Keto-enol tautomerism, conformations and structure of N-(2-hydroxy-5-methylphenyl),2-hydroxybenzaldehydeimine

N-(2-hydroxy-5-methylphenyl), 2-hydroxybenzaldehydeimine (C14H13NO2) has be en studied by X-ray analysis and AM1 semi-empirical quantum mechanical meth od. It crystallizes in the monoclinic space group P2(1)/c with a = 7.433(1) , b = 9.185(3), c = 186(4) Angstrom, beta = 97.13(1)degrees, V = 1164.3(5) Angstrom(3), Z = 4, D-c = 1.30 gcm(-3) and mu(MoK alpha) = 0.087 mm(-1). Th e structure was solved by direct methods and refined to R = 0.034 for 1407 reflections [I > 2 sigma(I)]. The title compound is photochromic and the mo lecule is not planar. Intramolecular hydrogen bonds occur between the pairs of atoms N(1) and O(1) [2.582(1) Angstrom], and N(1) and O2) [2.655(1) Ang strom], the H atom essentially being bonded to the N atom. Adjacent molecul es are linked via an intermolecular O-H ... O hydrogen bond [2.582(1) Angst rom] between neighbouring molecules. Tautomeric properties and conformation s of the title compound were investigated by semi-empirical quantum mechani cal AMI calculations and the results are compared with the X-ray results. ( C) 1999 Elsevier Science B.V. All rights reserved.