Electrophilic Behavior of the "Nucleophilic" Pyramidane: Reactivity of Ge-Pyramidane towards Organolithium Reagents.

The particular reactivity of the recently discovered class of the main group element polyhedral clusters, pyramidanes, remains largely unexplored. In this communication, we report the reaction of the germapyramidane with tert-butyllithium leading to the rather unusual organogermanium compound [Li(thf)]⋅2, as the product of the formal insertion of a Ge-apex into the C-Li bond. This reactivity mode exemplifies unusual electrophilic behaviour of a pyramidane, which is a priori considered as a nucleophilic reagent.

Facile approach to N,O,S-heteropentacycles via condensation of sterically crowded 3-phenoxazin-3-one with substituted anilines.

A convenient method for the synthesis of a series of 2-(arylamino)-3-phenoxazin-3-ones based on the nucleophilic substitution reaction between sterically crowded 3-phenoxazin-3-one and arylamines performed by short-term heating of the melted reactants at 220-250 °C is described, and the compounds were characterized by means of single-crystal X-ray crystallography, NMR, UV-vis, and IR spectroscopy, as well as cyclic voltammetry. The reaction with -amino-, -hydroxy-, and -mercapto-substituted arylamines widened the scope and provided an access to derivatives of N,O- and N,S-heteropentacyclic quinoxalinophenoxazine, triphenodioxazine and oxazinophenothiazine systems.

Reaction of quinaldine with 4,6-di(-butyl)-3-nitro-1,2-benzoquinone. Dependence of the outcome on the reaction conditions and a deeper insight into the mechanism.

Condensation of quinaldine with 4,6-di (-butyl)-3-nitro-1,2-benzoquinone results in the formation of 5,7-di (-butyl)-2-(quinoline-2-yl)-1,3-tropolone, 5,7-di (-butyl)-4-nitro-2-(quinoline-2-yl)-1,3-tropolone, 3,3-dimethyl-2-(5-hydroxy-4-nitro-3--butyl-6-quinoline-2-yl-pyridine-2-yl)butanoic acid, 6-(2,2-dimethylprop-3-yl)-5--butyl-4-nitro-2-(quinoline-2-yl)-pyridine-3-ol, 1,7-di (-butyl)-3-(quinoline-2-yl)-2-azabicyclo-[3.3.0]octa-2,7-diene-4,6-dione--oxide.

A new heteropentacyclic system coupling sterically crowded -benzoquinone with -phenylenediamines.

The reaction between 3,5-di(-butyl)--benzoquinone 1 and -phenylenediamine performed under oxidative conditions that is highly sensitive to the reaction conditions (type of solvent, ratio of reactants, and duration of the reaction) gives rise to various derivatives of a new condensed 10-quinoxalino[3,2,1-]phenoxazin-10-one heteropentacyclic system. The reaction of 1 with -phenyl--phenylenediamine results in the formation of three phenazine-like compounds and, unexpectedly, a derivative of a new spiro[1,3]dioxole-2,2'-furanyl-1-benzo[]imidazole system. The molecular structures of the prepared compounds were authenticated by NMR, mass spectra and X-ray crystallography data.

Magnetically bistable cobalt-dioxolene complexes with a tetradentate N-donor base.

Synthesis and magnetic characterization of a family of cobalt-dioxolene complexes [(MeTPA)Co(36-DBCat)] (1), [(MeTPA)Co(36-DBCat)](PF) (2) and [(MeTPA)Co(diox-(OMe))](BPh) (3) (MeTPA = bis(6-methyl-2-pyridyl)methyl-(2-pyridylmethyl)amine; 36-DBCat = dianion of 3,6-di--butylcatechol; diox-(OMe) - 2,5-di--butyl-3,3,4-trimethoxy-6-oxocyclohexa-1,4-dienolate) is reported. The neutral complex 1 is found to form hexa- (CoON, 1a) and pentacoordinated (CoON, 1b) isomers. Variable temperature single crystal X-ray diffraction analysis of 1a and 1b clearly indicates the presence of the high-spin divalent metal ion and the dianionic catecholate form of the dioxolene ligand.

