organic compounds
2-{4-[Bis(4-bromophenyl)amino]benzylidene}malononitrile
aDepartment of Material Chemistry, Huzhou University, Huzhou, Zhejiang 313000, People's Republic of China
*Correspondence e-mail: shengliangni@163.com
In the 22H13Br2N3, the two bromophenyl rings are rotated out of the plane of the central benzylidene ring by 68.7 (1) and 69.3 (1)°. Both cyano substituents are located nearly in the plane of the benzylidene ring, with the mean plane of the methylmalononitrile group being inclined to this ring by 5.8 (1)°. In the crystal, the molecules are linked by weak C—H⋯N hydrogen bonds into layers parallel to the bc plane.
of the title compound, CKeywords: crystal structure.
CCDC reference: 1008127
Related literature
For general background to arylamines such as triphenylamine as versatile optical materials, see: Ning et al. (2007); Noh et al. (2010). For related luminescent and electron-donating materials, see: Yao & Belfield (2005); Patra et al. (2007); Zhang et al. (2012). For the synthesis of the title compound, see: Chiang et al. (2005).
Experimental
Crystal data
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Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell CrysAlis CCD; data reduction: CrysAlis RED (Oxford Diffraction, 2006); 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: SHELXL97.
Supporting information
CCDC reference: 1008127
https://doi.org/10.1107/S1600536814013816/nc2326sup1.cif
contains datablocks ItcLa, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536814013816/nc2326Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S1600536814013816/nc2326Isup3.cml
The title compound was prepared by the reaction of 4–(bis(4–bromophenyl)amino) benzaldehyde (DiBr–TPA) and malononitrile (Chiang et al.,2005) DiBr–TPA (1.3 g, 3 mmol), malononitrile (0.8 g, 12.1 mmol), and basic aluminium oxide (Al2O3, 4.0 g) are stirred in toluene (30 ml) for 18 h at 100 °C. And then, the hot solution was cooled down to room temperature, the reaction solution was filtered. The crude product was purified by
using CH2Cl2/hexane (1/50) mixture as to obtain the compound (silica gel, ethyl acetate/petroleum ether: 1/9). A yellow powders was obtained with the yield of 43.1%. The yellow needle-like crystal was obtained by slowly evaporating a solution of DiCN–TPA in the mixed solvent (CH2Cl2/hexane = 1/9, v/v) at room temperature for two weeks.All C—H H-atoms bonded were positioned with idealized geometry and refined isotropic with Uiso(H) = 1.2 Ueq(C) using a riding model.
Arylamines such as triphenylamine (TPA) are versatile optical materials. The TPA derivatives containing the twisty arylamine exhibits good electron-donating ability and restrict the formation of an excimer complex, which further contributes to enhance fluorescence
(Ning et al., 2007; Noh et al., 2010). As a result, the fluorescence molecule with TPA are the excellent candidate as the luminescent and electron-donating materials (Yao & Belfield, 2005; Patra et al., 2007). Moreover, the molecular packing is relatively loose, leading to the piezofluorochromic properties due to the twisted conformation in the aggregated state. Our group always investigated the piezofluorochromic and optical properties of triphenylamine (TPA) derivatives (Zhang et al., 2012). It was found that the tiny change of the molecular structure had great effect on the piezofluorochromic behavior. The, dye DiCN-TPA with a simple molecular structure is an excellent candidate to investigate structure- property relationships. Within this project the crstal structure of the title compound was determined.The
consists of one molecule in a general position (Fig. 1). In the crystal structure,the two bromophenyl groups are rotated out of the central benzylidene ring by 68.7 (1) ° and 69.3 (1) °. Both cyano substituents are located nearly in the plane of the 6-membered ring and the dihedral angle between the plane C5–C10 and N2, N3 and C1 to C4 amount to 5.8 (1) °. In the crystal, the molecules self–assemble to form a hydrogen–bonded layer parallel to the bc crystallographic plane connected by weak C—H···N hydrogen bonds(C4—H4A···N3#1 = 169 °, C4···N3#1 = 3.438 (5) Å, C6—H6A···N2#2= 145 ° and C6···N2#2 = 3.404 (5) Å) (#1 = x, 5/2 - y, 1/2 + z; #2 = 2 - x, -1/2 + y, 3/2 - z). These layers are stacked along a axis and are stabilized by van der Waals interactions.For general background to arylamines such as triphenylamine as versatile optical materials, see: Ning et al. (2007); Noh et al. (2010). For related luminescent and electron-donating materials, see: Yao & Belfield (2005); Patra et al. (2007); Zhang et al. (2012). For the synthesis of the title compound, see: Chiang et al. (2005).
Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell
CrysAlis CCD (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); 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: SHELXL97 (Sheldrick, 2008).Fig. 1. ORTEP view of the title compound with labeling and displacement ellipsoids drawn at 45% probability level. |
C22H13Br2N3 | F(000) = 944 |
Mr = 479.17 | Dx = 1.624 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 2681 reflections |
a = 14.6846 (6) Å | θ = 2.9–29.3° |
b = 10.3997 (4) Å | µ = 4.15 mm−1 |
c = 13.1961 (4) Å | T = 298 K |
β = 103.501 (4)° | Needle-like, yellow |
V = 1959.56 (12) Å3 | 0.30 × 0.20 × 0.20 mm |
Z = 4 |
Oxford Diffraction CrysAlis CCD diffractometer | 3843 independent reflections |
Radiation source: Enhance (Mo) X-ray Source | 2702 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.024 |
ω scans | θmax = 26.0°, θmin = 3.2° |
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006) | h = −18→18 |
Tmin = 0.369, Tmax = 0.491 | k = −7→12 |
9075 measured reflections | l = −14→16 |
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)] = 0.041 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.094 | H-atom parameters constrained |
S = 1.02 | w = 1/[σ2(Fo2) + (0.0359P)2 + 1.3631P] where P = (Fo2 + 2Fc2)/3 |
3843 reflections | (Δ/σ)max = 0.003 |
244 parameters | Δρmax = 0.38 e Å−3 |
0 restraints | Δρmin = −0.57 e Å−3 |
C22H13Br2N3 | V = 1959.56 (12) Å3 |
Mr = 479.17 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 14.6846 (6) Å | µ = 4.15 mm−1 |
b = 10.3997 (4) Å | T = 298 K |
c = 13.1961 (4) Å | 0.30 × 0.20 × 0.20 mm |
β = 103.501 (4)° |
Oxford Diffraction CrysAlis CCD diffractometer | 3843 independent reflections |
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006) | 2702 reflections with I > 2σ(I) |
Tmin = 0.369, Tmax = 0.491 | Rint = 0.024 |
9075 measured reflections |
R[F2 > 2σ(F2)] = 0.041 | 0 restraints |
wR(F2) = 0.094 | H-atom parameters constrained |
S = 1.02 | Δρmax = 0.38 e Å−3 |
3843 reflections | Δρmin = −0.57 e Å−3 |
244 parameters |
Experimental. Absorption correction: CrysAlis RED, Oxford Diffraction Ltd., Version 1.171.32.5 (release 08–05-2007 CrysAlis171. NET) (compiled May 8 2007,13:10:02) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. |
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 | ||
N1 | 0.7072 (2) | 0.7143 (3) | 0.4629 (2) | 0.0468 (7) | |
N2 | 1.0781 (3) | 1.4223 (5) | 0.6211 (3) | 0.0959 (15) | |
N3 | 0.9718 (2) | 1.2359 (4) | 0.3307 (3) | 0.0669 (10) | |
C1 | 1.0307 (3) | 1.3420 (5) | 0.5799 (3) | 0.0624 (11) | |
C2 | 0.9707 (2) | 1.2363 (4) | 0.4169 (3) | 0.0470 (9) | |
C3 | 0.9731 (3) | 1.2405 (4) | 0.5257 (3) | 0.0451 (9) | |
C4 | 0.9304 (3) | 1.1577 (4) | 0.5774 (3) | 0.0468 (9) | |
H4A | 0.9400 | 1.1749 | 0.6483 | 0.056* | |
C5 | 0.8725 (2) | 1.0472 (3) | 0.5432 (2) | 0.0414 (8) | |
C6 | 0.8430 (2) | 0.9732 (4) | 0.6183 (2) | 0.0469 (9) | |
H6A | 0.8602 | 0.9987 | 0.6877 | 0.056* | |
