A fluorescence probe based on 6-phenylimidazo[2,1-b]thiazole and salicylaldehyde for the relay discerning of In3+ and Cr3+

Abstract

A new fluorescence probe, (E)-N′-(2-hydroxybenzylidene)-6-phenylimidazo[2,1-b]thiazole-3-carbohydrazide (LB1), based on 6-phenylimidazo[2,1-b]thiazole and salicylaldehyde was designed and synthesized. The chemical structures of LB1 and its intermediate were characterized via¹H NMR, ¹³C NMR, FTIR, and mass spectrometry. The LB1 probe exhibited high sensitivity and selectivity towards In³⁺ and Cr³⁺via a fluorescence ‘off–on–off’ response. The detection limits of In³⁺ and Cr³⁺ were 2.59 × 10⁻⁹ M and 8.05 × 10⁻⁷ M, respectively. The LB1 probe demonstrated ideal selectivity for In³⁺ among other competing ions and the newly formed complex [LB1 + In³⁺] could be further used as a new fluorescence platform towards Cr³⁺. The Job Plot of LB1 towards In³⁺ and Cr³⁺ was 1 : 1 and this was supported by mass spectrometry. The plausible binding modes and mechanisms were determined through DFT/TDDFT calculations using Gaussian 09.