Conformational study and structure of N-(2,5-methylphenyl)salicylaldimine

Abstract

N-(2,5-methylphenyl)salicylaldimine (C 15H 15NO) has been investigated by X-ray analysis and AM1 semi-empirical quantum mechanical method. The crystal is in the orthorhombic space group P2 12 12 1 with a = 6.839(1), b = 7.720(4), c = 23.183(3) A ̊ , V = 1224.1(2) A ̊ 3 , Z = 4, D c = 1.222 g cm −3 and μ(Mo K α) = 0.076 mm −1. The title structure was solved by direct methods and refined to R = 0.0364 for 1489 reflections [ I > 2 σ( I)] by full-matrix anisotropic least-squares methods. The title compound is photochromic and the molecule is not planar. There is a strong intramolecular hydrogen bond of distance 2.604(2) Å between the hydroxyl oxygen atom and imine nitrogen atom, the hydrogen atom essentially being bonded to the oxygen atom. Minimum energy conformations from AM1 were calculated as a function of three torsion angles, θ 1 (C8N1C7C6), θ 2 (C9C8N1C7) and θ 3 (N1C7C6C5), varied every 10°. The optimized geometry of the crystal structure corresponding to non-planar conformation is the most stable conformation in all calculations. The results strongly indicate that the minimum energy conformation is primarily determined by non-bonded hydrogen-hydrogen repulsions.