A Study of the Relationship between Alkyl Substituents,Position of Substituents,and the Fluorescence Lifetimes of Phenyl-N-Methylcarbamates

Abstract

Empirical data is presented to describe the relationship between the fluorescence lifetimes (τ_f) and the position of substituents on the parent molecule, Phenyl-N-Methylcarbamate. The fluorescence lifetimes are determined using time correlated single photon counting technique¹. It is found that increasing lifetimes with position of substitution follows the order, meta > para > ortho in the case of mono-alkyl substituted carbamates. Also, the results below indicate that the long fluorescence lifetime of 4-Dimethylamino-3,5-Xylyl-N-Methylcarbamate, τ_f 108 ns² originates from an n-II? lowest excited state and not the usual II-II? lowest excited states of the other N-Methylcarbamates studied.