organic compounds
r-1,t-3-Bis[4-(dimethylamino)phenyl]-c-2,t-4-bis(pyridin-4-yl)cyclobutane
aDepartment of Organic Chemistry, Faculty of Science, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China
*Correspondence e-mail: zhuangjp@mail.buct.edu.cn
The title compound, C30H32N4, was synthesized by the photodimerization of trans-4-{2-[4-(dimethylamino)phenyl]ethenyl}pyridine in benzene upon irradiation with UV light. This photodimer has a puckered cyclobutane ring with the four aryl substituents in an r-1,t-2,c-3,t conformation. The puckering angle of the cyclobutane ring is 32.22 (7)°, which is the largest among reported tetraaryl-substituted cyclobutanes. In the crystal, the molecules form a hollow, one-dimensional structure extending parallel to the c axis via two different pairs of C—H⋯π interactions.
CCDC reference: 984465
Related literature
For the photodimerization of styrylpryidines, see: Horner & Hünig (1982); Quina & Whitten (1975); Zhang, Zhang, Zheng, Shen & Zhuang (2000). For the single-crystal structures of tetraaryl cyclobutanes and related molecules, see: Busetti et al. (1980); Coe et al. (2005); Li et al. (2007); Zhang et al. (1998); Zhang, Zhang, Zheng, Wang & Zhao (2000); Zhuang & Zheng (2002). For the synthesis of the monomer, see: Wang et al. (2005).
Experimental
Crystal data
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Data collection: CrystalClear (Rigaku, 2009); cell CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL.
Supporting information
CCDC reference: 984465
10.1107/S1600536814002311/mw2110sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536814002311/mw2110Isup2.hkl
Supporting information file. DOI: 10.1107/S1600536814002311/mw2110Isup3.cml
A was synthesized according to the literature (Wang et al., 2005) and 1.97 g (8.78 mmol) was dissolved in 200 mL of benzene and irradiated with a water-cooled 125 W medium-pressure mercury lamp which was immersed in the solution. After irradiation for about 30 h, the solvent was evaporated to dryness and the crude product was separated by δ 8.35 (d, 4H, J=4.8 Hz), 7.00 (d, 4H, J=4.8 Hz), 6.94 (d, 4H, J=6.4 Hz), 6.53 (d, 4H, J=6.4 Hz), 4.38 (d, 2H, J=9.0 Hz), 74.28 (d, 2H, J=9.0 Hz) p.p.m.. The single-crystal of 2A, suitable for X-ray analysis, was grown by slow evaporation of a methanol solution of 2A.
(ethyl acetate: dichloromethane = 1: 1) to give 0.73 g of colorless crystals of 2 A. Yield, 37%; 1H NMR (CDCl3):H atoms were placed in calculated positions [C—H = 0.93–0.97 Å] and allowed to ride on the parent atoms, with Uiso values constrained to be 1.2Ueq of the parent atom.
Data collection: CrystalClear (Rigaku, 2009); cell
CrystalClear (Rigaku, 2009); data reduction: CrystalClear (Rigaku, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).Fig. 1. Molecular structure of 2A. Displacement ellipsoids are drawn at the 50% probability level. | |
Fig. 2. Packing diagram of 2A viewed along c axis. | |
