A systematic study of fluorescent coumarin sensors for the detection of aqueous copper ions and aqueous hydrogen sulphide

Abstract

ABSTRACT The induced quenching in fluorescence upon addition of copper (Cu2+) ions and subsequent regain with aqueous hydrogen sulphide (HS−) was studied with a series of coumarin di(picolyl)amine-based compounds, with varying electron withdrawing/donating abilities. The coumarin analogue with an amino group at the 7-position was the most emissive, followed by the methoxy-variant with both the t-butyl- and difluoro-variants being weakly emissive. The amino-variant was also most responsive to quenching upon the addition of Cu2+ ions and was the most responsive to the subsequent addition of HS− ions. All compounds were shown to form predominately a 1:1 copper(II) complex, supported by mass spectral studies and X-ray crystallography. This investigation sheds light on the structural aspects of the copper-sensor interactions and subsequent copper sequestration, contributing to the understanding of their fluorescence properties and potential applications in sensing and imaging.