) | C3—C4 | 1.395 (2) |
N1—C1 | 1.369 (2) | C4—C5 | 1.410 (2) |
N1—C9 | 1.454 (2) | C4—C7 | 1.450 (2) |
N1—C10 | 1.453 (2) | C5—C6 | 1.391 (3) |
N2—C8 | 1.468 (2) | C7—C8 | 1.345 (3) |
C1—C2 | 1.421 (2) | C8—C11 | 1.502 (2) |
C1—C6 | 1.408 (2) | C11—C12 | 1.527 (3) |
| | | |
C1—N1—C9 | 121.12 (15) | C3—C4—C5 | 116.54 (16) |
C1—N1—C10 | 120.01 (15) | C3—C4—C7 | 117.66 (15) |
C9—N1—C10 | 117.89 (15) | C5—C4—C7 | 125.68 (16) |
O1—N2—O2 | 122.23 (16) | C4—C5—C6 | 121.70 (16) |
O1—N2—C8 | 117.74 (15) | C1—C6—C5 | 121.05 (15) |
O2—N2—C8 | 120.01 (15) | C4—C7—C8 | 130.66 (16) |
N1—C1—C2 | 120.82 (15) | N2—C8—C7 | 115.37 (16) |
N1—C1—C6 | 121.69 (15) | N2—C8—C11 | 114.77 (16) |
C2—C1—C6 | 117.50 (15) | C7—C8—C11 | 129.85 (16) |
C1—C2—C3 | 120.11 (16) | C8—C11—C12 | 112.52 (14) |
C2—C3—C4 | 123.06 (15) | | |
| | | |
C5—C4—C7—C8 | −21.9 (3) | C7—C8—N2—O2 | −7.0 (3) |
C3—C4—C7—C8 | 162.26 (19) | C2—C1—N1—C9 | 10.4 (3) |
C4—C7—C8—N2 | 178.23 (17) | C6—C1—N1—C10 | −1.4 (3) |
C7—C8—N2—O1 | 174.21 (17) | C4—C7—C8—C11 | −3.3 (3) |
Hydrogen-bond geometry (Å, º) for (II) top
D—H···A | D—H | H···A | D···A | D—H···A |
C10—H101···O1i | 1.00 | 2.472 | 3.401 (2) | 153.78 |
C12—H121···O1ii | 1.00 | 2.502 | 3.499 (2) | 174.75 |
C9—H92···O2iii | 1.00 | 2.773 | 3.283 (2) | 112.12 |
C10—H102···O2iii | 1.00 | 2.817 | 3.310 (2) | 111.01 |
C11—H112···O2iv | 1.00 | 2.580 | 3.539 (2) | 160.74 |
Symmetry codes: (i) −x+1/2, −y, z+1/2; (ii) −x, y−1/2, −z+3/2; (iii) x−1/2, −y+1/2, −z+2; (iv) −x+1, y−1/2, −z+3/2. |
A large number of conjugated organic compounds have been studied experimentally and theoretically in order to establish the structure–property relationships inducing large nonlinear optical (NLO) properties. Among these, β-nitrostyrene derivatives have been very attractive (Oudar, 1977; Zyss, 1979, Dulcic et al., 1981; Cheng, Tam, Marder et al., 1991 or Cheng, Tam, Stevenson et al., 1991?; Keshari et al., 1993). Such work has tried to determine the role and importance of the number of conjugated double bonds, the electronic biasing strengths of various donor and acceptor groups, charge-transfer enhancement, and the pattern and polarity of multiple substituents. The results of these studies reveal that very large second-order nonlinearities can be obtained with relatively long conjugated molecules containing strongly interacting donor–acceptor groups. For compound (I), 4-dimethylamino-β-nitrostyrene, the NLO properties found for dilute solutions are very close to those for 4-dimethylamino-4'-nitrostilbene, usually quoted as an example of a conjugated molecule which exhibits very large nonlinearities (Chemla & Zyss, 1987; Cheng, Tam, Marder et al., 1991 or Cheng, Tam, Stevenson et al., 1991?). However, a strong steric effect of the methyl substituent was observed in a series of β-methyl-β-nitrostyrene derivatives (Cho et al., 1996). In particular, the distortion from planarity caused by steric repulsion is able to reduce the optical nonlinearities to nearly zero.
