Synthesis, crystal structure and photophysical properties of 1,4-bis­(1,3-di­aza­azulen-2-yl)benzene: a new π building block

A dimerized 1,3-di­aza­azulene derivative, namely 1,4-bis­(1,3-di­aza­azulen-2-yl)benzene [or 2,2′-(1,4-phenylene)bis(1,3-diazaazulene)], C₂₂H₁₄N₄, (I), has been synthesized successfully through the condensation reaction between 2-meth­oxy­tropone and benzene-1,4-dicarboximidamide hydro­chloride, and was characterized by ¹H NMR and ¹³C NMR spectroscopies, and ESI–MS. X-ray diffraction analysis reveals that (I) has a nearly planar structure with good π-electron delocalization, indicating that it might serve as a π building block. The crystal belongs to the monoclinic system. One-dimensional chains were formed along the a axis through π–π inter­actions and adjacent chains are stabilized by C—H...N inter­actions, forming a three-dimensional architecture. The solid emission of (I) in the crystalline form exhibited a 170 nm red shift compared with that in the solution state. The observed optical bandgap for (I) is 3.22 eV and a cyclic voltammetry experiment confirmed the energy levels of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). The calculated bandgap for (I) is 3.37 eV, which is very close to the experimental result. In addition, the polarizability and hyperpolarizability of (I) were appraised for its further application in second-order nonlinear optical materials.

Computing details

Data collection: CrysAlis PRO (Agilent, 2011); cell refinement: CrysAlis PRO (Agilent, 2011); data reduction: CrysAlis PRO (Agilent, 2011); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

2-[4-(Cyclohepta[d]imidazol-2-yl)phenyl]cyclohepta[d]imidazole

Crystal data

C22H14N4	F(000) = 348
Mr = 334.37	Dx = 1.181 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.7107 Å
a = 3.7610 (3) Å	Cell parameters from 868 reflections
b = 13.2538 (9) Å	θ = 3.2–29.1°
c = 18.8657 (19) Å	µ = 0.07 mm^−1
β = 91.226 (9)°	T = 106 K
V = 940.19 (14) Å^3	Needle, yellow
Z = 2	0.40 × 0.06 × 0.03 mm

Data collection

Agilent Xcalibur Eos Gemini diffractometer	1846 independent reflections
Radiation source: Enhance (Mo) X-ray Source	1396 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.030
Detector resolution: 16.0971 pixels mm^-1	θmax = 26.0°, θmin = 3.3°
ω scans	h = −4→4
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2011)	k = −16→9
Tmin = 0.974, Tmax = 1.000	l = −23→23
3520 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.054	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.155	H atoms treated by a mixture of independent and constrained refinement
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0762P)^2 + 0.1696P] where P = (Fo^2 + 2Fc^2)/3
1846 reflections	(Δ/σ)max < 0.001
118 parameters	Δρmax = 0.20 e Å^−3
0 restraints	Δρmin = −0.20 e Å^−3

Special details

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
N2	0.1546 (4)	0.52343 (13)	0.18448 (8)	0.0228 (4)
N1	0.2047 (4)	0.68447 (13)	0.13999 (9)	0.0218 (4)
C2	0.3804 (5)	0.54193 (16)	0.06353 (10)	0.0194 (5)
C1	0.2471 (5)	0.58368 (16)	0.12997 (10)	0.0199 (5)
C4	0.3503 (5)	0.43798 (16)	0.05077 (10)	0.0202 (5)
H4	0.2500	0.3965	0.0847	0.024*
C3	0.5311 (5)	0.60383 (15)	0.01219 (10)	0.0206 (5)
H3	0.5522	0.6729	0.0201	0.025*
C7	−0.0754 (5)	0.55841 (17)	0.30062 (11)	0.0288 (5)
H7	−0.0712	0.4894	0.3096	0.035*
C8	−0.1973 (5)	0.61972 (18)	0.35492 (12)	0.0293 (5)
H8	−0.2623	0.5862	0.3960	0.035*
C5	0.0698 (5)	0.69108 (16)	0.20612 (11)	0.0218 (5)
C6	0.0408 (5)	0.58873 (16)	0.23432 (10)	0.0220 (5)
C10	−0.1619 (5)	0.79588 (17)	0.30496 (11)	0.0285 (5)
H10	−0.2142	0.8622	0.3171	0.034*
C11	−0.0212 (5)	0.78228 (17)	0.23809 (11)	0.0261 (5)
H11	0.0165	0.8404	0.2117	0.031*
C9	−0.2352 (5)	0.72377 (18)	0.35631 (11)	0.0289 (5)
H9	−0.3238	0.7495	0.3983	0.035*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N2	0.0260 (9)	0.0237 (9)	0.0190 (9)	0.0004 (7)	0.0034 (7)	−0.0031 (7)
N1	0.0227 (8)	0.0240 (9)	0.0187 (8)	0.0019 (7)	0.0006 (7)	−0.0017 (7)
C2	0.0156 (9)	0.0254 (11)	0.0170 (10)	0.0012 (8)	−0.0021 (7)	−0.0007 (8)
C1	0.0165 (9)	0.0245 (10)	0.0187 (10)	−0.0008 (8)	−0.0019 (7)	−0.0015 (8)
C4	0.0189 (9)	0.0244 (11)	0.0174 (9)	0.0001 (8)	0.0002 (8)	0.0005 (9)
C3	0.0200 (9)	0.0202 (10)	0.0214 (10)	0.0016 (8)	−0.0012 (8)	−0.0008 (8)
C7	0.0334 (11)	0.0285 (12)	0.0248 (11)	−0.0039 (9)	0.0037 (9)	−0.0016 (10)
C8	0.0300 (11)	0.0368 (13)	0.0215 (11)	−0.0048 (10)	0.0066 (9)	−0.0045 (10)
C5	0.0180 (9)	0.0269 (11)	0.0202 (10)	−0.0007 (8)	−0.0023 (8)	−0.0026 (9)
C6	0.0215 (9)	0.0248 (10)	0.0198 (10)	−0.0014 (8)	−0.0006 (8)	−0.0038 (9)
C10	0.0262 (10)	0.0301 (12)	0.0290 (12)	0.0048 (9)	−0.0023 (9)	−0.0119 (10)
C11	0.0266 (10)	0.0242 (10)	0.0276 (11)	0.0025 (9)	−0.0009 (9)	−0.0034 (9)
C9	0.0264 (10)	0.0393 (13)	0.0212 (11)	0.0020 (10)	0.0009 (9)	−0.0114 (10)

