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.

Modulation of Charge Distribution in Cobalt-α-Diimine Complexes toward Valence Tautomerism.

Valence tautomerism (VT) and spin crossover (SCO) are promising avenues for developing a range of molecular materials for sensing, memory, and optoelectronic applications. However, these phenomena arise only when specific metal-ligand combinations are employed. The underexplored combination of cobalt(II/III) paired with bis((aryl)imino)acenapthene (Ar-BIAN) ligands, which can exist as neutral Ar-BIAN (L), monoanionic radical Ar-BIAN (L), and dianionic Ar-BIAN (L) forms, has potential to afford both VT and SCO.

Supramolecular D⋯A-layered structures based on germanium complexes with 2,3-dihydroxynaphthalene and ,'-bidentate ligands.

The concept of using redox-active ligands, which has become extremely widespread in organometallic chemistry, is often considered from 'their effect on the metal center properties' point of view and 'how to modify the ligands'. In this paper, we present the reverse side of this effective approach - a dramatic change of redox properties of ligands under the influence of a redox-inert metal. Germanium derivatives based on 2,3-dihydroxynaphthalene (1) and ,'-bidentate ligands, namely 2,2'-bipyridine (2) and 1,10-phenanthroline (3), were obtained and characterized by CV, UV-vis spectroscopy, DFT calculations and in the case of 3 X-ray diffraction.

One-Step versus Two-Step Valence Tautomeric Transitions in Tetraoxolene-Bridged Dinuclear Cobalt Compounds.

The syntheses of valence tautomeric compounds with multistep transitions using new redox-active ligands are the long-term goal of the field of bistable materials. The redox-active tetraoxolene ligand, 2,7-di--butylpyrene-4,5,9,10-tetraone (pyrene), is now developed to synthesize a pair of dinuclear compounds {[CoL](pyrene)}[Co(CO)]·CHCl·2CHCH (, = 2, L = 1,10-phenanthroline, phen; , = 1.5, L = 2,2'-bipyridine, bpy).

Therapeutic potential of highly functional codon-optimized microutrophin for muscle-specific expression.

High expectations have been set on gene therapy with an AAV-delivered shortened version of dystrophin (µDys) for Duchenne muscular dystrophy (DMD), with several drug candidates currently undergoing clinical trials. Safety concerns with this therapeutic approach include the immune response to introduced dystrophin antigens observed in some DMD patients. Recent reports highlighted microutrophin (µUtrn) as a less immunogenic functional dystrophin substitute for gene therapy.

Acene-Linked Zethrenes and Bisphenalenyls: A DFT Search for Organic Tetraradicals.

Polycyclic aromatic hydrocarbons are of special interest due to their promising nonlinear optical and magnetic properties. A series of acene-linked zethrenes and bisphenalenyls comprising from five to nine benzene rings in the linker group have been computationally studied by the DFT UB3LYP/6-311++G(d,p) quantum-chemical modeling of their electronic structure, possible spin states, and exchange interactions. The zethrenes with octacene and nonacene linkers as well as bisphenalenyls comprising heptacene, octacene, and nonacene linker groups have been revealed to possess tetraradicaloid nature, which makes them promising building blocks for organic optoelectronic and spintronic devices.

Understanding the Origin of One- or Two-Step Valence Tautomeric Transitions in Bis(dioxolene)-Bridged Dinuclear Cobalt Complexes.

Valence tautomerism (VT) involves a reversible stimulated intramolecular electron transfer between a redox-active ligand and redox-active metal. Bis(dioxolene)-bridged dinuclear cobalt compounds provide an avenue toward controlled two-step VT interconversions of the form {Co-cat-cat-Co} ⇌ {Co-cat-SQ-Co}⇌{Co-SQ-SQ-Co} (cat = catecholate, SQ = semiquinonate). Design flexibility for dinuclear VT complexes confers an advantage over two-step spin crossover complexes for future applications in devices or materials.

In vitro assay for the efficacy assessment of AAV vectors expressing microdystrophin.

AAV-delivered microdystrophin genes hold great promise for Duchenne muscular dystrophy (DMD) treatment. It is anticipated that the optimization of engineered dystrophin genes will be required to increase the efficacy and reduce the immunogenicity of transgenic proteins. An in vitro system is required for the efficacy testing of genetically engineered dystrophin genes.

Cysteine Prevents the Development of Experimental Diabetes Induced by Zinc-Binding Substances.

