Experimental and density functional theoretical study of the effects of chemical vapours on the vibrational spectra of nickel phthalocyanine thin films

We report the effects of chemical vapours on the Raman and infrared absorption spectra of α crystalline nickel phthalocyanine thin films. Transmission electron micrograph of the thin films suggests presence of nano-sized particles of nickel phthalocyanine in the thin film. Some vibrational bands show changes in their positions and/or intensities on exposure of thin films with chemical vapours. These changes have been interpreted on the basis of interactions of the vapours molecule with the central nickel ion and other peripheral atoms of the phthalocyanine ring. Density functional theory (DFT) calculations have been carried out to determine the probable geometric structures of the complexes of vapour and phthalocyanine molecules. Calculated geometric structures show in-plane and out-of-plane distortions in the phthalocyanine molecule. Calculations further suggest charge transfer between vapour and phthalocyanine molecules.