FLUORESCENCE SELF-QUENCHING THROUGH HYDROGEN BONDING

A new process of self-quenching has been observed which seems to involve the dissipation of excitation energy through the formation of hydrogen bonds or possibly a proton-transfer mechanism. Special derivatives of the basic chromophore 2-phenylindole which could not self-quench by normal processes were shown to have decreasing fluorescence and scintillation yields with increasing concentration in toluene solutions. All of these compounds had in common a hydrogen atom on the N atom of the indole part of the molecule. By replacement of that H atom with a methyl group all self-quenching was completely eliminated.