2-Bromo­benzo­[c]­cinnoline 6-oxide

The title compound, C₁₂H₇BrN₂O, is a 2-bromo, N6-oxide derivative of the ligand benzo­[c]­cinnoline. The benzo­[c]­cinnoline skeleton is nearly planar. The dihedral angle between the two benzeno­id rings is 2.1 (1)°.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C) = 0.006 Å
• R factor = 0.058
• wR factor = 0.051
• Data-to-parameter ratio = 12.2

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

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S1. Comment

The structures of benzo[c]cinnoline derivatives with different substituents bonded at different positions of the benzo[c]cinnoline skeleton have been the subject of much interest in our laboratory. Examples include 1-morpholinobenzo[c]cinnoline, (II) (Hökelek et al., 1990), 1-piperidinobenzo[c]cinnoline, (III), and 3-piperidinobenzo[c]cinnoline, (IV) (Hökelek et al., 1991a), 2-pyrrolidinobenzo[c]cinnoline, (V), and 4-pyrrolidinobenzo[c]cinnoline, (VI) (Hökelek et al., 1991b), 2-fluorobenzo[c]cinnoline, (VII) (Hökelek, 1991), and 1-nitrobenzo[c]cinnoline, (VIII) (Hökelek et al., 1999).

Benzo[c]cinnoline and some of its derivatives are known to have mutagenic (Leary et al., 1983), antirheumatic (Matter, 1957; Erlenmeyer, 1958), herbicidial (Entwistle et al., 1981) and carcinogenic (Ashby et al., 1980) physiological activities. They have also been used as bleach catalysts in the processing of photographic silver-dye bleach materials (Jan, 1980). The structures of benzo[c]cinnoline (Van der Meer, 1972) and octachlorobenzo[c]cinnoline (King et al., 1983) have been described as complexes with bis(tricarbonyliron) (Doedens, 1970) and benzoatocopper(I) (Toth et al., 1987).

Benzo[c]cinnoline derivatives including N-oxides have been reviewed by Barton & Cockett (1962). As far as we know, there are no reports on the structures of benzo[c]cinnolines substituted with alkyl, alkoxy, aminoalkyl, nitro or N-oxide groups. The structure determination of the title compound, (I), was undertaken in order to understand the effects of changing the types and positions of the substituent and to permit a comparison of its structure with those of previously reported benzo[c]cinnolines to be made.

Fig. 1 shows compound (I) with the atomic numbering. It is a 2-bromo, N6-oxide derivative of the ligand benzod[c]cinnoline. The benzo[c]cinnoline skeleton consists of almost planar rings. The maximum distances from the least-squares planes are 0.014 (4), -0.013 (4) and -0.010 (4) Å for rings α(C1–C5,C12), β(C5,N5,N6,C6,C11,C12) and γ(C6–C11), respectively. The rings are twisted slightly with respect to each other. The dihedral angles between their least-squares planes are α-β = 2.2 (1)°, α-γ = 2.1 (1)° and β-γ = 0.5 (1)°. In benzo[c]cinnoline (Van der Meer, 1972), the dihedral angle between the two benzenoid rings is α-γ = 2.5°. The dihedral angle α-γ depends on the steric interactions between the benzo[c]cinnoline and the substituents at different positions. The interaction is greatest with the substituents at position 1. The corresponding α-γ angles are reported as 11.7° in (II), 14.32 (6) and 3.4 (1)° in (III), 1.8 (1)° in (IV), 1.32 (6)° in (V), 4.95 (7)° in (VI), 0.50 (7)° in (VII) and 8.4 (2)° in (VIII).

There are steric interactions between the H atoms at C1 and C10 (H1···H101 = 2.23 Å), and between the H atom at C7 and the O atom at N6 (O1···H71 = 2.38 Å). The benzo[c]cinnoline skeleton has enlarged C1—C12—C11 [124.6 (4)°] and C10—C11—C12 [124.9 (3)°] angles and smaller ones at the opposite side. The 6-oxide substituent generated enlarged N5—N6—C6 [124.1 (3)°], N6—C6—C7 [119.1 (3)°], C7—C6—C11 [122.2 (4)°] and N5—C5—C12 [124.2 (4)°], and narrowed N6—C6—C11 [118.7 (4)°] and C5—N5—N6 [117.6 (3)°] angles in the benzo[c]cinnoline skeleton with respect to the previously reported corresponding ones (Table 2).

The N6—O1 [1.268 (4) Å] bond length is highly shorter than the pyridine N-oxide N—O [1.304 (15) Å; Allen et al., 1987], probably due to the electron resonating between the O atom and the benzo[c]cinnoline skeleton.

As a general trend, the C1—C2, C3—C4, C9—C10 and C11—C12 bonds, in the benzo[c]cinnoline skeleton are shorter than the other bonds as determined crystallographically in all of the benzo[c]cinnoline ligands. This determination is in agreement with the theoretical calculations made by Mulliken (1955) and Hoffman (1963).

S2. Experimental

The title compound, (I), was synthesized according to the literature method of Kılıç & Tüzün (1990). Crystals suitable for X-ray crystallography were obtained from dichloromethane–ethyl acetate (m.p. 518 K).

