Masaru Kato

Molecular structure and electrochemical behavior of uranyl(VI) complex with pentadentate Schiff base ligand: prevention of uranyl(V) cation-cation interaction by fully chelating equatorial coordination sites.

The U(VI) complex with a pentadentate Schiff base ligand (N,N-disalicylidenediethylenetriaminate = saldien(2-)) was prepared as a starting material of a potentially stable U(V) complex without any possibility of U(V)O(2)(+)...U(V)O(2)(+) cation-cation interaction and was found in three different crystal phases. Two of them had the same composition of U(VI)O(2)(saldien) x DMSO in orthorhombic and monoclinic systems (DMSO = dimethyl sulfoxide, 1a and 1c, respectively). The DMSO molecule in both 1a and 1c does not show any coordination to U(VI)O(2)(saldien), but it is just present as a solvent in the crystal structures. The other isolated crystals consisted only of U(VI)O(2)(saldien) without incorporation of solvent molecules (1b, orthorhombic). A different conformation of the coordinated saldien(2-) in 1c from those in 1a and 1b was observed. The conformers exchange each other in a solution through a flipping motion of the phenyl rings. The pentagonal equatorial coordination of U(VI)O(2)(saldien) remains unchanged even in strongly Lewis-basic solvents, DMSO and N,N-dimethylformamide. Cyclic voltammetry of U(VI)O(2)(saldien) in DMSO showed a quasireversible redox reaction without any successive reactions. The electron stoichiometry determined by the UV-vis-NIR spectroelectrochemical technique is close to 1, indicating that the reduction product of U(VI)O(2)(saldien) is [U(V)O(2)(saldien)](-), which is stable in DMSO. The standard redox potential of [U(V)O(2)(saldien)](-)/U(VI)O(2)(saldien) in DMSO is -1.584 V vs Fc/Fc(+). This U(V) complex shows the characteristic absorption bands due to f-f transitions in its 5f(1) configuration and charge-transfer from the axial oxygen to U(5+).

Anion influence on the coordination polymer structures of silver(I) complexes with 2-methylisothiazol-3(2H)-one

Silver(I) coordination polymers formed by self-assembly of ambidentate ligands, 2-methylisothiazol-3(2H)-one (MI) and 5-chloro-2-methylisothiazol-3(2H)-one (CMI), have been characterized by single crystal X-ray analysis. The structure of the cation in [AgI(μ-O-mi)2]X (X ClO4− (1); SbF6− (2)) is a one-dimensional chain while that in the nitrate salt, [AgI2(μ-O-mi)](NO3)2 (3), is a three-dimensional network. A silver(I) complex with CMI, [AgI(μ-O-cmi)2]ClO4 (4), has also been synthesized and the cation has a one-dimensional chain structure. Although both MI and CMI have both O- and S-donor moieties, the oxygen atom dominantly coordinates to the silver(I) centre. The anion influence on the chain structure is attributed to the competition for the coordination ability between anions and MI, and the flexibility of the coordination sphere of d10silver(I) ion.

(-)(545)-fac-Δ-Tris(l-prolinato)cobalt(III) trihydrate.

The absolute configuration of the octahedral fac-CoN3O3 title complex, [Co(C5H8NO2)3]·3H2O, has been determined by single-crystal X-ray analysis. A three-dimensional network of hydrogen bonds is observed between the proline carboxylate groups and the three uncoordinated water molecules.

Preferential behavior on donating atoms of an ambidentate ligand 2-methylisothiazol-3(2H)-one in its metal complexes.

