Ratiometric fluorescent Zn2+ and In3+ receptors of fused pyrazine with an aminopropanol chain in acetonitrile

Abstract

A series of new potential intramolecular charge transfer ICT fluorescent receptors of Zn²⁺, Cd²⁺, Hg²⁺, Ga³⁺, In³⁺, and Tl³⁺ ions based on N-aryl or N-alkyl variously fused pyridopyrrolopyrazine or pyrrolo[2,3-b]quinoxaline with an integrated donor group, such as 3-aminopropanol, were synthesized and verified. Among [N, N, O] tridentate donors 4a, 6a–d, 10a, 12e, and 14e, only the integrated fluorophore-receptors with the nitrogen atom at the N-5 position of heterocyclic systems, pyrido[2,3-b]pyrrolo[2,3-e]pyrazine 6a, selectively respond to zinc and indium with significant fluorescent enhancement and different mechanisms of binding. The first example of Z to E interconversion of enaminone forms of a ligand responsible for Zn²⁺ complex fluorescence enhancement was documented.