Polysaccharide derivatives as chiral stationary phases in HPLC

Twenty different tris(phenylcarbamate)s of cellulose were synthesized and evaluated as chiral stationary phases for HPLC. Optical resolving power of the tris(phenylcarbamate)s depends on the substituents introduced on the phenyl groups. Optical resolving abilities of amylose tris(phenylcarbamate)s were also evaluated. In most cases, either cellulose tris(3,5-dimethylphenylcarbamate) or amylose tris(3,5-dimethylphenylcarbamate) exhibited the highest optical resolving ability. Aralkylcarba-mates such as benzyl- and 1-phenylethylcarbamates of cellulose and amylose were also tested as chiral stationary phases. (S)-1-Phenylethylcarbamate of amylose showed a high optical resolving power.     

Theoretical study of Pt-Ng and Ng-Pt-Ng (Ng=Ar,Kr,Xe)

We have investigated the binding of noble-gas (Ng) atoms (Ng=Ar,Kr,Xe) with Pt atom by the ab initio coupled-cluster CCSD(T) method, taking into account the relativistic effects. It is shown that two Ng atoms can bind with Pt atom in linear geometry in the singlet lowest state where the second Ng atom attaches to Pt with the larger binding energy than the first Ng atom. The binding energy is evaluated as 8.2, 17.9, and 33.4 kcal/mol for Ar-Pt-Ar, Kr-Pt-Kr, and Xe-Pt-Xe, respectively, relative to the triplet ground state of the dissociation limit Pt ((3)D)+2Ng. The present results indicate that these Ng-Pt-Ng compounds are possible new gas-phase or matrix species.     

Pure through‐bond state in organic molecules for analysis of the relationship between intramolecular interactions and total energy

Ab initio configuration interaction through‐space/bond interaction analysis was proposed for the examination of specific intramolecular interactions including the effect of electron correlations. To test the effectiveness of our method, we applied it to rotational barrier in ethane. The results of our test suggest that the insensitivity of the ethane barrier to geometric relaxations is intimately connected with the cancellation of interactions through orbital overlaps and other factors. The orbital overlaps include exchange repulsion and hyperconjugation; other factors include classic Coulomb interaction and changes in bond orbital energy. The rotational state without the barrier (pure through‐bond state) can be achieved by deleting not only the “vicinal” interactions between the C? H bonds that belong to different methyl groups but also the “geminal” interactions within the methyl groups. Our mixing analysis of molecular orbitals supports the superiority of the staggered conformer by hyperconjugation. Moreover, it was demonstrated that our treatment could be applied to excited states as well as to the ground state, including electron correlation effects. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003     

Near-IR light-sensitized voltaic conversion system using nanocrystalline TiO2 film by Zn chlorophyll derivative aggregate

A Zn chlorophyll-a derivative, Zn chlorin-e6 (ZnChl-e6), adsorbed onto a nanocrystalline TiO2 film (ZnChl-e6/TiO2) electrode was prepared, and the photovoltaic properties of the ZnChl-e6/TiO2 electrode were studied. The absorption peaks of ZnChl-e6/TiO2 observed at 420, 654, and 795 nm were attributed to the ZnChl-e6 molecules aggregating onto TiO2 film. The fluorescence attributed to the ZnChl-e6 monomer and aggregate was observed at 710 and 820 nm, respectively, and the fluorescence in both cases was quenched by TiO2 particles. The maximum of the incident photon-to-current conversion efficiency (IPCE) value in the photocurrent action spectrum was 800 nm, and the IPCE value was 7.0%. ZnChl-e6 molecules formed aggregates on a nanocrystalline TiO2 film electrode. From the photocurrent-photovoltage characteristics of the ZnChl-e6/TiO2 electrode irradiated with 100 mW cm(-2), the short-circuit photocurrent (I(SC)) was found to be 0.19 mA cm(-2) and the open-circuit photovoltage (V(OC)) was found to be 375 mV. The maximum power was estimated to be 28.7 microW cm(-2), and the fill factor (FF) was estimated to be 40.1%. A near-IR light induced photovoltaic conversion system using a ZnChl-e6 aggregate formed onto a nanocrystalline TiO2 film electrode was achieved.     

Complex of cobalt(II) bromide with hexa­methyl­phospho­ric tri­amide

The title compound, di­bromo­bis­[tris­(di­methyl­amino)­phos­phine oxide]­cobalt(II), [CoBr₂(C₆H₁₈N₃OP)₂], displays tetrahedral coordination about cobalt. The mol­ecule has twofold crystallographic site symmetry. The short P—N bonds and the planarity of the di­methyl­amino groups indicate the importance of dπ–pπ interactions. One of the NMe₂ groups has an irregular conformation about the P—N bond and deviates from planarity. It is ascribed to the steric hindrance induced by coordination at the O atom of hexa­methyl­phospho­ric tri­amide.     

An analytical molecular orbital approach for modeling of low‐dimensional conductors in molecular crystals

In low‐dimensional molecular crystals that exhibit Peierls instability, the intercolumnar interaction plays an important role in the determination of the conducting property. To predict the crystal structure that exhibits an electronic conduction, we proposed a simple formula based on the molecular orbital theory. In this approach, analytical molecular orbitals of polyene were extended to be applicable for molecular crystals of charge–transfer complexes, and the Peierls distortion was represented by using the first‐ and second‐order perturbation theory. It was concluded that the energetic behaviors and structures calculated by the analytical method developed in the present work are identical to those obtained by the tight‐binding ab initio molecular orbital calculation. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001     

Thermal polymorphic transformation of p-tert-Butylcalix

Studies were made on the polymorphism of p-tert-butylcalix[4]arene derivatives having amino acid groups on the lower rim to stabilize their hydrophilic pseudocavity by circular intramolecular hydrogen bonding. The calixarenes exhibit a polymorphic transformation upon heating in the solid state. This transformation is controlled by the thermal history of solids, accompanying the change on the conformation of the calixarene skeleton and also the change of hydrogen bonding in the hydrophilic pseudocavity.