Theoretical studies on anionic clusters of sulfate anions and carbon dioxide, SO 4?1/?2 (CO2)n, n?=?1?4

Geometry optimizations were performed on monoanionic and dianionic clusters of sulfate anions with carbon dioxide, SO₄^−1/−2(CO₂) _n , for n = 1–4, using the B3PW91 density functional method with the 6-311 + G(3df) basis set. Limited calculations were carried out with the CCSD(T) and MP2 methods. Binding energies, as well as adiabatic and vertical electron detachment energies, were calculated. No covalent bonding is seen for monoanionic clusters, with O₃SO–CO₂ bond distances between 2.8 and 3.0 ?. Dianionic clusters show covalent bonding of type [O₃S–O–CO₂]⁻², [O₃S–O–C(O)O–CO₂]⁻², and [O₂C–O–S(O₂)–O–CO₂]⁻², where one or two oxygens of SO₄⁻² are shared with CO₂. Starting with n = 2, the dianionic clusters become adiabatically more stable than the corresponding monoanionic ones. Comparison with SO₄^−1/−2(SO₂) _n and CO₃^−1/−2(SO₂) _n clusters, the binding energies are smaller for the present SO₄^−1/−2(CO₂) _n systems, while stabilization of the dianion occurs at n = 2 for both SO₄⁻²(CO₂) _n and SO₄⁻²(SO₂) _n , but only at n = 3 for CO₃⁻²(SO₂) _n .     

O-Tolyl/benzyl dithiocarbonates of phosphorus(III) and (V): syntheses and characterization

Abstract  

O-Tolyl/benzyl dithiocarbonates, ROCS₂Na (R = o-, m-, or p-CH₃C₆H₄–, and –CH₂C₆H₅), were synthesized and characterized. These new ligands reacted with PCl₃/POCl₃ in refluxing toluene which resulted in the formation of phosphorus(III) and phosphorus(V) tolyl/benzyl dithiocarbonates corresponding to [(ROCS₂) _n PCl_3−n ] and [(ROCS₂) _n POCl_3−n ] (R = o-, m-, or p-CH₃C₆H₄–, and –CH₂C₆H₅; n = 1, 2, 3). These pale yellow liquid compounds were characterized by IR, mass, and NMR (¹H, ¹³C, and ³¹P) spectral studies, which suggest the dithiocarbonate ligands bind in a monodentate mode leading to P–S–C linkages in these derivatives.     

Heterotrinuclear manganese(II) and vanadium(IV) Schiff base complexes as epoxidation catalysts

The catalytic epoxidation of styrene using urea-hydrogen peroxide and heterotrinuclear Cu(II) complexes with general formula (ML ⁿ )₂Cu(acac)₂, where n = 1–3 and M = VO²⁺ or Mn²⁺ is reported. Schiff base complexes ML ⁿ involving a 3,4-diaminopyridine bridge with free coordination site were used as the ligand, where (Lⁿ)²⁻ is [(5-x-Sal)₂Py]² and x = H, Br or NO₂. The complexes were characterized by physico-chemical and spectroscopic methods. The electrochemical properties of M were modified upon trinuclear complex formation. The trinuclear complexes show high catalytic activity, with up to 86% conversion and 93% selectivity, while no catalytic properties were observed for the monomeric complexes. The catalyst could be reused with some loss of activity.     

Synthesis,Characterization, and Crystal Structures of Metal Amide Cage Complexes Containing a M<Subscript>4</Subscript>O<Subscript>4</Subscript> (M = Nb,Ta) Core Unit

