A Pyrimidine-Based Turn-On Fluorescent Probe for Highly Sensitive Detection of Copper(II) Ions in Environmental...

The detection of Cu(II) ions is crucial for environmental monitoring and human health, given their dual role as an essential micronutrient and potential toxins that can accumulate in water sources and biological systems. Building on this significance, we synthesized and applied a fluorescent probe, 2-amino-4-(4-chlorophenyl)-1,4-dihydrobenzo[4,5]imidazo[1,2-a]pyrimidine-3-carbonitrile (ACBIP-CN probe), designed for the selective and sensitive detection of Cu²⁺ ions. Upon binding with Cu²⁺, the probe exhibited a marked enhancement in fluorescence emission intensity, enabling rapid and selective detection. Selectivity studies revealed that the fluorescence response of the probe-Cu²⁺ complex remained robust in the presence of competing cations, demonstrating high specificity. Job's plot analysis confirmed a 1:1 stoichiometric binding mode, while Density functional theory (DFT) calculations (B3LYP/6-311G (2d,2p)/LANL2DZ) revealed stable bidentate coordination through nitrogen atoms and a substantial narrowing of the HOMO-LUMO gap, consistent with metal-induced electronic reorganization underlying the sensing mechanism. The ACBIP-CN probe displayed strong analytical performance, achieving a low detection limit of 0.28 µM and quantification limit of 0.86 µM, enabling reliable quantitative analysis at environmentally relevant concentrations. The fluorescence sensor demonstrated outstanding performance in real water samples, achieving recovery rates between 85% and 98.5% with relative standard deviations (RSDs) below 5%. This research demonstrates the potential of ACBIP-CN as a model system for developing advanced luminescent probes, bridging molecular design and analytical performance in Cu²⁺ sensing.