Five metal complexes of 2-methylisothiazol-3(2H)-one (MIO), [Co(III)(NH3)5(MIO)](3+), [Ru(II)(NH3)5(MIO)](2+), [Ru(III)(NH3)5(MIO)](3+), [Pt(II)Cl3(MIO)](-), and trans-[U(VI)O2(NO3)2(MIO)2], were synthesized, and their structures were determined by single-crystal X-ray crystallography. MIO is an ambidentate ligand and coordinates to metal centers through its oxygen atom in the cobalt(III), ruthenium(III), and uranium(VI) complexes and through its sulfur atom in the ruthenium(II) and platinum(III) complexes. This result suggests that MIO shows preferential behavior on its donating atoms. We also studied the electron-donor abilities of the oxygen and sulfur atoms of MIO. Various physical measurements on the conjugate acid of MIO and the MIO complexes allowed us to determine an acid dissociation constant (pKa) and donor number (DN) for the oxygen atom of MIO and Levers electrochemical parameter (EL) and a relative covalency parameter (kL) for the sulfur atom.

Structural and electrochemical studies on uranyl(VI) complex with pentadentate Schiff base ligand: A guide to stable uranyl(V)

A U(VI) complex with N,N-disalicylidenediethylenetriaminate (saldien2-) was characterized by single crystal X-ray analysis and X-ray absorption fine structure (XAFS) spectroscopy, and its electrochemical behavior in a DMSO solution was studied. The obtained U(VI)-saldien2- complex recrystallized from DMSO was identified as orthorhombic UVIO2(saldien)?DMSO. All coordination sites in the equatorial plane of UO22+ are occupied by coordinating O and N atoms of saldien2-. Comparing a k3-weighted U LIII-edge EXAFS spectra of UVIO2(saldien) in DMSO and DMF solutions with that in solid state, the molecular structure of UVIO2(saldien) remains even in the solutions. Quasi-reversible redox waves of UVIO2(saldien) were observed at E? = -1.582 ? 0.005 V vs. Fc/Fc+ (?Ep = 0.080-0.170 V at v = 0.010-0.500 V?s?1) in DMSO. UV-Vis-NIR absorption spectral change with the electrochemical reduction of UVIO2(saldien) using the spectroelectrochemical technique shows isosbestic points clearly, indicating that the electrochemical reaction of UVIO2(saldien) is only present. Using the absorbance change and the Nernstian equation, the electron stoichiometry in the reduction of UVIO2(saldien) in DMSO was determined as 0.929. This quantity close to unity reveals a redox reaction, UVIO2(saldien) + e? = [UVO2(saldien)]?, i.e., UVIO2(saldien) without unidentate ligands results in the stable U(V) complex, [UVO2(saldien)]?, in DMSO. This U(V) species also shows the characteristic absorption bands of U(V) at 630, 700, 830, 1390, and 1890 nm as well as other U(V) complexes.

3-Hydr­oxy-2-methyl­isothia­zolium chloride monohydrate: an inter­molecular three-dimensional network via O—H⋯O and O—H⋯Cl hydrogen bonds

The title compound, C4H6ClNOS·H2O, has a planar five-membered ring, with a delocalized positive charge. A three-dimensional network is formed through interxadmolecular O—H⋯O and O—H⋯Cl hydrogen bonds between 3-hydrxadoxy-2-methylxadisothiaxadzolium cations and water molxadecules, and between water molxadecules and chloride anions.

Tetra-n-propyl­ammonium perchlorate

The crystallographic analysis of the title compound, C12H28N+·ClO4−, (I), shows that interxadmolecular C—H⋯O interxadactions stabilize the crystal structure. The compound is isomorphous with tetra-n-propylxadammonium iodide, whose structure has been described by Yoshida et al. [Acta Cryst. (1994). C50, 1758–1760].

5‐Chloro‐2‐methylisothiazolin‐3‐one: intermolecular two‐dimensional networks via unusual C—Cl...O=C interactions

The title molxadecule, C4H4ClNOS, contains an essentially planar five-membered ring. The C xa0C(=O) bond is slightly longer than expected. In the crystal structure, two-dimensional networks are formed through interxadmolecular C—Cl⋯O=C interxadactions [Cl⋯O = 2.9811u2005(19)u2005A].