We present here the structure of (I) in order to establish the influence of charge transfer upon the molecular geometry, which affects the strength of the NLO properties. In parallel, in order to analyse the importance of steric effects upon conjugation, we also report the structure of (II), 4-dimethylamino-β-ethyl-β-nitrostyrene (Pianka, 1963). For both compounds, data collection at 100 K has allowed an increase up to an acceptable level of the ratio of the number of independent observable reflections to the number of least-squares parameters, compared with the data collection at 293 K. Furthermore, for (I) it appears that the structure is disordered. The static disorder consists of a 180° rotation of 17% of the molecules around their long axis and is similar to that found in trans-stilbene and trans-azobenzene (Brown, 1966a or b?; Bouwstra et al., 1983; Finder et al., 1974). In this paper, we report the molecular geometry and crystal packing of (I), obviously only with regard to the molecule with the most probable orientation, for which atomic displacement parameters have been refined anisotropically.
The molecular structure of (I) is shown in Fig. 1, while selected geometric parameters are given in Table 1. The molecule is almost planar, indicating a high degree of conjugation, with a strong push–pull effect between the nitro and dimethylamine groups through the styrene skeleton. Excluding the dimethylamine group (atom N1 has slightly pyramidal bonds), the highest mean square deviation from calculated mean plane is 0.014 (2) Å. The dihedral angle between the mean planes of these two parts of the molecule is 1.4 (2)°. The sum of the bond angles around N1 is 359.2 (3)°, close to 360°, revealing the delocalization of the lone pair toward the N1—C1 bond, which is too short [1.3595 (15) Å] for a single N—C bond. Conjugation through the styrene induces the quinoidal character of the hexagonal ring: the C21—C31 [1.390 (2) Å] and C51—C61 [1.373 (2) Å] bond lengths, roughly parallel to the molecular dipole, are significantly shorter than C1—C21 [1.418 (2) Å], C1—C61 [1.423 (2) Å], C31—C41 [1.4045 (17) Å] and C41—C51 [1.4057 (19) Å]. For the same reason, the C41—C71 bond [1.448 (2) Å] is shorter than a single bond.
A perspective view of (II) is shown in Fig. 2 and selected geometric parameters are given in Table 3. Several differences from the conformation of (I) are found. The most striking feature is the C5—C4—C7—C8 torsion angle of -21.9 (3)°, which pushes the nitro and ethyl substituent groups out of the benzene ring plane. The main consequence of this torsion is to decrease the conjugation between the C7═C8 double bond and the dimethylaminobenzene moiety, and hence explains the hypsochromic effect for (II), which is yellow, not red like (I). Nevertheless, a noticeable conjugation remains, evidenced by the shortening of several bonds [C2—C3 = 1.383 (2), C5—C6 = 1.391 (3), N1—C1 = 1.369 (2) and C4—C7 = 1.450 (2) Å]. The conjugation also explains why the N atom of the dimethylamine moiety has lost all pyramidal character [the sum of the bond angles around the N1 atom is 359.02 (5)°].
The aforementioned steric hindrance of the ethyl group on the molecular planarity of (II) must be compared with that of the methyl group in β-methyl-β-nitrostyrene compounds substituted by donors of various strengths on the benzene ring. The value of the torsion angle between the phenyl and nitropropene groups in 4-dimethylamino-β-methyl-β-nitrostyrene, with the same donor as in (II), is only 1.6 (8)° (Brito et al., 1991), while it is 27.1° in the 4-methoxy analogue (Boys et al., 1993) and 23.7° in the 4-hydroxy-3-methoxy (Zabel et al., 1980) analogue. These values illustrate how molecular conjugation, or in other words the planarity of the molecule, is counter-balanced between steric effects and the strength of donors.
In the crystal structure, molecules of (I) are stacked as dimers, interacting in an antiferroelectric manner, and consequently no second-order NLO effect is observed in the solid state. The distance between the mean planes of the dimer is 3.276 (2) Å, while the smallest distance between atoms C1 and N21 is 3.322 (2) Å. The dimers are organized in chains along the c axis (Fig. 3) via C—H···O interactions between donor and acceptor groups (Table 2). Each chain of dimers is symmetrically surrounded by four other chains, within which the molecular planes are almost perpendicular to the molecular plane of the central chain.
The packing of molecules of (II) in the crystal structure is realised by interactions between O atoms and methyl groups (see Table 4 and Fig. 4). The asymmetric interactions of the O atoms with the methyl groups of the dimethylamine moeity explain the difference between torsion angles C2—C1—N1—C9 = 10.4 (3)° and C6—C1—N1—C10 = -1.4 (3)°. Unfortunately in this non-centrosymmetric structure, the non-planarity of the molecules does not allow an efficient NLO effect.