The aqueous dependent sensing of hydrazine and phosphate anions using a bis-heteroleptic Ru(ii) complex with a phthalimide–anchored pyridine-triazole ligand

Abstract

Selective turn-on luminescence properties are shown by a non-luminescent metalloreceptor upon the addition of phosphate anions in CH₃CN and hydrazine in CH₃CN/H₂O (6/4, v/v). The non-luminescent metalloreceptors [Ru^II(phen)₂(TpH)]2PF₆⁻ (RtpH) and [Ru^II(Phen)₂(TpI)]2PF₆⁻ (RtpI) {phen = 1,10-phenanthroline; TpH = 2-(2-(4-(pyridin-2-yl)-1H-1,2,3-triazol-1-yl)ethyl)isoindoline-1,3-dione; and TpI = 2-(2-(5-iodo-4-(pyridin-2-yl)-1H-1,2,3-triazol-1-yl)ethyl)isoindoline-1,3-dione} were synthesized and characterized. Both metalloreceptors have excellent sensing properties for phosphate anions (H₂PO₄⁻ and H₂P₂O₇²⁻) over other anions in CH₃CN. The limit of detection (LOD) values were calculated to be 79 nM and 48 nM for H₂PO₄⁻ upon addition to RtpH and RtpI, respectively. Noncovalent interactions play a key role in the sensing of phosphate anions, among which the halogen-anion interaction showed superior recognition properties over the hydrogen-anion interaction. Comparative electrochemical experiments, ¹H NMR titration, ³¹P NMR titration, and lifetime studies also show that RtpI has better sensing properties, as evidenced by its more drastic emission response to H₂PO₄⁻ anions compared with RtpH. Moreover, the metalloreceptors showed a remarkable fluorescence increase (at ∼584 nm) upon the addition of hydrazine, without the interference of other amines in CH₃CN/H₂O (6/4, v/v). Interestingly, fluorescence enhancement was observed within live HeLa cells upon hydrazine addition, which is caused by the efficient photoinduced electron transfer process.