Induction of radiative forbidden transitions in an oxygen molecule in O<Subscript>2</Subscript>–H<Subscript>2</Subscript>O collision complexes

By the DFT/B3LYP method the equilibrium structures of oxygen complexes with water are calculated in various geometric conformations with symmetries C _2v and C _s . By the MRCI/CASSCF method potential energy surface cross-sections of the ^1.3[O₂–H₂O] complexation reaction are constructed. With taking into account the spin-orbit coupling, the forbidden transition moments a ¹Δ _g –X ³Σ _g ^?, b ¹Σ _g ⁺–a ¹Δ _g , c ¹Σ _u ^?–a ¹Δ _g , A ³Σ _u ⁺–X ³Σ _g ^? of the complexes are calculated and changes in their intensities at different geometric configurations of the complex are revealed.     

Molecular structure of ErCl<Subscript>3</Subscript> and YbCl<Subscript>3</Subscript> according to the data of the simultaneous electron diffraction and mass spectrometric experiment

The saturated vapors of ErCl₃ and YbCl₃ were studied in a simultaneous electron diffraction and mass spectrometric experiment at 1165 K and 1170 K, respectively. In the vapors of these compounds, we found up to 3 mol.% dimers along with the monomers. The parameters of the r _g effective configuration of the monomer molecules were determined. For ErCl₃ and YbCl₃, the internuclear distances r _g(Ln-Cl) were 2.436(5) Å and 2.416(5) Å, and the bond angles ∠_g(Cl-Ln-Cl) were 117.0(10)° and 117.2(10)°, respectively. The equilibrium configurations and vibration frequencies of the monomer and dimer molecules were calculated by the HF, B3LYP, and MP2 methods using the combination of the ECP_D energy-consistent quasirelativistic core potential, including 4f electrons [Kr4d ¹⁰4f ⁿ ], and the contracted [5s4p3d] valence basis set for Er and Yb atoms and the MIDIX [4s3p1d] basis set for Cl atoms. The parameters of the effective r _g configuration of the monomer molecules corresponding to the temperature of the experiment were calculated. The difference between the calculated equilibrium r _e(Ln-Cl) and temperature-averaged r _g(Ln-Cl) distances was found to be 0.001–0.002 Å and did not exceed the error of the r _g(Ln-Cl) parameter determined in the electron diffraction experiment. The experimental parameters of the r _g structure were shown to be consistent with the idea about the planar equilibrium geometrical configuration of ErCl₃ and YbCl₃ molecules.     

One-pot three-component process for the synthesis of substituted pyrano[2,3-<Emphasis Type="Italic">c</Emphasis>]pyrazoles catalyzed by nanostructured FSM-16-SO<Subscript>3</Subscript>H

A three-component process for the one-pot synthesis of 6-amino-4-aryl-5-cyano-3-methyl-1-phenyl-1,4-dihydropyrano[2,3-c]pyrazoles by the reaction of aldehydes, 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one, and malononitrile in the presence of FSM-16-SO₃H as an efficient mesoporous catalyst. The FSM-16-SO₃H was prepared and characterized by SEM, XRD, BET, and FT-IR techniques. The advantages of the presented method are high yields, short reaction times, easy purification of products, easy work-up, and reusability of the catalyst.     

Chromium ion incorporation in the crystal structure of BGO

Comprehensive investigations have been performed by EPR and optical spectroscopy for Bi₃GeO₄ crystals doped with chromium ions. It is demonstrated that the known optical absorption spectrum for chromium ions, specifically, the triplet in the region 600–900 nm has an analog in the EPR spectra — the center with electron spin S = 1. The spectrum is described by the spin-Hamiltonian with the parameters D = 550 G, E = 10 G, g _xx = g _yy = 1.915, g _zz = 1.932. The EPR spectrum is dictated by Cr⁴⁺ incorporation at the germanium sites. Luminescence observed in the region 1.2–1.7 μm is also caused by transitions of Cr⁴⁺ with tetrahedral surroundings to germanium sites. Original Russian Text Copyright ? 2005 N. V. Chernei, V. A. Nadolinnyi, N. V. Ivannikova, V. A. Gusev, I. N. Kupriyanov, V. N. Shlegel, and Ya. V. Vasiliev __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 46, No. 3, pp. 444–450, May–June, 2005.     