Fig. 3. Packing diagram of 2A viewed along b axis. |
C30H32N4 | F(000) = 960 |
Mr = 448.60 | Dx = 1.214 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -C 2yc | Cell parameters from 2660 reflections |
a = 23.166 (5) Å | θ = 1.8–27.9° |
b = 11.003 (2) Å | µ = 0.07 mm−1 |
c = 9.6330 (19) Å | T = 113 K |
β = 91.67 (3)° | Block, colourless |
V = 2454.4 (8) Å3 | 0.24 × 0.20 × 0.16 mm |
Z = 4 |
Rigaku Saturn 70 CCD diffractometer | 2934 independent reflections |
Radiation source: rotating anode | 2335 reflections with I > 2σ(I) |
Confocal monochromator | Rint = 0.043 |
ω scans | θmax = 27.9°, θmin = 1.8° |
Absorption correction: multi-scan (CrystalClear; Rigaku, 2009) | h = −30→30 |
Tmin = 0.983, Tmax = 0.989 | k = −14→14 |
14966 measured reflections | l = −12→12 |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.045 | H-atom parameters constrained |
wR(F2) = 0.121 | w = 1/[σ2(Fo2) + (0.0689P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.09 | (Δ/σ)max < 0.001 |
2934 reflections | Δρmax = 0.24 e Å−3 |
157 parameters | Δρmin = −0.26 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0115 (17) |
C30H32N4 | V = 2454.4 (8) Å3 |
Mr = 448.60 | Z = 4 |
Monoclinic, C2/c | Mo Kα radiation |
a = 23.166 (5) Å | µ = 0.07 mm−1 |
b = 11.003 (2) Å | T = 113 K |
c = 9.6330 (19) Å | 0.24 × 0.20 × 0.16 mm |
β = 91.67 (3)° |
Rigaku Saturn 70 CCD diffractometer | 2934 independent reflections |
Absorption correction: multi-scan (CrystalClear; Rigaku, 2009) | 2335 reflections with I > 2σ(I) |
Tmin = 0.983, Tmax = 0.989 | Rint = 0.043 |
14966 measured reflections |
R[F2 > 2σ(F2)] = 0.045 | 0 restraints |
wR(F2) = 0.121 | H-atom parameters constrained |
S = 1.09 | Δρmax = 0.24 e Å−3 |
2934 reflections | Δρmin = −0.26 e Å−3 |
157 parameters |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 | ||
N1 | −0.12781 (4) | 0.08386 (9) | 0.34546 (11) | 0.0261 (3) | |
N2 | 0.21597 (4) | 0.48468 (8) | 0.38134 (10) | 0.0201 (3) | |
C1 | −0.14278 (5) | 0.08343 (11) | 0.47858 (13) | 0.0215 (3) | |
H1 | −0.1758 | 0.0408 | 0.5017 | 0.026* | |
C2 | −0.11207 (5) | 0.14263 (10) | 0.58397 (12) | 0.0191 (3) | |
H2 | −0.1241 | 0.1375 | 0.6750 | 0.023* | |
C3 | −0.06316 (5) | 0.20975 (10) | 0.55322 (12) | 0.0166 (3) | |
C4 | −0.04739 (5) | 0.21074 (11) | 0.41486 (12) | 0.0233 (3) | |
H4 | −0.0151 | 0.2541 | 0.3884 | 0.028* | |
C5 | −0.08012 (6) | 0.14681 (12) | 0.31670 (13) | 0.0289 (3) | |
H5 | −0.0683 | 0.1477 | 0.2253 | 0.035* | |
C6 | −0.02904 (5) | 0.27871 (10) | 0.66140 (12) | 0.0170 (3) | |
H6 | −0.0342 | 0.3661 | 0.6456 | 0.020* | |
C7 | 0.03660 (4) | 0.25051 (10) | 0.68241 (11) | 0.0165 (3) | |
H7 | 0.0421 | 0.1627 | 0.6722 | 0.020* | |
C8 | 0.08169 (5) | 0.31420 (10) | 0.60052 (11) | 0.0165 (3) | |
C9 | 0.12213 (5) | 0.24764 (10) | 0.52824 (12) | 0.0191 (3) | |
H9 | 0.1200 | 0.1633 | 0.5298 | 0.023* | |
C10 | 0.16550 (5) | 0.30229 (10) | 0.45398 (12) | 0.0204 (3) | |
H10 | 0.1914 | 0.2541 | 0.4065 | 0.024* | |
C11 | 0.17092 (5) | 0.42906 (10) | 0.44948 (11) | 0.0172 (3) | |
