An intermediate structure trapped in solid-state tautomerization process of (E)-4-[(4-chlorophenylimino)methyl]benzene-1,2,3-triol

An intermediate structure between the benzenoid and cis-quinoid form of the title compound was trapped in solid-state tautomerization with the aid of OH⋯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 R22(10) supramolecular synthons between the Cs 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 OH⋯O type intermolecular H-bonds are fundamental in determining the crystallographically observed conformation of the intermediate structure.