Structure and dynamics of a free aquaporin (AQP1) by a coarse-grained Monte Carlo simulation

Structure and dynamics of a free aquaporin (AQP1) are studied by a coarse-grained Monte Carlo simulation as a function of temperature using a phenomenological potential with the input of a knowledge-based residue–residue interaction. Response of the radius of gyration (R _g) of the protein to the temperature (T) is found to be nonlinear: Decay of R _g at T ≤ T _c is followed by a continuous increase at T ≥ T _c before reaching its saturation. In thermo-responsive regime, the protein exhibits segmental globularization with the persistence of three regions along its sequence involving residues ¹M–²⁵V and ²⁵⁰V–²⁶⁹K toward the beginning and end segments with a narrow intermediate region around ¹⁵⁵A–¹⁶³D. A detail analysis of the structure factor S(q) shows a global random coil conformation at high temperatures with an effective dimension D _e ~ 1.74 and a globular structure (D _e ~ 3) at low temperatures. In thermo-responsive regime, the variation of S(q) with the wave vector q reveals a systematic redistribution of self-organizing residues (in globular and fibrous sections) that depends on the length scale and the temperature.     

The utility of sulfonic acid catalysts for silane water-crosslinked network formation in the ethylene–propylene copolymer system

Catalytic effects of Brönsted acid on the early kinetics of water-crosslinking reaction in the vinyltrimethoxysilane-grafted ethylene–propylene copolymer (EPR-g-VTMS) system were investigated by means of an attenuated total reflectance-Fourier transform infrared (ATR-FTIR) technique and gel fraction measurements. Four sulfonic acids with different substituent, including methanesulfonic acid (C1SO₃H), 1-propanesulfonic acid (C3SO₃H), 1-pentanesulfonic acid (C5SO₃H), and dodecylbenzenesulfonic acid (C12PhSO₃H), were selected to examine the progress and effect of progressive changes in the silane water-crosslinked network structure in comparison with a primary amine (n-octadecylamine, Lewis base). From the kinetic analysis using Arrhenius equation, we found that the frequency factors for both hydrolysis (ATR-FTIR) and condensation step (gel content) of EPR-g-VTMS decreased in the order of C1SO₃H > C3SO₃H > C5SO₃H > C12PhSO₃H, while the activation energy values for each reaction did not differ significantly. These relationships can be explained mainly on the basis of the diffusion factors of the sulfonic acids in EPR-g-VTMS system. Moreover, the stress–strain curve comparison between water-crosslinked EPR-g-VTMS samples containing sulfonic acid and amine compound clearly indicated the difference in their tensile properties as a result of the catalyst variation; the use of sulfonic acid as water-crosslinking catalyst eventually achieves to the soft and tough water-crosslinked EPR-g-VTMS, while the hard and strong one was produced using amine catalyst. Not only the catalytic activity but also the type of the catalyst has eventually significant effects upon the physical properties of the water-crosslinked EPR-g-VTMS.     

Structural characterization of a mixed-ligand complex of copper(II) with 1,10-phenanthroline and the <Emphasis Type="Italic">m</Emphasis>-aminobenzoate ion

A new copper(II) complex of 1,10-phenanthroline (C1₂H₈N₂) and the meta-aminobenzoate ion (m-amb; C₇H₆NO ₂ ^? ), having the formula Cu(C₁₂H₈N₂)(C₇H₆NO₂)Cl?0.5H₂O, is prepared and characterized by elemental analysis, IR spectroscopy, and single crystal X-ray diffraction. The structure is built up from monomeric units in which the coordination environment around the metal ion is a square plane arising from a bidentate 1,10-phenanthroline molecule, a monodentate m-amb anion, and a chloride ion. A very long (Cu–N = 2.856(5) Å) bond to the nitrogen atom of an adjacent m-amb ion generates [101] polymeric chains in the crystal. The crystal structure is consolidated by N–H???O and O–H???O hydrogen bonds and C–H???O, C–H???Cl, and aromatic π–π stacking interactions. Crystal data: C₁₉H₁₅ClCuN₃O_2.5, M _r = 424.33, monoclinic, P2₁/n (No. 14), a = 9.8200(5) Å, b = 10.9291(7) Å, c = 16.3803(9) Å, β = 105.293(3)°, V = 1695.74(17) ų, Z = 4, R(F) = 0.043, wR(F ²) = 0.122.     

