Koji Kubono

Ion-pair extraction behavior of divalent transition metal cations as charged complexes with N,N′-bis(2-pyridylmethylidene)-1,2-diiminoethane and its analogues

The use of neutral di-Schiff base ligands, N,N′-bis(2-pyridylmethylidene)-1,2-diiminoethane (BPIE) and its analogues, N,N′-bis[1-(2-pyridyl)ethylidene]-1,2-diiminoethane (BPEE) and N,N′-bis(2-pyridylmethylidene)-trans-1,2-diiminocyclohexane (BPIC), as complexation reagents for ion-pair extraction of divalent transition metal cations into nitrobenzene with picrate anion was investigated. The results of numerical analysis concerning the extraction behavior indicated that they act as imine-N bidentate ligands in the extraction system. Furthermore, the introduction of the alkyl substituents onto imine-C on BPIE led to the change in the extraction selectivity by steric distortion of the cationic complexes, whereas that onto ethylene-C only caused the enhancement of the extractability.

Photoinduced Color Change and Photomechanical Effect of Naphthalene Diimides Bearing Alkylamine Moieties in the Solid State

Photoinduced color change of naphthalene diimides (NDIs) bearing alkylamine moieties has been observed in the solid state. The color change is attributed to the generation of a NDI radical-anion species, which may be formed through a photoinduced electron-transfer process from the alkylamine moiety to the NDI. The photosensitivity of NDIs is highly dependent on the structures of the alkylamine moieties. Crystallographic analysis, kinetic analysis, UV/Vis/NIR spectroscopic measurements, and analysis of the photoproduct suggested that a radical anion was formed through an irreversible process initiated by proton abstraction between an amine radical cation and the neutral amine moiety. The radical anions formed stacks including mixed-valence stacks and radical-anion stacks, as shown by the broad absorption bands in near-IR spectra. These photosensitive NDIs also showed crystal bending upon photoirradiation, which may be associated with a change in the intermolecular distance of the NDI stacks by the formation of monomeric radical anions, mixed-valence stacks, and radical-anion stacks.

Selective extraction of gallium from aluminum and indium using tripod phenolic ligands

Solvent extraction of trivalent group 13 metal cations such as aluminum, gallium and indium with tripod quadridentate phenolic ligand, tris(2-hydroxy-3,5-dimethylbenzyl)amine (H(3)tdmba), was investigated as fundamental study for their mutual separation. Gallium was extracted almost quantitatively as Ga(tdmba) (logK(ex)=-6.66+/-0.06 on using chloroform as extraction solvent), whereas aluminum and indium were hardly extracted due to steric hindrance on complexation of them with the ligand. The extracted Ga species was estimated as trigonal bipyramidal complex with one H(2)O molecule. Furthermore, extractability of Ga was increased by changing the ligand to more acidic tris(5-chloro-2-hydroxy-3-methylbenzyl)amine (H(3)tcmba) (logK(ex)=-6.18+/-0.18 on using dichloroethane as extraction solvent).

Ion-pair extraction behavior of transition metal(II) cations as charged complexes with ethylenediamine derivatives having heterocyclic pendant arms

Abstract The use of N , N , N ′, N ′-tetrakis(1′-pyrazolylmethyl)-1,2-diaminoethane (tpzen), N , N , N ′, N ′-tetrakis(3′,5′-dimethylpyrazol-1′-ylmethyl)-1, 2-diaminoethane (Me 8 tpzen) and N , N , N ′, N ′-tetrakis(2′-pyridylmethyl)-1,2-diaminoethane (tpen) as complexation reagents for ion-pair extraction of metal(II) cations into nitrobenzene was investigated. The order of extractability of the metals was tpen > Me 8 tpzen > tpen. Although these molecules have four nitrogen-containing heterocyclic pendant arms and act as sexadentate ligands normally in aqueous solution, the result of numerical analysis concerning the extraction behavior indicated that they act as bidentate ligands in the extraction system. The pendant arms were not concerned in chelate formation and the arms acted to raise the hydrophobicity and the extractability of the complexes.

Monoclinic and orthorhombic polymorphs of 4,4',6,6'-tetrachloro-2,2'-(piperazine-1,4-diyldimethylene)diphenol.

