Solvent‐Selective Fluorescence Sensing of Mg²⁺ and Al³⁺ Ions by Pincer‐Type NNO Schiff Base Ligand: An Experimental and DFT Optimized Approach

Abstract

A newly developed dual-functional fluorescence sensing probe (phenylhydrazinyl pyridine) Schiff base (SB) has been designed with good selectivity for distinguishing Mg²⁺ and Al³⁺ metal ions in different solvent solutions. SB exhibits quick and visual turn-on fluorescence enhancement in response to Mg²⁺ and Al³⁺ detection. The addition of Mg²⁺ in ACN-HEPES buffer (1 : 1, v/v, pH 7.2) at (λ_max=390 nm) and Al³⁺ in MeOH-HEPES buffer (1 : 1, v/v, pH 7.2) at (λ_max=360 nm) resulted in significant enhancement of fluorescence, up to 7-9 times. These low detection limits of 7.1×10^-6 M (7.1 μM) and 5.15×10^-7 M (0.51 μM) for Mg²⁺ and Al³⁺, respectively, have been achieved by this solvent-controlled platform. Due to the sensing potential towards Mg²⁺, the probe was utilized as an imaging material for breast cancer cells. ¹H-NMR studies were utilized to explore SB's sensing mechanism through turn-on fluorescence. Density functional theory (DFT) calculations were utilized to validate optimized SB and its intricate geometries, which govern the sensing mechanism in the solvent environment. Such a probe has extensive potential applications in bioimaging and the assessment of the quality of wastewater.