A new ruthenium complex K[RuL(NO)(BSPP)] (L= N,N-bis(2-hydroxy-1-naphthalidene)phenylenediamine and BSPP=Bis(p-sulfonatophenyl)phenylphosphine)) was prepared, characterized completely by analytical methods, and employed as chemosensor for the detection of organophosphates pesticides after testing different molecules such as ethyl parathion (EP), methyl parathion (MP), malathion (MT), chlorpyrifos (CP) and glyphosate (GP). The results show that the complex detects efficiently CP in water medium as it is consistent with spectral binding, titration, and interference studies. In particular, the addition of CP to the ruthenium complex decreases the fluorescence intensity without interference from other pesticides. The limit of detection (LOD) was found in the micromolar range and the stoichiometric ratio for the ruthenium complex with CP determined by Jobs plot was 1:1. When [RuL(NO)(BSPP)]^- was irradiated at λ_ex= 330 nm, the emission was seen at 430 nm, observing the substitution of NO by a water molecule which was then replaced by CP molecule. This was seen in ³¹P NMR, where the signal corresponding to BSPP is trans positioned to NO shifting its signal to downfield due to water coordination to the complex and it was further shifted because of CP binding with the complex. Thus, the presence of equilibriums for [RuL(NO)(BSPP)]^- + H₂O to [RuL(OH₂)(BSPP)]^- + NO and [RuL(OH₂)(BSPP)]^- + CP to [RuL(CP)(BSPP)]^- + H₂O have been proposed since the NMR and UV-Vis experiments also confirm the existence of the CP coordination with Ru(III). The quenching of fluorescence intensity is linearly associated with the increasing concentration of CP.

Virginia Gómez Vidales

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