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RESEARCH PRODUCT

Hybrid Organic/Inorganic Molecular Materials Formed by Tetrathiafulvalene Radicals and Magnetic Trimeric Clusters of Dimetallic Oxalate‐Bridged Complexes: The Series (TTF) 4 {M II (H 2 O) 2 [M III (ox) 3 ] 2 }· n H 2 O (M II = Mn, Fe, Co, Ni, Cu and Zn; M III = Cr and Fe; ox = C 2 O 4 2− )

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The first examples of trimeric, dimetallic, pure oxalate-bridged complexes [ox = (C2O4)2−] have been synthesized and characterized structurally and magnetically for the two new series of crystalline molecular assemblies formulated as (TTF)4{MII(H2O)2[MIII(ox)3]2}·nH2O [for MIII = Cr; MII = Mn (1), Fe (2), Co (3), Ni (4), Cu (5) and Zn (6); for MIII = Fe; MII = Mn (7), Fe (8), Co (9), Ni (10) and Zn (11)]. Both series (Cr2M and Fe2M) are isostructural. The crystal structure of (TTF)4{Mn(H2O)2[Cr(ox)3]2}⋅14H2O (1) [monoclinic, space group C2/c (no. 15), a = 13.240(5) A, b = 19.450(5) A, c = 27.690(5) A, β = 97.63(5)°, V = 7068(3) A3 and Z = 4] shows alternating layers of the organic radical TTF, arranged in an unprecedented one-dimensional κ-type phase formed by parallel chains of orthogonal dimers along the a axis, and layers of centrosymmetrical Cr−Mn−Cr trimers with oxalate bridges. The magnetic measurements show ferromagnetic coupling within the trimers for the Cr2M series and antiferromagnetic for the Fe2M series, giving rise to high-spin molecules in both cases [S = 11/2, 10/2, 9/2, 8/2 and 7/2 in compounds (1−5), respectively, and S = 5/2, 6/2, 7/2 and 8/2 in compounds (7−10), respectively]. These high-spin ground states are confirmed by magnetization measurements at 2 K. The ESR spectra of all compounds confirm the presence of the metals and a small amount of isolated TTF radical in all the samples, which is typical for these kinds of radical salts. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)