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Topological Versatility of Oxalate-Based Bimetallic One-Dimensional (1D) Compounds Associated with Ammonium Cations

E. Pardo, C. Train, K. Boubekeur, G. Gontard, J. Cano, F. Lloret, K. Nakatani and M. Verdaguer Inorg. Chem., 2012, 51, 21, 11582-11593

A new family of oxalate-bridged chains of formula (C1)[Mn(H2O)3Cr(ox)3]·H2O (1), (C2)4[Mn2(H2O)3ClCr2(ox)6]Cl·H2O·2C2H6O (2a), (C2)4[Co2(H2O)3ClCr2(ox)6]Cl·2H2O·2C2H6O (2b), [Mn(C3)(H2O)2Cr(ox)3]·H2O (3), and (C4)4[Mn(H2O){Cr(ox)3}2]·H2O (4) [C1+ = tetramethylammonium, C2+ = 4-N,N-dimethylaminopyridinium, C3+ = 1-hydroxyethyl-4-N,N-dimethylamino-pyridinium, C4+ = 1-hydroxyethyl-4-(4′-dimethylamino-α-styryl)-pyridinium, ox2– = oxalate] have been synthesized by self-assembly of the (Cn)3[Cr(ox)3] (n = 1–4) mononuclear compound and the chloride salts of the corresponding metal(II) ions. The crystal structures of the five chain compounds have been determined by single-crystal X-ray diffraction. Compounds 1 and 2 crystallize in the Pc and P21/c centrosymmetrical space groups, respectively, whereas 3 and 4 crystallize in the C2cb and P1 noncentrosymmetrical space groups, respectively. Compounds 1, 2, and 3 adopt a zigzag chain structure while 4 exhibits a comb-like chain structure consisting of the repetition of the [Mn(H2O){Cr(μ-ox)(ox)2}{Cr(μ-ox)2(ox)}]4– entities. Compound 3 displays large second-order optical nonlinearity. The magnetic properties of 1–4 have been investigated in the temperature range 2–300 K. Monte Carlo simulations on 1, 2a, 2b, and 3 provide a quantitative description of the magnetic properties indicating ferromagnetic interactions through the bis(bidentate) oxalate bridges [J = +0.55 cm–1 (1), J = +1.02 cm–1 (2a), J = +3.83 cm–1 (2b), and J = +0.75 cm–1 (3) using Hamiltonian Ĥ = −J(Ŝi·Ŝj)]. On the other side, the fit of the magnetic susceptibility data of 4 by full-matrix diagonalization agrees with a ferromagnetic exchange interaction within the [Mn(H2O){Cr(μ-ox)(ox)2}{Cr(μ-ox)2(ox)}]4– trinuclear units (J = +2.07 cm–1) antiferromagnetically coupled along the chain. Compound 2b exhibits a metamagnetic behavior, the value of the critical field being HC = 1000 G, due to the occurrence of weak interchain antiferromagnetic interactions.

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Publication

Dates :

Paru le 22 octobre 2012

Informations complémentaires :

doi 10.1021/ic3014915