Photoionization of N,N,N′,N′-tetramethylbenzidine in dodecyltrimethylammonium chloride cationic micelles under 337 nm laser irradiation

Abstract

The 337 nm steady-state laser irradiation of N,N,N′,N′-tetramethylbenzidine (TMB) in dodecyltrimethylammonium chloride (DTAC) cationic micelle produces monophotonic ionization of the molecule. Rapid back reaction of the photoejected electron with the cation due to electron attraction by the positively charged micellar surface reduces the TMB⁺ radical cation yield to 0.002, one-fifth of the yield found in anionic micelles under similar irradiation conditions. The TMB⁺ visible absorption band shows a maximum at 465 nm, but broadens and loses vibronic structure in the cationic micelle in comparison with the anionic micelle. In the presence of anionic electron scavengers the radical cation yield increases to levels at which its electron spin resonance spectrum can be detected in room-temperature cationic micellar solutions.