Are luminescent Ru2+ chelated complexes selective coordinative sensors for the detection of heavy cations?

The ability of [Ru(bpy)₂(bpym)]²⁺ (bpy = 2,2'-bipyridine; bpym = 2,2'-bipyrimidine) to probe specifically heavy cations has been investigated by means of density functional theory for transition metals, group 12 elements and Pb²⁺. On the basis of the calculated Gibbs free energies of complexation in water it is shown that all reactions are favorable with negative enthalpies except for Hg²⁺, with the transition metal cations forming stable bi-metallic complexes by coordination to the bpym ligand. Comparison between the optical and photophysical properties of the Ru²⁺ probe and those of the coordination compounds does not demonstrate a high selectivity due to very similar characteristics of the absorption and emission spectra. Whereas by complexation the lowest metal-to-ligand-charge-transfer (MLCT) shoulder of [Ru(bpy)₂(bpym)]²⁺ at 462 nm is more or less shifted to the red as a function of the cation, the second MLCT band at 415 nm, less sensitive to the complexation, gains in intensity and is slightly blue-shifted. The visible MLCT emission of [Ru(bpy)₂(bpym)]²⁺ at 706 nm is altered by complexation leading to near IR (800-900 nm) emission in most of the coordination compounds. Complexation to some transition metal cations (Fe, Co, Rh and Pd) generates low-lying metal-centered (MC) excited states that quench luminescence. In contrast to the conclusion of experimental findings by Kumar et al. (Chem. Commun. 2014, 50, 8488-8490), [Ru(bpy)₂(bpym)]²⁺ cannot be proposed as a fast and selective probe for monitoring Pd²⁺ in aqueous media. Indeed, it does not possess the optical and photophysical characteristics necessary to discriminate Pd²⁺ ions over a variety of other cations.

Detection of Al3+ and Fe3+ ions by nitrobenzoxadiazole bearing pyridine-2,6-dicarboxamide based chemosensors: effect of solvents on detection

Hybrid chemosensors, based on a pyridine-2,6-dicarboxamide fragment while containing a 4-nitrobenzoxadiazole group, are used for the sensing of Al³⁺ and Fe³⁺ ions where detection was significantly controlled by the selection of a solvent.

A dual-responsive colorimetric probe for the detection of Cu2+ and Ni2+ species in real water samples and human serum

The monitoring of heavy transition metals has increasingly attracted great attention because they pollute the environment and have unique physiological functions. Chemosensors are useful tools for monitoring heavy transition metals due to their simple visualization, excellent sensitivity and high selectivity. Herein, we have developed a novel chemosensor for the detection of water-soluble Cu2+ and Ni2+ species with different mechanisms, and low detection limits of 2.1 nM for Cu2+ and 1.2 nM for Ni2+ were obtained. The colorimetric probe CPH has been applied to qualitative and quantitative detection of Cu2+ and Ni2+ species in real samples.

A multi-responsive thiosemicarbazone-based probe for detection and discrimination of group 12 metal ions and its application in logic gates

A new simple 3-in-1 multi-response thiosemicarbazone-based chemosensor has been synthesized and characterized.

A smart switchable module for the detection of multiple ions via turn-on dual-optical readout and their cell imaging studies

A rhodamine based switchable module, RHTH, displays multi-stimuli responses and logic gate based detection of Fe³⁺, Hg²⁺, CN⁻ and S²⁻ ions at ppm levels together with the imaging of these cations in HeLa cell lines.