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Exchange Coupling Constants (exchange + coupling_constant)
Selected AbstractsNucleophilic Addition of Water and Alcohols to Dicyanonitrosomethanide: Ligands with Diverse Bonding Modes in Magnetically Coupled d-Block ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2010Anthony S. R. Chesman Abstract Ligands resulting from the transition-metal-promoted nucleophilic addition of water or an alcohol to dicyanonitrosomethanide ions (dcnm) have been utilised in the formation of a large series of polynuclear complexes. Addition of water to dcnm results in formation of carbamoylcyanonitrosomethanide (ccnm); deprotonation of this ligand gives amidocarbonyl(cyano)nitrosomethanide (acnm), which has been incorporated into the trinuclear complex [Cu3(acnm)2(dmae)2(H2O)2] [dmae = 2-(dimethylamino)ethoxide] (1) which shows strong antiferromagnetic coupling with an exchange coupling constant, J = ,500 cm,1. [Cu(acnm)(NH3)2], (2) marks the first instance of acnm facilitating the formation of a coordination polymer, namely a 1D chain with intramolecular hydrogen bonding. Attempts to synthesise 2 through different reaction conditions instead resulted in the mononuclear [Cu(acnm)(NH3)2(py)] (py = pyridine) (3). The addition of ethanol to dcnm results in cyano[imino(ethoxy)methyl]nitrosomethanide (cenm) which features in the mononuclear [Cu(cenm)2(H2O)2] (4) and polymeric {[Cu(cenm)2]2·H2O}, (5). The latter is the first example of the cenm ligand in a coordination polymer and has a highly unusual coordination mode through the nitrile groups and extremely weak antiferromagnetic coupling. {[Mn3(ccnm)2(EtOH)2(OAc)4]·2EtOH}, (6) and (Et4N)2[Cu(ccnm)4] (7) contain previously unobserved coordination modes of the ccnm ligand while the complex [Mn(cmnm)3Mn(bipy)(MeOH)](ClO4) (8) {cmnm = cyano[imino(methoxy)methyl]nitrosomethanide, bipy = 2,2,-bipyridine} displays weak antiferromagnetic coupling between manganese atoms with J = ,1.44 cm,1. A change in the solvent systems used in the synthesis of 7 results in the formation of the mononuclear complexes [Mn(bipy)2(dcnm)2] (9) or [Mn(bipy)2(H2O)(dcnm)](dcnm)·H2O (10) and [Mn(bipy)2(dcnm)(H2O)](dcnm) (11). The addition of ethlyene glycol monomethyl ether to dcnm gives cyano[imino(2-methoxyethoxy)methyl]nitrosomethanide (cgnm) and the formation of [Cu(cgnm)2(H2O)2] (12). [source] A Magnetostructural and Electrochemical Study of CuII and FeIII Complexes Containing a Tetradentate Aminebis(phenolate) Ligand with a Pendent Tetrahydrofuran GroupEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2007Elham Safaei Abstract Ligating properties of a tetradentate ligand 2-{bis[(3,5-di- tert -butyl-2-hydroxybenzyl)amino]methyl}tetrahydrofuran,H2L, with [O,O,N,O]-donor atoms towards CuII and FeIII are described. The ligand H2L yields both mononuclear LFeIII(acac) (1) and dinuclear [L2FeIII2(,-OCH3)-(,-OH)] (2), [L2FeIII2(,-C2O4)] (3) and [L2CuII2] (4) complexes, which were characterized by various physical techniques, including X-ray diffraction, Mössbauer, electrochemical and magnetic susceptibility (2,290 K) measurements. That the electrochemical oxidations are ligand-centered, i.e. formation of phenoxyl radicals from the coordinated phenolates, have been shown by voltammetric methods. Complexes 2,4 display antiferromagnetic exchange coupling of the neighbouring metal centers. Comparison of the evaluated weak exchange coupling constants (J) with the literature values leads to the conclusion that the angle Cu,O,Cu, is not the only determinant for the nature of the exchange coupling and the capability of the bridging ligands as mediators for spin coupling in case of FeIII follows the order phenoxide , methoxide > hydroxide. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] About the calculation of exchange coupling constants in polynuclear transition metal complexesJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 8 2003Eliseo Ruiz Abstract The application of theoretical methods based on the density functional theory with hybrid functionals provides good estimates of the exchange coupling constants for polynuclear transition metal complexes. The accuracy is similar to that previously obtained for dinuclear compounds. We present test calculations on simple model systems based on H · · · He and CH2 · · · He units to compare with Hartree,Fock and multiconfigurational results. Calculations for complete, nonmodeled polynuclear transition metal complexes yield coupling constants in very good agreement with available experimental data. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 982,989, 2003 [source] | ||||||||||