Masanobu Tsuchimoto

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.

Crystal field splitting of the ground state of terbium(III) and dysprosium(III) complexes with a triimidazolyl tripod ligand and an acetate determined by magnetic analysis and luminescence.

Terbium(III) and dysprosium(III) complexes with a tripodal N7 ligand containing three imidazoles (H3L) and a bidentate acetate ion (OAc(-)), [Ln(III)(H3L)(OAc)](ClO4)2·MeOH·H2O (Ln = Tb, 1; Ln = Dy, 2), were synthesized and studied, where H3L = tris[2-(((imidazol-4-yl)methylidene)amino)ethyl]amine. The Tb(III) and Dy(III) complexes have an isomorphous structure, and each Tb(III) or Dy(III) ion is coordinated by the tripodal N7 and the bidentate acetate ligands, resulting in a nonacoordinated capped-square-antiprismatic geometry. The magnetic data, including temperature dependence of the magnetic susceptibilities and field dependence of the magnetization, were analyzed by a spin Hamiltonian, including the crystal field effect on the Tb(III) ion (4f(8), J = 6, S = 3, L = 3, g(J) = 3/2, (7)F6) and the Dy(III) ion (4f(9), J = 15/2, S = 5/2, L = 5, g(J) = 4/3, (6)H(15/2)). The Stark splittings of the ground states (7)F6 of the Tb(III) ion and (6)H(15/2) of the Dy(III) ion were evaluated from the magnetic analyses, and the energy diagram patterns indicated an easy axis (Ising type) anisotropy for both complexes, which is more pronounced for 2. The solid-state emission spectra of both complexes displayed sharp bands corresponding to the f-f transitions, and the fine structures assignable to the (5)D4 → (7)F6 transition for 1 and the (6)F(9/2) → (6)H(15/2) transition for 2 were related to the energy diagram patterns from the magnetic analyses. 1 and 2 showed an out-of-phase signal with frequency dependence in alternating current (ac) susceptibility under a dc bias field of 1000 Oe, indicative of a field-induced SIM.

Monomeric and polymeric structures of oxovanadium(IV) complexes with Schiff base ligands derived from (R,R)-2,4-pentanediamine: Synthesis and crystal structure

Abstract New tetradentate Schiff base–oxovanadium(IV) complexes which have electron donating or withdrawing groups at the 5-position of the salicylaldehyde moieties, [VO{Xsal-(R,R)-2,4-ptn}] (H2{Xsal-(R,R)-2,4-ptn}: N,N′-di-Xsalicylidene-(R,R)-2,4-pentanediamine; X=5-MeO (methoxy), 5-Br, and 5-NO2) were prepared. The structures and redox potentials for the V(V)/V(IV) couple of the complexes were compared with those of other [VO{Xsal-(R,R)-2,4-ptn}] (X=3-EtO (ethoxy), 3-MeO, and H). The 5-MeO substituted complex which has electron donating groups at the 5-position of the salicylaldehyde moieties forms a monomeric structure in the solid state. The 3-EtO substituted complex has both monomeric and polymeric structures. On the other hand, the other [VO{Xsal-(R,R)-2,4-ptn}] (X=H, 3-MeO, 5-Br, 5-NO2) complexes have only polymeric structures. X-ray crystal structure analysis of [VO{5-MeOsal-(R,R)-2,4-ptn}]⋅CH3OH (1) was carried out. Complex 1 has a monomeric five-coordinate square–pyramidal structure. The six-membered N–N chelate ring forms a distorted flattened boat form with two methyl groups in the axial positions.

endo-{6,6′-Diethoxy-2,2′-[(R)-propane-1,2- diylbis(nitrilomethylidene)]diphenolato-O,N,N′,O′}oxovanadium(IV)

In the title mononuclear oxovanadium(IV) complex, [VO(C 21 H 24 N 2 O 4 )], the methyl group of the central diamine moiety in the Schiff base ligand is directed opposite to the oxo ligand. This endo isomer elutes more slowly than the exo isomer when subjected to high-performance liquid reversed-phase chromatography using CH 3 CN-H 2 O (1:1 v/v) as the eluent. Crystals of both the endo and exo isomers decompose at 473 K, with no solid-state isomerization from endo to exo or vice versa.