S3. Refinement

The positions of the H atoms were calculated geometrically at a distance of 0.95 Å from the corresponding C atom, and a riding model was used during their refinement.

Computing details

Data collection: MolEN (Fair, 1990); cell refinement: MolEN; data reduction: MolEN; program(s) used to solve structure: SHELX86 (Sheldrick, 1990); program(s) used to refine structure: MolEN; molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: MolEN.

Figures

Fig. 1. An ORTEPII (Johnson, 1976) drawing of the title molecule with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.

(I)

Crystal data

C12H7BrN2O	F(000) = 544
Mr = 275.10	Dx = 1.813 Mg m^−3
Monoclinic, P21/a	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yab	Cell parameters from 25 reflections
a = 14.446 (3) Å	θ = 10–11°
b = 3.963 (1) Å	µ = 4.05 mm^−1
c = 17.807 (7) Å	T = 298 K
β = 98.59 (2)°	Rod-shaped, yellow
V = 1008.0 (5) Å^3	0.30 × 0.10 × 0.10 mm
Z = 4

Data collection

Enraf-Nonius CAD-4 diffractometer	Rint = 0.014
ω/2θ scans	θmax = 26.3°
Absorption correction: ψ scan (Fair, 1990)	h = −18→17
Tmin = 0.621, Tmax = 0.667	k = 0→4
2420 measured reflections	l = 0→22
2031 independent reflections	3 standard reflections every 120 min
1764 reflections with F > 0	intensity decay: 1%

Refinement

Refinement on F	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.058	w = 1 / [σ(F)^2 + (0.02 F)^2 + 1.0]
wR(F^2) = 0.051	(Δ/σ)max = 0.01
S = 1.12	Δρmax = 0.46 e Å^−3
1764 reflections	Δρmin = −0.51 e Å^−3
145 parameters

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

	x	y	z	Uiso*/Ueq
Br1	0.59995 (4)	0.4533 (1)	0.06961 (3)	0.0558 (3)
O1	1.0726 (2)	0.917 (1)	0.3468 (2)	0.0683 (4)
C1	0.7222 (3)	0.718 (1)	0.1946 (2)	0.0360 (3)
C2	0.7178 (3)	0.556 (1)	0.1263 (2)	0.0394 (4)
C3	0.7983 (3)	0.458 (1)	0.0970 (3)	0.0482 (4)
C4	0.8832 (3)	0.523 (1)	0.1385 (3)	0.0469 (3)
C5	0.8906 (3)	0.687 (1)	0.2083 (2)	0.0359 (3)
N5	0.9804 (2)	0.731 (1)	0.2456 (2)	0.0467 (3)
N6	0.9907 (2)	0.882 (1)	0.3109 (2)	0.0445 (3)
C6	0.9150 (3)	1.012 (1)	0.3455 (2)	0.0385 (3)
C7	0.9343 (3)	1.171 (1)	0.4156 (3)	0.0436 (3)
C8	0.8623 (3)	1.290 (1)	0.4496 (3)	0.0482 (4)
C9	0.7710 (3)	1.254 (1)	0.4137 (2)	0.0421 (5)
C10	0.7512 (3)	1.096 (1)	0.3448 (2)	0.0356 (4)
C11	0.8234 (3)	0.966 (1)	0.3086 (2)	0.0309 (4)
C12	0.8100 (3)	0.793 (1)	0.2368 (2)	0.0313 (3)
H1	0.666	0.783	0.213	0.0431
H3	0.793	0.346	0.049	0.0571
H4	0.938	0.454	0.119	0.0583
H71	0.997	1.197	0.440	0.0659
H81	0.875	1.397	0.498	0.0659
H91	0.721	1.340	0.437	0.0659
H101	0.688	1.075	0.321	0.0659

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0526 (3)	0.0628 (3)	0.0505 (2)	−0.0129 (3)	−0.0008 (2)	−0.0069 (3)
O1	0.026 (1)	0.093 (3)	0.083 (2)	0.004 (2)	−0.003 (2)	−0.010 (2)
C1	0.030 (2)	0.041 (2)	0.038 (2)	0.000 (2)	0.007 (2)	0.005 (2)
C2	0.044 (2)	0.036 (2)	0.039 (2)	−0.006 (2)	0.009 (2)	0.007 (2)
C3	0.056 (2)	0.047 (3)	0.042 (2)	0.000 (2)	0.014 (2)	−0.003 (2)
C4	0.043 (2)	0.048 (3)	0.052 (2)	0.006 (2)	0.019 (2)	0.001 (2)
C5	0.035 (2)	0.036 (2)	0.039 (2)	0.003 (2)	0.013 (2)	0.007 (2)
N5	0.028 (2)	0.057 (2)	0.055 (2)	0.007 (2)	0.010 (2)	0.002 (2)
N6	0.024 (2)	0.052 (2)	0.057 (2)	0.000 (2)	0.006 (2)	0.011 (2)
C6	0.029 (2)	0.042 (3)	0.045 (2)	−0.001 (2)	0.005 (2)	0.010 (2)
C7	0.034 (2)	0.045 (3)	0.048 (2)	−0.008 (2)	−0.006 (2)	0.005 (2)
C8	0.054 (3)	0.049 (3)	0.039 (2)	−0.006 (2)	0.004 (2)	−0.001 (2)
C9	0.041 (2)	0.044 (3)	0.043 (2)	−0.004 (2)	0.012 (2)	−0.001 (2)
C10	0.028 (2)	0.040 (2)	0.039 (2)	0.001 (2)	0.009 (2)	0.007 (2)
C11	0.028 (2)	0.030 (2)	0.035 (2)	−0.001 (2)	0.003 (2)	0.010 (2)
C12	0.031 (2)	0.030 (2)	0.035 (2)	0.002 (2)	0.009 (2)	0.008 (2)

