Studies on a vanadium(v) complex as highly selective fluorescence sensor for zirconium(iv) and yttrium(iii) along...

The amide-based imine derivative 2, 4-dihydroxy-benzoic acid (2-hydroxy-naphthalen-1-ylmethylene)-hydrazide (DNP = L¹) has been prepared from 2,4-dihydroxybenzoic acid hydrazide (DBA) by condensation with 2-hydroxynaphthaldehyde. Reaction of L¹ with VO²⁺ leads to the mononuclear compound [VO₂(L¹)]·dmf (1) (dmf = dimethylformamide). The structure of compound 1 has been determined using various spectroscopic techniques and confirmed by single-crystal X-ray diffraction analysis. Compound 1 selectively recognises ZrO²⁺ and Y³⁺ in aqueous dimethylsulfoxide (dmso) and aqueous propanol via generation of yellowish-green and sky-blue emissions, respectively. The binding constant values for ZrO²⁺ and Y³⁺ are 9.2 × 10⁴ M^-1 and 1.1 × 10⁴ M^-1, respectively. The displacement of VO₂ ⁺ from L¹ by ZrO²⁺ and Y³⁺ is responsible for such emissions. DFT studies validate the interaction and disclose the associated orbital energy parameters. Furthermore, compound 1 exhibits phosphatase-like catalytic activity that involves hydrolysis of p-nitrophenyl phosphate (p-NPP) under pseudo-first-order conditions with an apparent rate constant (K _cat), of 2.26 × 10^-3 s^-1. In addition, compound 1 displays catechol oxidase-like activity, with an associated rate constant (K _cat), of 75.64 × 10³ h^-1, indicating appreciable catalytic efficiency.