Synthesis,structure and electrochemical properties of some thiosemicarbazone complexes of iridium

Reaction of thiosemicarbazones of salicylaldehyde and 2-hydroxyacetophenone (H₂L¹ and H₂L²) with [Ir(PPh₃)₃Cl] affords complexes of type [Ir(PPh₃)₂(L)(H)] (L = L¹ or L²) in ethanol. A similar reaction carried out in toluene affords the [Ir(PPh₃)₂(L)(H)] complexes along with complexes of type [Ir(PPh₃)₂(L)Cl], where a chloride is coordinated to iridium instead of the hydride. The structure of the [Ir(PPh₃)₂(L²)(H)] and [Ir(PPh₃)₂(L²)Cl] complexes has been determined by X-ray crystallography. Crystal data for [Ir(PPh₃)₂(L²)(H)]: space group, P2₁/c; crystal system, monoclinic; a=12.110(2) Å, b=17.983(4) Å, c=18.437(4) Å, β=103.42(3)°, Z=4; R ₁=0.0591, wR ₂=0.1107. Crystal data for [Ir(PPh₃)₂(L²)Cl]: space group, P2₁/c; crystal system, monoclinic; a=17.9374(11) Å, b=19.2570(10) Å, c=24.9135(16) Å, β=108.145(5)°, Z=4; R ₁=0.0463, wR ₂=0.0901. In all the complexes the thiosemicarbazones are coordinated to the metal center as dianionic tridentate O, N, S-donors and the two triphenylphosphines are trans. The complexes are diamagnetic (low-spin d? ⁶, S=0) and show intense MLCT transitions in the visible region. Cyclic voltammetry on all the [Ir(PPh₃)₂(L)(H)] and [Ir(PPh₃)₂(L)Cl] complexes shows a quasi-reversible Ir(III)–Ir(IV) oxidation within 0.55–0.78 V vs. SCE followed by an irreversible oxidation of the thiosemicarbazone within 0.91–1.27 V vs. SCE. An irreversible reduction of the thiosemicarbazone is also observed within ?1.10 to ?1.23 V vs. SCE.     

Decomposition of pentaammineaquacobalt(III) perchlorate under laser radiation action

Photolytic decomposition of the complex [Co(NH₃)₅(H₂O)](ClO₄)₃ under the action of a laser with a wavelength of 355 nm, which is resonant in energy to the energy of the (¹ A _1g → ¹ T _2g ) d–d transition, was studied. Decomposition of the complex is accompanied by a release of ammonia with its subsequent oxidation to nitrogen oxides and by partial cobalt reduction with the formation of the mixed cobalt(II, III) oxide Co₃O₄.     

Structure and Chemical Bonding of the B<Subscript>3</Subscript>S<Stack><Subscript>n</Subscript><Superscript>0/−</Superscript></Stack> (<Emphasis Type="Italic">n</Emphasis> = 2–4) Boron Sulfide Clusters: A Density Functional Theory Investigation

