Journal of Physical Chemistry, Vol.99, No.20, 7935-7945, 1995
Band Deconvolution Analysis of the Absorption and Magnetic Circular-Dichroism Spectral Data of Znpc(-2) Recorded at Cryogenic Temperatures
Absorption, magnetic circular dichroism (MCD), and emission spectra recorded from vitrified solutions of zinc phthalocyanine, ZnPc(-2), are reported. A spectral band deconvolution analysis was performed on the absorption and MCD data using a fitting technique in which identical band parameters are used for both sets of data by the SIMPFIT program. A detailed study of the temperature dependence of the absorption and MCD spectra of ZnPc(-2) shows that a major fraction of the spectral intensity observed at room temperature can be assigned to "hot" bands. This results in a significant discrepancy between the absorption and MCD band widths in spectral data recorded at room temperature. The first spectral band deconvolution of the optical spectra of a main group metal phthalocyanine complex recorded at cryogenic temperatures is reported. The analysis identifies an n --> pi* transition, at 604 nm, that lies just to the blue of the lowest energy pi --> pi* transition, the phthalocyanine Q band at 671 nm. The B1 and B2 pi --> pi* transitions are assigned to overlapping bands in the 300-430 nm region. The origin of the vibrational bands associated with Q transition is resolved enabling a complete description of the optical spectrum in the UV-visible region to be made. A band at 509 nm in the spectrum of [ZnPc(-1)](+) is reassigned as an n --> pi* transition on the basis of an earlier spectral deconvolution calculation. The results of the spectral deconvolution calculations are compared with results reported for a number of other spectroscopic and theoretical techniques.
Keywords:PHTHALOCYANINE THIN-FILMS;COMPUTER-AIDED CHEMISTRY;ELECTRONIC-STRUCTURE;ZINC PHTHALOCYANINE;LANGMUIR-BLODGETT;MAGNESIUM PHTHALOCYANINE;MOLECULAR MATERIALS;OPTICAL-PROPERTIES;MCD SPECTRA;METAL-FREE