The Absorption and Fluorescence Spectra of the Ion-Pairs of 1,2,4,5-Tetracyanobenzene with Several Methyl Substituted Benzenes

Abstract

Abstract The absorption and fluorescence spectra and the fluorescence decay times were measured at 77 K for the photoirradiation products of the 1,2,4,5-tetracyanobenzene (TCNB) complexes with hexamethylbenzene (HMB), durene, mesitylene, and toluene. The absorption spectra of the photoproducts are similar in shape to that of the TCNB anion and have maxima at 469, 467, 466, and 465 nm for the TCNB complexes with HMB, durene, mesitylene, and toluene, respectively. The fluorescence maximum wavelengths and decay times of the photoproducts are also similar to those of the TCNB anion (505 nm, 19.6 ns for the TCNB-mesitylene system; 505 nm, 20.7 ns for the TCNB-toluene system). The red shift of the absorption maximum and the decrease in the fluorescence decay time by changing the electron donors from toluene to HMB are discussed in terms of ion-pair formation.