Examinando por Autor "Plaza-Pedroche, Rodrigo"
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Ítem Excited state intramolecular proton transfer (ESIPT) in 2-(2´-hydroxyphenyl)pyrimidines: synthesis, optical properties, and theoretical studies(ACS Publications, 2022-05-17) Plaza-Pedroche, Rodrigo; Fernández-Liencres, M. Paz; Jiménez-Pulido, Sonia B.; Illán-Cabeza, Nuria A.; Achelle, Sylvain; Navarro, Amparo; Rodríguez-López, JuliánThe development of fluorescence materials with switched on/of f emission has attracted great attention owing to the potential application of these materials in chemical sensing. In this work, the photophysical properties of a series of original 2-(2′-hydroxyphenyl)pyrimidines were thoroughly studied. The compounds were prepared by following well-established and straightforward methodologies and showed very little or null photoluminescence both in solution and in the solid state. This absence of emission can be explained by a fast proton transfer from the OH group to the nitrogen atoms of the pyrimidine ring to yield an excited tautomer that deactivates through a nonradiative pathway. The key role of the OH group in the emission quenching was demonstrated by the preparation of 2′-unsubstituted derivatives, all of which exhibited violet or blue luminescence. Single crystals of some compounds suitable for an X-ray diffraction analysis could be obtained, which permitted us to investigate inter- and intramolecular interactions and molecular packing structures. The protonation of the pyrimidine ring by an addition of trifluoroacetic acid inhibited the excited-state intramolecular proton transfer (ESIPT) process, causing a reversible switch on fluorescence response detectable by the naked eye. This acidochromic behavior allows 2-(2′-hydroxyphenyl)pyrimidines to be used as solid-state acid−base vapor sensors and anticounterfeiting agents. Extensive density functional theory and its time-dependent counterpart calculations at the M06-2X/6-31+G** level of theory were performed to rationalize all the experimental results and understand the impact of protonation on the different optical transitions.