Effects of chemical analytes on zinc tetraphenylporphine thin films studied by vibrational spectroscopy and density functional theory

We report the effects of methanol, pyridine, diethylamine, dichloromethane, acetonitrile, bromine and NO2 vapours on the Raman and infrared absorption spectra of zinc tetraphenylporphine thin films by recording their spectra before and after exposure with chemical vapours. Positions of some vibrational bands show detectable change on exposure. Changes in the intensity of some vibrational bands of the thin films have also been observed on exposure. Coordination of vapours molecules at the zinc ion and subsequent charge transfer are responsible for the shift in the vibrational bands. Density functional theory calculations have been carried out to determine the probable geometric structures of the porphyrin-vapour complexes. Calculated geometric structures show in-plane and out-of-plane distortions in the porphyrin macrocycle. Calculations also result in charge transfer between vapour and porphyrin molecules. (C) 2012 Elsevier B.V. All rights reserved.