Hydrogen bonding effects on charge distribution and vibrational spectra of N-(2-carboxyphenyl)salicylidenimine tautomers

Structures of the phenol-imine and quinoid tautomers of the titled ligand have been obtained from the ab initio and hybrid density functional methods. The phenol-imine tautomer having bifurcated NH hydrogen bonds (1.799 and 1.833 Å), has been predicted to be 14.9 kJ mol⁻¹ more stable than the quinoid tautomer wherein OH hydrogen bonded interactions are present. Charge distributions in these tautomers have been calculated using the molecular electrostatic potential as a tool. Consequences of hydrogen bonding to the vibrational spectra are discussed.