NMR and quantum chemical study on the OH...pi and CH...O interactions between trehalose and unsaturated fatty acids: implication for the mechanism of antioxidant function of trehalose

Trehalose is a disaccharide that attracts much attention as a stress protectant. In this study, we investigated the mechanism of the antioxidant function of trehalose. The spin-lattice relaxation times (T(1)) of (1)H and (13)C NMR spectra were measured to investigate the interaction between trehalose and unsaturated fatty acid (UFA). We selected several kinds of UFA that differ in the number of double bonds and in their configurations (cis or trans). Several other disaccharides (sucrose, maltose, neotrehalose, maltitol, and sorbitol) were also analyzed by NMR. The T(1) values for the (1)H and (13)C signals assigned to the olefin double bonds in UFA decrease with increasing concentration of trehalose and the changes reaches plateaus at integer ratios of trehalose to UFA. The characteristic T(1) change is observed only for the combination of trehalose and UFA with cis double bond(s). On the other hand, from the (13)C-T(1) measurements for trehalose, the T(1) values of the C-3 (C-3') and C-6' (C-6) are found to change remarkably by addition of UFA. (1)H[bond](1)H NOESY measurements provide direct evidence for complexation of trehalose with linoleic acid. These results indicate that one trehalose molecule stoichiometrically interacts with one cis-olefin double bond of UFA. Computer modeling study indicates that trehalose forms a stable complex with an olefin double bond through OH...pi and CH...O types of hydrogen bonding. Furthermore, a significant increase in the activation energy is found for hydrogen abstraction reaction from the methylene group located between the double bonds that are both interacting with the trehalose molecules. Therefore, trehalose has a significant depression effect on the oxidation of UFA through the weak interaction with the double bond(s). This is the first study to elucidate the antioxidant function of trehalose.     

Regioselectivity of Friedel-Crafts acylation of aromatic compounds with several cyclic anhydrides

The Friedel-Crafts acylations of various aromatic compounds with cyclic anhydrides such as 2-(p-substituted phenyl)butanedioic, 3-phenylpentanedioic and homophathlic anhydrides were carried out under various conditions in order to obtain informations about the regioselectivity of the ring opening of the cyclic anhydrides and about the possible reaction pathways in the acylations.     

The first total synthesis of (+)-(Z)-laureatin

The stereoselective total synthesis of (+)-(Z)-laureatin is described. The 3,8-dioxabicyclo[5.1.1]nonane skeleton possessing trans-orientated alkyl substituents at the α,α′-positions to the ether linkage was stereoselectively constructed via formation of the oxetane arising from 4-exo cyclization of hydroxy epoxide existing on the oxocene core.     

Electrical and magnetic properties of ion-exchangeable layered ruthenates

An ion-exchangeable ruthenate with a layered structure, K_0.2RuO_2.1, was prepared by solid-state reactions. The interlayer cation was exchanged with H⁺, C₂H₅NH₃⁺, and ((C₄H₉)₄N⁺) through proton-exchange, ion-exchange, and guest-exchange reactions. The electrical and magnetic properties of the products were characterized by DC resistivity and susceptibility measurements. Layered K_0.2RuO_2.1 exhibited metallic conduction between 300 and 13 K. The products exhibited similar magnetic behavior despite the differences in the type of interlayer cation, suggesting that the ruthenate sheet in the protonated form and the intercalation compounds possesses metallic nature.     

Crystal chemistry and thermodynamic properties of anisotropic Ce2Ni7H4.7 hydride

A new intermetallic deuteride Ce₂Ni₇D_4.7 with an anomalous volume expansion has been studied. Its structure was solved on the basis of in situ neutron diffraction data. Expansion proceeds along the c-axis and within the CeNi₂ slabs only. All D atoms are located inside these slabs and on the border between CeNi₂ and CeNi₅. Ordering of D atoms in the bulk of CeNi₂ is accompanied by substantial deformation of these slabs thus lowering the hexagonal symmetry to orthorhombic [space group Pmcn (No. 62); a=4.9251(3) Å, b=8.4933(4) Å, c=29.773(1) Å]. Inside the CeNi₂ layer the hydrogen sublattice is completely ordered; all D-D distances exceed 2.0 Å. Local coordination of Ni by D inside the CeNi₂ blocks is of “open”, saddle-like type. Hydrogen ordering is mainly determined by Ce-H and H-H interactions. The pressure-composition-temperature measurements yielded the following thermodynamic parameters of the formation of the hydride: ΔH=−22.4 kJ/mol_H, ΔS=−59.9 J/(K mol_H).     

Boron group element doping of Li1.5Al0.5Ge1.5(PO4)3 based on microwave sintering

Journal of Solid State Electrochemistry - We report effectiveness of dopants selected from group 13, such as B, Ga, and In, on the conductivity of Li1.5Al0.5Ge1.5(PO4)3 (LAGP) that is recognized as...     

