EFFECT OF AXIAL LIGANDS ON THE SPECTROELECTROCHEMICAL PROPERTIES OF ZINC PHTHALOCYANINE FILMS - IN-SITU RAMAN AND ELECTROREFLECTION SPECTRA

Electroreflection and Raman spectra (in situ and ex situ) of zinc phth alocyanine (ZnPc) films (80 nm thick) have been studied. Raman spectra were resonantly and preresonantly enhanced. Both electroreflection an d Raman experiments reveal the homogeneous inclusion of electrolyte an ions upon oxidation of the film. The anions coordinate preferentially axial positions of the ZnPc molecule. This process is accompanied by a n out-of-plane deformation of the phthalocyanine macrocycle, which res ults in the change of both electroreflection and Raman spectra. The Zn Pc molecule remains deformed when the film is saturated with anions. T he detailed analysis of new bands and altered intensities in the Raman spectrum indicates that the molecular symmetry point group changes fr om the D-4h point group to C-2v. The influence of ZnPc oxidation on th e Raman excitation mechanism has been also studied. Effects of axial l igands on the molecular geometry have been studied by quantum chemical calculations for the ZnPc(+), ZnPc(+)Cl(-) and ZnPc(+)(Cl-), species using the unrestricted Hartree-Fock variant of the MNDO method. Calcul ation results show that the ZnPc molecule undergoes an out-of-plane de formation when one axial position is coordinated by the anion.