Spectroscopic characteristics of dimethylsulfoxide molecules coordinated to Mg2+ cation. structure of complexes [Mg(DMSO)i(CH3CN)6-i]2+ from the data of quantum-chemical calculations and IR spectra of Mg(ClO4)2-DMSO-CH3CN Solutions

By the DFT B3LYP/6-31G** method the geometry was optimized and IR spectra were calculated of complexes [Mg(DMSO) _i (CH₃CN)_6-i ]²⁺ (i = 1–6). The values of free energy ΔG in the reaction of ligands substitution in the coordination sphere of the cation were determined. A satisfactory agreement between experimental and calculated values of structural parameters and infrared spectra of free molecules and coordinated to the cation DMSO was obtained. The regularities in the changes of the spectroscopic and structural characteristics of [Mg(DMSO) _i (CH₃CN)_6-i ]²⁺ complexes at varying their composition were revealed. The frequencies and absolute integral intensities of DMSO bands in the IR spectra of pure liquid, solutions in acetonitrile, and in three-component solutions Mg(ClO₄)₂-DMSO-CH₃CN were measured. A correspondence between the calculated change of the frequency and absolute intensity of the IR bands v(C≡N), v(C-C), v(S=O), and v(SC) of the complexes and the corresponding values in the IR spectra of the solutions with different content of components of binary solvent was found.     

Synthesis, molecular structure, and catalytic activity of borohydride complexes [(Me3Si)2NC(NPri)2]2Nd(BH4)2Li(thf)2 and [(Me3Si)2NC(NPri)2]2Sm(BH4)2Li(thf)2

The reactions of lanthanide tris(borohydrides) Ln(BH₄)₃(thf)₃ (Ln = Sm or Nd) with 2 equiv. of lithium N,N′-diisopropyl-N′-bis(trimethylsilyl)guanidinate in toluene produced the [(Me₃Si)₂NC(NPrⁱ)₂]Ln(BH₄)₂Li(thf)₂ complexes (Ln = Sm or Nd), which were isolated in 57 and 42% yields, respectively, by recrystallization from hexane. X-ray diffraction experiments and NMR and IR spectroscopic studies demonstrated that the reactions afford monomeric ate complexes, in which the lanthanide and lithium atoms are linked to each other by two bridging borohydride groups. The complexes exhibit catalytic activity in polymerization of methyl methacrylate. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 441–445, March, 2007.     

Theoretical study of the structure and stability of the Na2Cl+, NaCl 2? , Na3Cl 2+ , and Na2Cl 3? ions

The geometrical parameters, normal vibration frequencies, and thermochemical characteristics of the Na₂Cl⁺, NaCl ₂ ⁻ , Na₃Cl ₂ ⁺ , and Na₂Cl ₃ ⁻ ions in saturated vapors over sodium chloride were calculated by the ab initio methods including electron correlation. According to calculations, the Na₂Cl⁺ and NaCl ₂ ⁻ triatomic ions have a linear equilibrium D _∞h configuration. The pentaatomic ions can exist in the form of the D _∞h linear isomer, C _2v planar cyclic isomer, or D _3h bipyramidal isomer. At ∼1000 K the Na₃Cl ₂ ⁺ and Na₂Cl ₃ ⁻ ions exist predominantly in the form of the linear isomers. The energies and enthalpies of the ion-molecule reactions involving the above ions were calculated. The formation enthalpy of the ions Δ_f H ⁰(0 K) was determined: 230 ± 2 kJ/mol (Na₂Cl⁺), −96 ± 4 kJ/mol (Na₂Cl ₃ ⁻ ), −616 ± 2 kJ/mol (NaCl ₂ ⁻ ), and −935 ± 4 kJ/mol (Na₂Cl ₃ ⁻ ). Original Russian Text Copyright ? 2007 by T. P. Pogrebnaya, A. M. Pogrebnoi, and L. S. Kudin __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 48, No. 6, pp. 1053–1061, November–December, 2007.     

