Gennady L. Rusinov

Pentanuclear pivalate Ni(II) and Co(II) clusters: modulation of molecular structures and magnetic properties

Abstract Reaction of nickel cluster Ni9(HOOCCMe3)4(μ4-OH)3(μ3-OH)3(μn-OOCCMe3)12 (1) or cobalt pivalate polymer [Co(OH)n(OOCCMe3)2−n]x (7) with bis[3,5-(dimethylpyrazolyl)]-1,2,4,5-tetrazine (3) in MeCN solution was found as a result in the formation of isostructural pentanuclear clusters of composition M5(μ3-OH)2(μ-OOCCMe3)4(μ-N,N′,N″-3,5-Me2C3HN2C2(O)N4)4(MeCN)2 (M=Ni (4), Co (8)) with a planar spirane metal core. Reaction of cobalt complex 7 with 3 in benzene gives rise to a pentanuclear cluster Co5(μ3-OH)2(μ-OOCCMe3)4(μ-N,N′,N″-3,5-Me2C3HN2C2(O)N4)4(C5N2H8)2 (9), containing coordinated pyrazole molecules as terminating ligands instead of labile MeCN ligands in 8. The reaction of cluster 8 with 2,6-diaminopyridine (T=85 ° C ) in MeCN results in the substitution of MeCN ligands and formation of a new cluster Co5(μ3-OH)2(μ-OOCCMe3)4(μ-N,N′,N″-3,5-Me2C3HN2C2(O)N4)4(C5H7N3)2 (10) with two 2,6-diaminopyridine ligands instead of MeCN molecules. The reactions of 4 and 8 with NiCl2·6H2O in MeCN/EtOH solution (3:1) give rise to isostructural ferromagnetic pentanuclear chloro-bridged clusters M5(μ3-OH)2(μ-CI)2(μ-OOCCMe3)2(μ-N,N′,N″-3,5-Me2C3HN2C2(O)N4)2(μ-N,N′,N″,O-3,5-Me2C3HN2C2(O)N4)2(MeCN)2 (M=Co (11), Ni (12)).The reaction of 8 with solid CoCl2·6H2O in MeCN results in new seven-nuclear ferromagnetic cluster Co5(μ3-OH)2(μ-CI)2(μ-OOCCMe3)2(μ-N,N′,N″-3,5-Me2C3HN2C2(O)N4)2(μ-N,N′,N″,O-3,5-Me2C3HN2C2(O)N4)2(MeCN)2[Co(CH3CN)CI2]2 (13). The molecular structures of 4, 8, 9, 10, 12 and 13 established by X-ray diffraction studies and magnetic behavior of new nickel and cobalt pivalate clusters are discussed.

Synthesis, Photophysical and Redox Properties of the D–π–A Type Pyrimidine Dyes Bearing the 9-Phenyl-9H-Carbazole Moiety

Novel donor-π-acceptor dyes bearing the pyrimidine unit as an electron-withdrawing group have been synthesized by using combination of two processes, based on the microwave-assisted Suzuki cross-coupling reaction and nucleophilic aromatic substitution of hydrogen. Spectral properties of the obtained dyes in six aprotic solvents of various polarities have been studied by ultraviolet–visible and fluorescence spectroscopy. In contrast to the absorption spectra, fluorescence emission spectra displayed a strong dependence from their solvent polarities. The nature of the observed long wavelength maxima has been elucidated by means of quantum chemical calculations. The electrochemical properties of these dyes have been investigated by using cyclic voltammetry, while their photovoltaic performance was evaluated by a device fabrication study. The experimental and calculation data show that all of the dyes can be regarded as potentially good photosensitizers for dye-sensitized solar cells.

[4+2]-Cycloaddition of 3,6-bis(3,5-dimethyl-4-R-pyrazol-1-yl)-1,2,4,5-tetrazines with alkenes

A number of 1,4-dihydropyridazines and pyridazines were prepared by the Diels-Alder reaction with an inverse electron demand from cyclic heterodiene systems, 3,6-bis(3,5-dimethyl-4-R-pyrazol-1-yl)-1,2,4,5-tetrazines, and some enamines as well as from 4-vinylpyridine, butyl vinyl ether, phenylacetylene, and acrylamide. The reaction of 3,6-bis(3,5-dimethylpyrazol-1-yl)-1,2,4,5-tetrazine with styrene afforded 4,5-dihydropyridazine, which was readily oxidized by atmospheric oxygen to form the corresponding pyridazine. Electron-withdrawing substituents (Br or Cl) in the pyrazole rings accelerate [4+2]-cycloaddition. When heated, 1,4-dihydropyridazines, which were synthesized from tetrazines and enamines, eliminated amine to give pyridazines. The reactivities of tetrazines were evaluated by quantum-chemical methods.

Multicomponent sonochemical synthesis of podands.

An efficient sonochemical methodology is described for the synthesis of new podands containing substituted dihydropyrimidines.

Nano-sized octa-nuclear nickel cationic complex: self-assembly on supramolecular level

Abstract Microporous one-dimensional material was synthesized by reacting Ni-9 cluster compound Ni9(HOOCCMe3)4(μ4-OH)3(μ3-OH)3(OOCCMe3)12 with organic ligand 3-(3,5-dimethylpyrazol-1-yl)-6-(3,5-diamino-1,3,4-thiadiazolyl)-1,2,4,5-tetrazine) (L). According to X-ray data, the nano-sized endless tubes of the material consist of stacked cationic Ni(II) octa-nuclear cyclic complexes of formula [Ni8(μ-OH2)4(μ-OOCCMe3)4(η2-OOCCMe3)(OOCCMe3)10L4]+ and pivalate anions ordered regularly aside the tubes. The channels of the tubes are filled with acetonitrile molecules forming an inclusion compound.