Theoretical study of magnetic properties of oxovanadium(IV) complex self-assemblies with tetradentate Schiff base ligands.

The theoretical study of the magnetic properties of oxovanadium(IV) complex self-assemblies with tetradentate Schiff base ligands is discussed on the basis of DFT calculations. Large negative spin densities are found on the axial oxygens of the various oxovanadium(IV) complexes. The relationship between the effective exchange parameters J(ab) and the geometrical parameters for these complexes was studied by changing the position of the neighboring molecules for the purpose of clarifying the mechanism of the ferromagnetic coupling. The intermolecular ferromagnetic interaction of the oxovanadium(IV) complexes with tetradentate Schiff base ligands is significantly affected by the formation of polymeric octahedral structures in the solid state. The overlap between the 2p orbitals of the axial oxygen and the 3d orbitals of the adjacent vanadium is effective for the ferromagnetic coupling. On the other hand, the effect of overlap between the vanadium 3d(xy) orbitals is too small to lead to magnetic coupling. It was revealed that the intermolecular ferromagnetic interaction of the polynuclear oxovanadium(IV) complexes is significantly affected by the spin polarization on the axial oxygen.

[N,N′-Bis(3-carboxy­salicyl­idene)-1,2-di­phenyl-(RR,SS)-1,2-ethanediyl­diaminato-O,N,N′,O′]­(methanol-O)oxovanadium(IV) and [N,N′-bis(3-carboxy­salicyl­idene)-2,3-di­methyl-2,3-butanediyl­diaminato-O,N,N′,O′]oxo­vanadium(IV) mono­hydrate

The two title mononuclear oxovanadium (IV) complexes, [VO(C30H22N2O6)(CH3OH)] and [VO(C22H22N2O6)]·H2O, respectively, have distorted square-pyramidal coordination and the 3-carboxy groups form intramolecular hydrogen bonds with the coordinated salicyl O atoms. In (I), methanol coordinates to the vanadium atom trans with respect to the oxo ligand.

exo-[N,N′-Bis(3-tert-butyl­salicyl­idene)-1,2-di­phenyl-(RS,SR)-1,2-ethane­diyl­diaminato]­oxovanadium(IV)

The title mononuclear oxovanadium(IV) complex, [VO(C(36)H(38)N(2)O(2))], has a distorted square-pyramidal coordination. The complex was shown to be the exo isomer.

[1,2-Di­phenyl-N,N′-bis­(salicyl­idene)-(RR,SS)-1,2-ethane­diyl­diamin­ato]­nitrido­manganese(V)

The title compound, [MnN(C28H22N2O2)], has a distorted square-pyramidal coordination with an Mn≡N bond length of 1.516 (2) A at the apical position. The five-membered chelate ring adopts a gauche conformation with the two phenyl groups in equatorial orientations.

[N,N'-Bis(5-methoxysalicylidene)-1,2-diphenyl-1,2-ethenediamine]oxovanadium(IV)

The title complex, [VO(C 30 H 24 N 2 O 4 )], adopts a monomeric structure in the crystals, which are red due to the charge-transfer band from the conjugated π-system of the tetradentate Schiff base ligand. The geometry around the V IV atom is distorted square pyramidal. The V=O distance is 1.588 (3) A, and the V atom is displaced by 0.57 (1) A from the N 2 O 2 coordination plane towards the apical oxo ligand.

Redetermination of 2,3-dichloro-5,6-dicyano-1,4-dihydroxybenzene

The crystal structure of the title compound, C 8 H 2 Cl 2 N 2 O 2 , was reported recently [Reddy, Ovchinnikov, Shishkin, Struchkov & Desiraju (1996). J. Am. Chem. Soc. 118, 4085-4089]. However, the space group has been corrected from Pna2 1 to Pnma in the present study. The molecule lies on a mirror plane perpendicular to b.