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 R 2 2 ( 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.