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How does a coordinated radical ligand affect the spin crossover properties in an octahedral iron(II) complex?
Markus Schmitz1, Manuel Seibel, Harald Kelm
1Fachbereich Chemie, Technische Universität Kaiserslautern, Erwin-Schrödinger Strasse 54, 67663 Kaiserslautern (Germany) http://www.chemie.uni-kl.de/fachrichtungen/ac/krueger/
Abstract:
The influence of a coordinated π-radical on the spin crossover properties of an octahedral iron(II) complex was investigated by preparing and isolating the iron(II) complex containing the tetradentate N,N'-dimethyl-2,11-diaza[3.3](2,6)pyridinophane and the radical anion of N,N'-diphenyl-acenaphtene-1,2-diimine as ligands. This spin crossover complex was obtained by a reduction of the corresponding low-spin iron(II) complex with the neutral diimine ligand, demonstrating that the reduction of the strong π-acceptor ligand is accompanied by a decrease in the ligand field strength. Characterization of the iron(II) radical complex by structural, magnetochemical, and spectroscopic methods revealed that spin crossover equilibrium occurs above 240 K between an S=1/2 ground state and an S=3/2 excited spin state. The possible origins of the fast spin interconversion observed for this complex are discussed.
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