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91.
Rajapakshe A Gruhn NE Lichtenberger DL Basta R Arif AM Ernst RD 《Journal of the American Chemical Society》2004,126(43):14105-14116
Molecules of the form Cp(6,6-dmch)ZrX(2) (Cp = eta(5)-cyclopentadienyl, X = Cl, Br, I; 6,6-dmch = eta(5)-6,6-dimethylcyclohexadienyl) have been synthesized, and the molecular and electronic structures have been investigated. These molecules allow direct comparison of the bonding and properties of pentadienyl and cyclopentadienyl ligands in the same high-oxidation-state metal complexes. Unlike the well-known Cp(2)ZrX(2) analogues, these Cp(6,6-dmch)ZrX(2) molecules are intensely colored, indicating significantly different relative energies of the frontier orbitals. Also unusual, the average Zr-C distances to the 6,6-dmch pentadienyl ligand are about 0.1 A longer than the average Zr-C distances to the cyclopentadienyl ligand for these Zr(IV) complexes, opposite of what is observed for the Zr(II) complex Cp(2,6,6-tmch)Zr(PMe(3))(2) (tmch = eta(5)-2,6,6-trimethylcyclohexadienyl), reflecting a dramatic reversal in the favorability of the bonding depending on the metal oxidation state. The experimental and computational results indicate that the color of the Cp(6,6-dmch)ZrX(2) complexes is due to a 6,6-dmch ligand-to-metal charge-transfer band. Compared to the Cp(2)ZrX(2) analogues, the Cp(6,6-dmch)ZrX(2) molecules have a considerably less stable HOMO that is pentadienyl-based and an essentially unchanged metal-based LUMO. Also, the lowest unoccupied orbital of pentadienyl is stabilized relative to cyclopentadienyl and becomes a better potential delta electron acceptor, thus contributing to the differences in structure and reactivity of the low-valent and high-valent metal complexes. 相似文献
92.
Manzoori JL Amjadi M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(5):909-916
The characteristics of host-guest complexation between beta-cyclodextrin (beta-CD) and two forms of ibuprofen (protonated and deprotonated) were investigated by fluorescence spectrometry. 1:1 stoichiometries for both complexes were established and their association constants at different temperatures were calculated by applying a non-linear regression method to the change in the fluorescence of ibuprofen that brought about by the presence of beta-CD. The thermodynamic parameters (deltaH, deltaS and deltaG) associated with the inclusion process were also determined. Based on the obtained results, a sensitive spectrofluorimetric method for the determination of ibuprofen was developed with a linear range of 0.1-2 microg ml(-1) and a detection limit of 0.03 microg ml(-1). The method was applied satisfactorily to the determination of ibuprofen in pharmaceutical preparations. 相似文献
93.
Kamaladin Gharanjig Mokhtar Arami Shohre Rouhani Hajir Bahrami Barahman Movassagh Niyaz Mohammad Mahmoodi 《中国化学会会志》2007,54(4):1021-1028
Five novel monoazo disperse dyestuffs based on N‐ester‐1,8‐naphthalimide were synthesized. Acenaphthene was nitrated, then oxidized to 4‐nitro‐1,8‐naphthalic anhydride. 4‐Nitro‐1,8‐naphthalic anhydride was reacted with methyl and ethyl glycinate in alcoholic media, followed with reduction. 4‐Amino‐N‐methyl and ethyl glycinate‐1,8‐naphthalimide were obtained. These products were diazotized and coupled with appropriate aromatic amines to give bluish‐red or violet dyestuffs. All intermediates and dyestuffs were purified and characterized by 1H‐NMR, FTIR, DSC, UV‐VIS and Elemental Analysis. Dispersion of dyestuffs was prepared in water and applied to polyester fabrics. The dyed fabrics showed that four of the synthesized dyestuffs were suitable for coloring polyester fibers, producing deep bluish red with very good build up properties. 相似文献
94.
Hadis Azin Mohammad Hossein Heydari Fakhrodin Mohammadi 《Mathematical Methods in the Applied Sciences》2022,45(1):411-422
In this paper, the Vieta–Fibonacci wavelets as a new family of orthonormal wavelets are generated. An operational matrix concerning fractional integration of these wavelets is extracted. A numerical scheme is established based on these wavelets and their fractional integral matrix together with the collocation technique to solve fractional pantograph equations. The presented method reduces solving the problem under study into solving a system of algebraic equations. Several examples are provided to show the accuracy of the method. 相似文献
95.
Summary
Bis(cyclopentadienyl)titanium(IV) diisothiocyanate [(Cp)2-Ti(NCS)2] reacts with MCl2 (M = Cu, Pd or Pt), [CuCl(PPh3)3], [RuCl2(PPh3)3] and [RuCl2(DMSO)4] (DMSO = dimethylsulphoxide) giving solid compounds of stochiometry [(Cp)2Ti(-NCS)2MCl2] (M = Cu, Pd or Pt), [(Cp)2Ti(-NCS)2CuCl(PPh3)], [(Cp)2Ti(-NCS)2-RuCl(PPh3)2]Cl and [(Cp)2Ti(-NCS)2RuCl2(DMSO)2]. These products have been characterized by physicochemical and spectroscopic methods. 相似文献
96.
97.
Mohammad R. Ahmady Roberto R. Mendel 《Zeitschrift fur Physik C Particles and Fields》1995,65(2):263-265
The decay rates for the exclusiveB decaysBK
c
andBK*
c
are calculated in the context of the heavy quark effective theory. We obtain(BK
c
)/ (BK)=1.6±0.2 and(BK*
c
)/ (K*)=0.39±0.04. These results lead to estimates BR(BK
c
)=(0.11±0.02)% and BR(BK*
c
)=(0.05±0.01)% if we use the central current experimental values forB(K, K
*) branching ratios. 相似文献
98.
Ahmad Rouhollahi Mohammad Kazem Amini Mojtaba Shamsipur 《Journal of solution chemistry》1994,23(1):63-74
Proton NMR was used to study the complexation reaction between lead ion and 18-crown-6 in a number of binary acetonitrile-water mixtures. Formation constant for the resulting 11 complexes in different solvent mixtures was determined by computer fitting of the chemical shift-mole ratio data. There is an inverse relationship between the complex stability and amount of water in the mixed solvent. The dissociative kinetics of the complex was studied by proton line-shape analysis. The Arrhenius plots showed a distinct isokinetic temperature at about 25°C at which the decomplexation rate is more or less independent of the solvent composition. the complexation rate and the activation parameters E
a
, H and S, for the exchange have been determined and found to be strongly solvent dependent. There is actually a linear relationship between the mole fraction of acetonitrile in the mixed solvent and logarithm of the stability constant as well as activation parameters. 相似文献
99.
Behforouz M Haddad J Cai W Arnold MB Mohammadi F Sousa AC Horn MA 《The Journal of organic chemistry》1996,61(19):6552-6555
The novel 7-(N-formyl-, 7-(N-acetyl-, and 7-(N-isobutyrylamino)-2-methylquinoline-5,8-diones were synthesized in excellent overall yields in three steps via the nitration of the commercially available 8-hydroxy-2-methylquinoline followed by a reduction-acylation step and then oxidation. Acid hydrolysis of 7-(N-acetylamino)-2-methylquinoline-5,8-dione (14a) afforded the novel 7-aminoquinoline-5,8-dione 7 in excellent yields. Due to our efficient preparation of dione 14a, we now report a short and practical method for the total synthesis of the potent antitumor agent lavendamycin methyl ester (1b) with an excellent overall yield. 相似文献
100.