Platinum complexes featuring pyridine bis-N-heterocyclic-imidazol-2-ylidene/-mesoionic-triazol-5-ylidene donors as pincer ligands and chloro (-Cl), acetonitrile (-NCCH3) or cyano (-CN) groups as auxiliary ligands are prepared as highly strained organometallic phosphors. X-ray structures of four of these complexes confirm a distorted square planar geometry, where the pincer ligand and its mesityl wingtips occur in a twisted conformation to each other. Electrochemical and photophysical characterization have been carried out and the experimental results are interpreted with the aid of density functional theory calculations. Emission responses of complexes under exposure to different vapors and mechanical shear are reported. Notably, the platinum complex featuring pyridine bis-imidazol-2-ylidene and a weakly donating acetonitrile auxiliary ligand exhibited strong aquachromic and mechanochromic emission responses, showing color changes from sky blue to green or yellow-green.

A new series of ruthenium(II) carbonyl complexes with benzene-based CCC-pincer bis-(carbene) ligands, [((R)CCC(R))Ru(CO)2(X)](0/+) and [((R)CCC(R))Ru(CO)(NN)](+) ((R)CCC(R) = 2,6-bis-(1-alkylimidazolylidene)benzene, R = Me or (n)Bu; X = I, Br, CH3CN, or 6-(aminomethyl)pyridine (ampy); NN = 2·CH3CN, or chelating ampy or bipyridine), was synthesized and fully characterized. X-Ray structure determinations revealed that these eight complexes have pseudo-octahedral configurations around the ruthenium center with the pincer ligand occupying three meridional sites. These complexes prove to be efficient precatalysts demonstrating very good activity and reusability for the transfer hydrogenation of ketones.

No abstract

Photoactive platinum complexes of stoichiometry [Pt((R)CCC(R))L](0/+) (R = Me, nBu and L = -CN, -C≡CPh, -N≡CCH3, -Py, -CO) featuring pincer-type bis N-heterocyclic carbene (NHC) ligands ((R)CCC(R)) were synthesized. Organometallic syntheses of these complexes are facile and achievable through standard laboratory procedures. Control of intermolecular Pt⋅⋅⋅Pt interaction, π-π stacking, and emission tuning is achieved through suitable choice of the NHC-wingtip substituent (R) and the auxiliary ligand (L). Exposure to specific volatile organic compounds (VOCs) or mechanical grinding triggers changes in emission colors, which render these complexes photofunctional. Solid-state structures and photoluminescence results are described herein.

N-Pyridyl, N'-amido functionalized imidazolium bromides were obtained in high yields as an N-heterocyclic carbene (NHC) precursor and used as bidentate or a pincer ligands to obtain ruthenium complexes via a silver NHC transmetallation route. The incorporation of a phenyl group as an amido-N substituent (R = Ph) results in a bidentate coordination mode through the C(NHC) and N(pyridyl) donors, whereas in its absence (R = H) a pincer coordination mode was observed through the N(pyridyl)^C(NHC)^O(amido) donors. The ruthenium complex featuring a pincer type NCO coordination mode with a protic NH function adjacent to the coordinating O(amido) atom was found to efficiently catalyse the oxidation of activated alcohols effecting quantitative conversions within 30 minutes. However the oxidation of deactivated alcohols required longer reaction times to effect the quantitative transformation.

No abstract

Homoleptic ruthenium complexes [Ru(L n ) 2 ] 2+ bearing unsymmetric pyridine-based bis N-heterocyclic carbene (NHC) pincer ligands are synthesized and structurally characterized. These complexes feature the coexistence of a five-membered and a six-membered ruthenacycle within the same ligand framework, allowing an ideally octahedral C NHC − Ru−N Py bite angle close to 90°. In the solid state, impressive 3 MLCT lifetimes of microsecond regime were detected in all of the complexes, of which [Ru(L 4 ) 2 ] 2+ , featuring four benzimidazol-2-ylidene donors, exhibited the longest values. Electronic properties of all of the ruthenium complexes are investigated by cyclic voltammetry and spectroscopic techniques. Density functional theory results were used to support the experimental observations.

No abstract