Dual-color luminescence and visual detection of organophosphorus compounds using a π-extended Ru(II) polypyridyl complex

A ruthenium (II) polypyridyl complex, [Ru(phen)2(BDPPZ)]2+ was synthesized and evaluated as a luminescent coordination probe for the real-time detection of organophosphorus (OP) compounds. The complex displays an intense MLCT emission at 560 nm that responds distinctively to different OPs. Upon titration with fenthion and ethion (0–10 μM), the 560 nm band gradually quenches and red-shifts to ∼590 nm, accompanied by the emergence of a new emission near 430 nm. The resulting ratiometric fluorescence (I430/I560) increases linearly with concentration and is accompanied by a visible color change from yellow to pale blue and cyan blue for fenthion and ethion respectively under UV light. In contrast, malathion induces a turn-on emission at 560 nm without additional band formation, resulting in a brighter yellow luminescence. The sensor exhibits excellent analytical performance with low detection limits of 8 nM, 11.7 nM, and 34 nM for fenthion, ethion, and malathion, respectively. DFT and TDDFT calculations confirm the MLCT character of the observed emission and reveal that the phenanthroline ligands serve as the most favorable interaction sites for the OP molecules. The dual-emission and turn-on characteristics of this Ru (II) complex present a promising framework for designing sensitive luminescent sensors for real-time sensitive OP detection.