An Intermediate Structure Trapped in Solid-State Tautomerization Process of (E)-4

Abstract

An intermediate structure between the benzenoid and cis-quinoid form of the title compound was trapped in solid-state tautomerization with the aid of O{single bond}H⋯O type intermolecular H-bonds leading to multi-point self-recognition. X-ray crystallographic study reveals that an interesting extended structure, H-bonded polymeric chain, is formed by linking pseudocyclic centrosymmetric R<inf>2</inf>2 (10) supramolecular synthons between the C<inf>s</inf> symmetry monomer units. In order to better understand structural features in solid state, ab initio quantum chemical calculations at level of RHF/6-31G* were performed in both gas-phase and the extended structure containing five dimers. The results from the computational studies suggest that the gas-phase conformation of the title compound that closely matches the crystal structure corresponds to a local energy minimum between its benzenoid and cis-quinoid form and the O{single bond}H⋯O type intermolecular H-bonds are fundamental in determining the crystallographically observed conformation of the intermediate structure. © 2007 Elsevier B.V. All rights reserved.