Oxalate-bridged bimetallic complexes {NH(prol)3}[MCr(ox) 3] (M = MnII, FeII, CoII; NH(prol)3+ = tri(3-hydroxypropyl)ammonium) exhibiting coexistent ferromagnetism and proton conduction

Hisashi Okawa, Akihito Shigematsu, Masaaki Sadakiyo, Takuya Miyagawa, Ko Yoneda, Masaaki Ohba, Hiroshi Kitagawa

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    The oxalate-bridged bimetallic complexes {NH(prol)3}[M IICrIII(ox)3] (MII = Mn II, FeII, CoII) with hydrophilic tri(3-hydroxypropyl)ammonium (NH(prol)3+) were prepared by a new synthetic procedure, and the effects of the NH(prol)3 + ion upon the structure, magnetism, and electrical conduction were studied. An X-ray crystallographic study of the MnCr dihydrate, {NH(prol) 3}[MnCr(ox)3] ·2H2O, was performed. Crystal data: hexagonal, P63, a = b = 9.3808(14) Å, c = 15.8006(14) Å, Z = 2. The structure comprises oxalate-bridged bimetallic layers interleaved by NH(prol)3+ ions. The ions assume a tripodal configuration and are hydrogen bonded to the bimetallic layers together with water molecules, giving rise to a short interlayer separation (7.90 Å) and unsymmetrical faces to the bimetallic layer. Cryomagnetic studies demonstrate ferromagnetic ordering with transition temperature of 5.5 K for the MnCr complex, 9.0 K for the FeCr complex, and 10.0 K for the CoCr complex. The interlayer magnetic interaction is negligibly weak in all of the complexes despite the short interlayer separation. A slow magnetization is observed in all the complexes. This is explained by spin canting associated with the unsymmetrical feature of the bimetallic layer. The complexes show proton conduction of 1.2 x 10-10 to 4.4 x 10-10 S cm-1 under 40% relative humidity (RH) and ∼1 x 10-4 S cm-1 under 75% RH. On the basis of water adsorption/desorption profiles, the conduction under 40% RH is mediated through the hydrogen-bonded network formed by the bimetallic layer, NH(prol)3+ ions, and water molecules (two per MCr). Under 75% RH, additional water molecules (three per MCr) are concerned with the high proton conduction. This is the first example of a metal complex system exhibiting coexistent ferromagnetism and proton conduction.

    Original languageEnglish
    Pages (from-to)13516-13522
    Number of pages7
    JournalJournal of the American Chemical Society
    Issue number37
    Publication statusPublished - Sep 23 2009

    All Science Journal Classification (ASJC) codes

    • Catalysis
    • Chemistry(all)
    • Biochemistry
    • Colloid and Surface Chemistry

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