Synthesis and antituberculosis activity of novel 5-styryl-4-(hetero)aryl-pyrimidines via combination of the Pd-catalyzed Suzuki cross-coupling and S(N)(H) reactions.

Combination of the Suzuki cross-coupling and nucleophilic aromatic substitution of hydrogen (SN(H)) reactions proved to be a convenient method for the synthesis of 5-styryl-4-(hetero)aryl substituted pyrimidines from commercially available 5-bromopyrimidine. All intermediate 5-bromo-4-(hetero)aryl substituted pyrimidines and also the targeted 5-styryl-4-(hetero)arylpyrimidines were found to be active in micromolar concentrations in vitro against Mycobacterium tuberculosis H37Rv, avium, terrae, and multi-drug-resistant strain isolated from tuberculosis patients in Ural region (Russia). It has been found that some of these compounds possess a low toxicity and have a bacteriostatic effect, comparable and even higher with that of first-line antituberculosis drugs.

Asymmetric Biginelli Reaction Catalyzed by Silicon, Titanium and Aluminum Oxides

The asymmetric Biginelli reaction was investigated in the presence of N-[(2S,4R)-4-hydroxyprolyl]-(S)-1-phenylethylamine as chiral inducer and silicon, titanium or aluminum oxides (individual and mixed, bulk and nanosized) as heterogeneous catalysts. It has been shown that all studied oxides improve chemo- and stereoselectivity of the Biginelli reaction.Graphical Abstract

HETARYL DISPLACEMENT IN 3,6-DISUBSTITUTED 1,2,4,5-TETRAZINES WITH ANHYDRO BASES OF N-METHYLQUINALDINIUMS

3,6-Bis(4-R-3,5-dimethylpyrazol-1 -yl)-s-tetrazine, 3,6-bis(imidazol-1 -yl)-s-tetrazine, 3,6bis(benzotriazol-l-yl)-s-tetrazine,3,6-bis(4-methylimidazol-l-yl)-s-tetrazine react with anhydro bases of 1-methylquinaldium and 1,6-dimethylquinaldium to form products of C-nucleophilic substitution of azolyl fragment or Carboni-Lindsey reaction followed by subsequent pyridine ring cleavage in the quinoline moiety.

Synthesis and turbeculostatic activity of podands with fluoroquinolone fragments

Fluorine-substituted quinolonecarboxylic acids are known as synthetic antibacterial drugs with a broad spectrum of activity, which are successfully used for the therapy of various bacterial diseases, including tuberculosis [1 ]. Nevertheless, problems pertaining to the appearance of bacterial strains resistant to quinolones stimulate researchers to continue investigations aimed at a modification of the known fluroquinolones [2]. We have attempted to modify a fluoroquinolone fragment responsible for penetration into bacterial ceils, with the pttrpose of increasing the transport function of the molecule, since it is known that fluoroquinolones (in particular, pefloxacin) penetrate into bacterial cells by a simple diffusion mechanism [3]. In order to find reaction pathways to fluoroquinolones possessing increased penetrating ability with respect to the cell membranes, we have synthesized compounds containing podand residues that are known [4] to readily pass through the cellular barriers. Because of the low nucleophilicity of glycols, the oxygen-containing podands IV were obtained under rigid conditions from the ethyl ester of 1-ethyl-6,7-difluoro-4-oxo-l,4dihydro-3-quinolinecarboxylic acid (Ib), in which the mobility of a fluorine atom in position 7 is somewhat higher than in the acid (Ia). Podands V and VI were obtained by direct interaction of acid Ia with polyethylene polyamines. Potassium carbonate was used as the acceptor of hydrogen chloride in the synthesis of compounds IV and VI, whereas triethylamine was used for the same purpose in the synthesis of compounds V known to form strong complexes with potassium cations. Podands-hydrazones VII were obtained by heating formylpodands III with 7-hydrazino-4-oxo-6-ftor-l-ethyl-l,4dihydro-3-quinolinecarboxylic acid (II) in DMF.

Direct Modification of Benzoannelated Crown Ethers with 1,2,4-Triazin-5(2H)-one Moieties

A convenient method for one-step coupling of benzoannelated crown ethers with 1,2,4-triazinones based on the reaction of nucleophilic addition to unsubstituted carbon atom of the triazine ring has been worked out. It has been shown that the reaction of 3-substituted 1,2,4-triazin-5(2H)-ones (1) with benzocrown ethers (benzo-12-crown-4, benzo-15-crown-5, benzo-18-crown-6) in the presence of acetic or trifluoroacetic anhydride is accompanied by acylation of triazine ring and results in formation of 3-(1-acyl-5-oxo-1,4,5,6-tetrahydro-1,2,4-triazin-6-yl)benzocrown ethers (7-12). The latters were converted to 3-(5-oxo-2,5-dihydro-1,2,4-triazin-6-yl)benzocrown ethers (18-20) using two alternative routes: the elimination of acetic or trifluoroacetaldehyde or the deacylation followed by the oxidation of the 1,4,5,6-tetrahydro derivatives (13-15).