C12 | 0.12953 (5) | 0.49722 (10) | 0.52068 (12) | 0.0196 (3) | |
H12 | 0.1312 | 0.5816 | 0.5186 | 0.023* | |
C13 | 0.08643 (5) | 0.44051 (11) | 0.59377 (12) | 0.0193 (3) | |
H13 | 0.0599 | 0.4881 | 0.6397 | 0.023* | |
C14 | 0.24760 (5) | 0.41298 (11) | 0.28156 (13) | 0.0240 (3) | |
H14A | 0.2213 | 0.3836 | 0.2103 | 0.036* | |
H14B | 0.2658 | 0.3453 | 0.3281 | 0.036* | |
H14C | 0.2766 | 0.4628 | 0.2405 | 0.036* | |
C15 | 0.21211 (5) | 0.61429 (10) | 0.35107 (13) | 0.0230 (3) | |
H15A | 0.2091 | 0.6588 | 0.4363 | 0.034* | |
H15B | 0.1786 | 0.6297 | 0.2927 | 0.034* | |
H15C | 0.2461 | 0.6398 | 0.3043 | 0.034* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0243 (6) | 0.0315 (6) | 0.0226 (6) | −0.0049 (5) | 0.0012 (4) | −0.0045 (5) |
N2 | 0.0177 (5) | 0.0189 (5) | 0.0240 (5) | −0.0004 (4) | 0.0060 (4) | 0.0021 (4) |
C1 | 0.0181 (6) | 0.0226 (6) | 0.0239 (6) | −0.0010 (5) | 0.0020 (5) | −0.0015 (5) |
C2 | 0.0185 (6) | 0.0205 (6) | 0.0185 (6) | 0.0006 (4) | 0.0026 (5) | −0.0006 (5) |
C3 | 0.0156 (5) | 0.0155 (5) | 0.0186 (6) | 0.0037 (4) | 0.0004 (4) | 0.0003 (4) |
C4 | 0.0193 (6) | 0.0292 (7) | 0.0215 (6) | −0.0045 (5) | 0.0033 (5) | 0.0011 (5) |
C5 | 0.0278 (7) | 0.0404 (8) | 0.0185 (6) | −0.0058 (6) | 0.0036 (5) | −0.0033 (6) |
C6 | 0.0144 (5) | 0.0190 (6) | 0.0176 (6) | −0.0004 (4) | 0.0009 (4) | 0.0006 (5) |
C7 | 0.0155 (6) | 0.0158 (6) | 0.0181 (6) | 0.0014 (4) | 0.0015 (5) | −0.0004 (4) |
C8 | 0.0137 (5) | 0.0204 (6) | 0.0154 (6) | −0.0003 (4) | −0.0006 (4) | 0.0003 (5) |
C9 | 0.0201 (6) | 0.0158 (6) | 0.0215 (6) | −0.0002 (4) | 0.0023 (5) | 0.0004 (5) |
C10 | 0.0193 (6) | 0.0198 (6) | 0.0224 (6) | 0.0019 (5) | 0.0057 (5) | −0.0020 (5) |
C11 | 0.0146 (5) | 0.0199 (6) | 0.0173 (6) | −0.0006 (4) | 0.0000 (4) | 0.0019 (5) |
C12 | 0.0193 (6) | 0.0159 (6) | 0.0234 (6) | 0.0009 (4) | 0.0005 (5) | 0.0012 (5) |
C13 | 0.0157 (5) | 0.0187 (6) | 0.0237 (6) | 0.0027 (4) | 0.0031 (5) | −0.0002 (5) |
C14 | 0.0210 (6) | 0.0267 (7) | 0.0247 (7) | −0.0009 (5) | 0.0076 (5) | 0.0015 (5) |
C15 | 0.0213 (6) | 0.0214 (6) | 0.0264 (7) | −0.0023 (5) | 0.0034 (5) | 0.0047 (5) |
N1—C1 | 1.3381 (15) | C7—C6i | 1.5512 (15) |
N1—C5 | 1.3396 (16) | C7—H7 | 0.9800 |
N2—C11 | 1.3908 (14) | C8—C9 | 1.3918 (15) |
N2—C14 | 1.4576 (15) | C8—C13 | 1.3958 (16) |
N2—C15 | 1.4579 (14) | C9—C10 | 1.3874 (15) |
C1—C2 | 1.3853 (17) | C9—H9 | 0.9300 |
C1—H1 | 0.9300 | C10—C11 | 1.4013 (16) |
C2—C3 | 1.3916 (15) | C10—H10 | 0.9300 |
C2—H2 | 0.9300 | C11—C12 | 1.4109 (16) |
C3—C4 | 1.3923 (16) | C12—C13 | 1.3867 (16) |
C3—C6 | 1.4961 (16) | C12—H12 | 0.9300 |
C4—C5 | 1.3863 (17) | C13—H13 | 0.9300 |
C4—H4 | 0.9300 | C14—H14A | 0.9600 |
C5—H5 | 0.9300 | C14—H14B | 0.9600 |
C6—C7i | 1.5512 (15) | C14—H14C | 0.9600 |
C6—C7 | 1.5593 (15) | C15—H15A | 0.9600 |
C6—H6 | 0.9800 | C15—H15B | 0.9600 |
C7—C8 | 1.5008 (15) | C15—H15C | 0.9600 |
C1—N1—C5 | 116.00 (11) | C9—C8—C13 | 116.46 (10) |
C11—N2—C14 | 118.14 (10) | C9—C8—C7 | 120.41 (10) |
