Yoshimi Oka

Hydrothermal synthesis, crystal structure and characterization of a new hexanuclear cobalt(II) complex comprised of octahedral and tetrahedral cobalt ions

Abstract Reaction of Co(II) with phenylcinnamic acid and sodium hydroxide under hydrothermal conditions yields a new hexanuclear Co(II) complex, [Co6(OH)2(L)10] (L=phenylcinnamate). [Co6(OH)2(L)10] consists of two edge-sharing octahedral {CoO6} and four tetrahedral {CoO4} units linked through μ-carboxylate ligands and μ-hydroxide ions. The magnetic moment shows a large decrease from 300 to 25 K which amounts to antiferromagnetic coupling between cobalt ions in octahedral and tetrahedral sites leading to an s=3 ground-state at low temperatures.

Structure of Silver(I) Complex Prepared from Azobenzenonaphthalenophane, Photochemical Coordination Change of Silver(I) and Silver(I)-Induced Acceleration of Z―E Thermal Isomerization of Azobenzene Unit

A Ag(I) complex was prepared from azobenzenonaphthalenophane as a photoreactive multidentate ligand. The coordination of Ag(I) was reversibly controlled by photoisomerization of the azobenzene unit, and at the same time, Ag(I) accelerated the Z-E thermal isomerization of the azobenzene unit.

Hydrothermal synthesis and characterization of a two-dimensional nickel(II) complex containing benzenehexacarboxylic acid (mellitic acid)

Abstract The hydrothermal synthesis, single crystal X-ray structure and magnetic properties of a two-dimensional (2-D) coordination polymer, [Ni 4 (C 6 (COO) 6 )(OH) 2 (H 2 O) 6 ] ( 1 ), is described. Complex 1 consists of dimer motifs of pseudo octahedral NiO 6 linked through μ3-OH to generate one-dimensional (1-D) chains which are further bridged by the mellitate ligands to form non interpenetrated undulating sheet structure. The sheets are further connected by hydrogen bonding interaction to yield a three-dimensional (3-D) structure. The temperature dependence of magnetic susceptibilities revealed the presence of antiferromagnetic interaction between nickel centers.

Long-range magnetic ordering at 5.5 K for cobalt(II)-hydroxide diamond chains isolated by 17 Å with α-phenylcinnamate.

[Co(4)(phcina)(6)(OH)(2)(H(2)O)(4)]·2H(2)O (1) (phcina = α-phenylcinnamate), obtained as pink needles by hydrothermal technique, consists of two edge-sharing pairs of octahedral CoO(6) connected by their apexes to form diamond-chains. The magnetic chains are isolated from one another without chemical bond at 17 Å by the nonmagnetic bulky organic ligand. It exhibits hidden canting below the long-range antiferromagnetic (AF) ordering at 5.5 K. A metamagnetic critical field of only 30 Oe at 2 K suffices to overcome the weak through space magnetic interaction between chains and reverse the moments within the chains to give a canted AF reaching only (1)/(4) of the required moment for all parallel moment alignment. The anisotropy measured on aligned crystals, using dc and ac modes, estimates g(||b) = 6.5 and g(⊥b) = 3.25, thus eliminating an Ising or a Heisenberg magnetic dimensionality while suggesting an easy-plane AF. Weak frequency dependence of the ac-susceptibilities below the transition temperature is associated with domain structure in the ordered state, and absence of it well above T(N) eliminates single-chain magnetism. It is inferred that the competition between the strong AF coupling between the edge-sharing pairs, which dominates the high temperature susceptibility, and the ferromagnetic coupling within the pairs, results in a canting of the moments within each chain, where the moments are out of the ac-plane by an estimated 13°. In zero-field the moments of adjacent chains are antiparallel resulting in a compensated system, i.e., hidden canting.

Hydrothermal synthesis, structure and magnetism of square-grid cobalt(II)-carboxylate layered compounds with and without pillars

The hydrothermal synthesis, single crystal X-ray structures and magnetic properties of two layered cobalt(II)-carboxylate complexes, 2∞[CoII(H2O)2(O2CCHCHC6H5)2] (1) and 2∞[CoII(H2O)2(O2CCHCHC6H4CO2)2/2] (2), are described. Pale red crystals of Co(H2O)2L2, L = trans-cinnamate (C9H7O2−) (1) or L2 = 4-carboxycinnamate (C10H6O42−) (2), were obtained at 120 °C. The structures consist of square-grid 2D-coordination polymeric sheets, ⋯–OCO–Co(H2O)2–OCO–Co(H2O)2–⋯, separated by C6H5–CHCH– for (1) or pillared by –C6H4–CHCH– for (2). The magnetism was studied as a function of temperature and magnetic field. In both cases the magnetic moment decreases on lowering the temperature due to spin–orbit coupling and no interaction between cobalt ions. The data can alternatively be fitted to an unrealistic quadratic layer model for S = 3/2 without taking into account the effect of spin–orbit.

Hydrothermal synthesis and characterization of a two-dimensional cobalt (II) complex containing cinnamate anion

Synthesis, structure and magnetic properties of the hydrothermal reaction product of cobalt (II) ion and the mono-carboxylic acid, trans -cinnamic acid, (cina) are described. The 2-D coordination polymer, [Co(cina) 2 (H 2 O) 2 ] n , consists of square-grid layers with O-C-O bridging the cobalt atoms sandwich by m CHCHC 6 H 5 in the galleries. The temperature dependence of the magnetic moment revealed a lowering at low temperatures due to the presence of spin orbit coupling. cobalt cinnamic acid hydrothermal layered

Hydrothermal Synthesis and Structural and Magnetic Characterization of the Coordination Bonding Network Co II (H 2 O) 2 carboxy-cinnamate

The hydrothermal synthesis, single crystal X-ray structure and magnetic properties of a new cobalt(II)-carboxy-cinnamate complex is described. Reaction of Co(II), Carboxy-cinnamic acid (C 10 H 8 O 4 ) and NaOH at 120C yield the coordination network, Co(H 2 O) 2 carboxy-cinnamate ( 1 ). 1 crystallizes in the monoclinic system, a =11.3236(4), b =6.6084(4), c =7.2011(6) Å, g =101.948(5), V =527.2(1) Å 3 , space group P 2 1 /c, Z =2. 1 possesses a three-dimensional coordination-bonding network consisting of layers of CoO 6 bridged by the tetra-dendate carboxy-cinnamate. Its magnetic moment decreases on lowering temperature due to spin-orbit coupling and no interaction between cobalt ions is observed. carboxylate cobalt coordination polymer magnetic properties

Fluorescence Imaging of Disrupted Interfaces between Liquid-Ordered and Liquid-Disordered Domains by a Flavin-Labeled PNA Duplex

Lipid rafts and membrane-active peptides are attracting attention because they help understand basic membrane functions. In addition, we focus on flavoproteins playing some physiological roles and explore the model compounds. In this study, we demonstrate that a new flavin probe, composed of palmitoylated peptide nucleic acid (PNA) and its complementary PNA labeled with flavin, targets the liquid-ordered (lo) microdomains and disrupts its interfaces to liquid-disordered (ld) microdomains of giant unilamellar vesicles and can be visualized by using confocal laser scanning microscopy. Surprisingly, as shown in time-lapse images, vesiculation and probe aggregations appear in the lo–ld interfaces, which leads to local disruption of the membrane. We discuss a possible interpretation of the data based on a comparison with control experiments.