Mo(vi) complexes of amide–imine conjugates for tuning the selectivity of fluorescence recognition of Y(iii) vs. Pb(ii)

Abstract

Two amide–imine conjugates, viz. 3-methyl-benzoic acid (4-diethylamino-2-hydroxy-benzylidene)-hydrazide (L1) and 3-methyl-benzoic acid (2-hydroxy-naphthalen-1-ylmethylene)-hydrazide (L2), have been prepared and used for a further synthesis of Mo(VI) complexes (M1 and M2, respectively). Single crystal X-ray diffraction analysis confirmed their structures. Interestingly, M1 selectively recognizes Y³⁺ and Pb²⁺ at two different wavelengths, whereas M2 selectively interacts with Y³⁺ with a significantly high binding constant, 1.3 × 10⁵ M⁻¹. The proposed sensing mechanism involves the displacement of Mo(VI) by Y³⁺/Pb²⁺ from respective Mo(VI) complexes. The TCSPC experiment also substantiates the “turn-on” fluorescence process. A logic gate has been constructed utilizing the fluorescence recognition of cations by M1. DFT studies corroborated the cation–probe interactions and allowed exploring the orbital energy parameters.