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41.
Gilliam SJ Jensen JO Banerjee A Zeroka D Kirkby SJ Merrow CN 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(1-2):425-434
The first ab initio theoretical study of tetraantimony hexoxide (Sb4O6) is reported. The normal mode frequencies, intensities, and the corresponding vibrational assignments of Sb4O6 in T(d) symmetry were calculated using the GAUSSIAN 98 set of quantum chemistry codes at the Hartree-Fock (HF)/CEP-121G, M?ller-Plesset (MP2)/CEP-121G, and density functional theory (DFT)/B3LYP/CEP-121G levels of theory. By comparison to experimental data deduced by our laboratory and others, correction factors for the calculated vibrational frequencies were determined and compared. Normal modes were decomposed into three non-redundant motions (Sb-O-Sb stretch, Sb-O-Sb bend, and Sb-O-Sb wag). Percent relative errors found for the HF, DFT, and MP2 corrected frequencies when compared to experiment are 5.8, 6.1, and 5.7 cm(-1), respectively. Electron distributions for selected molecular orbitals are also considered. 相似文献
42.
43.
O-Alkylation of thiotetronic acids gives a mixture of 2- and 4-position enol ether products. Comparison of the physical data revealed that UV spectroscopy was the most reliable method of distinguishing between these related ethers. We have determined that 4-position ethers have a distinct absorption between 235-240 nm, while 2-position ethers have two absorbance peaks, one between 205-220 nm and the other between 305-310 nm. This report describes the synthesis and unambiguous characterization of 2- and 4-methoxy-3,5-dimethylthiotetronic acids. The UV absorption properties of several other pairs of thiotetronic acid ethers confirm that these differences are general features that provide a simple method for distinguishing between 2- and 4-substituted isomers. 相似文献
44.
We define and characterize a new abstract notion of quasiBoolean algebra, intermediate in nature between an (ortho)lattice and a Boolean algebra. It will turn out that such algebras are natural candidates for representing the simultaneously definite properties of a quantum system. We then prove a general theorem about maximal quasiBoolean subalgebras of an ortholattice which we use to derive a number of different proposals in the literature for what properties of a quantum system should be regarded as simultaneously definite. 相似文献
45.
Youxiang Wang Donald C. Jackman Clifton Woods D. Paul Rillema 《Journal of chemical crystallography》1995,25(9):549-553
The complex [Ru(bpy)2(dafo)](PF6)2, where bpy is 2,2-bipyridine and dafo is diazafluorenone crystallizes in the space group P21/n witha=9.505(3) Å,b=14.002(4) Å andc=25.783(8) Å. The coordination geometry of the Ru atom is that of a distorted octahedron with a RuN6 core. The two Ru-N bond distances to the dafo ligand are 2.13(1) and 2.15(1) Å; the four Ru-N bond distances to the bipyridine ligands are 2.03(1), 2.05(1), 2.06(1), and 2.07(1) Å. The three shortest Ru-N distances aretrans to the three longest Ru-N distances. The complex is oxidized and reduced reversibly at 1.41 and –0.65 V vs. SSCE, respectively. It displays absorptions at 438 nm (1.6×104), 285 nm (6.2×104), and 240 nm (4.1×104) and a broad emission centered at 626 nm in water at room temperature. The emission lifetime is 420 ns and the emission quantum yield is 5.3×10–4. 相似文献
46.
47.
ÜMMÜHAN OCAK HALIT KANTEKIN YAŞAR GÖK H. BASIR ŞENTÜRK 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(1-2):87-91
The selective liquid–liquid extraction of various transition metal cations from the aqueous phase to the organic phase was carried out using a 14-membered N2O2S2-macrobicycle. Metal picrates such as Pb2+, Co2+, Zn2+, Ni2+,Cu2+ and Cd2+ were used in this extraction studies. It was found that the ligand showed moderate selectivity towards Pb2+ only among the other metals. The extraction constant (log K
ex) was determined to be 13.8 for Pb2+ complex. 相似文献
48.