Geometric parameters (Å, º)

Br1—C2	1.892 (4)	C4—H4	0.950
N6—O1	1.268 (4)	C7—C8	1.358 (7)
C12—C5	1.401 (6)	C7—H71	0.950
C12—C11	1.438 (5)	C1—C2	1.368 (6)
C12—C1	1.404 (5)	C2—C3	1.396 (6)
C5—N5	1.377 (5)	C3—H3	0.950
C4—C5	1.393 (6)	C9—C10	1.367 (6)
N5—N6	1.298 (5)	C8—H81	0.950
C6—C11	1.397 (5)	C8—C9	1.386 (6)
C6—C7	1.389 (6)	C1—H1	0.950
C6—N6	1.426 (5)	C10—H101	0.950
C11—C10	1.402 (6)	C9—H91	0.950
C3—C4	1.359 (6)
C2—C1—C12	119.6 (4)	C7—C8—H81	120.5
C2—C1—H1	120.1	C9—C8—H81	119.9
C12—C1—H1	120.3	C8—C9—C10	121.3 (4)
Br1—C2—C1	119.9 (3)	C8—C9—H91	119.5
Br1—C2—C3	118.1 (3)	C10—C9—H91	119.1
C1—C2—C3	122.0 (4)	C9—C10—C11	120.6 (3)
C2—C3—C4	118.7 (4)	C9—C10—H101	119.9
C2—C3—H3	120.3	C11—C10—H101	119.5
C4—C3—H3	121.0	N5—C5—C12	124.2 (4)
C3—C4—C5	121.1 (4)	C5—N5—N6	117.6 (3)
C3—C4—H4	119.2	N5—N6—C6	124.1 (3)
C5—C4—H4	119.7	N5—N6—O1	118.5 (3)
C4—C5—N5	115.6 (4)	C6—N6—O1	117.4 (4)
C4—C5—C12	120.2 (3)	N6—C6—C7	119.1 (3)
N6—C6—C11	118.7 (4)	C6—C11—C10	116.7 (3)
C7—C6—C11	122.2 (4)	C6—C11—C12	118.4 (4)
C6—C7—C8	119.5 (4)	C10—C11—C12	124.9 (3)
C6—C7—H71	119.7	C1—C12—C5	118.5 (4)
C8—C7—H71	120.8	C1—C12—C11	124.6 (4)
C7—C8—C9	119.7 (4)	C5—C12—C11	116.9 (3)
C12—C1—C2—Br1	179.7 (3)	N5—N6—C6—C11	2.4 (6)
C12—C1—C2—C3	0.8 (7)	O1—N6—C6—C7	0.3 (6)
C2—C1—C12—C5	−2.3 (6)	O1—N6—C6—C11	−177.6 (4)
C2—C1—C12—C11	179.0 (4)	N6—C6—C7—C8	−178.7 (4)
Br1—C2—C3—C4	−178.1 (4)	C11—C6—C7—C8	−0.9 (7)
C1—C2—C3—C4	0.9 (7)	N6—C6—C11—C10	179.7 (4)
C2—C3—C4—C5	−0.9 (7)	N6—C6—C11—C12	−1.0 (6)
C3—C4—C5—N5	178.6 (4)	C7—C6—C11—C10	1.8 (6)
C3—C4—C5—C12	−0.7 (7)	C7—C6—C11—C12	−178.8 (4)
C4—C5—N5—N6	−179.9 (4)	C6—C7—C8—C9	−0.5 (7)
C12—C5—N5—N6	−0.7 (7)	C7—C8—C9—C10	0.8 (7)
C4—C5—C12—C1	2.2 (6)	C8—C9—C10—C11	0.1 (7)
C4—C5—C12—C11	−179.0 (4)	C9—C10—C11—C6	−1.4 (6)
N5—C5—C12—C1	−176.9 (4)	C9—C10—C11—C12	179.3 (4)
N5—C5—C12—C11	1.9 (6)	C6—C11—C12—C1	177.8 (4)
C5—N5—N6—C6	−1.5 (6)	C6—C11—C12—C5	−0.9 (6)
C5—N5—N6—O1	178.4 (4)	C10—C11—C12—C1	−2.9 (7)
N5—N6—C6—C7	−179.8 (4)	C10—C11—C12—C5	178.4 (4)