C7 | 0.7902 (3) | 0.8654 (4) | 0.5933 (2) | 0.0458 (9) | |
H7A | 0.7731 | 0.8181 | 0.6458 | 0.055* | |
C8 | 0.7612 (2) | 0.8249 (3) | 0.4900 (2) | 0.0407 (8) | |
C9 | 0.7887 (3) | 0.8989 (4) | 0.4134 (2) | 0.0473 (9) | |
H9A | 0.7700 | 0.8746 | 0.3438 | 0.057* | |
C10 | 0.8428 (2) | 1.0064 (4) | 0.4398 (2) | 0.0461 (9) | |
H10A | 0.8602 | 1.0536 | 0.3875 | 0.055* | |
C11 | 0.7119 (2) | 0.6094 (3) | 0.5341 (2) | 0.0413 (8) | |
C12 | 0.7968 (2) | 0.5562 (4) | 0.5836 (3) | 0.0501 (9) | |
H12A | 0.8522 | 0.5923 | 0.5742 | 0.060* | |
C13 | 0.8002 (2) | 0.4497 (4) | 0.6470 (3) | 0.0480 (9) | |
H13A | 0.8574 | 0.4137 | 0.6802 | 0.058* | |
C14 | 0.7180 (2) | 0.3981 (3) | 0.6603 (2) | 0.0426 (8) | |
C15 | 0.6331 (2) | 0.4516 (4) | 0.6153 (3) | 0.0496 (9) | |
H15A | 0.5781 | 0.4168 | 0.6269 | 0.060* | |
Br1 | 0.43314 (3) | 0.65644 (5) | 0.04171 (3) | 0.06879 (17) | |
C16 | 0.6305 (2) | 0.5586 (4) | 0.5520 (3) | 0.0484 (9) | |
H16A | 0.5733 | 0.5964 | 0.5214 | 0.058* | |
C17 | 0.6453 (2) | 0.7022 (3) | 0.3628 (2) | 0.0400 (8) | |
C18 | 0.6473 (3) | 0.5930 (4) | 0.3033 (3) | 0.0477 (9) | |
H18A | 0.6907 | 0.5285 | 0.3279 | 0.057* | |
C19 | 0.5850 (3) | 0.5793 (4) | 0.2072 (3) | 0.0502 (9) | |
H19A | 0.5861 | 0.5056 | 0.1676 | 0.060* | |
C20 | 0.5219 (2) | 0.6753 (3) | 0.1711 (2) | 0.0440 (9) | |
C21 | 0.5201 (3) | 0.7855 (4) | 0.2277 (3) | 0.0491 (9) | |
H21A | 0.4777 | 0.8507 | 0.2018 | 0.059* | |
C22 | 0.5820 (3) | 0.7985 (4) | 0.3238 (3) | 0.0482 (9) | |
H22A | 0.5810 | 0.8730 | 0.3625 | 0.058* | |
Br2 | 0.72147 (3) | 0.24595 (4) | 0.74116 (4) | 0.07151 (17) |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0552 (18) | 0.0382 (18) | 0.0415 (15) | −0.0087 (16) | 0.0003 (13) | 0.0082 (13) |
N2 | 0.141 (4) | 0.093 (3) | 0.055 (2) | −0.065 (3) | 0.026 (2) | −0.022 (2) |
N3 | 0.073 (2) | 0.080 (3) | 0.047 (2) | −0.018 (2) | 0.0127 (17) | −0.0022 (18) |
C1 | 0.087 (3) | 0.063 (3) | 0.040 (2) | −0.022 (3) | 0.021 (2) | −0.007 (2) |
C2 | 0.049 (2) | 0.047 (2) | 0.044 (2) | −0.0095 (19) | 0.0077 (16) | −0.0032 (17) |
C3 | 0.057 (2) | 0.040 (2) | 0.0378 (18) | −0.0081 (19) | 0.0088 (16) | −0.0075 (16) |
C4 | 0.061 (2) | 0.045 (2) | 0.0330 (16) | −0.003 (2) | 0.0094 (16) | −0.0063 (16) |
C5 | 0.052 (2) | 0.038 (2) | 0.0326 (16) | −0.0026 (18) | 0.0070 (15) | −0.0015 (15) |
C6 | 0.063 (2) | 0.044 (2) | 0.0316 (16) | −0.004 (2) | 0.0079 (16) | −0.0021 (16) |
C7 | 0.061 (2) | 0.045 (2) | 0.0321 (16) | −0.004 (2) | 0.0119 (16) | 0.0054 (16) |
C8 | 0.0444 (19) | 0.036 (2) | 0.0405 (17) | 0.0017 (17) | 0.0075 (15) | 0.0037 (15) |
C9 | 0.062 (2) | 0.046 (2) | 0.0310 (17) | −0.007 (2) | 0.0053 (16) | −0.0011 (16) |
C10 | 0.062 (2) | 0.041 (2) | 0.0337 (16) | −0.008 (2) | 0.0066 (16) | 0.0035 (15) |
C11 | 0.051 (2) | 0.0346 (19) | 0.0367 (17) | −0.0033 (18) | 0.0079 (15) | 0.0022 (15) |
C12 | 0.040 (2) | 0.053 (3) | 0.057 (2) | −0.0042 (19) | 0.0122 (17) | 0.0134 (19) |
C13 | 0.043 (2) | 0.046 (2) | 0.054 (2) | 0.0045 (19) | 0.0104 (17) | 0.0130 (18) |
