Relationship between the quantum yields of electron photoejection and fluorescence of aromatic carboxylate anions in aqueous solution

• Published in: Journal of photochemistry 1985-01, Vol.28 (3), p.383-391
• Main Authors: Köhler, G., Solar, S., Getoff, N., Holzwarth, A.R., Schaffner, K.
• Format: Article
• Language: English
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); Solvated and trapped electrons
• ISSN: 0047-2670
• DOI: 10.1016/0047-2670(85)85040-1

The quantum yield Ø(e aq) of photoejected electrons from aromatic carboxylate anions in aqueous solutions (pH 9.5 – 12.3) appreciably increases with increasing excitation energy; for example, Ø(e aq) for benzoate is 0.0025 for the S 1 state (excitation at 254 nm) and 0.0048 for the S 2 state (excitation at 214 nm). The Ø(e aq) value also increases with the number of CH 2 groups separating the phenyl and carboxylate groups; for example, for phenylbutyrate Ø(e aq) is 0.05 for the S 1 state and 0.010 for the S 2 state. Furthermore, increases of Ø(e aq) are linked with decreases in the quantum yield of fluorescence. In order to evaluate a possible consumption of the photoejected electrons by the ground state carboxylates, the rate constants k(e aq + substrate) for the reaction of solvated electrons with the corresponding substrates were determined.