C11—N2—C15 | 118.84 (9) | C13—C8—C7 | 123.12 (10) |
C14—N2—C15 | 115.26 (9) | C10—C9—C8 | 122.55 (11) |
N1—C1—C2 | 123.96 (11) | C10—C9—H9 | 118.7 |
N1—C1—H1 | 118.0 | C8—C9—H9 | 118.7 |
C2—C1—H1 | 118.0 | C9—C10—C11 | 120.95 (10) |
C1—C2—C3 | 119.84 (11) | C9—C10—H10 | 119.5 |
C1—C2—H2 | 120.1 | C11—C10—H10 | 119.5 |
C3—C2—H2 | 120.1 | N2—C11—C10 | 121.45 (10) |
C2—C3—C4 | 116.48 (11) | N2—C11—C12 | 121.70 (10) |
C2—C3—C6 | 122.53 (10) | C10—C11—C12 | 116.83 (10) |
C4—C3—C6 | 120.99 (10) | C13—C12—C11 | 121.14 (11) |
C5—C4—C3 | 119.70 (11) | C13—C12—H12 | 119.4 |
C5—C4—H4 | 120.2 | C11—C12—H12 | 119.4 |
C3—C4—H4 | 120.2 | C12—C13—C8 | 122.04 (10) |
N1—C5—C4 | 124.00 (11) | C12—C13—H13 | 119.0 |
N1—C5—H5 | 118.0 | C8—C13—H13 | 119.0 |
C4—C5—H5 | 118.0 | N2—C14—H14A | 109.5 |
C3—C6—C7i | 120.12 (9) | N2—C14—H14B | 109.5 |
C3—C6—C7 | 118.86 (9) | H14A—C14—H14B | 109.5 |
C7i—C6—C7 | 88.36 (9) | N2—C14—H14C | 109.5 |
C3—C6—H6 | 109.3 | H14A—C14—H14C | 109.5 |
C7i—C6—H6 | 109.3 | H14B—C14—H14C | 109.5 |
C7—C6—H6 | 109.3 | N2—C15—H15A | 109.5 |
C8—C7—C6i | 121.09 (10) | N2—C15—H15B | 109.5 |
C8—C7—C6 | 121.99 (9) | H15A—C15—H15B | 109.5 |
C6i—C7—C6 | 87.07 (9) | N2—C15—H15C | 109.5 |
C8—C7—H7 | 108.2 | H15A—C15—H15C | 109.5 |
C6i—C7—H7 | 108.2 | H15B—C15—H15C | 109.5 |
C6—C7—H7 | 108.2 | ||
C5—N1—C1—C2 | −0.30 (18) | C6—C7—C8—C9 | −126.96 (12) |
N1—C1—C2—C3 | 1.49 (18) | C6i—C7—C8—C13 | −53.68 (15) |
C1—C2—C3—C4 | −1.27 (16) | C6—C7—C8—C13 | 54.16 (16) |
C1—C2—C3—C6 | 178.20 (11) | C13—C8—C9—C10 | 0.62 (18) |
C2—C3—C4—C5 | 0.03 (17) | C7—C8—C9—C10 | −178.34 (10) |
C6—C3—C4—C5 | −179.44 (11) | C8—C9—C10—C11 | 0.61 (19) |
C1—N1—C5—C4 | −1.05 (19) | C14—N2—C11—C10 | 17.54 (17) |
C3—C4—C5—N1 | 1.2 (2) | C15—N2—C11—C10 | 165.43 (11) |
C2—C3—C6—C7i | 16.79 (16) | C14—N2—C11—C12 | −164.33 (11) |
C4—C3—C6—C7i | −163.77 (10) | C15—N2—C11—C12 | −16.44 (17) |
C2—C3—C6—C7 | 123.18 (12) | C9—C10—C11—N2 | 176.66 (11) |
C4—C3—C6—C7 | −57.38 (15) | C9—C10—C11—C12 | −1.55 (17) |
C3—C6—C7—C8 | 88.20 (13) | N2—C11—C12—C13 | −176.89 (11) |
C7i—C6—C7—C8 | −147.91 (9) | C10—C11—C12—C13 | 1.32 (17) |
C3—C6—C7—C6i | −146.52 (8) | C11—C12—C13—C8 | −0.12 (18) |
C7i—C6—C7—C6i | −22.63 (11) | C9—C8—C13—C12 | −0.86 (17) |
C6i—C7—C8—C9 | 125.21 (12) | C7—C8—C13—C12 | 178.07 (11) |
Symmetry code: (i) −x, y, −z+3/2. |
Cg1 and Cg2 are the centroids of the C8–C13 and N1/C1–C5 rings, respectively. |
D—H···A | D—H | H···A | D···A | D—H···A |
C15—H15B···Cg1ii | 0.96 | 2.82 | 3.679 (2) | 149 |
C12—H12···Cg2ii | 0.96 | 3.12 | 4.104 (2) | 161 |
Symmetry code: (ii) −x, −y+1, −z+1. |
Cg1 and Cg2 are the centroids of the C8–C13 and N1/C1–C5 rings, respectively. |
D—H···A | D—H | H···A | D···A | D—H···A |
C15—H15B···Cg1i | 0.96 | 2.82 | 3.679 (2) | 149 |
C12—H12···Cg2i | 0.96 | 3.12 | 4.104 (2) | 161 |
Symmetry code: (i) −x, −y+1, −z+1. |
Acknowledgements
This work was supported by the Youth Foundation of Beijing University of Chemical Technology.