Electronic structures of I2− and I4− ions in γ-irradiated rigid solutions

Radical-anions of iodine, bromine, and monoiodochloride are produced in γ-irradiated amorphous solids at 77 K, and their electronic and ESR spectra measured. On limited warming of the irradiated solution dimerization by the reaction I₂^? + I₂ → I₄^? occurs to produce the same species as reported by Fornier de Violet et al. The electronic structure of the dimeric anion is discussed in comparison with the monomeric anion.     

Electronic structure and reactivity of PO 43? , P2O 74? phosphate and SO 42? , S2O 72? sulfate anions

Group-theoretical analysis and molecular orbital methods were used to obtain (in analytical form) the electronic structure and reactivity of the PO ₄ ³⁻ , SO ₄ ²⁻ and P₂O ₇ ⁴⁻ , S₂O ₇ ²⁻ anions. The reactivity of the anions is dictated by the availability of lone electron pairs on the top quasidegenerate MOs in the form of linear combinations of group orbitals from atomic orbitals (AOs) of peripheral oxygen atoms for PO ₄ ³⁻ , SO ₄ ²⁻ and the central (bridging) atom for P₂O ₇ ⁴⁻ , S₂O ₇ ²⁻ . These electron pairs are responsible for the donor-acceptor interactions during complexation, clustering, and other (addition, substitution, etc.) reactions. Original Russian Text Copyright ? 2005 V. A. Zasukha, A. P. Shpak, V. V. Trachevskii, and E. V. Urubkova __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 46, No. 3, pp. 405–415, May–June, 2005.     

Thermal fragmentation of the guanidinato aluminum amide precursor [Me2NC(NPr)2]Al(NMe2)2: An investigation of reactive species by matrix-isolation FTIR spectroscopy and time-of-flight mass spectrometry

The gas-phase thermolysis of the guanidinato aluminum amide precursor [Me₂NC(NⁱPr)₂]Al(NMe₂)₂ (1) in the oven temperature range of ambient temperatures to 600 °C has been investigated with matrix-isolation FTIR spectroscopy and time-of-flight mass spectrometry (argon as carrier gas). Precursor 1 fragments above 300 °C to form iPrCNCiPr (2) and monomeric Al(NMe₂)₃ (3m). Independent thermolysis series with 2 and the aluminum amide dimer 3d, [Al(NMe₂)₃]₂, were conducted and been used to interpret the results of the fragmentation of precursor 1. Compound 3m was present in the thermolysis range of 350–450 °C and has been identified for the first time. Through a comparison of measured FTIR spectra with the calculated spectrum of 3m (D₃ point group symmetry; B3LYP/6-31G(d) level of theory) all expected IR bands were found and could be assigned to normal modes. At thermolysis temperatures of ?500 °C signals indicative for H₂CNCH₃ (4) were found, showing that 3m fragments further at higher temperature. The thermolysis product 2 (iPrCNCiPr) withstands the higher thermolysis temperatures. From our study one can conclude that precursor 1 cleanly delivers the monomeric aluminum alane 3m, which then acts as the reactive material forming species.     

Zur kenntnis von [O2]22+[Ti7F30]2−

[O₂]²⁺₂[Ti₇F₃₀]^2? has been obtained by reaction of TiO₂ with a mixture of fluorine and oxygen (p_F2/O2 ≈ 300–3500 atm., t ≈ 300–450°C) either as colourless powder or in form of colourless, clear needles. From single crystal studies the spacegroup is P$\text{3}$ - C_3i¹ (No. 147) with a = 10.19₂, c = 6.50_o Å, Z = 1. The crystal structure has been refined to R = 0.086 [R_w = 0.058] (748 unique reflexions [F_o > 2σ(F_o)]). From the structure determination [O₂]²⁺₂[Ti₇F₃₀]^2? has isolated columns of partially distorted [TiF₆] octahedra (- column structure) which are connected only quite loosely by (disordered) O₂⁺ cations. ν_O2+ is at 1857 cm^?1, the magnetic moment μ_eff = 2.35 B.M. (295 K) is quite as expected for a ‘spin-only’ case.     

