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Aromatic Ligands (aromatic + ligand)
Selected AbstractsChemInform Abstract: [Ta3O3]A (A: Li, Na, K) and [Ta3O3]B[Ta3O3] (B: Ca, Sr, Ba): Sandwich-Type Complexes Containing Ta3O3 - , and , Double Aromatic Ligands.CHEMINFORM, Issue 23 2008Si-Dian Li Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Partition of thermodynamic energies of drug,DNA complexationBIOPOLYMERS, Issue 9 2009V. V. Kostjukov Abstract We report a computation methodology, which leads to the ability to partition the Gibb's free energy for the complexation reaction of aromatic drug molecules with DNA. Using this approach, it is now possible to calculate the absolute values of the energy contributions of various physical factors to the DNA binding process, whose summation gives a value that is reasonably close to the experimentally measured Gibb's free energy of binding. Application of the methodology to binding of various aromatic drugs with DNA provides an answer to the question "What forces are the main contributors to the stabilization of aromatic ligand,DNA complexes?" © 2009 Wiley Periodicals, Inc. Biopolymers 91: 773,790, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Metal,Metal Electronic Coupling in syn and anti Stereoisomers of Mixed-Valent (FeCp)2 -, (RhL2)2 -, and (FeCp)(RhL2)- as -Indacenediide IonsCHEMISTRY - A EUROPEAN JOURNAL, Issue 28 2007Saverio Santi Prof. Abstract The extent of metal,metal electronic coupling was quantified for a series of syn and anti stereoisomers of (FeCp)2 -, (RhL2)2 - and (FeCp)(RhL2)- (L2=1,5-cyclooctadiene (cod), L=CO) as -indacenediide mixed-valent ions by spectroelectrochemical and DFT studies. The effect of the syn/anti orientation of the metal units with respect to the planar aromatic ligand indicates that electron transfer occurs through the bridge rather than through space. The nature of the metal was found to be crucial: while homobimetallic diiron species are localised valence-trapped ions (Class,II), the dirhodium analogues are almost delocalised mixed-valent ions (borderline and Class,III). Finally, despite their redox asymmetry, even in the heterobimetallic iron,rhodium as -indacenediide complexes, strong metal,metal coupling is present. In fact, oxidation of the iron centre is accompanied by electron transfer from rhodium to iron and formation of a reactive 17-electron rhodium site. syn and anti Fe,Rh as -indacenediide complexes are rare examples of heterobimetallic systems which can be classified as borderline Class,II/Class,III species. [source] Multicomponent Supramolecular Devices: Synthesis, Optical, and Electronic Properties of Bridged Bis-dirhodium and -diruthenium Complexes,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2006Anne Petitjean Abstract Four ruthenium- and rhodium-based metal,metal-bonded multicomponent systems have been synthesized, and their absorption, redox, spectroelectrochemical and structural properties have been studied. The absorption spectra of the four bis-dimetallic compounds M2LM2, where L is a bridging ligand and M is rhodium or ruthenium, exhibit very strong bands in the UV, visible and, for the diruthenium species, near-IR region. The low-energy absorption bands are assigned to charge-transfer transitions involving a metal,metal bonding orbital as the donor and an orbital centered on the bis-tetradentate aromatic ligands as the acceptor (metal,metal to ligand charge transfer, M2LCT). Each compound exhibits reversible bridging-ligand-centered reductions at mild potentials and several reversible oxidation processes. The oxidation signals of the two equivalent dimetallic centers of each bis-dimetallic compound are split, with the splitting , a measure of the electronic coupling , depending on both the metal and bridging ligand. The mixed-valence species of the dirhodium species was investigated, and the electronic coupling matrix element calculated from the experimental intervalence band parameters for one of them (86 cm,1) indicates a significant inter-component electronic interaction which compares well with good electron conducting anionic bridges such as cyanides. Although none of these compounds is luminescent, the M2LCT excited state of one of the bis-dirhodium complexes is relatively long-lived (about 6 ,s) in degassed acetonitrile at room temperature. The results presented here are promising for the development of linear poly-dimetallic complexes built on longer naphthyridine-based strands, with significant long-range electronic coupling and molecular-wire-like behavior. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Low- and high-spin iron (II) complexes studied by effective crystal field method combined with molecular mechanicsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 14 2003M. B. Darkhovskii Abstract A computational method targeted to Werner-type complexes is developed on the basis of quantum mechanical effective Hamiltonian crystal field (EHCF) methodology (previously proposed for describing electronic structure of transition metal complexes) combined with the Gillespie,Kepert version of molecular mechanics (MM). It is a special version of the hybrid quantum/MM approach. The MM part is responsible for representing the whole molecule, including ligand atoms and metal ion coordination sphere, but leaving out the effects of the d -shell. The quantum mechanical EHCF part is limited to the metal ion d -shell. The method reproduces with reasonable accuracy geometry and spin states of the Fe(II) complexes with monodentate and polydentate aromatic ligands with nitrogen donor atoms. In this setting a single set of MM parameters set is shown to be sufficient for handling all spin states of the complexes under consideration. © 2003 Wiley Periodicals, Inc. J Comput Chem 14: 1703,1719, 2003 [source] Structure,property transition-state model for the copolymerization of ethene and 1-hexene with experimental and theoretical applications to novel disilylene-bridged zirconocenesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2003Hanne Wigum Abstract Ethene homopolymerization and copolymerization with 1-hexene were performed with three new tetramethyldisilylene-bridged zirconocene catalysts with 2-indenyl ligand (A), 2-tetrahydroindenyl ligand (B), and tetramethyl-cyclopentadienyl ligand (C) and with methylaluminoxane as a cocatalyst. Catalysts A and B showed substantial comonomer incorporation, resulting in a copolymer melting temperature more than 20° lower than that of the corresponding homopolymer. In contrast, catalyst C produced a copolymer with a low 1-hexene content and a high melting temperature. The reduction in the molecular weight with 1-hexene addition also correlated well with the comonomer incorporation. For all three catalysts, the homopolymer and copolymer unsaturations indicated frequent chain termination after 1-hexene insertion and a high degree of chain-end isomerization during the homopolymerization of ethene. The chain transfer to Al in the cocatalyst also appeared to be important. The comonomer response could be correlated with the structural properties of the catalyst, as derived from quantum chemical calculations. A linear model, calibrated against recent experiments with unbridged (MenC5H5,n)2ZrCl2 catalysts, suggested that the low comonomer incorporation obtained with catalyst C was caused partly by a narrow opening angle between the aromatic ligands and partly by steric hindrance in the transition state of comonomer insertion. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1622,1631, 2003 [source] | ||||||||||