2-[(E)-(5-Amino-2,3-diphenyl­quinoxalin-6-yl)imino­meth­yl]-4-bromo­phenol

Hoong-Kun Fun; Reza Kia; Paul R Raithby

doi:10.1107/S1600536808017716

. 2008 Jun 13;64(Pt 7):o1271–o1272. doi: 10.1107/S1600536808017716

2-[(E)-(5-Amino-2,3-diphenylquinoxalin-6-yl)iminomethyl]-4-bromophenol

Hoong-Kun Fun ^a,^*, Reza Kia ^a,^‡, Paul R Raithby ^b,^§

PMCID: PMC2961755 PMID: 21202904

Abstract

The title compound, C₂₇H₁₉BrN₄O, is a mono-anil Schiff base ligand. Three intramolecular O—H⋯N and N—H⋯N hydrogen bonds involving the hydroxy and amino groups generate S(6) and S(5) ring motifs, respectively. In the crystal structure, weak intermolecular N—H⋯O and C—H⋯O hydrogen bonds together with π–π interactions [centroid–centroid distances = 3.628 (3)–3.729 (3) Å] link neighboring molecules.

Related literature

For details of hydrogen-bond motifs, see: Bernstein et al. (1995 ▶). For bond-length data, see: Allen et al. (1987 ▶). For related structures see, for example: Corden et al. (1996 ▶); Govindasamy et al. (1999 ▶). For applications and bioactivities see, for example: Blower (1998 ▶); Cohen & Schmidt (1964 ▶); Granovski et al. (1993 ▶); Kia et al. (2004 ▶); Li & Chang (1991 ▶); Shahrokhian et al. (2000 ▶); Uhlenbrock et al. (1996 ▶); Unaleroglu & Hokelek (2002 ▶). For related literature, see: Anderson et al. (1997 ▶); Blower (1998 ▶).

Experimental

Crystal data

C₂₇H₁₉BrN₄O
M _r = 495.37
Monoclinic,
a = 22.923 (5) Å
b = 7.344 (5) Å
c = 12.573 (5) Å
β = 92.070 (5)°
V = 2115.2 (17) Å³
Z = 4
Mo Kα radiation
μ = 1.97 mm⁻¹
T = 100.0 (1) K
0.39 × 0.37 × 0.08 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2005 ▶) T _min = 0.510, T _max = 0.853
22554 measured reflections
6205 independent reflections
3722 reflections with I > 2σ(I)
R _int = 0.070

Refinement

R[F ² > 2σ(F ²)] = 0.045
wR(F ²) = 0.142
S = 1.06
6205 reflections
305 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.61 e Å⁻³
Δρ_min = −1.07 e Å⁻³

Data collection: APEX2 (Bruker, 2005 ▶); cell refinement: APEX2; data reduction: SAINT (Bruker, 2005 ▶); program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2003 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808017716/sj2516sup1.cif

e-64-o1271-sup1.cif^{(23.1KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808017716/sj2516Isup2.hkl

e-64-o1271-Isup2.hkl^{(303.7KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1O1⋯N1	0.83	1.83	2.586 (4)	151
N2—H2N2⋯N4	0.88 (4)	2.35 (4)	2.740 (4)	107 (3)
N2—H1N2⋯N1	0.88 (4)	2.44 (4)	2.756 (4)	102 (3)

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Acknowledgments

HKF and RK thank the Malaysian Government and Universiti sains Malaysia for the Science Fund grant No. 305/PFIZIK/613312. RK thanks Universiti Sains Malaysia and the University of Bath for a post-doctoral research fellowship.

supplementary crystallographic information

Comment

Schiff bases are among the most prevalent mixed-donor ligands in coordination chemistry. Schiff bases and their biologically active complexes have been studied over several decades (Anderson et al., 1997; Blower 1998; Corden et al., 1996; Govindasamy et al., 1999; Granovski et al., 1993; Li & Chang, 1991; Shahrokhian et al., 2000). 2-hydroxy Schiff base ligands are of interest mainly due to the existence of O—H···N and O···H—N type hydrogen bonds and tautomerization between the phenol-imine and keto-amine forms (Unaleroglu & Hokelek, 2002; Kia et al., 2004). This type of tautomerism plays an important role for distinguishing their photochromic and thermochromic properties (Cohen & Schmidt, 1964). Knowing the structures of free Schiff bases in solution and in the solid state is important in view of the intramolecular hydrogen bonding and comparison with the structure of Schiff base complexes. In view of the importance of these organic ligands, the title compound (I) was synthesized and its crystal structure is reported here.

In the title compound (Fig. 1), intramolecular O—H···N, and N—H···N hydrogen bonds form six and five-membered rings, producing S(6) and S(5) ring motifs, respectively (Bernstein et al., 1995). The two phenyl substituents on the quinoxaline unit are inclined at an angle of 17.87 (17)° to one another. They also form dihedral angles of 38.96 (15) and 44.46 (15)° with the ten–membered quinoxaline ring. In the crystal packing (Fig. 2), molecules are stacked along the b axis by π···π interactions with Cg2···Cg3 distances ranging from 3.628 (3) – 3.729 (3) Å: symmetry codes 1 - x, 1/2 + y, 3/2 - z and 1 - x, -1/2 + y, 3/2 - z; Cg2 and Cg3 are the centroids of the C1–C6 and C8/C9/C10/C11/C14/C15 phenyl rings, respectively. The crystal structure is stabilized by intramolecular O—H···N, and N—H···N hydrogen bonds, weak intermolecular N—H···O and C—H···O hydrogen bonds, and π···π interactions.

Experimental

A mixture of o-diaminoquinoxaline (313 mg, 1 mmol) and 5-bromo salicylaldehyde (210 mg, 1 mmol) was suspended in 30 ml absolute ethanol. The reaction mixture was stirred under reflux for 1 h. After cooling, the precipitate was filtered, washed with ethanol and ether and dried under vacuum. Single crystals suitable for X-ray diffraction were obtained by evaporation of a mixed chloroform-ethanol (3/1, v/v) solution at room temperature.