TEMPERATURE EFFECTS ON THE PHOSPHORESCENCE OF TWO COMMON IRIDIUM PHTHALOCYANINE AGGREGATES IN $\alpha$-CHLORONAPHTHALENE

Abstract

Relative phosphorescence intensities and life times of two common iridium phthalocyanine aggregates in $\alpha-chloronapthalene$ between 5K and 80K were studied. From the data activation energies of intersystem crossing were obtained as follows: For crossing from the first excited singlet to the lowest triplet state $E_{a} = 44 \pm 10 cm^{-1}$ and $E_{a}=21 \pm 5 cm^{-1}$ respectively; for crossing from the lowest triplet to the ground singlet state $E_{a}^{p} =42 \pm 10 cm^{-1}$ and $E_{a}^{p}=29 \pm 10 cm^{-1}$ respectively. These activation energies are several times as large as those reported for monomeric platinum phthalocyanine in the same solvent (1). A tentative explanation of this difference will be offered.