VIBRONIC INTERACTION AND PHOTOPHYSICS OF CHALCONE DERIVATIVES

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.