Photoacidity of the N-salicylidene-5-chloroaminopyridine

• Published in: Journal of luminescence Vol. 184; pp. 268 - 272
• Main Authors: Barboza, Cristina Aparecida, Germino, José Carlos, Duarte, Luís Gustavo Teixeira Alves, Quites, Fernando Junior, Vazquez, Pedro Antônio Muniz, Atvars, Teresa Dib Zambon
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-04-2017
• Subjects: Dipole moment; Photoacidity; Salicylidenes; TCSPC; TD-DFT; TCSPC; Photoacidity; Salicylidenes; Dipole moment; TD-DFT
• ISSN: 0022-2313; 1872-7883
• DOI: 10.1016/j.jlumin.2016.12.045

Due to the occurrence of excited intramolecular proton transfer (ESIPT) in salicylidenes, in this article the photoacidity of the N-salicylidene-5-chloroaminopyridine (sal-5-Cl-py) was evaluated by electronic absorption and fluorescence spectroscopy. The results strongly suggest that sal-5-Cl-py in aqueous solution behaves as a superacid, ΔpKa=8.83, due to a large change of the dipole moment under electronic excitation between protonated and deprotonated species. Theoretical calculations under the density functional theory – DFT framework showed that as result of the ESIPT the electron density migrates from the phenol to the chloroaminepyridine ring. Such a charge migration is the driving force for the proton transfer reaction.