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.

New Reactions of Contraction of the -Quinone Ring with the Formation of Derivatives of 2-(2-Indolyl)-cyclopenta[b]pyrrole-3,4-diones and Pyrindino[1,2-a]indoles: A Combined Experimental and Density Functional Theory Investigation.

Derivatives of 2-(2-indolyl)-cyclopenta[b]pyrrole-3,4-diones and pyrindino[1,2-a]indoles were synthesized by a new reaction of contraction of the -quinone ring, and their structures were investigated by X-ray crystallography and nuclear magnetic resonance spectroscopy. The mechanisms of the reactions were suggested based on density functional theory calculations of the critical parts of the potential energy surfaces.

Computationally Designed Crystal Structures of the Supertetrahedral GaC and GaSi Solids.

The structural, mechanical, electrical, and optical properties of new supertetrahedral structures -GaX (X = C, Si) were studied by using a solid state DFT calculation. The crystal structures of -GaX are built based on a diamond crystal lattice, in which pairs of adjacent carbon atoms are replaced by GaX fragments, where Ga is a tetrahedron of gallium atoms. Calculations have shown that new mixed-type supertetrahedral structures are dynamically stable, have densities of 3.

Design, synthesis and biological evaluation of 2-quinolyl-1,3-tropolone derivatives as new anti-cancer agents.

Tropolones are promising organic compounds that can have important biologic effects. We developed a series of new 2-quinolyl-1,3-tropolones derivatives that were prepared by the acid-catalyzed reaction of 4,7-dichloro-2-methylquinolines with 1,2-benzoquinones. 2-Quinolyl-1,3-tropolones have been synthesized and tested for their anti-proliferative activity against several human cancer cell lines.

Synthesis and highly efficient light-induced rearrangements of diphenylmethylene(2-benzo[]thienyl)fulgides and fulgimides.

2-Benzo[]thienyl fulgides and fulgimides containing bulky diphenylmethylene substituents were synthesized in the form of their ring-opened - or isomers. In contrast to the majority of known fulgides/fulgimides, that form colored ring-closed structures under UV irradiation, the obtained compounds undergo an irreversible transformation leading to decoloration of their solutions. This rearrangement with the formation of the dihydronaphthalene core appeared to be by 2-3 orders of magnitude more efficient than for the known diphenylmethylene(aryl(hetaryl))fulgides.

Stability, electronic, and optical properties of two-dimensional phosphoborane.

The structure and properties of two-dimensional phosphoborane sheets were computationally investigated using Density Functional Theory calculations. The calculated phonon spectrum and band structure point to dynamic stability and allowed characterization of the predicted two-dimensional material as a direct-gap semiconductor with a band gap of ~1.5 eV.

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.

Superoctahedral two-dimensional metallic boron with peculiar magnetic properties.

Among the diversity of new materials, two-dimensional crystal structures have been attracting significant attention from the broad scientific community due to their promising applications in nanoscience. In this study we predict a novel two-dimensional ferromagnetic boron material, which has been exhaustively studied with DFT methods. The relaxed structure of the 2D-B6 monolayer consists of slightly flattened octahedral units connected with 2c-2e B-B σ-bonds.

Tuning Philicity of Dichlorosilylene: Nucleophilic Behavior of the Dichlorosilylene-NHC Complex ClSi-IPr.

Novel unsaturated four-membered ring disilene, 3,3-dichloro-1,2,4,4-tetrakis[di--butyl(methyl)silyl]-Δ-1,2,3,4-trisilagermetene, was synthesized by the ring expansion reaction of the three-membered ring 1-disilagermirene with the silylene-NHC complex ClSi-IPr. The mechanism of the unexpected formation of this compound was verified by high-level density functional theory computations, which revealed n-π as the dominant orbital interaction.