Theoretical study of the structure and stability of the heme dimer (FeC34H32N4O4)2 and its ion (FeC34H32N4O4) 2+

The electronic and geometric structures and the dissociation energies of the isolated molecule of heme dimer (heme)₂ = (FeC₃₄H₃₂O₄N₄)₂ and its ion (heme) ₂ ⁺ = (FeC₃₄H₃₂O₄N₄) ₂ ⁺ in the states with different multiplicities have been calculated by the density functional theory B3LYP method with the Gen-1 = 6-31G*(Fe) + 6-31G(C,H,N,O) and Gen-2 = 6-311++G*(Fe) + 6-31G*(C,H,N,O) basis sets. The computation results are compared with the analogous calculated data on monomeric heme and hemin⁺, as well as the previously considered dimeric ferriporphyrin X molecule and ion FeC₃₄H₃₁O₄N₄) ₂ ^{0, +} . In the heme dimer cation (heme) ₂ ⁺ , which is identified in mass spectra, the rings are linked with each other by a pair of Fe carbonyl bridges Fe⋯O_b = C(OH) and a pair of hydrogen bridges OH_b⋯N. According to the calculations, the most favorable state for (heme) ₂ ⁺ is the sextet in which five unpaired electrons are approximately uniformly distributed over the metal atoms, whereas the states with higher multiplicities 8 and 10 are, respectively, 0.15 and 0.20 eV higher on the energy scale. For the neutral dimer (heme)₂, the quintet is favorable in which each of the two Fe atoms has two unpaired electrons, and the states with the higher multiplicities 7 and 9 are only 0.10–0.15 eV higher. The calculated energies of dissociation D of the dimers into monomers point to a rather high stability of the (heme) ₂ ⁺ (D ∼ 1.4 1.4eV) and to a low stability of the neutral dimer (heme)₂ (D ∼ 0.3 eV). The R(Fe⋯O_b) distances in the bridges in (heme) ₂ ⁺ are 0.2–0.4 ? shorter than in (heme)₂. The trends in the behavior of the energetic and structural characteristics of the dimers (R(Fe-N), displacements of Fe atoms from the porphyrin ring plane, character of ring distortions, etc.) associated with the involvement of the and AOs of Fe atoms in bonding, as well as the spin density distribution over the Fe atoms and the rings, are analyzed as a function of the multiplicity and charge of the system. Differences in the character of interaction of the heme and ferriporphyrin dimers with molecular oxygen are discussed. Original Russian Text ? O.P. Charkin, N.M. Klimenko, D.O. Charkin, S.H. Lin, 2007, published in Zhurnal Neorganicheskoi Khimii, 2007, Vol. 52, No. 7, pp. 1166–1174.     

Interconverting WW Triple Bonds and W4 Clusters: Structures of W4(OPrn)16 and [Li2W2(OPrn)8(DME)]2*

Alcoholysis of W₂(NMe₂)₆ with excess n-propanol in hexane yields the tetranuclear cluster, W₄(OPrⁿ, I. Reduction of I with two equivalents of Li₂COT in THF gives a small yield of Li₂W₂(OPrⁿ)₈. Single crystals were isolated by cooling the product mixture in DME and were shown to be [Li₂W₂(OPrⁿ)₈(DME)]₂, II, which consists of a unique “dimer of dimers” structure. In this reaction sequence, W₄¹⁶⁺ cluster formation is followed by four electron reduction to reform the (W≡W)⁶⁺ unit. Better yields of the lithium salt can be obtained by the addition of LiOPrⁿ/HOPrⁿ solutions to W₂(OBu^t)₆ in which case Li₂W₂(OPrⁿ)₈ has been obtained as a 1:1 adduct with LiOPr. This identity of this salt was confirmed by solution NMR spectroscopy. In the alternative reaction, the (W≡W)⁶⁺ center remains intact from reactant to product. No attempt has been made to separate the product from excess LiOPr. DFT (ADF 2004.01) molecular orbital calculations on the model cluster W₄(OH)₁₆ are used to help elucidate the disruption of the W₄ cluster upon four electron reduction. The molecular structures of compounds I and II are reported.*Dedicated to Professor F. A Cotton on the occasion of his 75th birthday.     