In experimental rabbits, cysteine injected intravenously in a dose of 1000 mg/kg temporarily bound zinc in β cells and prevented the formation of chelate zinc complexes in response to subsequent injection of diabetogenic zinc-binding substances that induce cell destruction. Injection of cysteine to animals was associated with a sharply negative reaction to zinc in β cells, which attests to blockade of zinc ions. Injection of cysteine few minutes after dithizone and formation of zinc-dithizone complex was followed by displacement of dithizone from the complex and prevented the development of diabetes in most animals.

Electronic structure and magnetic properties of the triangular nanographenes with radical substituents: a DFT study.

A series of neutral triangular polycyclic aromatic hydrocarbons functionalized with various radical groups (dithiadiazolyl, verdazyl, nitronylnitroxyl, tert-butyl-nitroxyl and also (2,2,6,6-tetramethylpiperidin-1-yl)oxyl) has been computationally studied by the DFT UB3LYP/6-311++G(d,p) quantum-chemical modelling of their electronic structure and magnetic properties. The dependence of the nature and strength of the exchange interactions between paramagnetic centers on the size of the triangular core, the presence of heteroatoms in the polycyclic moiety, the type of the radical substituents and their spatial arrangement has been ascertained. The molecules with the high-spin electronic ground state possessing strong ferromagnetic exchange interactions and virtually non-interacting paramagnetic centers have been revealed, which makes them promising building blocks for organic spintronics devices.

Small anion-assisted electrochemical potential splitting in a new series of bistriarylamine derivatives: organic mixed valency across a urea bridge and zwitterionization.

We report the synthesis of a new bistriarylamine series having a urea bridge and investigate its mixed-valence (MV) states by electrochemical and spectroelectrochemical methods. We found that the supporting electrolytes had unusual effects on potential splitting during electrochemical behavior, in which a smaller counteranion thermodynamically stabilized a MV cation more substantially than did a bulky one. The effects contrary to those reported in conventional MV systems were explained by zwitterionization through hydrogen bonding between the urea bridge and the counteranions, increasing the electronic interactions between two triarylamino units.

Valence tautomerism and spin crossover in pyridinophane-cobalt-dioxolene complexes: an experimental and computational study.

Compounds [Co(L-NR)(dbdiox)](BPh) (L-NR = N,N'-di-alkyl-2,11-diaza[3.3]-(2,6)pyridinophane, R = iPr (1a), Et (2a); dbdiox = 3,5-di-tert-butyldioxolene) and [M(L-NiPr)(dbdiox)](BPh) (M = Mn (3a), Fe (4a)) have been synthesized and investigated with a view to possible valence tautomeric (VT) or spin crossover (SCO) interconversions. Single crystal X-ray diffraction data for all compounds at 100 or 130 K indicate trivalent metal cations and di-tert-butylcatecholate (dbcat) dioxolene ligands.

Features of the Molecular Structure and Luminescence of Rare-Earth Metal Complexes with Perfluorinated (Benzothiazolyl)phenolate Ligands.

A set of Sc, Nd, Sm, Eu, Ho, Gd, Er, Yb complexes with perfluorinated 2-(benzothiazol-2-yl)phenolate ligands Ln(SON)(DME) were synthesized by the reactions of silylamides Ln[N(SiMe)] with phenol H(SON). The structure of the initial phenol, Sc, and Er complexes was established using X-ray analysis, which revealed that the obtained compounds are mononuclear, in contrast to the binuclear non-fluorinated analogues [Ln(SON)] synthesized earlier. All the obtained complexes, both in solid state and in tetrahydrofuran (THF) solutions, upon excitation by light with λ 395 or 405 nm show intense luminance of the ligands at 440-470 nm.

Rational Design of Electronically Labile Dinuclear Fe and Co complexes with 1,10-Phenanthroline-5,6-Diimine: A DFT study.

A series of coordination compounds of redox-active 1,10-phenanthroline-5,6-diimine with Co bis-diketonates and Fe dihydrobis(pyrazolyl)borates has been computationally designed by means of density functional theory (DFT UB3LYP*/6-311++G(d,p)) calculations of their electronic structure, energy characteristics, and magnetic properties. Four types of complexes differing by the nature and position of the terminal metal-centered fragments have been considered. The performed systematic calculations have revealed the systems capable of undergoing thermally initiated spin-state switching rearrangements, including those governed by the synchronized mechanisms of spin crossover and valence tautomerism.

Europium and ytterbium complexes with o-iminoquinonato ligands: synthesis, structure, and magnetic behavior.

