Biomedical subjects

Yuji Kawanishi

Publications and source records attributed to Yuji Kawanishi.

4 recordsLinked to original sources

PubMed2005

Crystalline-state Z,E-photoisomerization of a series of (Z,E,Z)-1,6-diphenylhexa-1,3,5-triene 4,4'-dicarboxylic acid dialkyl esters. Chain length effects on the crystal structure and photoreactivity.

[reaction: see text] Crystalline-state Z,E-photoisomerization of a series of (Z,E,Z)-1,6-diphenylhexa-1,3,5-triene 4,4'-dicarboxylic acid dialkyl (R) esters [(Z,E,Z)-1a, R = Me; (Z,E,Z)-1b, R = Et; (Z,E,Z)-1c, R = n-Pr; (Z,E,Z)-1d, R = n-Bu] was investigated. All Z,E,Z isomers underwent one-way isomerization to the corresponding E,E,E isomers. The reaction efficiency was strongly enhanced as the length of the alkyl chain increased. Single-crystal X-ray analyses of (Z,E,Z)-1a-d showed that the alkyl chain part of the crystals became larger as the chain length increased. The conformational flexibility of the alkyl chains made the large change in the triene geometry in the lattice possible, leading to the enhancement of the photoreactivity in the crystalline state.

Journal Article↗

PubMed2005

2,6-diaminopyridine derivatives as models of molecular sensor for nucleic acid base detection: ab initio calculations of electronic effects induced by hydrogen bonds formation.

The performance of a molecular sensor for detecting nucleic acid base was studied by molecular orbital calculations of model compounds. The model compounds consist of a detecting unit (pyridine derivative), a conducting unit (benzene) and a connection between them. The changes of the HOMO, LUMO energy levels and charge distributions of the conducting unit by the hydrogen bonds formation between the detecting unit and thymine were studied. The calculations show that the choice of the connection and its position are significantly important to efficiently transmit the electronic effects to the conducting unit. The comparison with aminopyridine, where the pyridine ring plays both detecting and conducting units, shows that the electronic effects are transmitted quite efficiently, if the connection is properly selected. The size of the electronic effects by the formation of the hydrogen bonds were also compared with those induced by the change of the torsional angle between the pyridine and benzene rings and by substitution of the benzene ring.

Biosensing Techniques↗

PubMed2003

(E,E,E)-1,6-Bis(2,4-dichlorophenyl)hexa-1,3,5-triene.

The title molecule, C(18)H(12)Cl(4), lies about an inversion centre and the hexatriene chain is planar. The torsion angle of the single bond between the planes of the chain and the benzene ring is -8.6 (3) degrees. The dihedral angle between the planes defined by the chains of adjacent molecules is 50.0 (2) degrees. The shortest intermolecular distance between the Cl atoms is 3.514 (1) A. The molecules are joined through pi-pi-stacking and strong attractive Cl.Cl interactions.

Journal Article↗

PubMed1997

Electrochemical, Spectroscopic, and Spectroelectrochemical Properties of Synthetically Useful Supramolecular Light Absorbers with Mixed Polyazine Bridging Ligands.

The trimetallic complexes [{(bpy)(2)M(dpp)}(2)Ru(dpq)](6+) (M = Ru(II) or Os(II), bpy = 2,2'-bipyridine, dpp = 2,3-bis(2-pyridyl)pyrazine, and dpq = 2,3-bis(2-pyridyl)quinoxaline) have been prepared and the details of their spectroscopic, electrochemical, and spectroelectrochemical properties investigated. These mixed bridging ligand complexes are a new group of synthons that can be useful for the construction of supramolecular devices for a wide variety of functions. It is the presence of the terminal dpq ligand that allows for their incorporation into larger supramolecular systems. This dpq ligand serves as an acceptor ligand that will possess a lower lying pi orbital than the dpp ligands once these chromophores are incorporated into larger systems. The [{(bpy)(2)M(dpp)}(2)Ru(dpq)](6+) systems display overlapping terminal metal oxidations at 1.66 and 1.18 V vs Ag/AgCl for the Ru and Os systems, respectively. This indicates that within this framework, these terminal, M, metals are largely electronically uncoupled. No oxidative process for the central Ru metal center is observed within our solvent window. The [{(bpy)(2)M(dpp)}(2)Ru(dpq)](6+) systems have M --> dpp charge transfer (CT) lowest lying excited states. The [{(bpy)(2)Ru(dpp)}(2)Ru(dpq)](6+) Ru --> dpp CT state displays an emission centered at 775 nm with a lifetime of 65 ns at room temperature in deoxygenated CH(3)CN solution. The details of the electrochemical, spectroscopic, and spectroelectrochemical studies of these supramolecular light absorbers and the dichloro synthons, [{(bpy)(2)M(dpp)}(2)RuCl(2)](4+), are reported herein.

Journal Article↗