Fluorescent sensors based on phenanthroline derivatives for the detection of Zn(II) ions

Abstract

Two novel phenanthroline-based fluorescent probes, 1,2-diphenyl-1H-imidazo[4,5-f][1,10]phenanthroline (DIP) and 2-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline (PIP), were designed and synthesized for the highly sensitive and selective detection of Zn²⁺ in DMSO/H₂O solutions. These probes exhibit remarkable detection performance, achieving an impressive detection limit of 0.10 μM while maintaining excellent selectivity against competing metal ions, attributable to their efficient interaction with Zn²⁺. With the addition of Zn²⁺, a significant bathochromic shift of 55 nm in emission maxima was displayed, accompanied by a distinct colorimetric transition from blue to cyan with fluorescence quantum yield of 13.8 %. Particularly noteworthy is DIP's exceptional pH tolerance, maintaining its sensing capability across an unprecedented pH range from strongly acidic to alkaline conditions (pH 2–13). The binding stoichiometry and mechanism were systematically investigated through Job's plot analysis, fluorescence spectral studies, and DFT calculations. This study establishes a novel design paradigm for developing robust fluorescent probes capable of operating under extreme environmental conditions, offering promising potential for environmental monitoring and biological sensing applications.