Metal cage complexes [(Me₂N)₃MO]₄ (M = Nb, 3; Ta, 4) have been prepared from the reactions of M(NMe₂)₅ (M = Nb, 1; Ta, 2) with water. Single crystal X-ray diffraction studies of 3 and 4 reveal that they adopt cubane-like structures with M–O bridges. Variable-temperature NMR studies of –NMe_AMe_B rotations in 3 and 4 have been performed to give the following activation parameters for the exchanges: ΔH ^≠ = −1.4(1.1) kJ/mol, ΔS ^≠ = −209(8) J/mol K, \Updelta G _{30 8  \textK} ¹ = 6 4( 2)  \textkJ/\textmol \Updelta G_{{_{{ 30 8\;{\text{K}}}} }}^{{^{ \ne } }} = 6 4\left( 2\right)\;{\text{kJ}}/{\text{mol}} for 3, and ΔH ^≠ = −0.9(1.2) kJ/mol, ΔS ^≠ = −2.1(0.2) × 10² J/mol K, \Updelta G _{30 8  \textK} ¹ = 6 3( 6)  \textkJ/\textmol \Updelta G_{{ 30 8\;{\text{K}}}}^{{^{ \ne } }} = 6 3\left( 6\right)\;{\text{kJ}}/{\text{mol}} for 4.     

Processes of dissociative electron capture by 20-hydroxyecdysone molecules

The peculiarities of dissociative electron capture by 20-hydroxyecdysone molecules with the formation of fragment negative ions were studied. In the region of high electron energies (5–10 eV), processes of skeleton bond rupture are accompanied by the elimination of H₂O and H₂ molecules. In the region of thermal energies of electrons (≈0 eV), the mass spectrum is formed mainly by the [M−nH₂O]^.− (n=1–3) and [M−H₂−nH₂O]^.− (n=0−3) ions that are generated exclusively by the rearrangement. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 709–712, April, 2000.     

Thermodynamic and NMR studies of mixed-ligand complex formation of cadmium ethylenediaminetetraacetate with diamines in an aqueous solution

The mixed-ligand complex formation in the systems Cd2 + Edta4–(CH₂) _n (NH₂)₂, n = 2 (En), 6 (L) has been NMR and calorimetrically studied in aqueous solution at 298.15 K and the ionic strength of I = 0.5 (KNO₃). The thermodynamic parameters of formation of the CdEdtaL²⁻, CdEdtaHL⁻, (CdEdta)₂L⁴⁻, and (CdEdta)₂En⁴⁻ complexes have been determined. The most probable coordination mode for the complexone and the diamine ligand in the mixed-ligand complexes was discussed.     

The pressure effect study on the burning rate of ammonium nitrate-HTPB-based propellant with the influence catalysts

The burning rate of AN–HTPB-based propellant catalysed with chromium salt has been studied using conventional strand burner under the various pressure range, i.e. from atmospheric pressure to 6.897 MPa and verified with Piobert law, i.e. r = aP ⁿ . At atmospheric pressure, the burning rate AN–HTPB propellant was being accelerated with the chromium-based catalysts used. In case of lead chromate-catalysed system, burning rate was observed 2.655 times higher than burning rate (r = 0.200 mm s⁻¹) of virgin AN–HTPB propellant sample. However, the Copper chromate-catalysed propellant burned with slower rate (r = 0.160 mm s⁻¹) than the virgin AN–HTPB propellant sample. The burning rate of all catalysed propellant samples are found to be the pressure sensitive and accelerated higher with rise of pressure. The highest burning rate (r = 2.422 mm s⁻¹) was recorded with ammonium dichromate and lowest (r = 1.40 mm s⁻¹) with lead chromate-catalysed propellant sample with the rise of pressure up to 6.897 MPa at different pressures. A linear relationship was observed between the burning rate and pressure rise which followed the Piobert law, i.e. r = aP ⁿ . The pressure index (n) values of AN–HTPB-based samples were calculated higher when catalysed with ammonium dichromate, Copper Chromate, Cr₂O₃, Potassium dichromate (n = 0.525, 0.555, 0.429, and 0.408 respectively) and lower (n = 0.226) with lead chromate compared to virgin sample (n = 0.405). Higher value indicates the positive effect on accelerating the burning rate with catalyst at higher pressure ranges.     

