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

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 [RuII(phen)2(TpH)]2PF6- (RtpH) and [RuII(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.