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Biomedical subjects

Evgeny V Dikarev

Publications and source records attributed to Evgeny V Dikarev.

At least 19 recordsLinked to original sources
PubMed2006

Synthesis, structure, and chemistry of new, mixed group 14 and 16 heterocycles: nucleophile-induced ring contraction of mesocyclic dications.

More than 40 new 4- to 12-membered ring heterocycles containing various combinations of Group 14 and 16 elements Si, Sn, S, Se, and Te have been synthesized and fully characterized. Synthesis of these small-ring as well as medium-ring (mesocyclic) heterocycles from alpha,omega-dihalides is facilitated by the presence of gem-dialkylsilyl and gem-dialkylstannyl groups in the precursors. Conformations of several of the new ring systems in the solid state have been determined by X-ray crystal structure analysis. Oxidation of mixed S(Se, Te)/Si eight-membered ring mesocycles with NOPF6 or Br2 gives dications or a bicyclic dibromide, respectively, which can be characterized by NMR methods. On treatment with nucleophiles, mesocyclic dications, or the corresponding radical cations undergo ring contraction, giving five- or six-membered ring heterocycles. Photolysis of a S/Se four-membered ring heterocycle gives selenoformaldehyde, trapped in 80% yield with 2,3-dimethyl-1,3-butadiene.

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PubMed2006

Tuning the properties at heterobimetallic core: mixed-ligand bismuth-rhodium paddlewheel carboxylates.

Mixed-ligand heterometallic compounds [BiRh(O2CCF3)4-x(O2CR)x] (R = But, x = 2 (cis); R = Me, Bui, x = 1) have been obtained by gas-phase reactions of bismuth(II) trifluoroacetate with the corresponding rhodium(II) carboxylate. This synthetic approach was found to be very effective for tuning the properties and introduction of chiral ligands at a heterobimetallic core.

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PubMed2006

Unligated diruthenium(II,II) tetra(trifluoroacetate): the first X-ray structural study, thermal compressibility, Lewis acidity, and magnetism.

The title compound, [Ru(2)(O(2)CCF(3))(4)] (1), has been obtained without any exogenous ligands and crystallized by deposition from the gas phase at 170 degrees C. Its crystal structure has been determined for the first time to confirm an infinite chain motif built on axial Ru...O interactions of the diruthenium(II,II) units. The X-ray diffraction studies at variable temperatures showed no phase transitions in the range of 295-100 K but revealed a significant decrease in the volume per atom from 14.2 to 13.3 A(3). This noticeable thermal compressibility effect is discussed in connection with the solid-state packing of the [Ru(2)(O(2)CCF(3))(4)](infinity) chains. The highly electrophilic character of the diruthenium(II,II) units has been shown by the gas-phase deposition reaction of [Ru(2)(O(2)CCF(3))(4)] with an aromatic donor substrate, namely [2.2]paracyclophane (C(16)H(16)). As a result of the above reaction, a new arene adduct [Ru(2)(O(2)CCF(3))(4).C(16)H(16)] (2) has been isolated in crystalline form. It has an extended one-dimensional (1D) chain structure comprised of alternating building units and based on the rare bridging mode of [2.2]paracyclophane, [Ru(2)(O(2)CCF(3))(4).(mu(2)-eta(2):eta(2)-C(16)H(16))](infinity). The magnetic susceptibility of 1 and 2 has been measured and compared in the range of 1.8-300 K. In addition, in the course of synthesis of 1 by the carboxylate exchange reactions, a new mixed-carboxylate diruthenium(II,II) core complex [Ru(2)(O(2)CCF(3))(3)(O(2)CC(2)H(5))] (3), bearing no exogenous ligands, has also been isolated and structurally characterized. It exhibits an interesting polymeric structure in which the ruthenium(II) centers selectively form axial interdimer contacts with the O-atoms of the propionate groups only.

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PubMed2006

A new whitlockite, Ca8.42Na1.16V(PO4)7.

Single crystals of a new complex phosphate, calcium sodium vanadium phosphate, Ca8.42Na1.16V(PO4)7, have been grown from a melt under an inert atmosphere. The crystal structure has rhombohedral (R3c) symmetry and belongs to the whitlockite structure type. Vanadium(III) ions occupy nearly regular octahedral sites (M5 with 3 point symmetry), which share corners with six PO4 tetrahedra to form isolated units. The calcium ions occupy eight- and nine-coordinated sites. The sodium ions partially occupy one octahedral position and share one nine-coordinated position with a Ca atom.

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PubMed2005

Reduction of the host cationic framework charge by isoelectronic substitution: synthesis and structure of Hg7Ag2P8X6 (X = Br, I) and Hg6Ag4P8Br6.