Polyatomic anion versus acetonitrile in coordinating ability: structural properties of AgX-bearing 1,4-bis(2-isonicotinoyloxyethyl)piperazine (X??=?NO3?, CF3SO3?, ClO4?, BF4?, and PF6?)

Type studies on competitive polyatomic anion versus acetonitrile coordination in the self-assembly of a series of [Ag₂(X) _m (bip)(NCCH₃) _n ](X)_2−m (X⁻ = NO₃ ⁻, CF₃SO₃ ⁻, ClO₄ ⁻, BF₄ ⁻, and PF₆ ⁻; m = 0, 2; n = 0, 2, 4; bip = 1,4-bis(2-isonicotinoyloxyethyl)piperazine) were carried out. Each bip spacer acts as an N₄ tetradentate ligand and is linked to four silver(I) centers through two pyridine and two piperazine moieties, producing a double strand consisting of two 20-membered ring units. The coordinating environment around the silver(I) center is subtly determined by the competition of the polyatomic anions with acetonitrile, that is, by the Ag···NCCH₃ versus Ag···X interactions. The coordinating ability of acetonitrile is inversely proportional to the order of the coordination ability of the Hoffmeister series of polyatomic anions, NO₃ ⁻ ≫ CF₃SO₃ ⁻ > ClO₄ ⁻ > BF₄ ⁻ ≫ PF₆ ⁻.     

Synthesis and crystal and molecular structures of six-coordinate tin dibromides and diiodides containing lactamomethyl C,O-chelating ligands

New (O−Sn)-bischelate bis(lactamomethyl)dibromo- and-diiodostannanes [L⁽ⁿ⁾]₂SnX₂ (L is the bidentate lactamomethyl C,O-chelating ligand;n is the size of the lactam ring, 5–7; X=Br or I) were prepared both by the direct method from metallic tin and the correspondingN-(halomethyl)lactams and by the reactions of dichlorides [L⁽ⁿ )]₂SnCl₂ with lithium halides. According to the data of X-ray diffraction analysis, the tin atom in [L⁽ⁿ⁾]₂SnBr₂ (n=5–7) and [L⁽ⁿ⁾]₂SnI₂ (n=5 or 6) adopts an octahedral configuration with the carbon atoms intrans positions and the coordinating oxygen and halogen atoms incis-positions with respect to each other. A comparison with the structures of analogous lactamomethyl halide derivatives of five-and six-coordinate Si, Ge, and Sn demonstrates that the spatial structures of the hypervalent fragments containing six-coordinate atoms are less sensitive to the replacement of the halide ligands and the central atom. The covalence of the M−Hal bond increases and the covalence of the M−O bond decreases in the series M=Si, Ge, and Sn. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1988–1998, October, 1999.     

Solvothermal synthesis and structures of three novel heterometallic microporous coordination polymers assembled from 2-hydroxy-nicotinic acid

Abstract  

Three novel heterometallic microporous coordination polymers {M(Hnico)₃M′} _n (1, M = Co, M′ = K; 2, M = Ni, M′ = K; 3, M = Co, M′ = Na, Hnico is the anion of 2-hydroxy-nicotinic acid, where the proton is transferred from the phenolate hydroxy group to the nitrogen atom of imine pyridine ring) were synthesized by hydrothermal reaction between M(Ac)₂·4H₂O, M′OH and a multifunctional organic aromatic H₂nico ligand and characterized by IR spectrum, elemental analysis, raman spectrum and the single crystal X-ray diffractions. In complexes 1–3, the M²⁺ ions linked three different Hnico ligand formed [M(Hnico)₃]⁻ subunit which further interlinked the six-coordination M′⁺ cation constructed 3D network. The network topology of 1–3 can be simplified a rare 3D (4,4)-connected (4¹²6³) net.     