Donald F. Cook Neil F. Curtis Clifton E.F. Rickard Joyce M. Waters 《Polyhedron》2005,24(18):3022-3031
The imine functions of [Ni(mL1)](ClO4)2 (mL1 = meso-7RS,14SR-5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) are reduced by using NaBH4 in acetonitrile/methanol to form the meso–meso and rac–meso isomeric cyclic tetramine complex cations [Ni(mmL2)]2+ and [Ni(rmL2)]2+ (mml2 = 5RS,7RS,12SR,14SR- and rmL2 = 5SR,7RS,12SR,14SR-5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradecane) in ca. 8:1 proportions. [Ni(rmL2)]2+ is also prepared from rmL2, formed in <1% yield by the reduction of mL1 by NaBH4 in ethanol. Square planar singlet ground state (S = 1) salts [Ni(rmL2)](ClO4)2 and [Ni(rmL2)][ZnCl4] and triplet ground state (S = 3) trans-di-ligand octahedral compounds trans-[Ni(rmL2)X2] ,μ-Y-trans-[Ni(rmL2)Y] and folded macrocycle compounds cis-[Ni(rmL2)(acac)]CIO4 (acac− = pentane-2,4-dionato), cis-[{Ni(rmL2)}2(C2O4)](ClO4)2, cis-[Ni(rmL2)(H2O)2](ClO4)2 and cis-[Ni(rmL2)X2], X− = Cl−, Br−, are described. The S = 1 salt 1SR,4SR,5SR,7RS,8RS,11RS,12SR,14SR-[Ni(rmL2)](ClO4)2 · 0.5H2O has a disordered structure with Ni(II) in square planar coordination by the nitrogen atoms of the macrocycle, in N-configuration III, with Ni–Nmean = 1.96(2) Å. The six-membered chelate rings both have chair conformations, with the phenyl substituents equatorially oriented and with the methyl substituents disordered over axial and equatorial orientations. The S = 3 compound cis-1SR,4SR,5SR,7RS,8SR,11SR,12SR,14SR-[Ni(rmL2)(acac)]ClO4 has N-configuration V. The macrocycle is folded along N1–Ni–N8, adjacent to the phenyl substituents {N1–Ni–N8 = 176.45(6), N4–Ni–N11 = 98.16(6)°}, with mean Ni–N = 2.09(2) Å and mean Ni–O = 2.121(5) Å. Both six-membered chelate rings have chair conformations with the methyl substituents equatorially oriented, while one has the phenyl substituent equatorially and the other has it axially oriented. The structures of the isomeric [M(rmL2)(acac)]ClO4, [M(rrL2)(acac)]CIO4 and [M(mmL2)(acac)]ClO4 compounds are compared. 相似文献
49.
Gerard P. Jellison John B. Greenshields J. Clifton Hill 《Theoretical chemistry accounts》1981,60(1):1-10
HeH++ was selected as a simple model for the comparison of relative efficiencies of single and multi-centered Gaussian functions in computing molecular orbitals and their corresponding energies. One-, two-, and three-center linear combinations of twelve basis functions were applied to the calculation of potential curves for the ground state and lowest two excited sigma states of HeH++. A point-by-point comparison was made with the same states generated by an exact solution calculation. This comparison demonstrated that the multi-centered functions were capable of reproducing energy minima, potential curve crossings and dissociation modes in agreement with the exact calculation. The single center functions were not capable of duplicating this behavior. 相似文献
50.
Reaction between Os(CO)2(PPh3)3 and Me3SnH produces Os(SnMe3)H(CO)2(PPh3)2 (1). Multinuclear NMR studies of solutions of 1 reveal the presence of four geometrical isomers, the major one being that with mutually cis triphenylphosphine ligands and mutually trans CO ligands. Os(SnMe3)H(CO)2(PPh3)2 undergoes a redistribution reaction, at the trimethylstannyl ligand, when treated with Me2SnCl2 giving Os(SnMe2Cl)H(CO)2(PPh3)2 (2). Solutions of 2 again show the presence of four isomers but now the major isomer is that with mutually trans triphenylphosphine ligands and mutually cis CO ligands. The redistribution reaction of 1 with SnI4 produces Os(SnMeI2)H(CO)2(PPh3)2 (3) which exists in solution as only one isomer, that with mutually trans triphenylphosphine ligands and mutually trans CO ligands. Treatment of 3 with I2 cleaves the Os-H bond with retention of geometry giving Os(SnMeI2)I(CO)2(PPh3)2 (4). The crystal structure of 4 has been determined. No isomerization of the trans dicarbonyl complex 4 occurs when 4 is heated, instead there is a formal loss of “MeSnI” and formation of OsI2(CO)2(PPh3)2 (5). 相似文献