Benzoxazole and Benzothiazole Derivatives as Potential Fluorescence Imaging Agents

Abstract

Abstract: Substituted Benzoxazole (1-hydroxy-2-naphthoic benzoxazole and 2-hydroxy- 3-naphthoic benzoxazole) and benzothiazole (1-hydroxy-2-naphthoic benzoxazole and 2- hydroxy-3-naphthoic benzothiazole) derivatives previously complexed with Boroncontaining fragments in our lab, were reviewed for potential use in Fluorescence Lifetime Imaging Microscopy (FLIM) with Differential Interference Contrast (DIC) microscopy in adherent cells. The Excited State Intramolecular Proton Transfer (ESIPT), excited state tautomerization, and potential chelating properties inherent to these compounds prompted our research. The flexible nature of the molecules in two key bonds, when compared to that of other fluorophores, contributed to an inherent quantum inefficiency resulting in reduced brightness when compared to commercially available fluorescent dyes like fluorescein. The quantum chemical study of the photochemistry and conformational preference of these compounds was not able to accurately predict absorbance characteristics, but provided insight into the ESIPT process and established a strong conformational preference for one conformer. The unique properties of these ligands and similar compounds may still be of biophotochemical interest and warrant further investigation.