Hydrogenation of B 120/? : A Planar-to-Icosahedral Structural Transition in B12H n0/? (n?=?1–6) Boron Hydride Clusters

A systematic density functional theory and wave function theory investigation performed in this work reveals a planar-to-icosahedral structural transition between n = 4–5 in the partially hydrogenated B₁₂H _n ^0/− clusters (n = 1–6) upon hydrogenation of all-boron B₁₂^0/−. Coupled cluster calculations with triple excitations (CCSD(T)) indicate that a distorted icosahedral B₁₂H₆ cluster with C₂ symmetry is overwhelmingly favored (by 35 kcal/mol) over the recently proposed perfectly planar borozene (D_3h B₁₂H₆) (Szwacki et al., Nanoscale Res Lett 4:1085, 2009) which proves to be a high-lying local minimum. A similar 2D–3D structural transition occurs to the corresponding boron boronyl analogues of B₁₂(BO) _n with n –BO terminals. Detailed adaptive natural density partitioning (AdNDP) analyses reveal the bonding patterns of these quasi-planar or cage-like clusters which are characterized with delocalized σ and π molecular orbitals. The electron detachment energies of the concerned anions and excitation energies of the neutrals are also predicted to facilitate their future experimental characterizations.     

Adsorption behavior of 181W and 93mMo as lighter homologues of seaborgium (Sg) in HF/HNO3 on anion-exchange resin

Adsorption of carrier-free radiotracers ¹⁸¹W and ^93mMo produced in the ¹⁸¹Ta(p, n) and ^natNb(p, n) reactions, respectively, on anion-exchange resin was studied in mixed solution of HF and HNO₃ in a concentration range of 10⁻⁴–10⁻¹ M HF/0.1 M HNO₃. Distribution coefficients (K _d) of ¹⁸¹W and ^93mMo at 70 °C showed the V-shaped variation with the minimum at around 10⁻¹ M HF/0.1 M HNO₃, although variation of the K _d values for ^93mMo was quite small compared with that for ¹⁸¹W. Formation of oxofluoro complexes for W and Mo is briefly discussed.     

Theoretical study of the structure and stability of cage-substituted icosahedral closo-boranes, alanes, and gallanes MiM′12 ? iH 122? (M, M′ = B, Al, and Ga; i = 0–12)

The equilibrium geometric parameters and energetic and spectroscopic characteristics of low-lying conformers for several series of model cage-substituted (mixed) borane, alane, and gallane closo-dianions M _i M′_{12 − i} H₁₂²⁻(M, M′ = B, Al, Ga), as well as of “bare” gallium-aluminum anions Ga _i Al_12−i ⁻ with i = 0–12, were calculated within the B3LYP approximation of the density functional theory using 6–31G* and 6–311+G** basis sets. Differences in structure and stability between alanoborane clusters of similar composition are revealed. In clusters where the M and M’ heteroatoms are close in size and electronegativity (in gallonoalanes and gallium-aluminum anions), successive substitutions of M′ for M are accompanied by small energy changes and occur quasi-stochastically in different positions of the cage. When the substituents are significantly different (in alanoboranes), mixed clusters are unstable against disproportionation into homonuclear “predecessors” M₁₂H₁₂²⁻ and M′₁₂H₁₂²⁻, and the most favorable M _i M′_{12 − i} H₁₂²⁻ structures among them are those in which M _i M′_{12 − i} the cages are subdivided into homonuclear “subclusters” M _i and M′t′_12−i with a maximal number of homonuclear bonds (M-M and M′-M′) and a minimal number of heteronuclear bonds (M-M′).     

Density functional theory study on (F2AlN3) n (n = 1–4) clusters

Possible geometrical structures and relative stabilities of (F₂AlN₃) _n (n = 1–4) clusters were studied using density functional theory at the B3LYP/6-311+G* level. The optimized clusters (F₂AlN₃) _n (n = 2–4) possess cyclic structure containing Al–N_α–Al linkages, and azido in azides has linear structure. The IR spectra of the optimized (F₂AlN₃) _n (n = 1–4) clusters have three vibrational sections, the whole strongest vibrational peaks lie in 2218–2246 cm⁻¹, and the vibrational modes are N₃ asymmetric stretching vibrations. Trends in thermodynamic properties with temperature and oligomerization degree n are discussed, respectively. A study of their thermodynamic properties suggests that monomer 1A forms the most stable clusters (2A, 3A, and 4B) can occur spontaneously in the gas phase at temperatures up to 800 K.     

