COMPETITIVE ENERGY AND ELECTRON-TRANSFER REACTIONS OF THE TRIPLET-STATE OF 1-NITRONAPHTHALENE - A LASER FLASH-PHOTOLYSIS AND TIME-RESOLVED RESONANCE RAMAN-STUDY

A laser flash photolysis and time-resolved resonance Raman study of 1- nitronaphthalene (1NN) in sodium nitrite and trans-stilbene (tS) solut ion, in both polar and nonpolar solvents, is reported. The transient a bsorption data suggest that 1NN acts as an electron acceptor with nitr ite ions and tS in polar solvents but undergoes energy transfer to tS in nonpolar solutions. At high concentrations of tS the electron-trans fer reaction leads ultimately to the formation of a dimer radical cati on (tS(2))(.+). We report here the Raman spectrum of the radical anion of 2-nitronaphthalene and the differences in the Raman spectra of the monomeric and dimeric radical cation of trans-stilbene in the 1500-16 50 cm(-1) region. The switch from energy to electron transfer when goi ng from nonpolar to polar solutions is discussed in terms of the elect ronic and nuclear factors that govern these reactions.