Analytic energy gradient for second-order Møller-Plesset perturbation theory based on the fragment molecular orbital method

The first derivative of the total energy with respect to nuclear coordinates (the energy gradient) in the fragment molecular orbital (FMO) method is applied to second order M?ller-Plesset perturbation theory (MP2), resulting in the analytic derivative of the correlation energy in the external self-consistent electrostatic field. The completely analytic energy gradient equations are formulated at the FMO-MP2 level. Both for molecular clusters (H(2)O)(64) and a system with fragmentation across covalent bonds, a capped alanine decamer, the analytic FMO-MP2 energy gradients with the electrostatic dimer approximation are shown to be complete and accurate by comparing them with the corresponding numeric gradients. The developed gradient is parallelized with the parallel efficiency of about 97% on 32 Pentium4 nodes connected by Gigabit Ethernet.     

Selective photoinduced energy transfer from a thiophene rotaxane to acceptor

An energy transfer process was investigated using cyclodextrin-oligothiophene rotaxanes (2T-[2]rotaxane). The excited energy of 2T-[2]rotaxane is transferred to the sexithiophene derivative which is included in the cavity of β-CD stoppers of 2T-[2]rotaxane.     

Molecular Design of Polyoxometalate-Based Compounds for Environmentally-Friendly Functional Group Transformations: From Molecular Catalysts to Heterogeneous Catalysts

This review article summarizes our recent researches for molecular design of polyoxometalates (POMs) and their related compounds for environmentally-friendly functional group transformations. The divacant POM [γ-SiW₁₀O₃₄(H₂O)₂]⁴⁻ exhibits high catalytic performance for mono-oxygenation-type reactions including epoxidation of olefins and allylic alcohols, sulfoxidation, and hydroxylation of organosilanes with H₂O₂. We have successfully synthesized several POM-based molecular catalysts (metal-substituted POMs) with controlled active sites by the introduction of metal species into the divacant POM as a “structural motif”. These molecular catalysts can efficiently activate H₂O₂ (vanadium-substituted POM for epoxidation) and alkynes (copper-substituted POM for click reaction and oxidative homocoupling of alkynes). The aluminum-substituted POM exhibits Lewis acidic catalysis for diastereoselective cyclization of (+)-citronellal to (−)-isopulegol. In addition, we have developed POM-based “molecular heterogeneous catalysts” by the “solidification” and “immobilization” of catalytically active POMs.     

Systematic study of protein detection mechanism of self-assembling 19F NMR/MRI nanoprobes toward rational design and improved sensitivity

(19)F NMR/MRI probe is expected to be a powerful tool for selective sensing of biologically active agents owing to its high sensitivity and no background signals in live bodies. We have recently reported a unique supramolecular strategy for specific protein detection using a protein ligand-tethered self-assembling (19)F probe. This method is based on a recognition-driven disassembly of the nanoprobes, which induced a clear turn-on signal of (19)F NMR/MRI. In the present study, we conducted a systematic investigation of the relationship between structure and properties of the probe to elucidate the mechanism of this turn-on (19)F NMR sensing in detail. Newly synthesized (19)F probes showed three distinct behaviors in response to the target protein: off/on, always-on, and always-off modes. We clearly demonstrated that these differences in protein response could be explained by differences in the stability of the probe aggregates and that "moderate stability" of the aggregates produced an ideal turn-on response in protein detection. We also successfully controlled the aggregate stability by changing the hydrophobicity/hydrophilicity balance of the probes. The detailed understanding of the detection mechanism allowed us to rationally design a turn-on (19)F NMR probe with improved sensitivity, giving a higher image intensity for the target protein in (19)F MRI.     

