Fluorescence and intersystem crossing from the twisted intramolecular charge transfer (TICT) state of bianthryl in the presence of inorganic ions in polar solvents

Abstract

Quenching of bianthryl (BA) fluorescence by thiocyanide (SCN −), bromide (Br −) and iodide (I −) anions in acetonitrile and alcohols was investigated. The quantum yield of BA triplet formation as a function of the quencher concentration was determined using flash photolysis. A kinetic scheme is proposed to model the process following the fluorescence quenching of BA. It is found that the radical pairs produced by electron transfer quenching of the excited state of anthracene and of the twisted intramolecular charge transfer (TICT) state of BA recombine to the triplet and ground states with different efficiencies: ground state recovery seems to be more important in the case of BA. The discussion highlights the role of spin-orbit coupling in intersystem crossing and of the solvent polarity in the forward and reverse electron transfer processes.