A Photo-selection Study of the Charge-transfer Phosphorescence

Abstract

Abstract The polarization of the charge-transfer phosphorescence has been studied by the method of photo-selection. It has been measured relative to the electric vector of the excitation light corresponding to the charge-transfer band in wavelength for the complexes of tetracyanobenzene, o-, m-, and p-dicyanobenzenes, tetrachlorophthalic anhydride, and phthalic anhydride as electron acceptors, and methyl-substituted benzenes as electron donors, in organic glass at 77 K. It has been shown that the degree of polarization through excitation into the charge-transfer band is almost constant in the phosphorescence region, while it gradually decreases as the ionization potential of the donor increases for any of the acceptors. These observations can reasonably be interpreted in terms of a model in which the charge-transfer phosphorescence is polarized normal to the molecular plane, irrespective of the complex, and in which the change in the polarization degree of the charge-transfer phosphorescence is responsible for the change in the direction of the transition moment of the charge-transfer absorption band.