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Syntheses of high-spin and cluster molecules

Hiroki OSHIO (University of Tsukuba). Syntheses of high-spin and cluster molecules. Syntheses and Magnetic measurements Dr. M. Nihei, A. Yoshida, K. Koizumi, Yamashita ( Univ. of Tsukuba ) Dr. M. Nakano (Osaka Univ.) HF-EPR Prof. H. Nojiri (Okayama Univ.)

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Syntheses of high-spin and cluster molecules

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  1. Hiroki OSHIO (University of Tsukuba) Syntheses of high-spin and cluster molecules Syntheses and Magnetic measurements Dr. M. Nihei,A. Yoshida, K. Koizumi, Yamashita (Univ. of Tsukuba ) Dr. M. Nakano (Osaka Univ.) HF-EPR Prof. H. Nojiri (Okayama Univ.) Low-temperature Magnetic measurements Profs. A. Yamaguchi and Ishimoto (ISSP, Univ. of Tokyo) Solid State NMR Profs Y. Fujii (Fukui Univ.) and T. Goto (Kyoto Univ.) Workshop on Nano-magnets at Kyoto, Dec. 1 - 4, 2003

  2. Syntheses of · SMMs of Ferrous Cubes: Structurally controlled magnetic anisotropy · Mixed Valence Fe clusters · Hetero-metal SMM

  3. [Mn12O12(OAc)16(H2O)4] [FeII4(sae)4(MeOH)4] S = 8, D = -0.28 cm-1 S = 10, D = –0.46 cm-1 L. Thomas et al., Nature 1996, 383, 145 H. Oshio et al., J. Am. Chem. Soc. 2000, 112, 12602 Single Molecule Magnets [Mn(III,IV)12O12(O2CR)16(H2O)] (S = 10) (T. Lis, 1980) [Mn(III,IV)12O12(O2CR)16(H2O)4]- (S = 19/2) [Mn(III,IV)4O3X(O2CMe)(dbm)3] (S = 9/2) [Fe(III)8O2(OH)12(tacn)6]8+ (S = 10) [V(III)4O2(O2CR)7(L-L)]+ (S = 3) D. N. Hendrickson, G. Christou, and D. Gatteschi (1993)

  4. Syntheses of SMM Relatively high-spin ground state Negative D value DE Magnetization Direction DE = |D|Sz2 DE :Energy barrier to reorientate between two possible directions of magnetizations D : Zero Field Splitting parameters

  5. Accidental orthogonality Strategy for the High-spin Molecule Ferromagnetic Interactions by LMCT interactions AGK TheoryP. W. Anderson (1959), J. B. Goodenough (1958), J. Kanamori (1959) Strict orthogonality

  6. High-spin Cluster Orthogonal arrangements of the magnetic orbitals

  7. Fe(II) Cube of [FeII4(sae)4(MeOH)4] • triclinic P1- • a = 13.3625(7) Å, b = 13.7572(7) Å, c = 14.2004(7) Å • = 66.538(1)°, b = 74.973(1)°, g = 71.105(1), V = 2239.92(1) Å3, Z = 2 R1 = 0.0477, wR2 = 0.0959 S = 8 (4x2) J. Am. Chem. Soc. 2000. 122. 12603.

  8. AC measurements of [FeII4(sae)4(MeOH)4]

  9. Relaxation in [Fe4(sae)4(MeOH)4] with S =8 Ground State Ms = 0 Ms = 0 DE = |D|Sz2 Ms = -8 Ms = 8 t = t0exp(DE/kT) t = 1/(2pnAC) nAC : Freq. of AC Field T : Temp. of max. in c” DE = |D|Sz2= 64|D|

  10. Iron(II) cubes with S = 8 ground state SMM nonSMM nonSMM nonSMM [Fe4(sae)4(MeOH)4] [Fe4(sap)4(MeOH)4] [Fe4(3-MeO-sap)4(MeOH)4] [Fe4(sapd)4]

  11. Magnetization Experiments of High-spin Ferrous Cubes gD / cm-1 [Fe4(sae)4(MeOH)4] 2.126 -0.64 [Fe4(sap)4(MeOH)4] 2.261 +0.81 [Fe4(3-MeO-sap)4(MeOH)4] 2.243 +1.14 [Fe4(sapd)4] 2.180 +1.10

  12. Selected coordination bond distances (Å) in the cubes Equatorially compressed: D > 0 Elongated octahedron [Fe4(sae)4(MeOH)4] Fe(1)-O(1) 1.978(2) Fe(1)-O(2) 2.094(2) Fe(1)-N(1) 2.053(2) Fe(1)-O(4) 2.078(2) Fe(1)-O(9) 2.2908(18) Fe(1)-O(8) 2.2736(17) [Fe4(sap)4(MeOH)4]·2H2O Fe(1)-O(1) 2.029(2) Fe(1)-O(2) 2.045(2) Fe(1)-N(1) 2.127(2) Fe(1)-O(2)* 2.1616(15) Fe(1)-O(3) 2.2107(17) Fe(1)-O(2)* 2.2505(14) [Fe4(3MeO-msap)4(MeOH)4]·2MeOH Fe(1)-O(1) 1.991(5) Fe(1)-O(2) 2.037(4) Fe(1)-N(1) 2.104(6) Fe(1)-O(10) 2.137(4) Fe(1)-O(6) 2.238(4) Fe(1)-O(4) 2.242(5) [Fe4(bsap)4(MeOH)4] Fe(1)-O(1) 2.036(3) Fe(1)-O(2) 2.056(3) Fe(1)-N(1) 2.123(3) Fe(1)-O(2)* 2.159(3) Fe(1)-O(2) 2.259(2) Fe(1)-O(3) 2.263(3) strong ligand field Equatorially less compressed: D < 0 week ligand field

  13. Angular Overplap Model calculations ofEnergy splitting of the 5B2g state P = 0.5 week LF P = 1.0 strong LF week LF strong LF sap sae D < 0 D > 0 The variable p changes the equatorial ligand field strengths.

