Cyclometalated complexes [M­(Phbpy)­(CN)] (HPhbpy = 6-phenyl-2,2′-bipyridine) of the group 10 metals (Ni, Pd, and Pt) bearing a carbanionic –C∧N∧N pincer ligand were synthesized and studied in a combined experimental and computational DFT approach. All three complexes were crystallographically characterized showing closely packed dimers with head-to-tail stacking and short metal-metal contacts in the solid state. The computational models for geometries, excited states, and electronic transitions addressed both monomeric (Ni-mono, Pd-mono, and Pt-mono) and dimeric (Ni-dim, Pd-dim, and Pt-dim) entities. Photophysical properties and excited state dynamics of all title complexes were investigated in solution and in the solid at 298 and 77 K. [Ni­(Phbpy)­(CN)] and [Pd­(Phbpy)­(CN)] are virtually nonemissive in solution at 298 K, whereas [Pt­(Phbpy)­(CN)] shows phosphorescence in CH2Cl2 (DCM) solution (λ em = 562 nm) stemming from a mixed 3MLCT/ILCT (metal-to-ligand charge transfer/​intraligand charge transfer) state. At 77 K in a glassy frozen DCM:​MeOH matrix, [Pd­(Phbpy)­(CN)] shows a remarkable emission (λ em = 571 nm) with a photoluminescence quantum yield reaching almost unity, whereas [Ni­(Phbpy)­(CN)] is again nonemissive. Calculations on the monomeric models M-mono show that low-lying metal-centered states (MC, i.e., d-d* configuration) with dissociative character quench the photoluminescence. In the solid state, the complexes [M­(Phbpy)­(CN)] show defined photoluminescence bands (λ em = 561 nm for Pd and 701 nm for Pt). Calculations on the dimeric models M-dim shows that the axial M···M interactions alter the photophysical properties of Pd-dim and Pt-dim toward MMLCT (metal-metal-to-ligand charge transfer) excited states with Pd-dim showing temperature-dependent emission lifetimes, suggesting thermally activated delayed fluorescence, whereas Pt-dim displayed phosphorescence with excimeric character. The metal-metal interactions were analyzed in detail with the quantum theory of atoms in molecules approach.

The fully oxidized Lindqvist-type hexavanadate compounds decorated by phosphine-derivatized Au(I) moieties oriented in a transoid fashion (n-BuAu ) have been prepared by azide−alkyne cycloaddition reactions and characterized by various techniques, including NMR, IR, and UV/vis spectroscopy and electrospray ionization mass spectrometry. Electronic structure calculations unveil the potential of these model hybrid junctions for application in controlled charge-transport experiments on substrate surfaces.

A set of alkynyl-tris(2-pyridyl)phosphine Au(I) complexes was synthesized and characterized. Free coordination functions on the ligand environment periphery, namely ‘scorpionate’ PPy3 and C≡C bond, allowed these ditopic metalloligands to be...

No abstract

Mountain lakes in East Siberia have been studied for recent changes in water chemistry, turbidity and diatom assemblages preserved in bottom sediments. We performed a regional analysis of the relative effect of climate and glacier changes on change in diatom diversity and supply of meltware in proglacial lakes. We analysed sediment records from East Siberian glacier lakes using geochemical and diatoms proxies. We found that dramatic changes in communities and abundance of diatoms and biogenic proxy could be induced by low nutrient concentrations in glacial lakes and high turbidity due to active degradation of glaciers and snow patches as a result of the global increase in temperature in the Northern Hemisphere. Our evidences show that diatoms have been gradually decreased since ca. the 1880s. A significant tendency towards diatom reducing occurred at high summer regional temperatures. This tendency may be attributed to the fact that glaciers and snow patches thawed actively in East Siberia during ca. 1880-1958, which was induced by the beginning of the Recent Warming (ca. 1850-1860) and a long period of relatively warm regional climate from ca. 1900 to 1960.