Kinetic analysis of the thermal decomposition of copper (I) complexes with heterocyclic thiones

Two series of copper (I) halide complexes formulated as [(L)CuX(μ₂-L)₂CuX(L)] and [(L)₂Cu(μ₂-L)₂Cu(L)₂]²⁺ 2Χ⁻, respectively (X = Cl, Br and L = 4,6-dimethylpyrimidine-2-thione (dmpymtH)) were prepared. From the thermogravimetric curves it was found that among the four studied materials, [Cu₂(dmpymtH)₆]²⁺2Cl⁻ presents a lower thermal stability. For the determination of the activation energy (E) two different methods have been used comparatively, since every method has its own error. These methods were the isoconversional methods of Ozawa, Flynn and Wall (OFW), and Friedman. The dependence of the E on the value of the mass conversion α, as calculated with OFW and Friedman’s methods, can be separated in three distinct regions. The decomposition mechanism is very complex and can be described using at least three different mechanisms with different activation energies. The best fitting of experimental data with theoretical models gave nth-order for all the three mechanisms (Fn–Fn–Fn).     

Three-propeller-blade-shaped electride: remarkable alkali-metal-doped effect on the first hyperpolarizability

Significant alkali-metal-doped effects on the structure and the first hyperpolarizability (β ₀) of effective multi-nitrogen complexant tris[(2-imidazolyl)methyl]amine (TIMA) are investigated. Three imidazoles of TIMA like three blades of propeller connect with methyls by the C–C single bonds. Because of the three C–C single-bond cooperative rotations, the TIMA behaves with great flexibility, and it is a high-performance multi-nitrogen complexant for the alkali metal doping. Thus, the new complexes A_m-TIMA (A_m = Li, Na, and K) with electride characteristic have diffuse excess electron than the reported electride-type system due to the strong interaction between the complexant TIMA and alkali metal. For the first hyperpolarizability, three engaging electrides A_m-TIMA with the diffuse excess electrons exhibit considerably large β ₀ values using the MP2 (full) method and the β ₀ values of new electrides are greatly larger (3,464–29,705 times) than that (338 au) of TIMA. Surprisingly, the K-TIMA sets a new record β ₀ value to be 1.00 × 10⁷ au which far exceeds than that (3,694–76,978 au) of the reported electride-type system Li@calix[4]pyrrole (J Am Chem Soc 127:10977–10981, 2005) and Li_n−H−(CF₂−CH₂)₃−H (n = 1, 2) (J Am Chem Soc 129:2967–2970, 2007) and 31,123 au of the organometallic system (J Am Chem Soc 121:4047–4053, 1999) Ru(trans-4,4′-diethylaminostyryl-2,2′-bipyridine)₃²⁺, as well as 1.23 × 10⁶ au of the large donor-CNT systems (Nano Lett 8:2814–2818, 2008). Clearly, the alkali-metal-doped effect on the first hyperpolarizability is very dramatic for the high-performance multi-nitrogen complexant TIMA. Considering simple possibility from molecule to material, the β ₀ values of optimized Li-TIMA-dimer and Li-TIMA-tetramer are investigated by BHandHLYP method. Interestingly, results show that the order of β ₀ value is Li-TIMA-monomer < Li-TIMA-dimer < Li-TIMA-tetramer. So the new three-propeller-blade-shaped electrides can be considered as candidates for high-performance nonlinear optical materials.     

