Fluorescence quenching by the stable free radical di-t-butylnitroxide

Abstract

Bimolecular rate constants (k_Q) were measured for the fluorescence quenching of a series of aromatic hydrocarbons by di‐t‐butylnitroxide (DTBN). In methylcyclohexane, measured values of k_Q were close to the diffusion limit with only a 6.5‐fold variation through the hydrocarbon series. A study of the viscosity dependence of the quenching reaction, in the Smoluchowski manner, suggests an interaction distance of 4–6 Å. A comparison is made of the efficiency of the DTBN and O₂ fluorescence quenching reactions. Possible mechanisms are discussed.