Ring-opening polymerization of l-lactide by organotin(IV)alkoxides,R2Sn(OPr)2: Estimation of the activation parameters

The ring-opening polymerization of l-lactide, l-LA, to give poly-l-lactide by R₂Sn(OPrⁱ)₂ compounds, where R = Buⁿ and p-XC₆H₄ (X = CF₃, F, H, Me and OMe) has been studied in benzene over a temperature range. There is a relatively small variation in ΔH^≠ as a function of R with all the values falling within the range 11 ± 2 kcal mol⁻¹. The entropy of activation, ΔS^≠, is consistently large and negative, −50 ± 5 eu, supporting the view that the ring-opening event, the enchainment step involves a highly ordered transition state. The crystal and molecular structures of the compounds Ph₂Sn(OPrⁱ)₂, (p-FC₆H₄)₂Sn(OPrⁱ)₂ and (p-Me₂NC₆H₄)₃SnOPrⁱ are also reported. While the latter compound is monomeric in the solid state the former are both dimeric with a pair of bridging OPrⁱ ligands.     

EXAFS Spectroscopy of the Alkoxide Precursor Zr(OnBu)4 and its Modification in Solution

The molecular structure of the transition metal alkoxide Zr(OⁿBu)₄ in toluene and its modification by addition of i-propanol, tetrahydrofurane, and the coordinating ligand pentane-1,3-dione (Hacac) were investigated by extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) spectroscopy. Zr(OⁿBu)₄ dissolved in toluene forms dimers. It was proved that cluster size is a function of the number of added equivalents ligand. In contrast, the addition of i-propanol or tetrahydrofurane caused no structural changes observable by EXAFS spectroscopy. A detailed discussion of the structural models is given in terms of possible alternatives and errors within the EXAFS analysis.     

Crystal and molecular structure of the mixed-ligand complex ZnPhen((i-C3H7O)2PS2)2

Bis(diisopropyldithiophosphato)zinc(II) Zni-PrO)₂PS_{2 2} (I) possesses high volatility, which is useful for gas-chromatographic determination of zinc [1]. In the solid state the compound has a dimeric structure [2]. As shown for dimeric zinc(II) dialkyldithiocarbamates and tetrameric zinc(II) alkylxanthates, reactions of these chelates with nitrogen heterocycles [1,10-phenanthroline (Phen) or 2,2′-bipyridyl (2,2′-Bipy)] form volatile mixed-ligand compounds having a monomeric structure [3, 4]. It is interesting to synthesize and study the mixed-ligand compounds of chelate I with nitrogen-containing heterocycles. Synthesis of a mixed-ligand complex of this chelate with Phen was reported in [5, 6] but no structure determination was performed for the compound. We synthesized the compound ZnPhen[(i-PrO)₂PS₂]₂ (II) using a slightly modified procedure [5], grew single crystals, and investigated its molecular and crystal structure. Translated from Zhumal Struktumoi Khimii, Vol. 41, No. 1, pp. 191-195, January-February, 2000.     

Mn2+掺杂准二维钙钛矿(PEA)2PbyMn1-yBr4的制备及其电致发光性能

制备了具有高荧光量子产率(photoluminescence quantum yield, PLQY)的 Mn²⁺掺杂准二维钙钛矿(PEA)₂Pb_yMn_1-yBr₄(PEA为苯乙胺, y 为 Pb²⁺占 Mn²⁺和 Pb²⁺总含量的物质的量分数)薄膜。宽带隙的(PEA)₂PbBr₄作为给体, 掺杂杂质 Mn²⁺作为受体, 构筑了双发射的激发态传递系统。通过调控 Mn²⁺掺杂的不同比例对(PEA)₂Pb_yMn_1-yBr₄的发光性能和薄膜形貌的影响, 发现当前驱体溶液中 Mn²⁺与 Pb²⁺的物质的量之比为 1:4 时, 薄膜有着最高的 PLQY 和最低的表面粗糙度。利用飞秒瞬态吸收(transientabsorption, TA)光谱, 追踪其动力学过程, 发现主客体之间的激发态传递是通过电荷转移来实现的。为了研究材料的电致发光特性, 我们将(PEA)₂Pb_yMn_1-yBr₄作为活性层, 加工得到了发光二极管(light emitting diodes, LEDs)。在室温下, 器件发出明亮的橙色, 其最高的发光强度为 0.21 cd·m^-2, 外量子效率(external quantum efficiency, EQE)为 0.002 5 %。     