C14 | 0.052 (2) | 0.035 (2) | 0.0400 (18) | −0.0036 (18) | 0.0094 (16) | 0.0011 (15) |
C15 | 0.044 (2) | 0.049 (2) | 0.057 (2) | −0.012 (2) | 0.0133 (17) | 0.0034 (19) |
Br1 | 0.0867 (3) | 0.0633 (3) | 0.0449 (2) | 0.0030 (3) | −0.00761 (19) | −0.0020 (2) |
C16 | 0.041 (2) | 0.051 (2) | 0.050 (2) | 0.0016 (19) | 0.0056 (16) | 0.0080 (18) |
C17 | 0.046 (2) | 0.0343 (18) | 0.0387 (17) | −0.0067 (18) | 0.0072 (15) | 0.0031 (15) |
C18 | 0.056 (2) | 0.035 (2) | 0.049 (2) | 0.0065 (19) | 0.0071 (17) | 0.0022 (17) |
C19 | 0.069 (2) | 0.038 (2) | 0.0426 (19) | 0.001 (2) | 0.0118 (18) | −0.0046 (17) |
C20 | 0.052 (2) | 0.041 (2) | 0.0370 (17) | −0.0025 (19) | 0.0066 (15) | 0.0047 (16) |
C21 | 0.055 (2) | 0.040 (2) | 0.049 (2) | 0.0092 (19) | 0.0045 (17) | 0.0026 (17) |
C22 | 0.059 (2) | 0.036 (2) | 0.0460 (19) | 0.004 (2) | 0.0064 (17) | −0.0016 (17) |
Br2 | 0.0765 (3) | 0.0511 (3) | 0.0828 (3) | −0.0111 (2) | 0.0102 (2) | 0.0252 (2) |
N1—C8 | 1.395 (4) | C11—C12 | 1.381 (5) |
N1—C17 | 1.424 (4) | C12—C13 | 1.382 (5) |
N1—C11 | 1.431 (4) | C12—H12A | 0.9300 |
N2—C1 | 1.140 (5) | C13—C14 | 1.369 (5) |
N3—C2 | 1.142 (4) | C13—H13A | 0.9300 |
C1—C3 | 1.436 (6) | C14—C15 | 1.368 (5) |
C2—C3 | 1.428 (5) | C14—Br2 | 1.903 (3) |
C3—C4 | 1.341 (5) | C15—C16 | 1.386 (5) |
C4—C5 | 1.438 (5) | C15—H15A | 0.9300 |
C4—H4A | 0.9300 | Br1—C20 | 1.900 (3) |
C5—C10 | 1.399 (4) | C16—H16A | 0.9300 |
C5—C6 | 1.401 (5) | C17—C22 | 1.382 (5) |
C6—C7 | 1.359 (5) | C17—C18 | 1.384 (5) |
C6—H6A | 0.9300 | C18—C19 | 1.387 (5) |
C7—C8 | 1.396 (4) | C18—H18A | 0.9300 |
C7—H7A | 0.9300 | C19—C20 | 1.370 (5) |
C8—C9 | 1.403 (5) | C19—H19A | 0.9300 |
C9—C10 | 1.368 (5) | C20—C21 | 1.372 (5) |
C9—H9A | 0.9300 | C21—C22 | 1.384 (5) |
C10—H10A | 0.9300 | C21—H21A | 0.9300 |
C11—C16 | 1.377 (5) | C22—H22A | 0.9300 |
C8—N1—C17 | 120.8 (3) | C11—C12—H12A | 119.7 |
C8—N1—C11 | 121.5 (3) | C13—C12—H12A | 119.7 |
C17—N1—C11 | 117.6 (3) | C14—C13—C12 | 118.8 (3) |
N2—C1—C3 | 178.0 (5) | C14—C13—H13A | 120.6 |
N3—C2—C3 | 177.4 (4) | C12—C13—H13A | 120.6 |
C4—C3—C2 | 126.0 (3) | C15—C14—C13 | 121.8 (3) |
C4—C3—C1 | 120.6 (3) | C15—C14—Br2 | 118.9 (3) |
C2—C3—C1 | 113.3 (3) | C13—C14—Br2 | 119.2 (3) |
C3—C4—C5 | 131.7 (3) | C14—C15—C16 | 118.8 (3) |
C3—C4—H4A | 114.2 | C14—C15—H15A | 120.6 |
C5—C4—H4A | 114.2 | C16—C15—H15A | 120.6 |
C10—C5—C6 | 116.4 (3) | C11—C16—C15 | 120.6 (3) |
C10—C5—C4 | 125.2 (3) | C11—C16—H16A | 119.7 |
C6—C5—C4 | 118.4 (3) | C15—C16—H16A | 119.7 |
C7—C6—C5 | 122.4 (3) | C22—C17—C18 | 119.0 (3) |
C7—C6—H6A | 118.8 | C22—C17—N1 | 120.7 (3) |
C5—C6—H6A | 118.8 | C18—C17—N1 | 120.3 (3) |
C6—C7—C8 | 120.8 (3) | C17—C18—C19 | 120.4 (3) |
C6—C7—H7A | 119.6 | C17—C18—H18A | 119.8 |
C8—C7—H7A | 119.6 | C19—C18—H18A | 119.8 |
N1—C8—C7 | 121.6 (3) | C20—C19—C18 | 119.5 (3) |
N1—C8—C9 | 120.6 (3) | C20—C19—H19A | 120.3 |
C7—C8—C9 | 117.7 (3) | C18—C19—H19A | 120.3 |
C10—C9—C8 | 120.8 (3) | C19—C20—C21 | 121.1 (3) |
