Some Hydrated Molecular Complexes of 4-Cyanophenylboronic Acid: Significance of Water in the Structure Stabilization by Theoretical Investigation

Abstract

Molecular complexes 1a – 1c of 4-cyanophenylboronic acid, 1, with N -donor compounds, 4,4′-bipyridine ( a ), 1,2-bis(4-pyridyl)ethene ( b ), and melamine ( c ), respectively, have been prepared, in the form of single crystals, by slow solvent evaporation method. Crystal structures of all the complexes have been determined by the X-ray diffraction technique. All the complexes 1a – 1c were noted to be crystallized as hydrates. Variations in the patterns of intermolecular interactions among the complexes and the geometrical features of 1 have been analyzed comparing with the features found in the native structure of 1 by determining its crystal structure also. The -B(OH) 2 moiety in the native form of 1 and also in the molecular complexes 1a – 1c adopts syn – anti conformation. Further, calculations were performed, using the DFT-D3 method, to rationalize the propensity of formation of hydrate structures and to deliberate the observed structural features with respect to the strength of the intermolecular interactions, for instance, hydrogen bonds.