The first compounds, Hg(7)Ag(2)P(8)X(6) (X = Br, I) and Hg(6)Ag(4)P(8)Br(6), featuring the partial isoelectronic substitution of Hg(2+) for Ag(1+) in mercury-pnicogen frameworks have been obtained and structurally characterized. The new compounds are the supramolecular assemblies built of the covalently bonded metal-pnicogen frameworks trapping guests of different complexity. The frameworks feature the perfect ordering of Hg(2+) and Ag(1+) cations and contain P(2)(4)(-) and P(6)(6)(-) phosphorus clusters. The substitution of Hg(2+) with Ag(1+) leads to the reduction in charge of the host cluster-containing cationic matrix and concomitant replacement of the monatomic X(-) guest by a lesser amount of the AgBr(3)(2)(-) anions.

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PubMed2005

Heterometallic bismuth-transition metal homoleptic beta-diketonates.

Bismuth(III) hexafluoroacetylacetonate reacts readily with the first row transition-metal species to produce trinuclear heterobimetallic coordination complexes Bi2M(beta-diketonate)8 (M = Mn, Fe, Co, Ni, Cu, Zn). This unique, general approach may offer new possibilities for developing single-source molecular precursors for advance oxide materials.

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PubMed2004

Bulk material vs. single crystal: powder diffraction to the rescue.

The crystal structure of bulk microcrystalline material obtained by interaction of two rigid building blocks, namely dirhodium(ii) tetra(trifluoroacetate), [Rh2(O2CCF3)4], and bis(4'-pyridyl)diphenylsilane, (C6H5)2Si(C5H4N)2, has been solved ab initio using X-ray powder diffraction data. The title product of the 1 [ratio] 1 composition, [Rh2(O2CCF3)4.(mu2-(C6H5)2Si(C5H4N)2)], is a one-dimensional zigzag polymer built on axial Rh...N interactions averaged at 2.16 A. Its structural characterization complements the previously reported product of the 2:1 composition obtained from the same reaction, namely {[Rh2(O2CCF3)4]2.(mu4-(C6H5)2Si(C5H4N)2)}. The latter has a 2D layered network revealed by the single crystal diffraction study. A combination of powder and single crystal X-ray techniques is shown to be methodologically important and complementary for understanding of product assembling in the system.

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PubMed2004

Powder diffraction study of a coordination polymer comprised of rigid building blocks: [Rh2(O2CCH3)4.mu2-Se2C5H8-Se,Se']infinity.

The crystal structure of a new hybrid product comprised of two rigid building blocks, namely dirhodium(II) tetraacetate, [Rh(2)(O(2)CCH(3))(4)] (1), and 2,6-diselenaspiro[3.3]heptane, Se(2)C(5)H(8) (2), has been solved ab initio using laboratory source X-ray powder diffraction (XRPD) data. The rigid body refinement approach has been applied to assist in finding an adequate model and to reduce the number of the refined parameters. Complex [Rh(2)(O(2)CCH(3))(4).mu(2)-Se(2)C(5)H(8)-Se,Se'] (3) conforms to the triclinic unit cell with lattice parameters of a = 8.1357(4), b = 8.7736(4), and c = 15.2183(8) A, alpha = 77.417(3), beta = 88.837(3), and gamma = 69.276(4) degrees, V = 989.66(8) A(3), and Z = 2. The centrosymmetric P space group was selected for calculations. The final values of the reduced wR(p), R(p), and chi(2) were calculated at 0.0579, 0.0433, and 5.95, respectively. The structure of 3 is a one-dimensional zigzag polymer built on axial Rh...Se interactions at 2.632(6) A. The 2,6-diselenaspiro[3.3]heptane ligand acts as a bidentate linker bridging dirhodium units via both selenium atoms. The geometrical parameters of individual groups for rigid body refinement have been obtained from X-ray powder data for dirhodium(II) tetraacetate (1) and from single-crystal X-ray diffraction for diselenium molecule 2. The crystal structures of 1 and 2 are reported here for the first time. For 1 indexing based on XRPD data has resulted in the triclinic unit cell P with lattice parameters of a = 8.3392(7), b = 5.2216(5), and c = 7.5264(6) A, alpha = 95.547(10), beta = 78.101(6), and gamma = 104.714(13) degrees, V = 309.51(5) A(3), and Z = 1. The final values were wR(p) = 0.0452, R(p) = 0.0340, and chi(2) = 1.99. The 1D polymeric motif built on axial Rh.O interactions of the centrosymmetric dirhodium units has been confirmed for the solid-state structure of 1. Compound 2,6-diselenaspiro[3.3]heptane (2) conforms to the monoclinic space group P2(1)/c with the unit cell parameters of a = 5.9123(4), b = 19.6400(13), and c = 5.8877(4) A, beta = 108.5500(10) degrees, V = 648.15(8) A(3), and Z = 4.

