Magnetic properties of six-coordinated high-spin cobalt(II) complexes: Theoretical background and its application

Abstract In this contribution we study and analyse the influence of the different parameters involved in the magnetic susceptibility of six-coordinated high-spin Co(II) complexes. We propose an empirical expression to fit the magnetic susceptibility of polycrystalline samples of mononuclear Co(II) complexes with an axial distortion, the variable parameters being Δ (axial distortion), α (orbital reduction factor) and λ (spin–orbit coupling). This expression avoids solving the 12 × 12 matrix associated to the distortion of the 4 T 1g term. In order to take into account the magnetic coupling ( J ) in the polynuclear Co(II) complexes, a perturbational approach is proposed to describe their magnetic susceptibility in the whole temperature range (2–300 K) as a function of J , Δ , α and λ . This approach is valid in the limit of the weak magnetic coupling as compared to the spin–orbit coupling, | J / λ |  S eff  = 1/2. That causes a drastic reduction of the matrix size of the polynuclear compounds from 12 n  × 12 n to 2 n  × 2 n , n being the number of Co(II) ions in the complex. The main advantage of the model is to make possible the fit of the magnetic susceptibility data of those polynuclear Co(II) complexes whose high nuclearity involved intractable matrices.

[1]  A. Pasini,et al.  Binuclear Co(II)Co(II), Co(II)Co(III) and Co(III)Co(III) complexes of “short” salen homologues derived from the condensation of salicylaldehyde and methanediamine or phenylmethanediamines. Synthesis, structures and magnetism , 2001 .

[2]  F. Costantino,et al.  The influence of ligand field effects on the magnetic exchange of high-spin Co(II)-semiquinonate complexes. , 2006, Dalton transactions.

[3]  C. Rovira,et al.  Coexistence of ferro- and antiferromagnetic interactions in a metal-organic radical-based (6,3)-helical network with large channels. , 2005, Chemical communications.

[4]  B. Abrahams,et al.  Mixed-valent cobalt spin clusters: a hexanuclear complex and a one-dimensional coordination polymer comprised of alternating hepta- and mononuclear fragments. , 2006, Inorganic chemistry.

[5]  M. E. Lines,et al.  Orbital Angular Momentum in the Theory of Paramagnetic Clusters , 1971 .

[6]  F. Lloret,et al.  Crystal structures and magnetic properties of two octacyanotungstate(IV) and (V)-cobalt(II) three-dimensional bimetallic frameworks. , 2003, Inorganic chemistry.

[7]  J. Sanchiz,et al.  Synthesis, crystal structure and magnetic properties of two-dimensional malonato-bridged cobalt(II) and nickel(II) compounds , 2004 .

[8]  D. Hodgson,et al.  Magnetic and structural characterization of dibromo- and dichlorobis(thiazole)copper(II) , 1978 .

[9]  T. Hambley,et al.  The chemistry of cobalt acetate—III. The isolation and crystal structure characterisation of the mixed valence octacobalt oligomer, [Co8(O)4(CH3CO2)6(OMe)4]Cl4(OHn)4 · 6H2O (n = 1 or 2), derived from the preparation of cobalt(III) acetate , 1997 .

[10]  A. Caneschi,et al.  2,2′-Bipyrimidine (bipym)-bridged dinuclear complexes. Part 4. Synthesis, crystal structure and magnetic properties of [CO2(H2O)8(bipym)][NO3]4, [CO2(H2O)8(bipym)][SO4]2·2H2O and [CO2(bipym)3(NCS)4] , 1994 .

[11]  L. Banci,et al.  Spectral-structural correlations in high-spin cobalt(II) complexes , 1982 .

[12]  A. G. Whittaker,et al.  Synthesis, structural characterisation and preliminary magnetic studies of a tetraicosanuclear cobalt coordination complex , 1997 .

[13]  A. Terzis,et al.  Defective Double-Cubane, Tetranuclear Manganese(II) and Cobalt(II) Complexes with Simultaneous μ1,1-Azido and μ-O Bridges , 2001 .

[14]  N. Masciocchi,et al.  Hexacyanocobaltate(III) anions as precursors of Co(II)-Ni(II) cyano-bridged multidimensional assemblies: hydrothermal syntheses, crystal and powder X-ray structures, and magnetic properties. , 2005, Inorganic chemistry.

[15]  H. Sakiyama,et al.  Magnetic behavior of dinuclear cobalt(II) complexes assumed to be caused by a paramagnetic impurity can be explained by tilts of local distortion axes , 2007 .