Synthesis and spectral properties of titanium(iv) polynuclear hydroxo complexes stabilized in solution by the [PW11O39]7− heteropolyanion

Unsaturated heteropolyanions (HPA) [PW₁₁O₃₉]⁷⁻ stabilize Ti^IV hydroxo complexes in aqueous solutions (Ti: PW₁₁ [PW₁₁O₃₉]⁷⁻⪯12, pH 1–3). Spectral studies (optical,¹⁷O and³¹P NMR, and IR spectra) and studies by the differential dissolution method demonstrated that Ti^IV hydroxo complexes are stabilized through interactions of polynuclear Ti^IV hydroxo cations with heteropolyanions [PW₁₁TiO₄₀ ⁵⁻ formed. Depending on the reaction conditions, hydroxo cations Ti _n−1O _x H _y ^m+ either add to oxygen atoms of the W−O−Ti bridges of the heteropolyanions to form the complex [PW₁₁TiO₄₀·Ti _n−1O _x H _y ] ^k− (at [HPA]=0.01 mol L⁻¹) or interact with Ti^IV of the heteropolyanions through the terminal o atom to give the polynuclear complexes [PW₁₁O₃₉Ti−O−Ti _n−1O _x H _y ]^q− (at [HPA]=0.2 mol L⁻¹). When the complexes of the first type were treated with H₂O₂, Ti^IV ions added peroxo groups. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 914–920, May, 1997.     

Regularities of self-propagating high-temperature synthesis in the solid 8-hydroxyquinoline—chloramine B system

The regularities of chemical reactions in solid 8-hydroxyquinoline—chloramine B mixtures were studied under conditions of organic self-propagating high-temperature synthesis (SHS), isothermal reaction, and thermal explosion in the 20–220 °C temperature range. Comprehensive physicochemical analysis and microstructural study of the reaction products were carried out. The temperature of SHS initiation (58 °C), the heat of the reaction (129±9 kJ mol⁻¹), the stoichiometric coefficient (1), the maximum temperature (T _max=98–140 °C), and the velocity of SHS wave propagation (u=0.15–0.55 mm s⁻¹) were determined. Depending on the ratio of the reactants (n), a low-temperature non-degeerate stable gasless mode (n≤1,T _max=115 °C,E _a=42 kcal mol⁻¹) and a high-temperature mode (n>1,T _max=140 °C,E _a=0.4 kcal mol⁻¹) are possible for SHS. The SHS affords monohydroxy and monochloro derivatives of 8-hydroxyquinoline, benzenesulfonamide, NaCl, NaOH, and H₂O. The mechanism of the solid-phase reaction at temperatures below 58 °C includes surface, solid-phase, and gas-phase diffusion; that for SHS is capillary spreading of the hydroxyquinoline melt. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2271–2284, December, 1999.     

Synthesis and Anticancer Activity of Long-Chain Isonicotinic Ester Ligand-Containing Arene Ruthenium Complexes and Nanoparticles

Arene ruthenium complexes containing long-chain N-ligands L¹ = NC₅H₄–4-COO–C₆H₄–4-O–(CH₂)₉–CH₃ or L² = NC₅H₄–4-COO–(CH₂)₁₀–O–C₆H₄–4-COO–C₆H₄–4-C₆H₄–4-CN derived from isonicotinic acid, of the type [(arene)Ru(L)Cl₂] (arene = C₆H₆, L = L¹: 1; arene = p-MeC₆H₄Pr ⁱ , L = L¹: 2; arene = C₆Me₆, L = L¹: 3; arene = C₆H₆, L = L²: 4; arene = p-MeC₆H₄Pr ⁱ , L = L²: 5; arene = C₆Me₆, L = L²: 6) have been synthesized from the corresponding [(arene)RuCl₂]₂ precursor with the long-chain N-ligand L in dichloromethane. Ruthenium nanoparticles stabilized by L¹ have been prepared by the solvent-free reduction of 1 with hydrogen or by reducing [(arene)Ru(H₂O)₃]SO₄ in ethanol in the presence of L¹ with hydrogen. These complexes and nanoparticles show a high anticancer activity towards human ovarian cell lines, the highest cytotoxicity being obtained for complex 2 (IC₅₀ = 2 μM for A2780 and 7 μM for A2780cisR).