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PubMed2004

Rational syntheses, structure, and properties of the first bismuth(II) carboxylate.

Bismuth(II) trifluoroacetate (1), the first inorganic salt of bismuth in oxidation state +2, has been obtained in its pure, unstabilized form. Several synthetic routes suggested for the isolation of the new compound include (i) mild oxidation of elemental bismuth with some metal trifluoroacetates, e.g., Ag(I) and Hg(II); (ii) mild reduction of bismuth(III) trifluoroacetate with metals, such as Zn; (iii) comproportionation reaction between Bi and Bi(O(2)CCF(3))(3). The last approach gives the title compound 1 in quantitative yield as a sole product. Bismuth(II) trifluoroacetate has been characterized by NMR, IR, and UV-vis spectroscopy as well as by single-crystal X-ray diffraction. Crystallographic study reveals the dinuclear paddle-wheel structure for diamagnetic molecules Bi(2)(O(2)CCF(3))(4). The Bi-Bi bond distances in dimetal units of 1 are averaged to 2.9462(3) A, and there are no axial intermolecular contacts between these units in the solid state. The compound is volatile and exists in vapor phase up to 220 degrees C when it disproportionates back to Bi(0) and Bi(III) species, i.e., by the reverse of the synthetic route iii. In contrast, the solution chemistry is quite limited: the bismuth(II) trifluoroacetate is decomposed by the majority of common solvents, but it can be stabilized by aromatic systems. The dibismuth unit has been shown to be preserved in the latter solvents and can be crystallized out in a form of pi-adducts with arenes. Two such adducts, Bi(2)(O(2)CCF(3))(4).(C(6)H(5)Me) (2) and Bi(2)(O(2)CCF(3))(4).(1,4-C(6)H(4)Me(2))(2) (3), have been isolated as single crystals and characterized by X-ray diffraction techniques. In the structures of both 2 and 3, the bismuth(II) centers exhibit weak eta(6)-coordination to aromatic rings.

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PubMed2004

On the road to a termolecular complex with acetone: a heterometallic supramolecular network [[Rh(2)(O(2)CCF(3))(4)].micro(2)-OCMe(2).[Cu(4)(O(2)CCF(3))(4)]].

A novel heterometallic supramolecular network [[Rh(2)(O(2)CCF(3))(4)].micro(2)-OCMe(2).[Cu(4)(O(2)CCF(3))(4)]](2)( infinity ) has been prepared by codeposition of the volatile mono(acetone) adduct [Rh(2)(O(2)CCF(3))(4).eta(1)-OCMe(2)](2) and copper(I) trifluoroacetate, [Cu(4)(O(2)CCF(3))(4)]. The product is of interest from the viewpoints of gas-phase supramolecular synthesis and a rare bridging coordination mode of acetone. It has been fully characterized by IR and NMR spectroscopy, elemental analysis, and X-ray diffraction. An X-ray structure revealed a layered 2D arrangement of the heterometallic [[Rh(2)(O(2)CCF(3))(4)].micro(2)-OCMe(2).[Cu(4)(O(2)CCF(3))(4)]] units built by axial intermolecular interactions of the open electrophilic Rh(II) and Cu(I) centers and O-atoms of neighboring carboxylate groups. The coordination of the acetone molecules within the [[Rh(2)(O(2)CCF(3))(4)].micro(2)-OCMe(2).[Cu(4)(O(2)CCF(3))(4)]] unit is asymmetric with the Rh-O and Cu-O distances being 2.2173(15) and 2.7197(17) A, respectively. This work shows the potential of gas-phase deposition that may provide additional possibilities in supramolecular synthesis by utilizing intermolecular interactions and coordination bonds in a new way compared with conventional solution chemistry.

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PubMed2004

Unusually high chemical compressibility of normally rigid type-I clathrate framework: synthesis and structural study of Sn(24)P(19.3)Br(x)I(8)(-)(x) solid solution, the prospective thermoelectric material.