Geometric parameters (Å, º)

N2—C1	1.353 (3)	C7—C8	1.393 (3)
N2—C6	1.354 (3)	C7—C6	1.393 (3)
N1—C1	1.359 (3)	C8—H8	0.9300
N1—C5	1.360 (3)	C8—C9	1.387 (3)
C2—C1	1.468 (3)	C5—C6	1.462 (3)
C2—C4	1.403 (3)	C5—C11	1.397 (3)
C2—C3	1.399 (3)	C10—H10	0.9300
C4—H4	0.9300	C10—C11	1.390 (3)
C4—C3^i	1.393 (3)	C10—C9	1.393 (3)
C3—C4^i	1.393 (3)	C11—H11	0.9300
C3—H3	0.9300	C9—H9	0.9300
C7—H7	0.9300
C1—N2—C6	103.92 (17)	C9—C8—C7	129.0 (2)
C1—N1—C5	103.78 (17)	C9—C8—H8	115.5
C4—C2—C1	119.27 (17)	N1—C5—C6	107.83 (17)
C3—C2—C1	121.40 (19)	N1—C5—C11	123.49 (19)
C3—C2—C4	119.32 (17)	C11—C5—C6	128.68 (19)
N2—C1—N1	116.20 (16)	N2—C6—C7	123.3 (2)
N2—C1—C2	121.62 (19)	N2—C6—C5	108.26 (17)
N1—C1—C2	122.17 (18)	C7—C6—C5	128.43 (19)
C2—C4—H4	119.6	C11—C10—H10	115.6
C3^i—C4—C2	120.73 (18)	C11—C10—C9	128.8 (2)
C3^i—C4—H4	119.6	C9—C10—H10	115.6
C2—C3—H3	120.0	C5—C11—H11	116.4
C4^i—C3—C2	119.95 (18)	C10—C11—C5	127.3 (2)
C4^i—C3—H3	120.0	C10—C11—H11	116.4
C8—C7—H7	116.3	C8—C9—C10	130.3 (2)
C8—C7—C6	127.4 (2)	C8—C9—H9	114.8
C6—C7—H7	116.3	C10—C9—H9	114.8
C7—C8—H8	115.5
N1—C5—C6—N2	−0.7 (2)	C3—C2—C4—C3^i	0.1 (3)
N1—C5—C6—C7	178.37 (19)	C7—C8—C9—C10	−0.4 (4)
N1—C5—C11—C10	179.60 (19)	C8—C7—C6—N2	−179.84 (19)
C1—N2—C6—C7	−178.87 (18)	C8—C7—C6—C5	1.3 (3)
C1—N2—C6—C5	0.2 (2)	C5—N1—C1—N2	−0.7 (2)
C1—N1—C5—C6	0.8 (2)	C5—N1—C1—C2	178.42 (16)
C1—N1—C5—C11	−178.90 (19)	C6—N2—C1—N1	0.3 (2)
C1—C2—C4—C3^i	178.97 (16)	C6—N2—C1—C2	−178.84 (16)
C1—C2—C3—C4^i	−178.94 (16)	C6—C7—C8—C9	0.6 (4)
C4—C2—C1—N2	12.0 (3)	C6—C5—C11—C10	0.0 (4)
C4—C2—C1—N1	−167.08 (18)	C11—C5—C6—N2	178.99 (19)
C4—C2—C3—C4^i	−0.1 (3)	C11—C5—C6—C7	−2.0 (3)
C3—C2—C1—N2	−169.12 (17)	C11—C10—C9—C8	−1.6 (4)
C3—C2—C1—N1	11.8 (3)	C9—C10—C11—C5	2.1 (4)

Symmetry code: (i) −x+1, −y+1, −z.