T. Okutsu et al., EXCITED-STATE DYNAMICS OF P-CHLOROTOLUENE IN RIGID GLASS MATRICES, Journal of photochemistry and photobiology. A, Chemistry, 115(3), 1998, pp. 243-247
Excited state dynamics of dual phosphorescent p-chlorotoluene (PCT) wa
s investigated in 3-methylpentane (3MP), methylcyclohexane (MCH), etha
nol/methanol (EtOH/MeOH) and EPA rigid matrices in the temperature ran
ge of 77-110 K. Dual phosphorescence was ascribed to two low-lying tri
plet states, (3)pi pi and 3 pi sigma*. The rate of intersystem crossi
ng (ISC) from S-1 to (3)pi pi and (3)pi sigma* states depends both on
the temperature and solvent. Mutual conversion process between (3)pi
pi and 3 pi sigma* states was observed above 87 K in 3MP, 92 K in MCH
and 105 K in EtOH/MeOH matrices. Non-radiative decay rate constants s
trongly depend on the viscosity of the solvent; in the more viscous so
lvent, non-radiative decay rates become smaller. The activation energi
es depend on the solvent viscosity and it was ascertained that the mut
ual conversion process between (3)pi pi and (3)pi sigma* requires con
formational change. (C) 1998 Elsevier Science S.A. All rights reserved
.