Satoshi Takamizawa

Synthesis and gas-occlusion properties of dinuclear molybdenum(II) dicarboxylates (fumarate, terephthalate, trans-trans-muconate, pyridine-2,5-dicarboxylate, and trans-1,4-cyclohexanedicarboxylate)

The bis-μ-dicarboxylate molybdenum(II) complexes Mo(II)2L2 (L = trans-O2C-CH-CH-CO2 (1), p-O2C-C6H4-CO2 (2), trans-trans-O2C-CH-CH-CH-CH-CO2 (3), 2,5-O2C-C5H3N-CO2 (4), and trans-O2C-C6H10-CO2 (5)) were prepared and their gas-occlusion properties were characterized. The dinuclear complexes have quadruple Mo-Mo bonds, with the ground electronic configuration (σ)2(π)4(δ)2. All of these complexes are capable of occluding a large amount of gas (1 or 2 mol of N2 gas per 1 mol of molybdenum atoms). Investigation of the structures of these complexes indicates that gases are most probably occluded in homogeneous and linear micropores which are composed of micropore units surrounded by four dicarboxylate bridges. 13C-CP/MAS NMR measurements indicate that gas molecules are held in the micropores created by the dicarboxylate ligands.

Magnetic properties of oxygen physisorbed in Cu-trans-1,4-cyclohexanedicarboxylic acid

Abstract Magnetic properties of oxygen physisorbed in Cu-trans-1,4-cyclohexanedicarboxylic acid having one-dimensional micropores are studied. O2 is well known as a magnetic molecule with S=1. In the case of the low adsorption, temperature dependence of the susceptibility shows the Schottky-type broad peak and the high-field magnetization process has a step at around 34T with saturation moment of 2 μ B/O2. These results are interpreted by the dimer model of S=½ with an antiferromagnetic exchange interaction. Broadening of the step of magnetization with increasing the adsorption may be due to the inter-dimer interaction or the distribution of the intra-dimer exchange interaction. Linear magnetization process which is characteristic of one-dimensional Heisenberg antiferromagnet has not been observed even in the full pore region.

The gas-occlusion properties of dicarboxylate (fumarate, trans-trans-muconate and terephthalate) ruthenium(II,III) dinuclear complexes

Abstract The gas-occlusion properties of some ruthenium(II,III) dicarboxylate derivatives are reported.

Theoretical studies of spin arrangement of adsorbed organic radicals in metal-organic nanoporous cavity

Abstract The adsorption properties in nanoporous crystals of a metal-organic framework were studied theoretically. The Zn3(BDC)3·6CH3OH (BDC=1,4-benzenedicarboxylate) crystal was mainly treated as a stable metal-organic assembled species, which was reported by O.M. Yaghi and co-workers. Its crystalline structure very much resembles several crystals that have been reported by W. Mori et al. For adsorbed molecules, N2, CO2, Ar and H2 for nonmagnetic species and O2 for magnetic radical species were treated. The following systematic procedures were carried out: (1) decision of parameters for MC simulations; (2) execute MC simulation; (3) search of configuration of O2 molecules by MM method; and (4) study of magnetic interactions by means of ab initio HF, post-HF and DFT methods. Finally, magnetic interactions between O2 pairs exist and this cooperation might run in the nanoporous cavity.

Synthesis and Gas-Occlusion Properties of Ruthenium(II,III) Dicarboxylates (Fumarate, trans-trans-Muconate and Terephthalate) Bridged by Halogen Atoms

Abstract The bis-μ-dicarboxylate ruthenium (II,III) complexes, Ru (II,III)2L2Br (L=trans-O2C-CH═CH-CO2 (1), trans-trans-O2C-CH═CH-CH═CH-CO2 (2), and p-O2C-C6H4-CO2 (3)), were prepared and their gas-occlusion properties were measured. The effective magnetic moments at room temperature are in the range 3.76 and 4.02 BM per dinuclear, consistent with the values of Ru(II)-Ru(III) compounds. All these complexes are capable of occluding a large amount of gas. The maximum amounts of occluded nitrogen for 1-3 are 0.6, 0.9, and 1.4 moles per one mole of ruthenium atoms, respectively. These amounts are almost the same as those of the correspondent chloride complexes. This suggests that bromide complexes 1-3 would form a highly similar capillary structure to that of ruthenium (II,III) dicarboxylate bridged by chloride atoms.

