Effect of the presence of metallic ions and cucurbit[n]urils on the phototautomerism of hydroxylated phenylimidazoles

• Grant number: 17/09407-7
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Start date: July 05, 2017
• End date: February 09, 2018
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Organic Chemistry
• Principal Investigator: Fernando Heering Bartoloni
• Grantee: Ronaldo Barros Orfão Junior
• Supervisor: Cornelia Bohne
• Host Institution: Centro de Ciências Naturais e Humanas (CCNH). Universidade Federal do ABC (UFABC). Ministério da Educação (Brasil). Santo André , SP, Brazil
• Institution abroad: University of Victoria (UVic), Canada
• Associated to the scholarship: 14/05813-2 - Use of fluorophores containing phenolic and nitrogenated groups on metal detection by light emission, BP.DR

Abstract

The fluorescence emission of hydroxylated phenylimidazole derivatives operates based on an excited state intramolecular proton transfer (ESIPT). This process is interpreted as a keto/enol equilibrium disturbance that occurs after the absorption of a photon. The equilibrium between these enol and keto tautomers can also be shifted due to the presence of metallic ions, changes in the solvation medium, or addition of small amounts of protic solvents in a nonpolar matrix. Particularly, at the presence of certain metallic ions, the keto tautomer emission is quenched and a new emission signal appears, attributed to the coordinated compound generated by the interaction between the imidazole derivative and the metallic species. In this research project, the study of the fluorescence decay of hydroxylated 2,4,5-triphenylimidazole and 2-phenylimidazole derivatives with time-resolved fluorescence techniques is proposed, in order to investigate the ESIPT process in the absence and presence of metallic cations. This allows to correlate the observed emission with the tautomers' identity, and also to rationalize the operating quenching mechanisms (i.e., static or dynamic) with increasing concentration of metallic ions. Also, fluorescence assays will be performed in the presence of cucurbit[n]uril, to verify the influence of microenvironments formation and of the interaction between these two species on the ESIPT phenomenon.