A density functional theory investigation on the structural and bonding properties of B₃S _n ^?/0 (n = 2–4) series has been performed. Based on B3LYP and CCSD(T) calculations, we present the linear D _∞h B₃S₂ ^? (1, ³Σ_g) and D _∞h B₃S₂ (2, ²Π_u), the Y-shaped C _2v B₃S₃ ^? (3, ¹A₁) and C _2v B₃S₃ (4, ²B₂), and perfectly planar structures C _2v B₃S₄ ^? (5, ¹A₁) and C _2v B₃S₄ (6, ²B₂) that contain rhombic B₂S₂ rings. The 1–6 ground-state structures are planar with linear “B–B–B” core, in which the first and the second S atoms prefer to bond terminally to the terminal B, and the third S atom bonds to the center B, however, when the third S atom is added with the fourth, the atoms tend to be in the bridging positions of two adjacent B atoms. The growth pattern of B₃S _n ^?/0 (n = 2–4) clusters helps to understand the structural properties of the other small boron sulfide clusters. Bonding analyses reveal that a dual or single three-center one-electron (3c–1e) π hypervalent bonds located over the “B–B–B” core of D _∞h B₃S₂ ^? (1) and B₃S₂ (2), respectively. While C _2v B₃S₄ ^? (5) and B₃S₄ (6) with rhombic B₂S₂ rings as the center with –BS and –S units all possess 4c–4e bonds (o-bonds) in the rhombic B₂S₂ rings.     

Quantum-chemical study of lutetium,ytterbium, and gadolinium phthalocyaninates PcLnCl

Structural parameters and IR spectra of the (¹A₁//C_4v)-PcLuCl, (²B₂//C_4v)-PcYbCl, and (⁸A₂//C_4v)-PcGdCl molecules, (²A₂//C_4v)-Pc⁺LuCl, (3B₁//C_4v)-Pc⁺YbCl, and (⁹A₁//C_4v)-Pc⁺GdCl cations, (¹A_g//D_2h)-PcLuCl₂LuPc dimer, and PcLuCl···PcLuCl coaxial molecular pair have been simulated using the DFT (U) PBE0/SDD method. The PcLnCl (Ln = Lu, Yb, Gd) molecules have exhibited the equilibrium Ln–N bond length of 222, 223, and 230 pm, the Ln–Cl bond length of 245, 246, and 253 pm, the dipole moment of 4.73, 4.57, and 4.84 D directed from Cl to Ln, and ionization potential of 6.6 eV. β-Decay (¹A₁//C_4v)-Pc¹⁷⁷LuCl → (¹A₁//C_4v)-(Pc^177mHfCl)⁺ occurs with no significant change of the charge on the metal atom.     

Crystal structure and properties of polymeric hexaaqua-<Emphasis Type="Italic">hexakis</Emphasis>-(2-thiobarbiturato)-disamarium(III)

The structure (CIF file CCDC No. 1401886) of the hexaaqua-hexakis(2-thiobarbiturato)-disamarium [Sm₂(H₂O)₆(HTBA)₆] _n polymeric complex (I), where H₂ТВА is 2-thiobarbituric acid, is determined; its thermal decomposition and IR spectrum are studied. The crystals of I are monoclinic: a = 14.072(1) Å, b = 10.0842(6) Å, c = 15.323(1) Å, β = 110.408(2)°, V = 2037.9(2) ų, space group P2/n, Z = 2. All three independent thiobarbiturate anions HTBA^– coordinate to Sm³⁺ through oxygen atoms. To one of independent Sm³⁺ ions six (two terminal and four bridging) HTBA^– ions and two water molecules are coordinated; the second is bonded with four bridging HTBA^– and four water molecules, forming square antiprisms. The bridging HТВА–anions arrange antiprisms in layers. The structure is stabilized by hydrogen bonds and a π–π interaction between the HТВА^– ions. The topology of the polymer network of I is analyzed.     

New monomer based on thienopyrazine with fluorocarbazole substituents as a promising building block for organic electronics

A new monomer, 2,3-bis[6-fluoro-9-(2-octyldodecyl)-9H-carbazol-3-yl]-3,3'-[5,7-di(5-bromothienyl-2)thieno[3,4-b]pyrazine, M1, based on thienopyrazine containing fluorocarbazole substituents in the pyrazine ring has been synthesized. The structure of the compound has been proved by ¹H and ¹³C NMR and elemental analysis. The HOMO and LUMO energies for monomer M1 and its precursor 3 determined by the electrochemical method are–5.03 and–3.31 eV, as well as–5.28 and–3.36 eV, respectively. Band gap widths E _g ^ec are 1.72 and 1.92 eV for compounds M1 and 3, respectively. The new structural fragment has rather deep energy levels of frontier molecular orbitals and a small band gap width; therefore, it is a promising building block for the synthesis of polymers for organic electronics.     

