4-Chloro-2-[(E)-(4-nitro­phen­yl)diazenyl]phenol

Leonid A Aslanov; Ksenia A Paseshnichenko; Alexandr V Yatsenko

doi:10.1107/S1600536809003675

. 2009 Feb 11;65(Pt 3):o497. doi: 10.1107/S1600536809003675

4-Chloro-2-[(E)-(4-nitrophenyl)diazenyl]phenol

Leonid A Aslanov ^a,^*, Ksenia A Paseshnichenko ^a, Alexandr V Yatsenko ^a

PMCID: PMC2968552 PMID: 21582162

Abstract

The title compound, C₁₂H₈ClN₃O₃, in the crystalline state and in solution, exists in the azo form, as predicted by density functional theory (DFT) calculations. The molecule is approximately planar [the dihedral angle between the rings is 1.83 (8)°], with the nitro group slightly twisted [13.4 (2)°] relative to the benzene ring. Translationally related molecules form stacks along [010] with an interplanar distance of 3.400 (2) Å. The hydroxy group forms an intramolecular hydrogen bond with the azo N atom.

Related literature

For the crystal structure of a closely related molecule, (1Z)-4-hydroxybenzo-1,2-quinone-1-[(2-chloro-4-nitrophenyl)hydrazone, that crystallizes as a hydrazone tautomer, see: You et al. (2004 ▶). For reference structural data, see: Allen (2002 ▶). For details of the synthetic procedure, see: Fierz-David & Blangey (1949 ▶). For background on DFT calculations, see: Becke (1993 ▶); Klamt & Schüürmann (1993 ▶); Krishnan et al. (1980 ▶); Lee et al. (1988 ▶); Schmidt et al. (1993 ▶). For the concept of resonance-assisted hydrogen bonds, see: Gilli et al. (1989 ▶).

Experimental

Crystal data

C₁₂H₈ClN₃O₃
M _r = 277.66
Monoclinic,
a = 19.008 (5) Å
b = 4.817 (2) Å
c = 12.862 (4) Å
β = 92.65 (2)°
V = 1176.4 (7) Å³
Z = 4
Mo Kα radiation
μ = 0.33 mm⁻¹
T = 291 (2) K
0.40 × 0.20 × 0.15 mm

Data collection

Enraf–Nonius CAD-4 diffractometer
Absorption correction: none
2567 measured reflections
2567 independent reflections
2110 reflections with I > 2σ(I)
3 standard reflections frequency: 90 min intensity decay: 4%

Refinement

R[F ² > 2σ(F ²)] = 0.037
wR(F ²) = 0.098
S = 1.56
2567 reflections
173 parameters
H-atom parameters constrained
Δρ_max = 0.25 e Å⁻³
Δρ_min = −0.14 e Å⁻³

Data collection: CAD-4 Software (Enraf–Nonius, 1989 ▶); cell refinement: CAD-4 Software; data reduction: PROFIT (Streltsov & Zavodnik, 1989 ▶) routine of WinGX (Farrugia, 1999 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: PLATON (Spek, 2003 ▶); software used to prepare material for publication: PLATON.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809003675/gk2186sup1.cif

e-65-0o497-sup1.cif^{(16.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809003675/gk2186Isup2.hkl

e-65-0o497-Isup2.hkl^{(126.1KB, 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—H1⋯N2	0.82	1.88	2.5777 (17)	143

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Acknowledgments

KAP and AVY thank the ICDD for financial assistance (grant No. 93-05).

supplementary crystallographic information

Comment

The present work was fulfilled in the course of study of the hydroxyazo-ketohydrazone tautomerism in phenylazophenols. The title compound, (I), exists in crystals as the azo form (Fig. 1). It is evidenced, firstly, by the fact that the H atom was found and refined in the vicinity of O atom, and secondly, by comparison of the molecular geometry with numerous structures of azo tautomers found in the Cambridge Structural Database (Allen, 2002). Since the UV–visible spectra of the crystalline title compound resemble its spectra in solutions, the azo tautomer has to predominate in solutions as well.

However, recently it has been reported that (1Z)-4-hydroxybenzo-1,2-quinone 1-[(2-chloro-4-nitrophenyl)hydrazone (II), the compound closely related to (I), exists in crystals as the hydrazone tautomer (You et al., 2004).

The azo–hydrazone equilibrium is known to be shifted by the effect of donor and acceptor substituents and also by intra- and intermolecular hydrogen bonds. In order to evaluate the relative importance of these factors, we have performed the DFT calculations of azo and hydrazone tautomers of (I) and (II). Calculations were carried out using GAMESS (Schmidt et al., 1993) with B3LYP exchange-correlation functional (Becke, 1993; Lee et al., 1988) and 6-311G** basis set (Krishnan et al., 1980). After geometry of an isolated molecule has been optimized, molecular structure was fixed, and the effect of nonspecific intermolecular interactions was accounted by COSMO method (Klamt & Schüürmann, 1993), taking the dielectric permeability equal to 10. The results indicate that for 2-phenyldiazenylphenol (III), the azo form is by 10.5 kJ/mol more stable than the hydrazone form. For compound (I), this difference decreases to 7.5 kJ/mol and for (II) - to 6.8 kJ/mol, but nonetheless the azo form is still preferable.

Thus, the difference between (I) and (II) most probably arises from specific intermolecular interactions. In (I), there is the only worthnoting intermolecular contact C15—H15···O2 (-x, -1 - y, -z) (H15···O2 2.56 Å, C15···O2 3.452 (2) Å, C15—H15···O2 161°), which cannot have any effect on the relative stability of tautomers. In (II), the keto group forms a strong hydrogen bond with the hydroxy group of a neighboring molecule (O···H 1.74 Å, O···O 2.581 (2) Å, O—H···O 173°). This interaction stabilizes the hydrazone tautomer, according to the conception of resonance-assisted hydrogen bonds (Gilli et al., 1989). So, the shift of tautomeric equilibrium in (II) towards the hydrazone form should be most probably rationalized by formation of intermolecular hydrogen bonds.

Experimental

The title compound was prepared by coupling of p-nitrophenyldiazonium chloride with p-chlorphenol. For details of the synthetic procedure, see Fierz-David & Blangey (1949). Single crystals were grown by slow evaporation of ethanol solution.