  14. Sign of DCube values sae: Equatorially compressed: DFe > 0: Orthogonal alignments of four ions with hard axis sap: equatorially less compressed: DFe < 0: Orthogonal alignments of four ions with easy axis

  15. [Fe4(3,5-Cl2-sae)4(MeOH)4] DE = 26 KD = -0.29 cm-1TB = 1.1 K

  16. [Fe4(5-Br-sae)4(MeOH)4] DE = 30 KD = -0.33 cm-1TB = 1.2 K

  17. SummaryStructurally controlled magnetic anisotropy • Compounds in red are SMM. • The g, C, and  values were obtained from temperature dependence of the magnetic susceptibility. D values were estimated by the analyses of magnetization data at 1.8 K, supposing the only S = 8 being populated. E and TB values were estimated from the ac magnetic susceptibility measurements.

  18. [FeIII3] [FeIII2] [FeII3FeIII] [NaFeIII6] [FeIIIFeII6] [FeIIFeIII6] New Cluster Molecules with higher nuclearity

  19. Ferric wheel of [NaFeIII6(5-MeO-sae)6(m2-OMe)]ClO4 +NaClO4 [FeIII3Cl2(5-MeO-sae)3 (m3-OMe)(MeOH)] (m3-alkoxo bridges)

  20. (m3-alkoxo bridge) [FeIIFeIII6(5-MeO-sae)6(m2-OMe)6]Cl2 7FeCl2·4H2O + 6H2(5-MeO-sae) + 2/7(t-Bu4N)(MnO4)  ? Spin frustrated system g(Fe3+) = 2.0 and g(Fe2+) =2.10(5) J(spoke) = -7.3 cm-1 and J(rim) = -8.7 cm-1

  21. [FeII6FeIII(5-MeO-saeH) 6(m3-OMe)6]Cl3 7FeCl2·4H2O + 6(5-MeO-saeH2) + 1/21(t-Bu4N)(MnO4)  m2-phenoxo bridges S = 29/2 and D = +0.53 cm-1 Angew.Chem. 2003.

  22. Next target molecules Air insensitive SMM Heteronuclear SMM The smallest SMM

  23. CuCl2·2H2O Hetero-nuclear SMM + MnCl2·4H2O [MnIII3(m-O)(Br-sap)3(H2O)3]Cl

  24. [MnIIICuII(Br-sap)2Cl(MeOH)] Mn Cu Selected Bond Distances (Å) Mn-Cl 2.616(4) Mn-O1S 2.658(9) Other bonds 1.871(5) - 1.973(6) Mn3+: Axially elongated octahedron for d4

  25. Magnetic susceptibility and magnetization data of [MnIIICuII(Br-sap)2Cl(MeOH)] Ferromagnetic interactions between Mn3+ and Cu2+ ions S = 5/2 ground state

  26. O Mn Cu dx2-y2 O dxy dz2 dxz dyz MO diagram of Mn3+-Cu2+ system Tetragonally elongated quasi D4h Square-planar quasi D4h dx2-y2 dz2 LMCT from O- dxy dxz dyz Mn3+ Cu2+ Strickt orthogonality

  27. Quasi-single Crystal HF-EPR OF [MnIIICuII(Br-sap)2Cl(MeOH)] 381.5 GHz 1/23/2 -5/2-3/2 -3/2-1/2 -1/21/2 H. Nojiri (Okayama Univ.) *Magnetic field is tilted 13° with respect to the principal axis.

  28. Plots of resonance fields (Hr) vs. the value of Ms [MnIIICuII(Br-sap)2Cl(MeOH)] g = 2.04 D = -1.70 cm-1 B40’= -0.0074 cm-1

  29. Single Crystal AC magnetic susceptibility [MnIIICuII(Br-sap)2Cl(MeOH)] Yamaguchi, Ishimoto (ISSP)

  30. Packing diagrams of [MnIIICuII(Br-sap)2Cl(MeOH)] ac projection view ab projection view bc projection view

  31. X No-spin tunneling at Hext=0 Integer Spin Half-Integer Spin Magnetization data for [MnIIICuII(Br-sap)2Cl(MeOH)] with S =5/2 ground state TB = 500 mK DE = 10.5 K Yamaguchi, Ishimoto (ISSP)

  32. N N 0 0 S -1 1 2 -2 -3 3 S -4 4 Tunneling 5 -5 -6 6 7 -7 Ms = -8 Ms = 8 Nano magnets Summary: Nano Magnets with different sizes Cu [MnIIICuII] S = 5/2with TB = 0.8 K Mn 4核:[FeII4] S = 8with TB = 1.1K 1.5 nm Fe 6核:[MnIII6] S = 12with TB = 1.0 K [FeII6FeIII] with S = 29/2 2.0 nm [MnIII4MnIV2CuII8(O)6] Strong correlated electron oxide clusters 2.5 nm ？ [MnIII8MnIV4CuII8(O)16]

  33. Organizer Tadashi Sugawara (University of Tokyo) General Secretaries Hiroki Oshio (Tsukuba University) Kunio Awaga (Nagoya University)Kazuhito Hashimoto (Unrsity of Tokyo)

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