A novel tin phosphide bromide, Sn(24)P(19.3(2))Br(8), and Sn(24)P(19.3(2))Br(x)()I(8)(-)(x) (x = 0-8) solid solution have been prepared and structurally characterized. All compounds crystallize with the type-I clathrate structure in the cubic space group Pmn (No. 223). The clathrate framework of the title solid solution shows a remarkable chemical compressibility: the unit cell parameter drops from 10.954(1) to 10.820(1) A on going from x = 0 to x = 8, a feature that has never been observed for normally rigid clathrate frameworks. The chemical compressibility as well as non-Vegard dependence of the unit cell parameter upon the bromine content is attributed to the nonuniform distribution of the guest halogen atoms in the polyhedral cavities of the clathrate framework. The temperature-dependent structural study performed on Sn(24)P(19.3(2))Br(8) has shown that, in contrast to the chemical compressibility, the thermal compressibility (linear contraction) of the phase is similar to that observed for the Group 14 anionic clathrates. The tin phosphide bromide does not undergo phase transition down to 90 K, and the atomic displacement parameters for all atoms decrease linearly upon lowering the temperature. These linear dependencies have been used to assess such physical constants as Debye temperature, 220 K, and the lattice part of thermal conductivity, 0.7 W/(m K). Principal differences between the title compounds and the group 14 anionic clathrates are highlighted, and the prospects of creating new thermoelectric materials based on cationic clathrates are briefly discussed.

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PubMed2004

Chloromethanesulfonylethene and dichloromethanesulfonylethene: new reagents for tandem Diels-Alder/Ramberg-Bäcklund reactions.

[reaction: see text] Chloromethanesulfonylethene (3a) and dichloromethanesulfonylethene (3b) were prepared by oxidation of the adducts of ethylene and ClCH(2)SCl or Cl(2)CHSCl, respectively, followed by NaHCO(3) dehydrochlorination. With dienes, 3a gave Diels-Alder adducts that, with base, underwent Ramberg-Bäcklund reaction, giving products corresponding to the adducts of the dienes and allene. Similarly, 3b gave Diels-Alder adducts that, with base in the presence of the novel chlorine source MeSO(2)CCl(3), cleanly afforded products corresponding to the adducts of the dienes and 1,1-dichloropropa-1,2-diene.

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PubMed2003

The first coordination complexes of selenones: a structural comparison with complexes of sulfones.

Reactivity of the two classes of very weak donors R(2)XO(2) (X = S, R = Me (1) and Ph (2); X = Se, R = Me (3) and Ph (4)) have been studied. Coordination properties of sulfones and selenones in solution and in the gas phase have been compared for the first time using a model bidentate metal complex, [Rh(2)(O(2)CCF(3))(4)]. Two coordination modes, bridging mu(2)-O,O' and terminal eta(1)-O, have been detected. These types of binding were realized in two series of sulfone and selenone metal complexes, polymeric mono-adducts [Rh(2)(O(2)CCF(3))(4).(R(2)XO(2))]( infinity ) (X = S, R = Me (1a); R = Ph (2a); X = Se, R = Ph (4a)) and discrete bis-adducts [Rh(2)(O(2)CCF(3))(4).(R(2)XO(2))(2)] (X = S, R = Ph (2b); X = Se, R = Me (3b)). The compositions and structures of new compounds have been confirmed by NMR and IR spectroscopy, chemical analyses, and X-ray diffraction studies. Compounds 3b and 4a are the first crystallographically characterized metal complexes having selenone ligands coordinated to the metal centers. Preparation and X-ray study of analogous metal complexes of sulfone and selenone ligands allow, for the first time, tracking the structural changes induced by metal coordination. In addition, the X-ray structure of dimethyl selenone, Me(2)SeO(2) (3), an analogue of Me(2)SO(2), has been determined. Geometries of coordinated sulfone and selenones ligands have been compared with those of the corresponding "free" molecules.

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PubMed2003

Small organoselenium molecules. 1. Dimethyl selenoxide: structure, complexation, and gas-phase transformation.

For the first time the structural characterization of dimethyl selenoxide coordinated to metal complexes has been performed confirming the Me(2)SeO arrangement assigned by spectroscopic techniques for the molecule in solution and solid state. The structure of Me(2)SeO is trigonal pyramidal with Se-O and Se-C bond lengths of 1.70 and 1.92 A, respectively, and sigma(X-Se-Y) = 301 degrees. As a ligand, dimethyl selenoxide was found to bind to the rhodium centers of various Lewis acidity strengths by using only its oxo functionality in both terminal and bridging fashions. This O-directed coordination preference contrasts with an ambidentate (-S and -O) binding character revealed by dimethyl sulfoxide upon formation of analogous donor-acceptor complexes. The study of dimethyl selenoxide in the gas phase at 135-140 degrees C resulted in a thermal degradation of this molecule. The major decomposition product has been entrapped by a metal complex and identified as dimethyl selenide. The isolation of the coordinated Me(2)Se fragment clearly demonstrates that the Me(2)SeO molecule is less thermally stable than Me(2)SO, which under similar reaction conditions shows no sign of decomposition at temperatures up to 160 degrees C.

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