A new rhodamine derivative as a single optical probe for the recognition of Cu2+ and Zn2+ ions

Abstract

A bifunctional colorimetric and fluorescent chemosensor of type 3,5-dinitro-2-hydroxy benzaldehyde rhodamine hydrazone (RHDN) was synthesized by the condensation of 3,5-dinitro salicylaldehyde and rhodamine B hydrazide. It was characterized using spectroscopic techniques and single crystal studies. The chemosensor RHDN exhibited remarkably enhanced absorbance and colour changes from colourless to pink color on binding with Cu²⁺ ions. In contrast, Zn²⁺ ions were identified by their selective binding with RHDN showing OFF–ON type fluorescence, which changes from colorless to orange color in ultra violet-light. The absorbance and emission pattern of RHDN adduct separately with Cu²⁺ and Zn²⁺ ions were restored with the addition of an aqueous solution of disodium salt of ethylenediaminetetraacetic acid. Thus, RHDN was found to be very robust and reversible in its binding with Cu²⁺ and Zn²⁺ ions separately.