Syntheses of high-spin and cluster molecules Hiroki OSHIO (University of Tsukuba) 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 , 2003 Syntheses of SMMs of Ferrous Cubes: Structurally controlled magnetic anisotropy Mixed Valence Fe clusters Hetero-metal SMM Single Molecule Magnets [Mn(III,IV) 12 O 12 (O 2 CR) 16 (H 2 O)](S = 10) (T. Lis, 1980) [Mn(III,IV) 12 O 12 (O 2 CR) 16 (H 2 O) 4 ] - (S = 19/2) [Mn(III,IV) 4 O 3 X(O 2 CMe)(dbm) 3 ](S = 9/2) [Fe(III) 8 O 2 (OH) 12 (tacn) 6 ] 8+ (S = 10) [V(III) 4 O 2 (O 2 CR) 7 (L-L)] + (S = 3) D. N. Hendrickson, G. Christou, and D. Gatteschi (1993) S = 10, D = 0.46 cm -1 L. Thomas et al., Nature 1996, 383, 145 [Mn 12 O 12 (OAc) 16 (H 2 O) 4 ] [Fe II 4 (sae) 4 (MeOH) 4 ] H. Oshio et al., J. Am. Chem. Soc. 2000, 112, S = 8, D = cm -1 Syntheses of SMM EE Magnetization Direction E = |D|S z 2 E :Energy barrier to reorientate between two possible directions of magnetizations D : Zero Field Splitting parameters Relatively high-spin ground state Negative D value Strategy for the High-spin Molecule Ferromagnetic Interactions by LMCT interactions AGK Theory P. W. Anderson (1959), J. B. Goodenough (1958), J. Kanamori (1959) Strict orthogonality Accidental orthogonality High-spin Cluster Orthogonal arrangements of the magnetic orbitals Fe(II) Cube of [Fe II 4 (sae) 4 (MeOH) 4 ] triclinic P1- a = (7) , b = (7) , c = (7) = (1), = (1), = (1), V = (1) 3, Z = 2 R1 = , wR2 = J. Am. Chem. Soc S = 8 (4x2) AC measurements of [Fe II 4 (sae) 4 (MeOH) 4 ] Relaxation in [Fe 4 (sae) 4 (MeOH) 4 ] with S =8 Ground State = 0 exp( E/kT) = 1/(2 AC ) AC : Freq. of AC Field T : Temp. of max. in E = |D|S z 2 = 64|D| M s = -8M s = 8 M s = 0 E = |D|S z 2 Iron(II) cubes with S = 8 ground state SMM nonSMM nonSMM nonSMM [Fe 4 (sae) 4 (MeOH) 4 ] [Fe 4 (sap) 4 (MeOH) 4 ] [Fe 4 (3-MeO-sap) 4 (MeOH) 4 ] [Fe 4 (sapd) 4 ] Magnetization Experiments of High-spin Ferrous Cubes g D / cm -1 [Fe 4 (sae) 4 (MeOH) 4 ] [Fe 4 (sap) 4 (MeOH) 4 ] [Fe 4 (3-MeO-sap) 4 (MeOH) 4 ] [Fe 4 (sapd) 4 ] [Fe 4 (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) (18)Fe(1)-O(8) (17) [Fe 4 (sap) 4 (MeOH) 4 ]2H 2 O 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)* (15) Fe(1)-O(3) (17)Fe(1)-O(2)* (14) [Fe 4 (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) [Fe 4 (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) Selected coordination bond distances () in the cubes Equatorially less compressed: D < 0 Equatorially compressed: D > 0 Elongated octahedron strong ligand field week ligand field Angular Overplap Model calculations of Energy splitting of the 5 B 2g state The variable p changes the equatorial ligand field strengths. P = 0.5 week LF P = 1.0 strong LF D < 0D > 0 saesap week LFstrong LF Sign of D Cube values sap : equatorially less compressed: D Fe < 0: Orthogonal alignments of four ions with easy axis sae : Equatorially compressed: D Fe > 0: Orthogonal alignments of four ions with hard axis [Fe 4 (3,5-Cl 2 -sae) 4 (MeOH) 4 ] E = 26 K D = cm -1 T B = 1.1 K E = 30 K D = cm -1 T B = 1.2 K [Fe 4 (5-Br-sae) 4 (MeOH) 