Structure and Magnetism of [M3]6/7+ Metal Chain Complexes from Density Functional Theory: Analysis for Copper and Predictions for Silver

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• 作者：M. Bé ; nard ; J. F. Berry ; F. A. Cotton ; C. Gaudin ; X. L&oacute ; pez ; C. A. Murillo ; and M.-M. Rohmer
• 刊名：Inorganic Chemistry
• 出版年：2006
• 出版时间：May 15, 2006
• 年：2006
• 卷：45
• 期：10
• 页码：3932 - 3940
• 全文大小：244K
• 年卷期：v.45,no.10(May 15, 2006)
• ISSN：1520-510X

文摘

The ground-state electronic structure of the trinuclear complex Cu₃(dpa)₄Cl₂ (1), where dpa is the anion of di(2-pyridyl)amine, has been investigated within the framework of density functional theory (DFT) and compared withthat obtained for other known M₃(dpa)₄Cl₂ complexes (M = Cr, Co, Ni) and for the still hypothetical Ag₃(dpa)₄Cl₂compound. Both coinage metal compounds display three singly occupied x²-y²-like (mages/gifchars/delta.gif" BORDER=0 >) orbitals oriented toward thenitrogen environment of each metal atom, generating antibonding M-(N₄) interactions. All other metal orbitalcombinations are doubly occupied, resulting in no delocalized metal-metal bonding. This is at variance with theother known symmetric M₃(dpa)₄Cl₂ complexes of the first transition series, which all display some delocalizedbonding through the metal backbone, with formal bond multiplicity decreasing in the order Cr > Co > Ni. Anantiferromagnetic coupling develops between the singly occupied MOs via a superexchange mechanism involvingthe bridging dpa ligands. This magnetic interaction can be considered as an extension to the three aligned Cu^IIatoms of the well-documented exchange coupling observed in carboxylato-bridged dinuclear copper compounds.Broken-symmetry calculations with approximate spin projection adequately reproduce the coupling constant observedfor 1. Oxidation of 1 removes an electron from the magnetic orbital located on the central Cu atom and its ligandenvironment; 1⁺ displays a much weaker antiferromagnetic interaction coupling the terminal Cu-N₄ moieties viafour ligand pathways converging through the x²-y² orbital of the central metal. The silver homologues of 1 and 1⁺display similar electronic ground states, but the calculated magnetic couplings are stronger by factors of about 3and 4, respectively, resulting from a better overlap between the metal centers and their equatorial ligand environmentwithin the magnetic orbitals.