Complexing tendencies of UO 22+ and Th4+ in their mixed ligand complexes with aminopolycarboxylates and resorcinol or its derivatives

Formation contants (log K _MAL ^MA ) of mixed ligand complexes MAL, where M = UO ₂ ²⁺ or Th⁴⁺, A = IMDA, NTA, HEDTA, EDTA, CDTA or DTPA, and L = resorcinol (res), 2-methyl resorcinol (2-Me-res), 5-methyl resorcinol (5-Me-res) or 4-chloro resorcinol (4-Cl-res), have been determined pH-metrically by the Irving-Rossotti approach at 25°C and at an ionic strength,I = 0.2(moldm⁻³KNO₃). The observed stability sequences are IMDA > NTA > HEDTA > EDTA > CDTA > DTPA, and 4-Cl-res > 5-Me-res > 2-Me-res > res with respect to primary and secondary ligands, respectively. Th⁴⁺ forms more stable mixed complexes than UO ₂ ²⁺ . The A ΔlogK values are negative due mainly to the charge repulsion involved in the complexation MA + L⇋MAL.     

Circular dichroism of Mn2+ ions in α-Zn(H2O)6SeO4 crystal

The circular dichroism (CD) of Mn²⁺ ions in α-Zn(H₂O)₆SeO₄. crystal has been measured at 77–300°K. CD lines associated with the spin forbidden transition ⁶A₁ → ⁴A₁,⁴_aE are observed, and compared with uniaxial rotational strengths calculated on the basis of ligand field theory. The CD bands of Mn²⁺ and Ni²⁺ simultaneously doped into a Zn(H₂O)₆SeO₄ crystal have the same sign, which accords with a theoretical prediction.     

2∞[Yb2(NH2)2( Pz )4][Yb(NH3)2( Pz )3 Pz H]: Electride Induced Synthesis of a 2D-Ytterbium-Pyrazolate Network

Summary. ² _∞[Yb₂(NH₂)₂(Pz)₄][Yb(NH₃)₂(Pz)₃ PzH], Pz ⁻ = pyrazolate anion, PzH = pyrazole, C₃H₄N₂ is obtained by the reaction of ytterbium metal with pyrazole in liquid ammonia and subsequent increase of the temperature to 200°C resulting in the formation of colorless single crystals of the compound. The X-ray single crystal analysis reveals that the structure consists of ² _∞[Yb₂(NH₂)₂(Pz)₄] planes with neutral [Yb(NH₃)₂(Pz)₃ PzH] monomeric molecules that are located between the planes and ytterbium is trivalent. This is the first example of a two-dimensional network structure of an organic amine of the rare earth elements that derives from an electride induced synthesis. The product decomposes under release of ammonia outside its sealed reaction vessel, viz. if the NH₃ pressure is removed.     

2∞[Yb2(NH2)2(Pz)4][Yb(NH3)2(Pz)3PzH]: Electride Induced Synthesis of a 2D-Ytterbium-Pyrazolate Network

² _∞[Yb₂(NH₂)₂(Pz)₄][Yb(NH₃)₂(Pz)₃ PzH], Pz ⁻ = pyrazolate anion, PzH = pyrazole, C₃H₄N₂ is obtained by the reaction of ytterbium metal with pyrazole in liquid ammonia and subsequent increase of the temperature to 200°C resulting in the formation of colorless single crystals of the compound. The X-ray single crystal analysis reveals that the structure consists of ² _∞[Yb₂(NH₂)₂(Pz)₄] planes with neutral [Yb(NH₃)₂(Pz)₃ PzH] monomeric molecules that are located between the planes and ytterbium is trivalent. This is the first example of a two-dimensional network structure of an organic amine of the rare earth elements that derives from an electride induced synthesis. The product decomposes under release of ammonia outside its sealed reaction vessel, viz. if the NH₃ pressure is removed.     