References
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This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
The photodimerization of styrylpyridines has been studied extensively in the past few decades (Horner & Hünig, 1982; Quina & Whitten, 1975; Zhang, Zhang, Zheng, Shen & Zhuang, 2000). As the protonation of the pyridine ring increases the solubility and dipolar interactions of styrylpyridines in water, most photodimerization reactions were carried out in acidic aqueous solution. The main tetraaryl substituted cyclobutane photodimers usually have head-to-tail central symmetric structures. However, the photodimerization of trans-4-[2-(4-dimethylaminophenyl)ethenyl]pyridine (A) in acidic aqueous solution failed (Zhang, Zhang, Zheng, Shen & Zhuang, 2000). Herein, the photodimerization of A was carried out in benzene and the photodimer (2A, Fig. 1) was successfully synthesized in 37% yield.
The structure of 2A shows that the four aryl substituents adopt the r-1,t-2,c-3,t-4 conformation, whereas the styrylpyridine photodimers synthesized in acidic aqueous solution adopt the head-to-tail r-1,c-2,t-3,t-4 conformation. In addition, the photodimer of 2-[2-(4-dimethylaminophenyl)ethenyl]benzoxazole synthesized in acetonitrile also adopts the head-to-tail r-1,c-2,t-3,t-4 conformation (Li et al., 2007). This difference is ascribed to solvent effects. The steric hindrance of the dimethylamino groups prevents A to align in a parallel manner in the non-polar benzene solvent, resulting in the all trans conformation of the adjacent aryl groups in 2A.
Several styrylpyridine photodimers such as r-1,c-2,t-3,t-4–1,3-bis[2-(4-R-phenyl)]-2,4-di(pyridin-4-yl)cyclobutane (R=Cl, CH3 and C6H5) have been reported (Busetti et al., 1980; Zhang et al., 1998; Zhang, Zhang, Zheng, Wang & Zhao, 2000). The average dihedral angles of the cyclobutane rings are 19.2, 24.6 and 16.4°, respectively. In addition, the trans-head-to-head photodimer of 1-(4-methoxyphenyl)-2-(5-phenyl-1,3,4-oxadiazolyl)ethene also has a puckered cyclobutane ring with a dihedral angle of 30° (Zhuang & Zheng, 2002). Though the adjacent aryl groups of 2A adopt the all trans conformation, the dihedral angle of the cyclobutane ring is 32.22 (7)° which is the largest one among reported tetraaryl substituted cyclobutanes.
The C6—C7 and C6—C7A bond distances are 1.5594 (16) Å and 1.5519 (16) Å, and the C3—C6 and C7—C8 bond distances are 1.4962 (18) Å and 1.5011 (16) Å, which are similar to the corresponding bond distances in other tetraaryl substituted cyclobutanes (Zhang et al., 1998; Zhang, Zhang, Zheng, Wang & Zhao, 2000). The two phenyl rings (C8—C9—C10—C11—C12—C13 and C8A—C9A—C10A—C11A—C12A—C13A) are almost coplanar with the dihedral angle between them being only 1.78 (7)°.
The dimethylamino plane and the phenyl ring (C8—C9—C10—C11—C12—C13) are not coplanar, the torsion angle (C14—N2—C11—C10) is 17.48 (18)° which is larger than that in c-2, t-4-bis(2-benzoxazol-2-yl)-r-1,t-3-bis[4-(dimethylamino)phenyl]cyclobutane (Li et al., 2007). The distances of the two methyl groups (C14 and C15) from the mean plane of the phenyl ring are 0.2629 (22) and 0.2335 (22) Å respectively, indicating that the lone electron pair of the N atom is not completely conjugated with the phenyl ring. While the dimethylaminophenyl ring in trans-4-[(4-dimethylaminophenyl)ethenyl]-N-methylquinolinium p-toluenesulfonate monohydrate (Coe et al., 2005) is essentially planar because of the strong p-π conjugation between the dimethylamino group and the planar diarylethene molecule.
As shown in Figure 2, the molecules of 2A pack with each other to form a hollow, one-dimensional structure along the c axis. This arrangement appears to be directed by two sets of C—H···π interactions with that involving H15B stronger than that using H12 (Table 1).