Bridge-Dependent Donor-Metal-Acceptor-Metal-Donor (D-M-A-M-D) Systems: From Charge Transfer to Electron Transfer in Dioxolene-Ge-Diimine Complexes.

Synthesis and structural characterization of a family of germanium-dioxolene complexes with ditopic N-donor ligands (L-L) (L=1,2-bis(pyridin-2-ylmethylene)hydrazine L=1,6-bis-(pyridin-2-yl)-2,5-diaza-1,5-hexadiene, L=N,N-bis(pyridin-2-ylmethylene)-1,4-benzenediamine, L=N,N-bis(pyridin-2-ylmethylene)-(biphenyl)-4,4-diamine, L=2,2'-azopyridine) is reported. The reaction of germanium bis-catecholate with bridging ligands L - L, differing by the nature of the linker between pyridine sites gives rise to dinuclear digermanium complexes (36CatGe)L (36Cat=dianion of 3,6-di-tert-butylcatechol) 1-4 of DMAMD type (donor-metal-acceptor-metal-donor) with a charge transfer in the UV-Vis region. In opposite, the interaction of the 36CatGe with 2,2'-azopyridine (L) results in the two-electron transfer from the donor 36Cat ligands to the azopyridine bridge forming stable open-shell complex 5 [(36SQ)(36CatGe)](L) (36SQ=radical-anionic semiquinonate ligand).

Molecular Twist-Induced Single-Crystal Isomerization and Valence Tautomeric Transitions in a Cobalt-Dioxolene Complex.

A mononuclear valence tautomeric (VT) complex, [Co(pycz)(Sq)(Cat)] (1-trans), where pycz = 9-(pyridin-4-yl)-9H-carbazole, Sq⋅ = 3,5-di-tert-butyl-semiquinonato, and Cat = 3,5-di-tert-butyl-catecholato, is synthesized in the trans configuration, which undergoes one-step valence tautomeric transition above room temperature. Remarkably, 1-trans can transform into its isomeric structure, [Co(pycz)(Sq)(Sq)] (1-cis), at temperature above 350 K in a single-crystal-to-single-crystal way by in situ molecular twist, and the resulting 1-cis exhibits a pronounced two-step VT transition during magnetic measurements that is rare for mononuclear VT complexes. Such drastic solid-state structural transformation is reported in VT compounds for the first time, which is actuated by a crystal surface's melting-recrystallization induced phase transition process.

Tuning valence tautomerism in a family of dinuclear cobalt complexes incorporating a conjugated bridging bis(dioxolene) ligand with weak communication.

Valence tautomerism (VT) involves the stimulated reversible intramolecular electron transfer between a redox-active metal and ligand. Dinuclear cobalt complexes bridged by bis(dioxolene) ligands can undergo thermally-induced VT with access to {Co-cat-cat-Co}, {Co-cat-SQ-Co} and {Co-SQ-SQ-Co} states (cat = catecholate, SQ˙ = semiquinonate, Co refers to low spin Co, Co refers to high spin Co). The resulting potential for two-step VT interconversions offers increased functionality over mononuclear examples.

Controlling Spin Crossover in a Family of Dinuclear Fe(III) Complexes via the Bis(catecholate) Bridging Ligand.

Spin crossover (SCO) complexes can reversibly switch between low spin (LS) and high spin (HS) states, affording possible applications in sensing, displays, and molecular electronics. Dinuclear SCO complexes with access to [LS-LS], [LS-HS], and [HS-HS] states may offer increased levels of functionality. The nature of the SCO interconversion in dinuclear complexes is influenced by the local electronic environment.

Petrogenesis of juvenile pelletal lapilli in ultramafic lamprophyres.

The Chadobets alkaline-carbonatite complex (Siberian craton) is a natural laboratory for all varieties of ultramafic lamprophyres, including damtjernites formed by fluid-explosion mechanisms, which contain a large number of pelletal lapilli. Data obtained from comprehensive mineralogical, structural and chemical studies of these pelletal lapilli show strong similarity with the main magmatic mineral assemblage of damtjernites, suggesting a juvenile composition for them. The composition of phlogopite, carbonate and fluorapatite in pelletal lapilli is mostly constrained toward primitive compositions (beginning) of mineral crystallization trends in ultramafic lamprophyres.