Tomoka Yamaguchi

Synthesis, Structures, and Magnetic Properties of Face-Sharing Heterodinuclear Ni(II)−Ln(III) (Ln = Eu, Gd, Tb, Dy) Complexes

Heterodinuclear [(Ni (II)L)Ln (III)(hfac) 2(EtOH)] (H 3L = 1,1,1-tris[(salicylideneamino)methyl]ethane; Ln = Eu, Gd, Tb, and Dy; hfac = hexafluoroacetylacetonate) complexes ( 1.Ln) were prepared by treating [Ni(H 1.5L)]Cl 0.5 ( 1) with [Ln(hfac) 3(H 2O) 2] and triethylamine in ethanol (1:1:1). All 1.Ln complexes ( 1.Eu, 1.Gd, 1.Tb, and 1.Dy) crystallized in the triclinic space group P1 (No. 2) with Z = 2 with very similar structures. Each complex is a face-sharing dinuclear molecule. The Ni (II) ion is coordinated by the L (3-) ligand in a N 3O 3 coordination sphere, and the three phenolate oxygen atoms coordinate to an Ln (III) ion as bridging atoms. The Ln (III) ion is eight-coordinate, with four oxygen atoms of two hfac (-)s, three phenolate oxygen atoms of L (3-), and one ethanol oxygen atom coordinated. Temperature-dependent magnetic susceptibility and field-dependent magnetization measurements showed a ferromagnetic interaction between Ni (II) and Gd (III) in 1.Gd. The Ni (II)-Ln (III) magnetic interactions in 1.Eu, 1.Tb, and 1.Dy were evaluated by comparing their magnetic susceptibilities with those of the isostructural Zn (II)-Ln (III) complexes, [(ZnL)Ln(hfac) 2(EtOH)] ( 2.Ln) containing a diamagnetic Zn (II) ion. A ferromagnetic interaction was indicated in 1.Tb and 1.Dy, while the interaction between Ni (II) and Eu (III) was negligible in 1.Eu. The magnetic behaviors of 1.Dy and 2.Dy were analyzed theoretically to give insight into the sublevel structures of the Dy (III) ion and its coupling with Ni (II). Frequency dependence in the ac susceptibility signals was observed in 1.Dy.

Experimental evidence for the participation of 5d Gd(III) orbitals in the magnetic interaction in Ni-Gd complexes.

The syntheses, structural determinations, and magnetic studies of two trinuclear Ni-Gd-Ni complexes are described. The structural studies demonstrate that the two complexes present a linear arrangement of the Ni and Gd ions, with Ni ions in slightly distorted square-pyramidal or octahedral environments in complexes 1 and 2, respectively. The Ni and Gd ions are linked by two or three phenoxo bridges, so that complexes 1 and 2 present edge-sharing or face-sharing bridging cores. Ferromagnetic interactions operate in these complexes. While a unique J parameter is able to fit the magnetic data of complex 2, two very different J constants are needed for 1. This result is at first sight surprising, for the structural data of the two Ni-O(2)-Gd cores in complex 1 are quite similar (similar Ni-O and Gd-O bond lengths, similar angles, and dihedral angles), the only difference coming from the angle between the planes defined by the Gd ion and the two bridging phenoxo oxygen atoms of each Ni-O(2)-Gd half core. This latter magnetic behavior can be considered as a signature for the participation of 5d Gd(III) orbitals in the exchange interaction mechanism and can explain why edge-sharing complexes have larger J parameters than face-sharing complexes.

Ferromagnetic NiII–GdIII interactions in complexes with NiGd, NiGdNi, and NiGdGdNi cores supported by tripodal ligands

Dinuclear [(NiL)Gd(hfac)(2)(EtOH)](H(3)L = 1,1,1-tris(N-salicylideneaminomethyl)ethane, Hhfac = hexafluoroacetylacetone), trinuclear [(NiL)(2)Gd(NO(3))], and tetranuclear [(NiL)Gd(CH(3)CO(2))(2)(MeOH)](2) complexes, were prepared by treating [Ni(HL)] with [Gd(hfac)(3)(H(2)O)(2)], Gd(NO(3))(3).6H(2)O, and Gd(CH(3)CO(2))(3).4H(2)O, respectively, in the presence of Et(3)N. All the complexes show that ferromagnetic interactions occur between the Ni(II) and Gd(III) ions.

A single tripodal ligand stabilizing three different oxidation states (II, III, and IV) of manganese

A series of mononuclear Mn(II), Mn(III), and Mn(IV) complexes was prepared using a single tripodal ligand (H(3)L). Addition of a cation (NH(4)(+), K(+), Na(+)) to [Mn(III)L] showed a pronounced effect on the redox potentials. Different variants of Jahn-Teller distortion, axial elongation and compression, were observed in the Mn(III) complexes.

Mononuclear nickel(II) and zinc(II) complexes with deprotonated forms of the tripodal hexadentate ligand 1,3-bis(2-hydroxybenzylidene)-2-(2-hydroxybenzylideneaminomethyl)-2-methylpropane-1,3-diamine.

In the crystal structures of both title compounds, [1,3-bis(2-hydroxybenzylidene)-2-methyl-2-(2-oxidobenzylideneaminomethyl)propane-1,3-diamine]nickel(II) [2-(2-hydroxybenzylideneaminomethyl)-2-methyl-1,3-bis(2-oxidobenzylidene)propane-1,3-diamine]nickel(II) chloride methanol disolvate, [Ni(C(26)H(25.5)N(3)O(3))](2)Cl x 2 CH(4)O, and [1,3-bis(2-hydroxybenzylidene)-2-methyl-2-(2-oxidobenzylideneaminomethyl)propane-1,3-diamine]zinc(II) perchlorate [2-(2-hydroxybenzylideneaminomethyl)-2-methyl-1,3-bis(2-oxidobenzylidene)propane-1,3-diamine]zinc(II) methanol trisolvate, [Zn(C(26)H(25)N(3)O(3))]ClO(4) x [Zn(C(26)H(26)N(3)O(3))] x 3 CH(4)O, the 3d metal ion is in an approximately octahedral environment composed of three facially coordinated imine N atoms and three phenol O atoms. The two mononuclear units are linked by three phenol-phenolate O-H...O hydrogen bonds to form a dimeric structure. In the Ni compound, the asymmetric unit consists of one mononuclear unit, one-half of a chloride anion and a methanol solvent molecule. In the O-H...O hydrogen bonds, two H atoms are located near the centre of O...O and one H atom is disordered over two positions. The Ni(II) compound is thus formulated as [Ni(H(1.5)L)](2)Cl x 2 CH(3)OH [H(3)L is 1,3-bis(2-hydroxybenzylidene)-2-(2-hydroxybenzylideneaminomethyl)-2-methylpropane-1,3-diamine]. In the analogous Zn(II) compound, the asymmetric unit consists of two crystallographically independent mononuclear units, one perchlorate anion and three methanol solvent molecules. The mode of hydrogen bonding connecting the two mononuclear units is slightly different, and the formula can be written as [Zn(H(2)L)]ClO(4) x [Zn(HL)] x 3 CH(3)OH. In both compounds, each mononuclear unit is chiral with either a Delta or a Lambda configuration because of the screw coordination arrangement of the achiral tripodal ligand around the 3d metal ion. In the dimeric structure, molecules with Delta-Delta and Lambda-Lambda pairs co-exist in the crystal structure to form a racemic crystal. A notable difference is observed between the M-O(phenol) and M-O(phenolate) bond lengths, the former being longer than the latter. In addition, as the ionic radius of the metal ion decreases, the M-O and M-N bond distances decrease.