Issue 9, 2010

Structural, electronic and magnetic properties of Cu(ii) complexes of 2-substituted tropones bearing a ferrocenylgroup at 5-position

Abstract

Heterotrinuclear Fe(II)Cu(II)Fe(II) complexes [Cu(FcTropOMe)2(H2O)2](OTf)2 (FcTropOMe = 5-ferrocenyl-2-methoxytropone) (1), [Cu(FcTropNEt2)2](OTf)2 (FcTropNEt2 = 2-(N,N-diethylamino)-5-ferrocenyltropone) (2) and [Cu(FcTropNEt)2] (FcTropNEt = 2-(N-ethylamino)-5-ferrocenyltroponate) (3) were synthesized. In addition, a hexafluorophosphate salt of heterotrinuclear Fe(III)Cu(II)Fe(III) complex [Cu(FcTropNEt)2]2+ (32+) was successfully obtained as single crystals by electrochemical oxidation of 3. By comparing the X-ray structures and absorption spectra of dicationic complexes 1 and 2, the 2-(diethylamino)tropone ligand was found to induce a greater intramolecular charge transfer (CT) from ferrocenyl to tropone–Cu(II) moieties than the 2-methoxytropone ligand. On the other hand, 32+ showed a broad CT band in the near-infrared (NIR) region similar to 2, which can be assigned to a transition from troponato–Cu(II) to ferrocenium moieties. As for the magnetic properties of 32+(PF6)2, measurements of temperature dependence of magnetic susceptibility and ESR on the solid state and in solution revealed the presence of a strong ferromagnetic interaction (JFe–Cu = +12.0 cm−1) between the low spin Fe(III) ion with S = 1/2 and Cu(II) ion with S = 1/2 despite a long distance pathway via the aminotroponato and cyclopentadienyl moieties. DFT calculations supported this intramolecular ferromagnetism, which is induced by a spin polarization mechanism through the π-spacers.

Graphical abstract: Structural, electronic and magnetic properties of Cu(ii) complexes of 2-substituted tropones bearing a ferrocenyl group at 5-position

Supplementary files

Article information

Article type
Paper
Submitted
23 Jun 2009
Accepted
12 Nov 2009
First published
11 Jan 2010

Dalton Trans., 2010,39, 2293-2300

Structural, electronic and magnetic properties of Cu(II) complexes of 2-substituted tropones bearing a ferrocenyl group at 5-position

T. Nishinaga, T. Aono, E. Isomura, S. Watanabe, Y. Miyake, A. Miyazaki, T. Enoki, H. Miyasaka, H. Otani and M. Iyoda, Dalton Trans., 2010, 39, 2293 DOI: 10.1039/B912255A

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