A new series of fluorescent 5-methoxy-2-pyridylthiazoles with a pH-sensitive dual-emission

Abstract

A new series of fluorophores, 5-methoxy-2-(2-, 3- or 4-pyridyl)thiazoles (2-, 3- or 4-MPT, respectively), were synthesized and their photophysical properties investigated. 2- and 4-MPT are highly fluorescent in polar solvents. Combined with theoretical calculations, studies of the excited state lifetimes in different solvents reveal that their fluorescence mainly results from the internal charge transfer excited state. Acidobasic properties of their ground states and excited states were studied with steady and transient fluorescence spectroscopy. 2- and 4-MPT displayed a pH sensitive fluorescent behavior with a dual-emission in the range 2 to 6 in an aqueous system.