Triplet 1-nitronaphthalene and competitive energy and electron transfer reactions with trans-stilbene

A time resolved resonance Raman (TR3) study of 1-nitronaphthalene (1NN) fir st triplet excited stare in various solvents is combined with ab initio cal culations to determine the nature and the geometry of this state in environ ments of different polarity. A transient absorption and TR3 study of the re actions of tripler 1NN with trans-stilbene (tS) in solution in both non-pol ar and polar solvents is reported. In polar solution, (3)1NN acts as an ele ctron acceptor whereas in non-polar solution only energy transfer to tS is observed. Moreover, at high concentrations of tS, the radical cation tS(+) reacts with ground-state tS to form a dimer radical cation (tS(2))(+). Diff erences between the Raman spectra of the monomeric and the dimeric radical cations are reported in the 1500-1650cm(-1) region. The switch from energy to electron transfer when going from nonpolar to polar solutions is discuss ed in terms of the Marcus Hush theory of electron transfer.