A comprehensive photophysical study of 1-(4-methoxy-1-phenyl)-3-(l-nap
hthyl) prop-2-en-1-one (MPNPO) and naptho (1, 2b) furan (NF) in differ
ent solvents at room temperature and at 77 K in ethanolic and methylcy
clohexane glass shows a strong phosphorescence emission in NF. The pho
sphorescence emission and excitation spectra of NF along with their po
larizations and phosphorescence lifetimes suggest that the perturbatio
n of the zero point level of the emitting state ((3) pi, pi) by a nea
rby ((3) pi, pi) state leads to a number of spectral features, which
are not expected from ((3) pi, pi) phosphorescence. It is concluded t
hat the strong solvent dependent triplet quantum yield and lifetime of
NF at 77 K is due to the dependence of radiationless transitions on v
ibronic spin-orbit coupling between ((1)n, pi) and ((3) pi, pi*) stat
es.