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.

Molecular dynamics study of a new metastable allotropic crystalline form of gallium-supertetrahedral gallium.

A new metastable crystalline form of gallium has been computationally designed using density functional calculations with imposing periodic boundary conditions. The geometric and electronic structures of the predicted new allotrope were calculated on the basis of a diamond lattice in which all carbon atoms are replaced by gallium Ga tetrahedra. This form does not have any imaginary phonons, thus it is a metastable crystalline form of gallium.

Computationally Designed Crystal Structures of the Supertetrahedral AlX (X = B, C, Al, Si) Solids.

New metastable crystalline forms of the supertetrahedral AlX (X = B, C, Al, Si) solids have been computationally designed using density functional theory calculations with imposing of periodic boundary conditions. The geometric and electronic structures of the predicted new systems were calculated on the basis of the diamond lattice in which all carbon atoms are replaced by the AlX structural units, where X is boron, carbon, aluminum, and silicon atoms. The calculations showed that the dynamic stability of the AlX crystal structures critically depends on the nature of the bridging atom X: supertetrahedral AlC and AlSi solids are dynamically stable, whereas AlB and AlAl ones are unstable.

Difluorophosphorane-Flattened Phosphorene through Difluorination.

We computationally showed that by difluorination of phosphorene we can make a new material difluorphosphorane (DFP) with perfectly planar honeycomb structure out of phosphorus atoms with fluorine atoms attached to every phosphorus atom from above and below. The structure is dynamically stable. It is a semiconductor with a direct band gap of 4.

Metalcarbonyl analogues of annelated cyclooctatetraene and cyclodecapentaene derivatives with a planar core cycle: a quantum chemical study.

With the help of DFT calculations the possibility of stabilizing non-standard flat conformations of cyclooctatetraene and cyclodecapentaene by equatorially located metalcarbonyl substituents has been predicted. Structures and stabilities of a new family of metalcarbonyl Cr(CO)5, Fe(CO)4, Ni(CO)3, Ti(CO)4, and Ni(CO)2 cyclooctatetraene and cyclodecapentaene derivatives have been studied. All cyclooctatetraene derivatives, except the Ti(CO)4 derivative, have planar structures and are characterized by the pronounced anti-aromaticity of the core cycle.

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.

Arsagermene, a compound with an -As[double bond, length as m-dash]Ge[double bond splayed right] double bond.

The first compound featuring an As[double bond, length as m-dash]Ge double bond, arsagermene Mes*As[double bond, length as m-dash]Ge(SiMetBu2)2, was synthesized, isolated and fully characterized. Crystallographic studies revealed that arsagermene has a planar Ge[double bond, length as m-dash]As bond of 2.2731(8) Å, which is notably shorter than the standard Ge-As single bond.

From Borapyramidane to Borole Dianion.

Nonclassical pyramidanes with their inverted tetrahedral configuration of the apical atom are among the most challenging synthetic targets in cluster chemistry. In this Communication, we report on the synthesis and structure of the first representative of pyramidal compounds with the group 13 element at the apex, namely, chloroborapyramidane 2. Reduction of 2 with excess of lithium metal unexpectedly produced the cage-opening product, borole dianion derivative {3·[Li(thf)]}, a 6π-electron aromatic system.

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.

Bis(stibahousene).

Strained hydrocarbons constitute one of the most prominent classes of organic compounds. Among them, bicyclo[2.1.

A Simple Way for the Preparation of Natural Antioxidant Quercetin from Rutin by Subcritical Water.

Context: Quercetin (QR) is a natural strong antioxidant of the plant origins. It is used for treating conditions of heart and blood vessels including "hardening of arteries" (atherosclerosis), high cholesterol, heart disease, circulation problems, preventing cancer, for treating chronic infections of the prostate, etc.

Aims: The aim of this work was to development and study of an acid-free technique for the preparation of QR from rutin (RT) that requires no use of acids and toxic organic solvents.