Synthesis, structure and characterization of dinuclear nickel(II) complexes containing the derivatives of N,N,N′,N′-tetrakis- [(2-benzimidazolyl)methyl]-2-hydroxy-1,3-diaminopropane and an acetate or a propionate ion

The dinuclear nickel(II) complexes [Ni 2 (L 1 )(OAc)(H 2 O) 2 ](ClO 4 ) 2 ·3H 2 O ( 1 ), [Ni 2 (L 2 )(OAc)(H 2 O) 2 ](ClO 4 ) 2 ( 2 ) and [Ni 2 (L 2 )(OPr)(H 2 O) 2 ](ClO 4 ) 2 ·H 2 O ( 3 ) (HL 1 = N,N,N′,N′ -tetrakis[(1-methyl-2-benzimidazolyl)methyl]-2-hydroxy-1,3-diaminopropane, HL 2 = N,N,N′,N′ -tetrakis[(1-ethyl-2-benzimidazolyl)methyl]-2-hydroxy-1,3-diaminopropane, OPr = propionate anion) were synthesized and characterized. The crystal structures of [Ni 2 (L 2 )(OAc)(CH 3 OH) 2 ](ClO 4 ) 2 ·CH 3 OH·H 2 O ( 2 ′) and [Ni 2 (L 2 )(OPr)(CH 3 OH) 2 ](ClO 4 ) 2 ·CH 3 OH·2H 2 O ( 3 ′), which become 2 and 3 upon exposure of 2 ′ and 3 ′ to air, respectively, were determined by X-ray diffraction. 2 ′ and 3 ′ are isostructural. They consist of dinuclear cations and uncoordinated perchlorate ions. In the complex cations, the two nickel(II) centers are in a distorted octahedral coordination with an alkoxo and an acetato or a propionato bridge. The distances between the two nickel(II) ions are 3.521(2) and 3.507(2) A for 2 ′ and 3 ′, respectively. Variable temperature magnetic susceptibility measurements of 2 and 3 show an antiferromagnetic exchange coupling (2 J = −43.2 cm −1 for 2 , and 2 J = −34.4 cm −1 for 3 , H = −2 JS 1 · S 2 ) between two nickel(II) ions.

Theoretical study of the antiferromagnetic model clusters for K2MX4 type solids

Abstract Magnetic properties for the K2MX4 type solids (M=Cu2+, Ni2+ X=F−, O2−. Cl−) were investigated by the ab initio calculations using UHF and the hybrid Density Functional methods (B2VWN, S2VWN and UB3LYP). It was found that these type solids had the antiferromagnetic interactions.

MOLECULAR DESIGN AND SYNTHESIS OF FERRO- AND FERRI-MAGNETIC INORGANIC POLYMERS AND COMPLEXES WITH TETRATHIOLATE LIGANDS

Abstract The orbital-symmetry rules for superexchange couplings of unpaired electrons via ligands were applied to one-dimensional (ID) polymers composed of heteropoly transition-metal tetrathiolates (poly(M1TM2), T: tetrathiolate). The polymers composed of the Cu(II)-Fe(I?)(LS) and Ni(II)(HS)-Fe(III)(LS) units are predicted to be ferromagnetic within ID chains, whereas several polymers such as the Co(II)(HS)-Cu(II) alternating one are considered to be ferrimagnetic. Ferromagnetic metals, dense Kondo and spin-mediated superconductors composed of trinuclear M2TM1TM2 complexes (M1═Ni) are also designed on the basis of the theoretical results. According to these guiding principles, we have performed the synthesis of ferro-and ferrimagnetic polymers composed of heteropoly transition-metal tetrathiolates (poly(M1TM2), T: tetrathiolate). The magnetic measurements of the solids were also carried out and the observed intrachain effective exchange integrals are summarized.

Theoretical Studies on Radical Spin Arrangements in the Cavity of Nanoporous Complexes

Abstract Adsorption properties in nanoporous crystals, especially Zn(BDC) (BDC=1.4-benzenedicar-boxylate) crystal, were studied theoretically. For sorbed molecules N2 and CO2 were employed and gas adsorption isotherms were obtained. In addition, O2 as S=1 magnetic radical species was also treated in order to study the magnetic properties. Magnetic interaction between O2 pairs exists and these cooperation might run in the nanoporous cavity. These results lead new approach to arrangement of organic spin radical sources and it is found that nanoporous organic-metal crystals are useful for controlling their position and orientation.

Ab Initio mo Calculations of Superexchange Integrals For Transition-Metal Fluorides: MFM3+ (M=Cu(?), Ni(II) and Mn(II)). Active Control of the Magnetic States

Abstract Ab initio UMP calculations were carried out for binuclear transition- metal fluorides in order to elucidate variations of the superexchange integrals with intermetallic distances. It was shown that the antiferromagnetic superexchange integrals calculated for tricentric systems MFM+3 (M=divalent ions) by the approximately spin-projected UMPn (n= 1–4) method with the triple zeta basis set are about −134, −22 and −1 cm−1 in the cases of Cu(?), Ni(II) and Mn(II), respectively. These are consistent with the experimental results available. The hole-or electron doping into antiferromagnetic systems is also discussed in relation to previous proposals to obtain the switching type molecular magnets controlled by thermal, photochemical, electrochemical and other techniques.