The title compound, C(18)H(18)Cl(4)N(2)O(2), crystallizes as monoclinic and orthorhombic polymorphs from CHCl3-CH(3)OH solution. In both polymorphic forms, the molecule lies on a crystallographic centre of inversion (at the piperazine ring centroid) and exhibits an intramolecular O-H...N hydrogen bond. In the monoclinic polymorph (space group P2(1)/c), the molecules are linked by intermolecular C-H...Cl hydrogen bonds into a ribbon sheet built from R8(8)(34) rings. In the orthorhombic polymorph (space group Pbcn), the molecules are linked by intermolecular C-H...O hydrogen bonds into a ribbon sheet of R6(6)(34) rings. The sheets in the orthorhombic polymorph are crosslinked into a three-dimensional framework by pi-pi stacking interactions.

Dynamical Excimer Formation in Rigid Carbazolophane via Charge Transfer State

Formation dynamics of intramolecular excimer in dioxa[3.3](3,6)carbazolophane (CzOCz) was studied by time-resolved spectroscopic methods and computational calculations. In the ground state, the most stable conformer in CzOCz is the anti-conformation where two carbazole rings are in antiparallel alignment. No other isomers were observed even after the solution was heated up to 150 °C, although three characteristic isomers were found by the molecular mechanics calculation: the first is the anti-conformer, the second is the syn-conformer where two carbazole rings are stacked in the same direction, and the third is the int-conformer where two carbazole rings are aligned in an edge-to-face geometry. Because of the anti-conformation, the interchromophoric interaction in CzOCz is negligible in the ground state. Nonetheless, the intramolecular excimer in CzOCz was dynamically formed in an acetonitrile (MeCN) solution, indicating strong interchromophoric interaction and the isomerization from the anti- to syn-conformation in the excited state. The excimer formation in CzOCz is more efficient in polar solvents than in less polar solvents, suggesting the contribution of the charge transfer (CT) state to the excimer formation. The stabilization in the excited state is discussed in terms of molecular orbital interaction between two carbazole rings. The solvent-polarity-induced excimer formation is discussed in terms of the CT character in the int-conformation.

Aqua­{4,4′,6,6′-tetra­fluoro-2,2′-[(piperazine-1,4-di­yl)dimethyl­ene]diphenolato}copper(II)

In the title compound, [Cu(C18H16F4N2O2)(H2O)], the CuII atom shows a distorted square-pyramidal coordination geometry with the N,N′,O,O′-tetradentate piperazine–diphenolate ligand forming the basal plane. The apical site is occupied by the O atom of a coordinated water molecule. Neighbouring complexes are associated through intermolecular O—H⋯O and O—H⋯F hydrogen bonds between the water molecule and a phenolate O atom or an F atom from an adjacent ligand, respectively, forming a centrosymmetric dimer. Dimers are linked by additional intermolecular C—H⋯O and C—H⋯F hydrogen bonds, giving infinite chains propagating along the a axis.

Bis[μ-4,4',6,6'-tetra-chloro-2,2'-(piperazine-1,4-diyldimethyl-ene)diphenolato]dicopper(II).

In the centrosymmetric dinuclear CuII title complex, [Cu2(C18H16Cl4N2O2)2], the CuII atom adopts a square-pyramidal geometry with a tetradentate ligand in the basal plane. The apical site is occupied by a phenolate O atom from an adjacent ligand, forming a dimer. The molecular structure is stabilized by intramolecular C—H⋯O and C—H⋯Cl hydrogen bonds.

A monoclinic polymorph of 4,4′-dichloro-2,2′-(piperazine-1,4-diyl­dimethyl­ene)diphenol

The titile compound, C18H20Cl2N2O2, crystallizes as a monoclinic form in the space group P21/n, with Z′ = 1/2. It is polymorphic with the previously reported orthorhombic form [Kubono, Tsuno, Tani & Yokoi (2008). Acta Cryst. E64, o2309]. In the present polymorph, the molecule lies on a crystallographic inversion centre at the piperazine ring centroid. An intramolecular O—H⋯N hydrogen bond forms an S(6) ring motif. Intermolecular C—H⋯O hydrogen bonding generates a C(5) chain motif propagating along the b axis, forming sheets parallel to (02) with a first-level graph set S(6)C(5)R 6 6(34).

4,4′-Dichloro-2,2′-(piperazine-1,4-diyldimethyl­ene)diphenol

In the titile compound, C18H20Cl2N2O2, the piperazine ring adopts a chair conformation. The molecule has a non-crystallographic inversion centre in the middle of the piperazine ring at approximate position (3/4, 1/8, 3/8). There are intramolecular O—H⋯N hydrogen bonds forming S(6) ring motifs. Intermolecular C—H⋯O hydrogen bonds generate antiparallel C(5) chain motifs propagating along the b axis, forming sheets parallel to the bc plane with a first-level graph-set S(6)C(5)R 6 6(26).