Facile synthesis of 5A zeolite from attapulgite clay for adsorption of <Emphasis Type="Italic">n</Emphasis>-paraffins

5A zeolites were facilely synthesized from attapulgite clay and sodium aluminate precursors. The optimum synthesis condition for 4A zeolite (Na-form) were H₂O/attapulgite ratio of 40:1 volume/mass, NaOH/attapulgite mass ratio of 2.35:1, the crystallization time was 4 h at 80–85 °C. The 4A zeolite was converted to related 5A zeolite (Ca-form) through ionic exchanges using calcium chloride solution with the Si/Al mole ratio of 1.3. SEM images demonstrated that as-synthesized 5A zeolites are ordered cubic crystals, average crystals length dimension is 1–2 μm. And the zeolites product had a specific surface area of 482 m² g^?1 and total pore volume of 0.274 cm³ g^?1. The static adsorption experiments showed that the equilibrium adsorption capacities of n-decane and n-pentadecane on produced 5A zeolite were 0.253 and 0.510 g g^?1, respectively. And the adsorption equilibrium time of n-decane and n-pentadecane on 5A zeolite were 45 and 60 min, respectively. The experimental adsorption data of n-decane and n-pentadecane on three zeolites could be properly fitted by the Langmuir–Freundlich isotherm model.     

Synthesis,scope, <Superscript>1</Superscript>H and <Superscript>13</Superscript>C spectral assignments of isomeric dibenzofuran carboxaldehydes

Two isomeric dibenzofuran carboxaldehydes, namely 2-methoxydibenzo[b,d]furan-1-carbaldehyde (4) and 2-methoxydibenzo[b,d]furan-3-carbaldehyde (5), were synthesized. Formylation of 2-methoxydibenzo[b,d]furan (3) with α,α-dichloromethyl methyl ether and tin(IV) chloride gave a mixture of aldehydes 4 and 5 in 95 % yield and in a 35:65 ratio. Their ¹H and ¹³C NMR spectral signals were not sufficiently resolved in CDCl₃ solution to achieve their complete assignment, but this was possible in DMSO-d ₆ with the help of 2D-NMR techniques: NOESY for ¹H–¹H interactions and HSQC and HMQC experiments for ¹H–¹³C correlations. These aldehydes were used in the synthesis of novel β-phenylethylamines and NBOMe derivatives, which are undergoing biological evaluation.     

Microbial Transformation of Curcumin to Its Derivatives with a Novel <Emphasis Type="Italic">Pichia kudriavzevii</Emphasis> ZJPH0802 Strain

Curcumin, a polyphenolic compound, has shown a wide range of pharmacological activities and has been widely used as a food additive. However, the clinical use of curcumin is limited to some extent because of its poor water solubility and low bioavailability. To overcome these problems, many approaches have been attempted and structural modification of curcumin by microbial transformation has been proven to be an alternative. In this study, we isolated a novel yeast strain Pichia kudriavzevii ZJPH0802 from a soil sample, which is capable of converting curcumin to its derivatives. The transformed products by this strain were evaluated by HPLC, (+) electrospray ionization (ESI)-MSⁿ, and ¹H nuclear magnetic resonance methods. Compared with controls, two new peaks of the transformed broth appeared at retention times of 26 min (I) and 62 min (II) by HPLC analysis. The two transformed products were then further identified by (+) ESI-MSⁿ. The spectrum showed that compound I had an accurate [M+H+NH₃]⁺ ion at m/z 392, [M+H]⁺ ion at m/z 375, [M+H–H₂O]⁺ ion at m/z 357, and (+) ESI-MS³ spectrum showed that ion at m/z 357 could further form fragment ions at m/z 339, 177, and 163; compound II had an accurate [M+H]⁺ ion at m/z 373, [M+H–H₂O]⁺ ion at m/z 355, and (+) ESI-MS³ spectrum showed that ion at m/z 355 could further form fragment ions at m/z 219, 179, 177, 163, and 137. These two transformed products thereby were confirmed as hexahydrocurcumin (I) and tetrahydrocurcumin (II).     