[16]  M. Lines.  The quadratic-layer antiferromagnet , 1970 .

[17]  J. J. Borrás-Almenar,et al.  Microscopic approach to the pseudo-spin-1/2 Hamiltonian for Kramers doublets in exchange coupled Co(II) pairs. , 2003, Inorganic chemistry.

[18]  KondoKazuhiro,et al.  Novel Tetranulear Cobalt(II)-Cobalt(III) Mixed-Valence Complexes with a Significant Difference in Magnetism , 2000 .

[19]  H. Sakiyama.  Magnetic susceptibility equation for dinuclear high-spin cobalt(II) complexes considering the exchange interaction between two axially distorted octahedral cobalt(II) ions , 2006 .

[20]  博史 崎山,et al.  軸対称二核高スピンコバルト(II)錯体の磁化率解析ソフト「名称: MagSaki」の開発 , 2001 .

[21]  S. Teat,et al.  Synthesis and characterization of a cobalt(II) single-molecule magnet. , 2003, Angewandte Chemie.

[22]  C. Ruiz-Pérez,et al.  Ligand design for heterobimetallic single-chain magnets: synthesis, crystal structures, and magnetic properties of MIICuII (M=Mn, Co) chains with sterically hindered methyl-substituted phenyloxamate bridging ligands. , 2007, Chemistry.

[23]  R. Sessoli,et al.  Quantum tunneling of magnetization and related phenomena in molecular materials. , 2003, Angewandte Chemie.

[24]  A. Caneschi,et al.  Cobalt(II)-Nitronyl Nitroxide Chains as Molecular Magnetic Nanowires The financial support of Italian MURST and CNR and of Brazilian CNPq and FUJB is acknowledged. The support from the European Community through the TMR program 3MD (contract no ERB4061PL97-0197) is also acknowledged. , 2001, Angewandte Chemie.

[25]  A. Caneschi,et al.  Magnetic bistability in a metal-ion cluster , 1993, Nature.

[26]  C. Rovira,et al.  First-row transition-metal complexes based on a carboxylate polychlorotriphenylmethyl radical: trends in metal-radical exchange interactions. , 2007, Inorganic chemistry.

[27]  M. R. Bermejo,et al.  Dinuclear Co(III)/Co(III) and Co(II)/Co(III) mixed-valent complexes: synthetic control of the cobalt oxidation level. , 2006, Dalton transactions.

[28]  C. Ruiz-Pérez,et al.  Cobalt(II)–Copper(II) Bimetallic Chains as a New Class of Single‐Chain Magnets , 2004 .

[29]  W. Low.  Paramagnetic and Optical Spectra of Divalent Cobalt in Cubic Crystalline Fields , 1958 .

[30]  W. Haase,et al.  Orbital angular momentum contribution to the magneto-optical behavior of a binuclear cobalt(II) complex. , 2006, Inorganic chemistry.

[31]  K. Inoue,et al.  Dinuclear Cobalt(II) Complexes of an Acyclic Phenol‐Based Dinucleating Ligand with Four Methoxyethyl Chelating Arms − First Magnetic Analyses in an Axially Distorted Octahedral Field , 2001 .

[32]  S. Teat,et al.  Synthesis and structural and magnetic characterization of cobalt(II) phosphonate cage compounds. , 2008, Inorganic chemistry.

[33]  A. Terzis,et al.  The first cobalt metallacrowns: preparation and characterization of mixed-valence cobalt(II/III), inverse 12-metallacrown-4 complexes. , 2005, Inorganic chemistry.

[34]  Cobalt(II)-Nitronyl Nitroxide Chains as Molecular Magnetic Nanowires The financial support of Italian MURST and CNR and of Brazilian CNPq and FUJB is acknowledged. The support from the European Community through the TMR program 3MD (contract no ERB4061PL97-0197) is also acknowledged. , 2001, Angewandte Chemie.

[35]  A. Sharma,et al.  Phenolate- and Acetate (Both μ2-1,1 and μ2-1,3 Mode)-Bridged Face-Shared Trioctahedral Linear NiII3, NiII2MII (M = Mn, Co) Complexes: Ferro- and Antiferromagnetic Coupling , 2007 .

[36]  F. Lloret,et al.  Unprecedented stabilization of cobalt(II) in a tetrahedral S2O2 environment: the use of a redox-noninnocent ligand. , 2000, Inorganic chemistry.