Complexes of divalent ytterbium (1) and europium (2) with a dianionic o-amidophenolate ligand were prepared by both the direct reduction of 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzoquinone (dpp-IQ) and the salt metathesis reaction of potassium o-amidophenolate with LnI2 (Ln = Yb, Eu). Oxidation of o-amidophenolates 1, 2 with one equivalent of dpp-IQ as well as the salt metathesis reaction of potassium o-iminosemiquinolate with LnI2 afforded ligand mixed-valent o-iminosemiquinonato-amidophenolato complexes of trivalent ytterbium (3) and europium (4). All novel complexes 1-4 were fully characterized, including the solid state structures of 1 and 2 determined by single crystal X-ray diffraction.

Halogen-free GeO conversion: electrochemical reduction vs. complexation in (DTBC)Ge[Py(CN)] (n = 0…2) complexes.

3,5-di-tert-Butylcatecholate (DTBC) germanium complexes (DTBC)2Ge[Py(CN)n]2 (n = 0…2) have been synthesized from GeO2, 3,5-di-tert-butylcatechol and cyano-substituted pyridines Py(CN)n and characterized by elemental analysis, NMR, IR and UV-VIS spectroscopy. The structure of 1 (with 4-cyanopyridine) has been determined by X-ray single crystal analysis. UV-VIS spectra have shown that these complexes are stable in CH3CN, toluene and CH2Cl2 solutions; in contrast, they are rapidly decomposed by dimethylformamide and tetrahydrofuran.

The structurally variable network of spin couplings and migrating paramagnetic centers in binuclear o-quinone Co complexes with biradical acene linkers: a computational DFT study.

A series of new magnetically-active coordination compounds comprising binuclear mixed-ligand complexes of cobalt bis-diketonates with acene linkers functionalized by two redox-active o-quinone moieties has been designed by means of density functional theory (DFT UB3LYP*/6-311++G(d,p)) calculations of their electronic structure, energy characteristics and magnetic properties. Two types of redox-active ligands include those with an acene linker bridging two o-benzoquinone fragments and the ligands containing an integrated π-conjugated system formed by annulation of o-quinone rings to the polycyclic core. The calculations reveal the dependence of spin density distribution in the compounds under study on the type of ligand.

Computational Assessment of an Elusive Aromatic NP Molecule.

We computationally proved that the planar aromatic hexagonal isomer NP with the alteration of N and P is the second most stable structure for the NP stoichiometry. We found that the aromatic isomer has high barriers for transition into the global minimum structure or into the three isolated NP molecules, making this structure kinetically stable. We showed that the sandwich NPCrNP molecule corresponds to a minimum on the potential energy surface; thus, the aromatic NP molecule has a potential to be a new ligand in chemistry.

Dinuclear adducts of di-o-iminoquinone ligands with Co diketonates: computational insights into two-step valence tautomeric rearrangements.

Density functional theory (DFT) computational modeling [B3LYP*/6-311++G(d,p)] of a series of potentially valence tautomeric (VT) dinuclear 2:1 adducts of Co bis-acetylacetonate, bis-trifluoroacetylacetonate and bis-hexafluoroacetylacetonate with redox-active tetradentate di-o-iminoquinone ligands has been performed. The significant energy preference of the low-spin electromeric forms of the complexes on the basis of Co bis-acetylacetonate points to a low probability of VT in these compounds. Electron-withdrawing CF-groups in the diketonate moiety of the mixed-ligand complexes promote narrowing of the energy gaps between the electronic states, which allows one-step VT rearrangements to be expected in the adducts of Co bis-trifluoromethylacetylacetonate.

Features of proteolytic properties of tetraphenylporphyrin complex with lanthanide group metals.

Unlabelled: Demetallation of metalloporphyrin molecules is one of the essential degradation reactions in photosynthesis. The effect of metalloporphyrin nature on removal of central metals from tetraphenylporphyrin complexes based on lanthanide group metals (Dy, Er, Lu, Ho) has been studied. pH values, at which the metal ions leave the metalloporphyrin complex were established using two-phase spectrophotometric titration with potentiometric pH-control.

Usefulness of the σ-Aromaticity and σ-Antiaromaticity Concepts for Clusters and Solid-State Compounds.

In this Review we present examples of clusters, molecules, and solid-state compounds, for which the use of σ-aromaticity and σ-antiaromaticity concepts is essential for understanding of chemical bonding. We show that the bonding patterns in these σ-aromatic and σ-antiaromatic compounds are similar to those of the corresponding π-aromatic and π-antiaromatic chemical systems, respectively. Undoubtedly, σ-aromaticity helps us understand why the high symmetry isomers are the most stable among myriads of other potential structures.