C10—C9—H9A | 119.6 | C19—C20—Br1 | 120.3 (3) |
C8—C9—H9A | 119.6 | C21—C20—Br1 | 118.6 (3) |
C9—C10—C5 | 121.8 (3) | C20—C21—C22 | 119.2 (3) |
C9—C10—H10A | 119.1 | C20—C21—H21A | 120.4 |
C5—C10—H10A | 119.1 | C22—C21—H21A | 120.4 |
C16—C11—C12 | 119.2 (3) | C17—C22—C21 | 120.8 (3) |
C16—C11—N1 | 119.7 (3) | C17—C22—H22A | 119.6 |
C12—C11—N1 | 121.1 (3) | C21—C22—H22A | 119.6 |
C11—C12—C13 | 120.6 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
C4—H4A···N3i | 0.93 | 2.52 | 3.438 (5) | 169 |
C6—H6A···N2ii | 0.93 | 2.60 | 3.404 (5) | 145 |
Symmetry codes: (i) x, −y+5/2, z+1/2; (ii) −x+2, y−1/2, −z+3/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
C4—H4A···N3i | 0.93 | 2.52 | 3.438 (5) | 169 |
C6—H6A···N2ii | 0.93 | 2.60 | 3.404 (5) | 145 |
Symmetry codes: (i) x, −y+5/2, z+1/2; (ii) −x+2, y−1/2, −z+3/2. |
Acknowledgements
The authors gratefully thank the National Natural Science Foundation of China (51203138, 51273179) and the International S&T Cooperation Program, China (2012DFA51210) for support.
References
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Arylamines such as triphenylamine (TPA) are versatile optical materials. The TPA derivatives containing the twisty arylamine exhibits good electron-donating ability and restrict the formation of an excimer complex, which further contributes to enhance fluorescence quantum efficiency (Ning et al., 2007; Noh et al., 2010). As a result, the fluorescence molecule with TPA are the excellent candidate as the luminescent and electron-donating materials (Yao & Belfield, 2005; Patra et al., 2007). Moreover, the molecular packing is relatively loose, leading to the piezofluorochromic properties due to the twisted conformation in the aggregated state. Our group always investigated the piezofluorochromic and optical properties of triphenylamine (TPA) derivatives (Zhang et al., 2012). It was found that the tiny change of the molecular structure had great effect on the piezofluorochromic behavior. The, dye DiCN-TPA with a simple molecular structure is an excellent candidate to investigate structure- property relationships. Within this project the crstal structure of the title compound was determined.
The asymmetric unit consists of one molecule in a general position (Fig. 1). In the crystal structure,the two bromophenyl groups are rotated out of the central benzylidene ring by 68.7 (1) ° and 69.3 (1) °. Both cyano substituents are located nearly in the plane of the 6-membered ring and the dihedral angle between the plane C5–C10 and N2, N3 and C1 to C4 amount to 5.8 (1) °. In the crystal, the molecules self–assemble to form a hydrogen–bonded layer parallel to the bc crystallographic plane connected by weak C—H···N hydrogen bonds(C4—H4A···N3#1 = 169 °, C4···N3#1 = 3.438 (5) Å, C6—H6A···N2#2= 145 ° and C6···N2#2 = 3.404 (5) Å) (#1 = x, 5/2 - y, 1/2 + z; #2 = 2 - x, -1/2 + y, 3/2 - z). These layers are stacked along a axis and are stabilized by van der Waals interactions.