Spin Crossover in a Family of Iron(II) Complexes with Hexadentate ligands: Ligand Strain as a Factor Determining the Transition Temperature |
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Authors: | Galina S. Matouzenko Dr. Serguei A. Borshch Dr. Erwann Jeanneau Dr. Mark B. Bushuev Dr. |
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Affiliation: | 1. Laboratoire de Chimie (UMR CNRS and ENS-Lyon no.5182), École Normale Supérieure de Lyon, 46, allée d'Italie, 69364 Lyon cedex 07 (France), Fax: (+33)47272-8860;2. Laboratoire des Multimatériaux et Interfaces (UMR CNRS no.5615), Université Claude Bernard Lyon-1, 69622 Villeurbanne cedex (France);3. Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, 3, Akad. Lavrentiev Av., Novosibirsk, 630090 (Russia) |
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Abstract: | This paper reports the synthesis of a family of mononuclear complexes [Fe(L)]X2 (X=BF4, PF6, ClO4) with hexadentate ligands L=Hpy-DAPP ({bis[N-(2-pyridylmethyl)-3-aminopropyl](2-pyridylmethyl)amine}), Hpy-EPPA ({[N-(2-pyridylmethyl)-3-aminopropyl][N-(2-pyridylmethyl)-2-aminoethyl](2-pyridylmethyl)amine}) and Hpy-DEPA ({bis[N-(2-pyridylmethyl)-2-aminoethyl](2-pyridylmethyl)amine}). The systematic change of the length of amino-aliphatic chains in these ligands results in chelate rings of different size: two six-membered rings for Hpy-DAPP, one five- and one six-membered rings for Hpy-EPPA, and two five-membered rings for Hpy-DEPA. The X-ray analysis of three low-spin complexes [Fe(L)](BF4)2 revealed similarities in their molecular and crystal structures. The magnetic measurements have shown that all synthesized complexes display spin-crossover behavior. The spin-transition temperature increases upon the change from six-membered to five-membered chelate rings, clearly demonstrating the role of the ligand strain. This effect does not depend on the nature of the counter ion. We discuss the structural features accountable for the strain effect on the spin-transition temperature. |
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Keywords: | chelates iron magnetic properties N ligands spin crossover |
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