4 ] Summary Structurally 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 T B values were estimated from the ac magnetic susceptibility measurements. gC [emu mol -1 K] [K] D [cm -1 ] E [K] T B [K] [Fe 4 (sap) 4 (MeOH) 4 ]2H 2 O [Fe 4 (5-Br-sap) 4 (MeOH) 4 ] [Fe 4 (3-MeO-sap) 4 (MeOH) 4 ] [Fe 4 (sapd) 4 ]4MeOH2H 2 O [Fe 4 (sae) 4 (MeOH) 4 ] [Fe 4 (5-Br-sae) 4 (MeOH) 4 ]MeOH [Fe 4 (3,5-Cl 2 -sae) 4 (MeOH) 4 ] [NaFe III 6 ] New Cluster Molecules with higher nuclearity [Fe II Fe III 6 ] [Fe III 2 ] [Fe III 3 ] [Fe II 3 Fe III ] [Fe III Fe II 6 ] Ferric wheel of [NaFe III 6 (5-MeO-sae) 6 ( 2 -OMe)]ClO 4 +NaClO 4 [Fe III 3 Cl 2 (5-MeO-sae) 3 ( 3 -OMe)(MeOH)] ( 3 -alkoxo bridges) [Fe II Fe III 6 (5-MeO-sae) 6 ( 2 -OMe) 6 ]Cl 2 7FeCl 2 4H 2 O + 6H 2 (5-MeO-sae) + 2/7(t-Bu 4 N)(MnO 4 ) ( 3 -alkoxo bridge) g(Fe 3+ ) = 2.0 and g(Fe 2+ ) =2.10(5) J(spoke) = -7.3 cm -1 and J(rim) = -8.7 cm -1 ? Spin frustrated system [Fe II 6 Fe III (5-MeO-saeH) 6 ( 3 -OMe) 6 ]Cl 3 7FeCl 2 4H 2 O + 6(5-MeO-saeH 2 ) + 1/21(t-Bu 4 N)(MnO 4 ) 2 -phenoxo bridges S = 29/2 and D = cm -1 Angew.Chem Next target molecules Air insensitive SMM Heteronuclear SMM The smallest SMM Hetero-nuclear SMM CuCl 2 2H 2 O [Mn III 3 ( -O)(Br-sap) 3 (H 2 O) 3 ]Cl + MnCl 2 4H 2 O [Mn III Cu II (Br-sap) 2 Cl(MeOH)] Selected Bond Distances () Mn-Cl 2.616(4) Mn-O1S 2.658(9) Other bonds 1.871(5) (6) Mn 3+ : Axially elongated octahedron for d 4 MnCu Magnetic susceptibility and magnetization data of [Mn III Cu II (Br-sap) 2 Cl(MeOH)] Ferromagnetic interactions between Mn 3+ and Cu 2+ ions S = 5/2 ground state MO diagram of Mn 3+ -Cu 2+ system Tetragonally elongated quasi D 4h Mn 3+ Square-planar quasi D 4h d xz d yz dz2dz2 d xy d x 2 -y 2 dz2dz2 d xy d xz d yz Cu 2+ O CuMn O LMCT from O - Strickt orthogonality Quasi-single Crystal HF-EPR OF [Mn III Cu II (Br-sap) 2 Cl(MeOH)] -5/2 -3/2 -3/2 -1/2-1/2 1/2 1/2 3/ GHz *Magnetic field is tilted 13 with respect to the principal axis. H. Nojiri (Okayama Univ.) Plots of resonance fields (H r ) vs. the value of Ms [Mn III Cu II (Br-sap) 2 Cl(MeOH)] g = 2.04 D = cm -1 B 4 0 = cm -1 Yamaguchi, Ishimoto (ISSP) Single Crystal AC magnetic susceptibility [Mn III Cu II (Br-sap) 2 Cl(MeOH)] Packing diagrams of [Mn III Cu II (Br-sap) 2 Cl(MeOH)] ac projection view bc projection view ab projection view Magnetization data for [Mn III Cu II (Br-sap) 2 Cl(MeOH)] with S =5/2 ground state Yamaguchi, Ishimoto (ISSP) Integer SpinHalf-Integer Spin No-spin tunneling at H ext =0 X T B = 500 mK E = 10.5 K Summary: Nano Magnets with different sizes Mn Cu Fe [Mn III Cu II ] S = 5/2 with T B = 0.8 K 4 :[Fe II 4 ] S = 8 with T B = 1.1K 6 :[Mn III 6 ] S = 12 with T B = 1.0 K [Fe II 6 Fe III ] with S = 29/2 [Mn III 4 Mn IV 2 Cu II 8 (O) 6 ] 1.5 nm 2.0 nm 2.5 nm [Mn III 8 Mn IV 4 Cu II 8 (O) 16 ] Strong correlated electron oxide clusters S N Tunneling M s = S N Nano magnets M s = -8 Organizer Tadashi Sugawara (University of Tokyo) General Secretaries Hiroki Oshio (Tsukuba University) Kunio Awaga (Nagoya University) Kazuhito Hashimoto (Unrsity of Tokyo)