Chemosensing ability of hydroxynaphthylidene derivatives of hydrazine towards Cu 2 + : Experimental and computational studies

Abstract

2-Hydroxynaphthylidene derivatives of hydrazine, namely L 1 , L 2 and L 3 , were synthesized by going through two-step reactions and the products were characterized. The ion recognition properties of these receptors were studied using fluorescence and absorption spectroscopy. The receptors were found to be sensitive and selective towards Cu2+ in methanol solution among the 13 metal ions studied, namely Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, Pb2+, Na+, K+, Ca2+ and Mg2+, by exhibiting switch off fluorescence. The stoichiometry of the complexed species was found to be 2:1. The fluorescence quenching with Cu2+ is in the order of L 1 > L 2 > L 3 . These conjugates were also found to act as colorimetric sensors for Cu2+ in solution by exhibiting visual colour change. The 2:1 complex shows a centrosymmetric structure based on DFT computations. 2-Hydroxynaphthylidene derivative of hydrazine has been shown by fluorescence and absorption spectroscopy as switch-off fluorescence receptor for Cu2+ among 13 different ions studied. The colour change supports this. The species of recognition is a 2:1 complex of the receptor and Cu2+, which was confirmed based on ESI MS. It forms a centrosymmetric structure as established on the basis of DFT computations.