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+, Zn 2+, 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. © 2014 Indian Academy of Sciences.