The quenching of the fluorescence of aromatic hydrocarbons by tertiary derivatives of group V elements

Abstract

A study is made of the quenching of fluorescence of a number of aromatic compounds by triphenyl derivatives of group V elements and by triethylamine in both non-polar and polar solvents. Whilst quenching is observed in many cases, the lack of correlation of the quenching rate with the ionization potential of the quencher suggests that this does not simply involve electron or charge transfer. Evidence is presented that a heavy atom effect involving the group V element is also important. Further, a search has been made for evidence of exciplex formation in the quenching of azulene S 2 fluorescence by a variety of compounds. However, no new emissions attributable to such a species are observed under the conditions studied. In addition, in polar solvents there is no evidence for an overall electron-transfer reaction in the quenching suggesting that if an intermediate charge-transfer or ion pair state is formed this may be of higher energy than the lowest singlet or triplet state, and may decay to yield one of these levels.