A new dioxo-molybdenum complex derived from an amide-based imine derivative for the fluorescence recognition of Zr(iv) with phosphatase activity.

Abstract

An amide-imine conjugate, namely, 2,4-dihydroxy-benzoic acid-(2-hydroxy-benzylidene)-hydrazide [DBASL], was prepared from 2,4-dihydroxy benzoic acid hydrazide (DBA) and salicylaldehyde and further used for the synthesis of the corresponding Mo(vi) complex (DBASLM). The structure of DBASLM was established using different spectroscopic techniques and confirmed by single-crystal X-ray diffraction (SC-XRD) analysis. Interestingly, DBASLM selectively recognizes ZrO²⁺ <i>via</i> 'turn-on' sky-blue emission, with notably strong binding constant of 1.3 × 10⁵ M^-1. The proposed sensing mechanism involves the displacement of Mo(vi) from DBASLM by ZrO²⁺. DFT studies also corroborate the interactions and allow the exploration of the associated orbital energy parameters. Silica-immobilized DBASLM is very effective for the solid-phase extractive separation/recovery of ZrO²⁺. A DBASLM-impregnated paper strip allows the low-cost, facile and instant optical detection of ZrO²⁺ in real samples. DBASLM promotes phospho-ester bond hydrolysis in <i>p</i>-nitrophenyl phosphate (<i>p</i>-NPP), which is one of the vital biological processes that play a key role in the destruction of poisonous organo-phosphorus substrates such as pesticides and insecticides used in the agricultural industry.