Dual functioning dioxo-molybdenum complex of an amide-based imine derivative: fluorescence recognition of Zr(iv) and...

An amide-based imine derivative, namely, 2,4-dihydroxy-benzoic acid (2-hydroxy-naphthalen-1-ylmethylene)-hydrazide [DBANP], is prepared by the condensation of 2,4-dihydroxybenzoic acid hydrazide (DBA) and 2-hydroxynaphthaldehyde. Further, DBANP is employed to prepare the corresponding Mo(vi) complex (DBANPM), the structure of which is established by different spectroscopic techniques and authenticated by single-crystal X-ray diffraction (SC-XRD) analysis. Notably, DBANPM selectively recognizes ZrO²⁺ and Y³⁺ in two different media, namely, aqueous ethanol and ethyl acetate, via the generation of sky-blue emission. The binding constant values for ZrO²⁺ and Y³⁺ are 7.9 × 10⁴ M^-1 and 7.2 × 10⁴ M^-1, respectively. The displacement of Mo(vi) from DBANPM by ZrO²⁺ and Y³⁺ is responsible for this sky-blue emission. DFT studies substantiate the interactions and unveil the associated orbital energy parameters. Silica-immobilized DBANPM allows the solid-phase extractive recovery of ZrO²⁺, while the solvent extraction of Y³⁺ from water to ethyl acetate is achieved using DBANPM. A DBANPM-impregnated paper strip allows for the low-cost, facile and instant fluorescence detection of Y³⁺ in real samples. DBANPM also exhibits a catechol oxidase-like activity.