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 (λmax = 390 nm) and Al3+ in MeOH–HEPES buffer (1:1, v/v, pH 7.2) at (λmax = 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.