Metal–metal interactions in dinuclear ruthenium complexes containing bridging 4,5-di(2-pyridyl)imidazolates and related ligands

Determination of dissolved nickel in natural waters using a rapid microplate fluorescence assay method

A new microplate analytical procedure is described for the determination of nickel (Ni²⁺) ions in natural water samples. A lophine analogue fluorescent sensor was synthesized and a spectral study showed a selective fluorescence quenching effect of chemical sensor by Ni²⁺ under optimized conditions. Density functional theory (DFT) calculations confirmed the formation of a Ni(II)L₃ complex obtained by the Job plot. The calculations showed that the fluorescence emission peak of L collapses due to the distortion of L in the complex. The simple and fast microplate procedure allowed us to quantify Ni²⁺ with a linear response from 1.6 to 40 µg L^-1 and a quantification limit of 5.4 µg L^-1 without the need of a preconcentration step. The optimized procedure using high-throughput microplate assay has been applied for the determination of Ni²⁺ in natural water samples with good analytical performances.

A Bisamide Ruthenium Polypyridyl Complex as a Robust and Efficient Photosensitizer for Hydrogen Production

A photosensitizer based on a ruthenium complex of a bisamide-polypyridyl ligand gives rise to a large improvement in photocatalytic stability, rate of activity, and efficiency in photocatalytic H₂ production compared to [Ru(bpy)₃ ]²⁺ (bpy=2,2'-bpyridine). The bisamide ruthenium polypyridyl complex combined with a cobaltoxime-based photocatalyst was found to be highly efficient under blue-light (turnover number (TON)=7800) and green-light irradiation (TON=7200) whereas [Ru(bpy)₃ ]²⁺ was significantly less effective with a TON of 2600 and 1100, respectively. The greatest improvement was under red-light-emitting diodes, with bisamide ruthenium polypyridyl complex and cobaltoxime exhibiting a TON of 4200 compared to [Ru(bpy)₃ ]²⁺ and cobaltoxime at a TON of only 71.

Preparation, electrochemical behavior, and variable-temperature magnetic properties of Co(3,5-DBSQ)2 complexes of imidazole- or pyrazole-substituted ligands

Herein we describe the preparation of four new Co(3,5-DBSQ)2 containing known 2-(2-pyridyl)benzimidazole 1, 2,2′-bisbenzimidazole 2, or 2,2-(1H-pyrazole-3,5-diyl)dipyridine 3. We investigate the electronic and variable-temperature magnetic susceptibility properties of these complexes. Complexes containing 2 and 3 are bimetallic and variable-temperature magnetic susceptibility data suggest observation of a stable intermediate (high-spin and low-spin) state for the bimetallic complex with 3, which does undergo valence tautomerism. Complexes 4–6 containing imidazole-based ligands 1 and 2 feature high-spin ground states and no valence tautomerism is observed in these materials. This experimental finding is corroborated with density functional theory calculations, which support the existence of a stable high-spin ground state in these complexes.

Enhanced stereoselectivity in a di-Ru(ii) complex of an achiral bis-bidentate ligand

The diastereoselective formation of a meso-dinuclear Ru(ii) complex of a novel bis-bidentate ligand is reported along with its electrochemical and photophysical properties.

Ruthenium(II) Complexes of New Chelating Indolizino[2,3-b]pyrazine- and Indolizino[2,3-b]quinoxaline-Derived Ligands: Syntheses, Electrochemistry and Absorption Spectroscopy

The highly conjugated chelating ligands 5-(2-pyridyl)indolizino[2,3-b]pyrazine 1, 5-(2-pyridyl)indolizino[2,3-b]quinoxaline 2, and 8,9-dimethyl-5-(2-pyridyl)indolizino[2,3-b]quinoxaline 3 were prepared in one step, with good yields, from di-2-pyridylmethane and 2,3-dichloropyrazine, 2,3-dichloroquinoxaline, and 8,9-dimethyl-2,3-dichloroquinoxaline, respectively. Compounds 1–3 display long-wavelength absorption maxima in the green (1) and yellow (2 and 3) to give intensely coloured red and purple solutions, respectively. Bis(2,2′-bipyridyl)ruthenium(ii) and bis(4,4′-dimethyl-2,2′-bipyridyl)ruthenium(ii) complexes were prepared in moderate to good yields, characterized by NMR spectroscopy and mass spectrometry, and studied by cyclic voltammetry and absorption spectroscopy. Copper(ii) and silver(i) nitrate complexes of the ligands were prepared and complexes [Cu(NO3)2(1)], [Cu(NO3)2(2)]2, and [Ag(NO3)(3)2] were characterized by X-ray crystallography. These structures revealed the planar nature of the ligands and confirmed the proposed chelating mode.

Synthesis and characterisation of eight isomeric bis(2-pyridyloxy)naphthalenes

Eight isomeric bis(2-pyridyloxy)naphthalenes have been prepared from reactions of 2-bromopyridine with the appropriate dihydroxynaphthalene and the products fully characterised by 1- and 2-D NMR spectroscopy.