Synthesis,crystal structure and charge transport characteristics of stable peri-tetracene analogues

peri-Acenes have shown great potential for use as functional materials because of their open-shell singlet biradical character. However, only a limited number of peri-acene derivatives larger than peri-tetracene have been synthesized to date, presumably owing to the low stability of the target compounds in addition to the complicated synthesis scheme. Here, a very simple synthesis route for the tetrabenzo[a,f,j,o]perylene (TBP) structure enables the development of highly stable peri-tetracene analogues. Despite a high degree of singlet biradical character, the compounds with four substituents at the zigzag edge show a remarkable stability in solution under ambient conditions, which is better than that of acene derivatives with a closed-shell electronic configuration. The crystal structures of the TBP derivatives were obtained for the first time; these are valuable to understand the relationship between the structure and biradical character of peri-acenes. The application of peri-acenes in electronic devices should also be investigated. Therefore, the semiconducting properties of the TBP derivative were investigated by fabricating the field-effect transistors.

Highly stable peri-tetracene analogues with a high degree of singlet biradical character were synthesized in a very simple route, and their crystal structures and semiconducting properties were investigated.     

Synthesis,Structure, Optical,and Electrochemical Properties of Triple‐ and Quadruple‐Decker Co‐facial Tetrathiafulvalene Arrays

Understanding the details of the electronic structure in face‐to‐face arranged tetrathiafulvalenes (TTFs) is very important for the design of supramolecular functional materials and superior conductive organic materials. This article is a comprehensive study of the interactions among columnar stacked TTFs using trimeric (trimer) and tetrameric (tetramer) TTFs linked by alkylenedithio groups (‐S(CH₂)_nS‐, n=1–4) as models of triple‐ and quadruple‐decker TTF arrays. Single‐crystal X‐ray analyses of neutral trimeric TTFs revealed that the three TTF moieties are oriented in a zigzag arrangement. Cyclic voltammetry measurements (CV) reveal that the trimer and tetramer exhibited diverse reversible redox processes with multi‐electron transfers, depending on the length of the ‐S(CH₂)_nS‐ units and substituents. The electronic spectra of the radical cations, prepared by electrochemical oxidation, showed charge resonance (CR) bands in the NIR/IR region (1630–1850 nm), attributed to a mixed valence (MV) state of the triple‐ and quadruple‐decker TTF arrays. In the trimeric systems, the dicationic state (+2; 0.66 cation per TTF unit) was found to be a stable state, whereas the monocationic state (+1) was not observed in the electronic spectra. In the tetrameric system, substituent‐dependent redox processes were observed. Moreover, π‐trimers and π‐tetramers, which show a significant Davydov blueshift in the spectra, are formed in the tricationic (trimer) and tetracationic (tetramer) state. In addition, these attractive interactions are strongly dependent on the length of the linkage unit.     

9,10‐Diaminoanthracenes Revisited: The Influence of N‐Substituents on Their Electronic States

The electronic and molecular structures of 9,10‐diamino‐substituted anthracenes with different N‐substituents have been re‐examined. In particular, different N‐substituents influence both the electronic and molecular structures of the oxidized species of 9,10‐diaminoanthracenes. The anthrylene moiety of 9,10‐bis(N,N‐di(p‐anisyl)amino)anthracene retains its planarity during the course of two successive one‐electron oxidations, whereas 9,10‐bis(N,N‐dimethylamino)anthracene and 9,10‐bis(N‐p‐anisyl‐N‐methylamino)anthracene undergo a substantial structural change to a butterfly‐like structure through a two‐electron oxidation process. The structural changes observed for the oxidized states are ascribed to significant differences in the frontier molecular orbitals of the above‐mentioned three kinds of 9,10‐diaminoanthracenes due to different extents of mixing between the amine‐localized and anthrylene‐localized orbitals.     

Structures of 17,19-hexatriacontadiyne monolayers on Au(111) studied by infrared reflection absorption spectroscopy and scanning tunneling microscopy

The aggregation and reaction of 17,19-hexatriacontadiyne molecules are studied on a Au(111) surface. The molecular orientation and arrangement are elucidated by infrared reflection absorption spectroscopy (IRAS) and scanning tunneling microscopy (STM). A vapor-deposited monolayer and a multilayered film formed by adsorption from the solution provide IRA spectra with bands due to the antisymmetric and symmetric stretching of methylenes in the gauche conformation. After the adsorbed film is rinsed with the solvent, however, the spectrum loses the gauche bands and is characterized by the enhanced C-H(distal) and C-H(proximal) stretching bands, which means that all-trans molecules are laid flat. Only STM images for the rinsed film display columnar structures on the herringbones of the reconstructed Au(111) surface; the alkyl chain direction is found to be parallel to the Au atom row. The results indicate that an ordered monolayer is formed first at the liquid-solid interface, and then, disordered overlayers with the gauche conformation are grown but removed by a rinse. Upon exposure to UV light, thus obtained monomer columns are converted into oligomers with flexible backbones and an increased gauche population in the alkyl chains, which resemble red phase polydiacetylenes in LB films.