Vibronic interaction and photophysics of chalcone derivatives

A comprehensive photophysical study of 1-(4-methoxy-1-phenyl)-3-(l-naphthyl) prop-2-en-1-one (MPNPO) and naptho (1, 2b) furan (NF) in different solvents at room temperature and at 77 K in ethanolic and methylcyclohexane glass shows a strong phosphorescence emission in NF. The phosphorescence emission and excitation spectra of NF along with their polarizations and phosphorescence lifetimes suggest that the perturbation of the zero point level of the emitting state ((3) pi, pi*) by a nearby ((3) pi, pi*) state leads to a number of spectral features, which are not expected from ((3) pi, pi*) phosphorescence. It is concluded that the strong solvent dependent triplet quantum yield and lifetime of NF at 77 K is due to the dependence of radiationless transitions on vibronic spin-orbit coupling between ((1)n, pi*) and ((3) pi, pi*) states.