Abstracts

Radziszewski was the first to describe a organic chemiluminescent system in 1877, in which he observed an yellow emission from the reaction between 1,2,4-triphenylimidazole, oxygen and a strong base. In this work, two series of 1,2,4,5-tetraphenylimidazole (TEPI) compounds were synthesized with different substituents on the 1-phenyl ring, which differed only by the absence (series a) or presence (series b) of an o-OH on the 2-phenyl ring. It was observed that the Excited State Intramolecular Proton Transfer (ESIPT) assigns significant differences in the chemiluminesent characteristics of series b when compared to series a. Electron-donor substituents, in general, had higher ΦFL values. The chemiluminescent assays showed that TEPI derivatives can be used as activators in the peroxyoxalate reaction, probably through the mechanism known as Chemically Initiated Electron Exchange Luminescence (CIEEL). Derivatives from series a exhibited lower values of ΦS∞ and ΦCL∞, and higher kCAT/kD when compared to series b. Compared to other systems, series a derivatives had their chemiluminescent parameters analogous to inefficient activators. For series b, these values were equivalent to lophines and classical activators such as anthracene and 2,5-diphenyloxazole. Linear Hammett correlations using the parameters ΦS∞ and kCAT/kD revealed that there is a possibility of an inverted CIEEL mechanism occurring during chemiexcitation, however, the determination of the electrochemical properties of these compounds is necessary to sustain this hypothesis.