Synthesis, crystal structure and spectroscopic study of para substituted 2-hydroxy-3-methoxybenzalideneanilines

Eight Schiff bases derived from 2-hydroxy-3-methoxybenzaldehyde and different Para substituted anilines have been synthesized and their structures were elucidated by physical measurements and FT-IR. NMR assignments were made using H-1, C-13 NMR and aided by 2D COSY homonuclear, HMQC and HMBC heteronuclear correlation techniques. IR spectral analysis of the model compounds was found useful in understanding the degree of stabilization upon this series of enol-imino tautomers, which possess different substituents in the aniline fragment. In order to rationalize the stabilization of tautomer in solid state, the crystallography data of 1-{(4-methylphenylimino)methyl} - and 1-{(4-chlorophenylimino)methyl}-2-hydroxy-3-methoxyphenol were adopted wherein the 4-chloro (4-Cl) and 4-methyl (4-CH3) containing compounds crystallized into orthorhombic lattice with a non-centrosymmetric space group P2(1)2(1)2(1). The relationship between the stabilization of bonding involved in heteronuclear six-membered ring of the tautomer and the conformation of the molecules in crystal phase was reported. (C) 2003 Elsevier B.V. All rights reserved.