Synthesis, crystal structures and magnetic properties of M(II)Cu(II) chains (M = Mn and Co) with sterically hindered alkyl-substituted phenyloxamate bridging ligands |
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Authors: | Ferrando-Soria Jesús Pardo Emilio Ruiz-García Rafael Cano Joan Lloret Francisco Julve Miguel Journaux Yves Pasán Jorge Ruiz-Pérez Catalina |
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Affiliation: | 1. Departament de Química Inorgànica/Instituto de Ciencia Molecular (ICMol), Universitat de València, Paterna, Valencia, 46980 (Spain), Fax: (+34)?963544322;2. Fundació General de la Universitat de València (FGUV), Universitat de València, Valencia, 46002 (Spain);3. Institut Parisien de Chimie Moléculaire, UMR CNRS 7071, UPMC‐Univ. Paris 06, Paris, 75005 (France), Fax: (+33)?144273841;4. Laboratorio de Rayos X y Materiales Moleculares, Departamento de Física Fundamental II, Facultad de Física, Universidad de la Laguna, La Laguna, Tenerife, 38201 (Spain) |
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Abstract: | A series of neutral oxamato‐bridged heterobimetallic chains of general formula [MCu(Lx)2(S)2] ? p S ? q H2O [p=0–1, q=0–2.5; L1=N‐2,6‐dimethylphenyloxamate, S=DMF with M=Mn ( 1 a ) and Co ( 1 b ); L2=N‐2,6‐diethylphenyloxamate, S=DMF with M=Mn ( 2 a ) and Co ( 2 b ) or S=DMSO with M=Mn ( 2 c ) and Co ( 2 d ); L3=N‐2,6‐diisopropylphenyloxamate, S=DMF with M=Mn ( 3 a ) and Co ( 3 b ) or S=DMSO with M=Mn ( 3 c ) and Co ( 3 d )] were prepared by treating the corresponding anionic oxamatocopper(II) complexes [Cu(Lx)2]2? (x=1–3) with M2+ cations (M=Mn and Co) in DMF or DMSO as the solvent. The single‐crystal X‐ray structures of 2 a and 3 a reveal the occurrence of well‐isolated, zigzag, oxamato‐bridged manganese(II)–copper(II) chains. The intrachain Cu ??? Mn distances across the oxamato bridge are 5.3761(7) and 5.4002(17) Å for 2 a and 3 a , respectively, whereas the shortest interchain Mn ??? Mn distances are 9.4475(16) and 8.1649(14) Å for 2 a and 3 a , respectively. All of these MIICuII chains (M=Mn and Co) exhibit 1D ferrimagnetic behaviour with moderately strong intrachain antiferromagnetic coupling between the square‐planar CuII and octahedral high‐spin MII ions across the oxamato bridge [?J=31.4–35.2 and 33.4–44.8 cm?1, respectively; H =∑i?J S M,i( S Cu,i+ S Cu,i?1)]. Only the CoIICuII chains show slow magnetic relaxation effects characteristic of single‐chain magnets (SCMs). Analysis of the magnetic relaxation dynamics of 3 d shows a thermally activated mechanism (Arrhenius law dependence) with values of the pre‐exponential factor (τ0=2.6×10?9 s) and activation energy (Ea=7.7 cm?1) that are typical of SCMs. In contrast, two relaxation regimes are observed for 2 d in different temperature regions (τ0=3.2×10?10 s and Ea=24.7 cm?1 for T<4.5 K and τ0=3.2×10?14 s and Ea=37.5 cm?1 for T>4.5 K). |
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Keywords: | chain structures cobalt copper magnetic properties manganese |
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