[37]  W. Wernsdorfer,et al.  A mixed-valence Co7 single-molecule magnet with C3 symmetry. , 2007, Chemical communications.

[38]  David O. Miller,et al.  Self-assembly by ligand disassembly?--Formation of an unusual dodecanuclear [Co(II)6Co(III)6] cluster. , 2004, Chemical Communications.

[39]  F. Lloret,et al.  Hexanuclear manganese(III) single-molecule magnets. , 2004, Angewandte Chemie.

[40]  O. Fabelo,et al.  Structural versatility in cobalt(II) complexes with 1,2,4,5-benzenetetracarboxylic acid (H4bta) and 4,4′-bipyridine-N,N′-dioxide (dpo) , 2007 .

[41]  G. Seisenbaeva,et al.  Synthesis, X-ray single crystal and magnetic study of new heteroleptic late transition metal alkoxides with tetranuclear square planar metal core, Co4Cl2(OC2H4OEt)6, Co4(OMe)2(acac)6(MeOH)2 and Zn4(OMe)2(acac)6(C7H8) , 2003 .

[42]  D. Gatteschi.  Molecular Magnetism: A basis for new materials , 1994 .

[43]  C. Ruiz-Pérez,et al.  Design of single chain magnets through cyanide-bearing six-coordinate complexes , 2005 .

[44]  W. Haase,et al.  Magnetic properties of dinuclear cobalt complexes , 2002 .

[45]  Yoshimasa Hoshino,et al.  Changing Mixed-valence State of Hexacobalt Cluster by Substituting Central Metal Ion and by Electrochemical Reduction —Different Mixed-valence States of [M{Co(prolinato)2}6]4+ (M = Ba2+ and La3+) , 2005 .

[46]  J. J. Borrás-Almenar,et al.  Orbitally dependent magnetic coupling between cobalt(II) ions: The problem of the magnetic anisotropy , 2003 .

[47]  J. Griffith,et al.  The Theory of Transition-Metal Ions , 1962 .

[48]  A. Caneschi,et al.  Antiferromagnetic coupling in a six-coordinate high spin cobalt(II)-semiquinonato complex. , 2002, Inorganic chemistry.

[49]  O. Fabelo,et al.  Unusual (μ-aqua)bis(μ-carboxylate) Bridge in Homometallic M(II) (M = Mn, Co and Ni) Two-Dimensional Compounds Based on the 1,2,3,4-Butanetetracarboxylic Acid: Synthesis, Structure, and Magnetic Properties , 2007 .

[50]  Gang Su,et al.  An azide-bridged homospin single-chain magnet: [Co(2,2'-bithiazoline)(N3)2]n. , 2003, Journal of the American Chemical Society.

[51]  Song Gao,et al.  Synthesis, crystal structures, and magnetic properties of cyano-bridged heterobimetallic chains based on [(Tp)Fe(CN)3]-. , 2006, Inorganic Chemistry.

[52]  R. Shulman,et al.  Covalency Effects in KNi F 3 . III. Theoretical Studies , 1963 .

[53]  W. Wernsdorfer,et al.  Ferromagnetic cobalt metallocycles. , 2006, Inorganic chemistry.

[54]  W. Wernsdorfer,et al.  Cyanide-bridged iron(III)-cobalt(II) double zigzag ferromagnetic chains: two new molecular magnetic nanowires. , 2003, Angewandte Chemie.

[55]  F. Lloret,et al.  Synthesis, crystal structure and magnetic properties of the cobalt(II) chain [Co(bipym)(H2O)2](NO3)2 and the dinuclear compounds [Co2(bipym)3(H2O)4](NO3)4·2H2O and [Co2(bipym)3(H2O)2(SO4)2]·12H2O , 1998 .

[56]  F. Lloret,et al.  Coordination versatility of 1,3-bis[3-(2-pyridyl)pyrazol-1-yl]propane: Co(II) and Ni(II) complexes , 2006 .

[57]  E. Coronado,et al.  Anisotropic exchange in the cobalt-cobalt and cobalt-copper dinuclear EDTA hydrate (Co2(EDTA).cntdot.6H2O, CoCu(EDTA).cntdot.6H2O) bimetallic ordered chains. Low temperature investigation of the thermal and magnetic properties , 1988 .

[58]  J. Renard,et al.  Magnetism of A-copper(II) bimetallic chain compounds (A = iron, cobalt, nickel): one- and three-dimensional behaviors. , 1990, Inorganic chemistry.