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Takahiro Kusukawa

Publications and source records attributed to Takahiro Kusukawa.

14 recordsLinked to original sources
PubMed2005

Endohedral clusterization of ten water molecules into a "molecular ice"within the hydrophobic pocket of a self-assembled cage.

An adamantanoid (H2O)10 cluster is formed within the hydrophobic cavity of a self-assembled coordination cage. This cluster is termed "molecular ice" because it is the smallest unit of naturally occurring Ic-type ice. X-ray structural analysis, coupled with neutron diffraction study, reveals that the molecular ice is formed not by a simple space-filling effect but by efficient molecular recognition within the cage via H2O:...pi interaction.

Journal Article↗
PubMed2003

Phenylenebis(ethynyl)-tethered bis-BINOL ligands for enantioselective catalyst based on dimeric TiIV aggregate.

Bis-BINOLs 7a-c in which two BINOL units are tethered by phenylenebis(ethynyl) groups react with titanium tetraisopropoxide (2 equiv) to form intramolecular dimeric titanium(IV) aggregates 2a-c. Of these, 2a,b with an o-phenylenebis(ethynyl) tether are stable in the presence of excess titanium tetraisopropoxide. Complex 2a exhibits a relatively high enantioselectivity in asymmetric addition of diethylzinc to an aldehyde. [structure: see text]

Journal Article↗
PubMed2002

Self-assembled M(6)L(4)-type coordination nanocage with 2,2'-bipyridine ancillary ligands. Facile crystallization and X-ray analysis of shape-selective enclathration of neutral guests in the cage.

Hollow and roughly spherical cage 1 (ca. 2 nm in diameter) is self-assembled from 2,4,6-tri(4-pyridyl)-1,3,5-triazine (2) and Pd(diamine)(ONO(2))(2) (3). This cage compound enclathrates a variety of neutral organic molecules in an aqueous phase. Unlike cage 1a, which possesses ancillary ethylenediamine ligands on the metal centers, 2,2'-bipyridine(bipy)-protected cage 1b is easily crystallized, making possible the detailed analysis of the enclathration geometry of guests by X-ray crystallographic study. It is found that guests are enclathrated in three different manners, depending upon the shape and the size of the guests: tetrahedral 1:4 complexation, orthogonal 1:2 complexation, and a simple 1:1 complexation. The solution structures elucidated by NMR are in good accordance with the solid structure, showing that the enclathration geometries in the solid state are kept even in solution.

Journal Article↗
PubMed2002

Electrochemically driven clathration/declathration of ferrocene and its derivatives by a nanometer-sized coordination cage.

The electrochemical, NMR, and crystallographic studies clearly indicate that the clathration and declathration of ferrocene and its derivatives in a self-assmbled Pd(II)-linked nanometer-sized cage can be controlled by the oxidation state of the guest. Namely, the guests are clathrated when they are reduced but declathrated when they are oxidized. The process is rapid on the NMR time scale but slow on the CV time scale.

Journal Article↗
PubMed2002

Synthesis of optically active trifluoromethylated indolizidine derivatives via stereoselective radical cyclization.

[reaction: see text]. Asymmetric Michael reaction of lithiated trifluoroacetone SAMP-hydrazone with alkylidenemalonates gave addition products stereoselectively. Hydrolyzed enantiomerically pure ketoacids were cyclized to dihydropyridinones. N-Iodopropylation followed by radical cyclization gave optically active trifluoromethylated indolizidinones stereoselectively.

Crystallography, X-Ray↗
PubMed2002

Multicomponent metal-ligand self-assembly.

Self-assembly of pre-designed organic ligands with transition metal atoms is a powerful method for construction of novel supramolecular architectures. Particularly, various discrete 3-D hollow structures such as cages, cones, capsules and boxes have been obtained by multicomponent self-assembly of exo-multidentate ligands with cis-protected square planar metal complexes, [(L)M](NO(3))(2) (where L is ethylenediamine or 2,2'-bipyridine and M is Pd or Pt). Furthermore, these hollow structures act as molecular flasks to encapsulate guest molecules and regulate/promote specific reactions; for example, oligomerization of silanetriols and [2+2] intermolecular photodimerization of olefins.

Alkanes↗