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111.
Complexes of aromatic or α,β-unsaturated nitriles YCN of the type (YCN)2(PR3)2Mo(CO)2 and (YCN)(PR3)3Mo(CO)2 are new chromophores. Their intense electronic absorption band in the visible spectrum is strongly influenced by substituents and solvent polarity. Acceptor properties of nitriles are discussed on the basis of CNDO-calculations. CT-character and solvato-chromism can be interpreted in terms of the back-bonding ability of the nitriles in electron-rich metal complexes. 相似文献
112.
Goher Mohamed A. S. Abdou Azza E. H. Abu-Youssef Morsy A. M. Mautner Franz A. 《Transition Metal Chemistry》2001,26(1-2):39-43
Two new copper(II) azido complexes, namely bis-(tetraethylammonium)[tetraazidocuprate(II)] (1) and catena-di--1,1-azido-[di--1,1-azido-bis-(2,4-dimethylpyridine)dicopper(II)] (2), have been prepared and characterized by spectroscopic and crystallographic methods. Complex (1) consists of isolated NEt+
4 cations and [Cu(N3)4]2– anions. The site symmetry around the copper atom in the anion is 4/m. Complex (2) features a 1 D chain structure, five coordinated square pyramidal copper(II) atoms with both azides functioning as -1,1-bridges. The i.r. spectra reveal that both complexes contain asymmetric azido ligands. The solid and solution electronic spectra of (1) and (2) show very strong absorption bands in the visible region associated with N–
3 CuII charge-transfer transitions. The e.p.r. spectra of powder samples and solutions at room temperature were recorded and discussed. 相似文献
113.
Jan Franz 《International journal of quantum chemistry》2006,106(4):773-786
This work presents multi‐state multi‐reference Møller–Plesset second‐order perturbation theory as a variant of multi‐reference perturbation theory to treat electron correlation in molecules. An effective Hamiltonian is constructed from the first‐order wave operator to treat several strongly interacting electronic states simultaneously. The wave operator is obtained by solving the generalized Bloch equation within the first‐order interaction space using a multi‐partitioning of the Hamiltonian based on multi‐reference Møller–Plesset second‐order perturbation theory. The corresponding zeroth‐order Hamiltonians are nondiagonal. To reduce the computational effort that arises from the nondiagonal generalized Fock operator, a selection procedure is used that divides the configurations of the first‐order interaction space into two sets based on the strength of the interaction with the reference space. In the weaker interacting set, only the projected diagonal part of the zeroth‐order Hamiltonian is taken into account. The justification of the approach is demonstrated in two examples: the mixing of valence Rydberg states in ethylene, and the avoided crossing of neutral and ionic potential curves in LiF. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 相似文献
114.
Franz Wochner Laszlo Zsolnai Gottfried Huttner Hans H. Brintzinger 《Journal of organometallic chemistry》1985,288(1):69-77
Ethylene-bridged titanocene and zirconocene derivatives with permethylated ring ligands, C2H4(C5(CH3)4)2TiCl2 and C2H4(C5(CH3)4)2ZrCl2, have been synthesized and their crystal structures determined. 相似文献
115.
Franz Troxler 《Helvetica chimica acta》1973,56(5):1815-1818
The main product of the reaction between 1-methyl-1, 4, 5, 6-tetrahydronicotin-amide and ethyl bromoacetate is shown to be the 2-(1-methyl-1, 4, 5, 6-tetrahydropyridyl-3)-2-oxazoline-4-one which on partial hydrogenation followed by reaction with alkali affords O-(1-methylnipecotinoyl)glycolic amide, presumably via the tautomeric cyclol. 相似文献
116.
The relation of the solution and bioactive conformation of sialyl Lewis x (sLe(x)) has been addressed by chemical means. To mimic the preferred solution conformation of sLe(x) 1, the more rigid analog 2 has been designed and synthesized. The sialic acid residue of 1 was replaced by a carboxylic acid function which is fixed in the equatorial position of a six membered ring acetal fused to galactose. Due to entropic considerations, an increased biological activity could be expected if the preferred solution conformation and bound form of sLe(x) were similar. Since mimic 2 was found to be inactive in an E-selectin binding assay, the bound form of sLe(x) most probably differs from the prevailing solution conformation. 相似文献
117.
1,6-Dialkoxy-3,4-diones 3 are easily accessible by acylation of enol ethers 1 with oxalyl chloride and subsequent elimination of hydrogen chloride using triethylamine. The open-chain 2,5-dimethyl derivative 3b is converted with amidines 4a-c and S-methylisothiourea (4d) , respectively, to give 2,2′-disubstituted 5,5′-dimethyl-4,4′-bipyrimidines 5a-d . The dihydrofuran and dihydropyran derivatives 3c and 3d , however, react with benzamidine (4c) in dimethylformamide only in the presence of calcium hydride as condensation agent yielding 5,5′-bis(2-hydroxyethyl)- and 5,5′-bis(3-hydroxypropyl)-2,2′-diphenyl-4,4′-bipyrimidine 6a and b. 相似文献
118.
119.
Antonie J. W. G. Visser Jan L. De Wit Franz Müller Herman J. C. Berendsen 《Helvetica chimica acta》1982,65(8):2422-2430
The water relaxation rates of several flavoproteins in the semiquinone state have been investigated by the spin echo technique. The results indicate a rather unspecific interaction between water and the protein-bound flavosemiquinones. An average interaction distance of 0.3-0.5 nm has been estimated. From the temperature dependence of the rate constants the free energy of activation for proton exchange is calculated to be about 17 kJ/mol. The rate of proton exchange is around 1011 s?1 for the flavosemiquinones investigated are accessible to water regardless of their ionic state. The large difference in relaxation rates of water protons between D - and L - amino-acid oxidases is noticeable. Oxynitrilase exhibits the highest whereas Azotobacter vinelandii flavodoxin shows the lowest water relaxation rate of the flavoproteins studied. The results are discussed in relation to the visible-light absorption properties of the flavoproteins. 相似文献
120.
Extended cavity calix[4]pyrroles and a calix[6]pyrrole were synthesized by cyclization of 5-methyl-5-(4-nitrophenyl)dipyrromethane with acetone in the presence of acid. The solid-state structures of the novel macrocycles were determined by X-ray crystallography. The host-guest chemistry of these receptors towards halide ions was investigated in solution by 1H NMR titration techniques and compared with those of the meso-octamethylcalix[4]pyrrole and meso-dodecamethylcalix[6]pyrrole. The binding of chloride anions was observed to occur with different affinities on the two faces of the novel calix[6]pyrrole derivative described here. 相似文献