Molecular mechanism of propane oxidative dehydrogenation on surface oxygen radical sites of VO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/TiO<Subscript>2</Subscript> catalysts

Minimum energy pathways of propane oxidative dehydrogenation to propene and propanol on supported vanadium oxide catalyst VO _x /TiO₂ were studied by periodic discrete Fourier transform (DFT) using a surface oxygen radical as the active site. The propene formation pathway was shown to consist of two consecutive hydrogen abstraction steps. The first step includes C_β–H bond activation of propane followed by the formation of a surface hydroxyl group V–O _t H and a propyl radical n-C₃H₇. This step with the activation energy E* = 0.56 eV (54.1 kJ/mol) appears to be rate-determining. The second step involves the reaction of the bridging O _b oxygen atom with the methylene C–H bond of propyl radical n-C₃H₇ followed by the formation of a hydroxylated surface site HO _t –V⁴⁺–O _b H and propene. The initial steps of the C–H bond activation during propane conversion to propanol and propene by ODH on V⁵⁺–(O _t O _b )^? active sites are identical. The obtained results demonstrate that participation of surface oxygen radicals as the active sites of propane ODH makes it possible to explain relatively low activation energies observed for this reaction on the most active catalysts. The presence of very active radical species in low concentration seems to be the key factor for obtaining high selectivity.     

A Search for a Direct Relationship Between Chromatographic and Adsorption Data

Shifts of chromatographic peak maxima and centres of gravity have been investigated for different amounts of propane injected on to a chromatographic column in ideal, non-linear chromatography. Specific retention volumes (V _{g (273)}, corrected to the standard temperature, 273.15 K), propane adsorption isotherms, and the first and second derivatives of the isotherms, (da/dp) _T and (d²a/dp²) _T , were determined for samples of active carbon and for different amounts of propane injected on column. Relationships between specific retention volume and the molar differential work of adsorption, A, were calculated on the basis of the propane isotherms and using the retention times of the peak maxima and the centres of gravity of the peaks. The equations obtained, ln V _{g (273)}=f₁(A) and(dW/dA) _{T, F c} = f₂(ln V _{g (273)}), have been used to explain the relationships between (i) chromatographic peak profiles and (ii) the distribution function of pore volumes filled with propane and the molar differential work of adsorption at different column temperatures (303–318 K).     

Hirshfeld Surface Analysis,Crystal Structure and Spectroscopic Studies of a New Cu(II) Halocuprate Salt with Protonated N-Amino-Ethyl-Piperazine

(C₆H₁₈N₃)₄[CuCl₅]₂[CuCl₄]₃·1.42H₂O is prepared and characterized by various physicochemical techniques. The single crystal X-ray diffraction structural analysis reveals that the title compound belongs to the orthorhombic system with the space group Cmca. Its unit cell dimensions are: a = 24.286(2) Å, b = 14.3082(14) Å, c = 16.6160(16) Å, Z = 4, V = 5773.8(10) ų. Its crystal structure is determined and refined down to R = 0.024 and wR(F²) = 0.059. The structure contains three crystallographically independent Cu²⁺ ions coordinated to chlorine anions in various fashions. Cu1 is five-coordinated in a distorted square pyramidal fashion, while Cu2 and Cu3 are four-coordinated in square planar and distorted tetrahedral fashions, respectively. The entities are interconnected by means of the hydrogen bonding [O(W)–H…Cl, N–H…Cl, C–H…Cl and C–H…O(W)], forming a three-dimensional network. Intermolecular interactions are investigated by Hirshfeld surfaces and the contacts of the eight different chloride atoms are notably compared. The vibrational absorption bands are identified by infrared spectroscopy. The optical study is performed by UV-vis absorption.