Fluorescence quenching of ultraviolet excited aromatic solutions by chloroform and several related chlorinated methanes

摘要

Relative fluorescence quenching rate constants for solvent excitation toS1,S2, andS3are reported for a number of the solventndash;quencher (Sndash;Q) systems in which the solvent was either benzene, toluene,ohyphen;xylene,phyphen;xylene, or anisole and the quencher was either CH2Cl2, CHCl3, CDCl3, CH3CCl3, CFCl3, or CCl4. The magnitude of the experimental rate constants are found to follow qualitatively, but not quantitatively, the hypothesis that the ratehyphen;determining step in the quenching process is the formation of aDSAQ(donorndash;acceptor) exciplex by an excited solvent molecule (Sn,n=1, 2, or 3) and a quencher molecule. Tentative explanations are offered for these findings.