Structure and Characterization of the [Rbx (NH4)1-x]2TeCl6 Tellurate Family at Room Temperature

The crystal structure of rubidium-ammonium hexachlorotellurate [Rb_0.94(NH₄)_0.06]₂TeCl₆ was determined by X-ray single crystal analysis at room temperature. The space group is Fm3m with the lattice parameter a = 10.2503(5) ? and Z = 4. The refinement converged to R(F) = 0.015 and wR(F ²) = 0.032. As in the studied [Rb0.94(NH₄)₀.06]2TeCl6 family, this compound has an antifluorite-type arrangement. Tellurium atoms are surrounded by an octahedron of chlorine atoms. The Rb or N atoms are located between TeCl₂⁶ octahedra ensuring the stabilization of the structure by ionic and hydrogen bonding contacts N-HCl. The substitution of rubidium by ammonium groups does not affect the structural arrangement, but it leads to a decrease in the a lattice cell dimension. IR and Raman spectroscopic studies at room temperature were performed to confirm the X-ray crystallographic results.     

Theoretical study of the structure and stability of the dimers of heme analogues (MC34H32N4O4)2 and their ions (MC34H32N4O4) 2+ with 3 d -metal atoms M

The electronic and geometric structures and the energetic characteristics of a series of monomeric MC₃₄H₃₂N₄O ₄ ^0,+ and dimeric (MC₃₄H₃₂N₄O₄) ₂ ^0,+ molecules, heme analogues and their positively charged ions with 3d-metal atoms M = Ti, V, Cr, and Mn, have been calculated by the density functional theory B3LYP method with the Gen−1 = 6−31G^*(Fe) + 6−31G(C, H, N, O) and Gen−2 = 6−311+G^*(Fe) + 6−31G^*(C, H, N, O) basis sets. The computation results are compared with the analogous calculated data on the heme dimers (heme) ₂ ^0,+ . Computations show that for the (MC₃₄H₃₂N₄O₄) ₂ ^0,+ dimers, high-spin states are preferable. In these dimers, the rings are linked with each other by a pair of M-carbonyl bridges M⋯O_b=C(OH) and a pair of hydrogen bridges OH_b⋯N. The calculated energies of dissociation D of the dimers into monomers point to a rather high stability of the dimers at the beginning of the 3d series (D ∼ 2.3–3.6 eV for M = Ti, V), which decreases rapidly as the atomic number of M increases (D ∼ 0.5 eV for M = Cr and ∼0.4 eV for (heme)₂). The positive ions (MC₃₄H₃₂N₄O₄) ₂ ⁺ are ∼0.8–1.0 eV are more stable to dissociation than their neutral congeners (MC₃₄H₃₂N₄O₄)₂. The trends in the behavior of the energetic and structural characteristics of the dimers (distances R(M—N), displacements of M atoms from the porphyrin ring plane, parameters of the carbonyl and hydrogen bridges, character of ring distortions, etc.), as well as in the spin density distribution between the metal atoms and the rings in the monomers MC₃₄H₃₂N₄O₄ and dimers (MC₃₄H₃₂N₄O₄)₂ caused by their ionization and going along the 3d series, are examined. In the mixed dimer (FeC₃₄H₃₂N₄O₄)(VC₃₄H₃₂N₄O₄), the rings are linked by only one strong carbonyl bridge V⋯O_b=C(OH), with some contribution made by the neighboring hydrogen bridge. The dissociation energy of this mixed dimer into monomers is close to a half of the dissociation energy of the “symmetric” dimer (VC₃₄H₃₂N₄O₄)₂. Original Russian Text ? O.P. Charkin, N.M. Klimenko, D.O. Charkin, S.H. Lin, 2007, published in Zhurnal Neorganicheskoi Khimii, 2007, Vol. 52, No. 8, pp. 1332–1346.     

Excess properties of the (Ln2−2xCaxThx)(PO4)2 (Ln = La, Ce) solid solutions

X-ray powder diffraction at room temperature and drop calorimetry at T = 1005 K were performed on LnPO₄–CaTh(PO₄)₂ (Ln = La, Ce) solid solutions. The results show excess molar volume and excess enthalpy indicating deviations from ideal behaviour that have been interpreted in terms of lattice strains resulting from the ion size effects of substitution of the Ln³⁺ with (Ca²⁺ + Th⁴⁺).