Layered assemblies of a dialuminum-substituted silicotungstate trimer and the reversible interlayer cation-exchange properties

Two polyoxometalate assemblies, TBA(9)[{γ-H(2)SiW(10)O(36)Al(2)(μ-OH)(2)(μ-OH)}(3)] (1; TBA = tetra-n-butylammonium) and TBA(6)Li(3)[{γ-H(2)SiW(10)O(36)Al(2)(μ-OH)(2)(μ-OH)}(3)]·18H(2)O (2), were synthesized by trimerization of a dialuminum-substituted silicotungstate monomer. Both 1 and 2 possessed a layered structure composed of a basal sheet unit [TBA(3){γ-H(2)SiW(10)O(36)Al(2)(μ-OH)(2)(μ-OH)}(3)](6-) and interlayer cations. The interconversion between 1 and 2 reversibly took place through interlayer cation exchange.     

The thermal stabilities of luminescence and microstructures of Eu2+-doped KBaPO4 and NaSrPO4 with β-K2SO4 type structure

Eu(2+)-doped monophosphates NaSrPO(4) and KBaPO(4) with the β-K(2)SO(4) structure were synthesized using the conventional high temperature solid state reaction. The X-ray powder diffraction, photoluminescence excitation, and emission spectra and decay curves were measured. The phosphors can be efficiently excited by UV-visible light from 220 to 430 nm to realize emission in the visible range. The natures of the Eu(2+) emission, e.g., the chromaticity coordinates, the Stokes shifts, and the luminescence absolute quantum efficiencies, were reported. The luminescence quenching temperatures and the thermal activation energies for NaSrPO(4):Eu(2+) and KBaPO(4):Eu(2+) were obtained from the temperature dependent (10-435 K) luminescence intensities and decay curves. KBaPO(4):Eu(2+) presents only one emission center; however, Eu(2+) ions have a "disordered environment" in NaSrPO(4) lattices. The relationship between the luminescence thermal stabilities and the crystal structures was discussed. The crystallographic occupations of rare earth ions doped in these hosts were analyzed by the site-selective emission spectra and the excitation spectra of Eu(3+) ions in the (7)F(0)→(5)D(0) transitions using a pulsed, tunable, and narrow-band dye laser. In KBaPO(4), the Eu(3+) ions could be distributed in the host with a high "ordered state" in only one site in the lattices. However, the multiple site structure of Eu(3+) ions with highly disordered distributions in NaSrPO(4) lattices was suggested.     

Experimental assessment of quasi-binary picture of thermotropics: induced smectic A phase in 7CB-n-heptane system

Quasi-binary (QB) picture of thermotropics, which regards a neat thermotropic liquid crystal as a binary system consisting of (semi)rigid core and molten alkyl chain, was assessed experimentally for the most famous (and representative) thermotropic mesogenic series nCB. By adding n-heptane as solvent, the smectic A phase was induced in 7CB-n-heptane system. Small angle x-ray diffraction showed that the QB picture holds not only in the phase behavior but also in the structure. It is suggested that the melting of 8CB and 9CB to isotropic liquid via smectic and nematic liquid crystals can be understood as a thermotropic-lyotropic crossover.     

Electroless galvanic inks on inorganic WO3/Al boards

A tungsten trioxide (WO(3)) coated aluminium (Al) substrate exhibits a reversible color change without light irradiation or an electric power supply. The sample turns blue upon exposure to an aqueous acid solution, but exposure to oxygen restores the original light yellow color. This color change is due to the galvanic redox reaction between WO(3) and Al.     

Location of [60]fullerene incorporation in lipid membranes

We confirmed that most C(60) fullerene units are located in the hydrophobic core of the lipid bilayer membrane in water-soluble lipid membrane incorporated C(60) (LMIC(60)) complexes using differential scanning calorimetry (DSC) and (13)C NMR spectra in the presence of radical labels.     

New method for comprehensive detection of chemical warfare agents using an electron-cyclotron-resonance ion-source mass spectrometer

We developed a detection technology for vapor forms of chemical warfare agents (CWAs) with an element analysis system using an electron cyclotron resonance ion source. After the vapor sample was introduced directly into the ion source, the molecular material was decomposed into elements using electron cyclotron resonance plasma and ionized. The following CWAs and stimulants were examined: diisopropyl fluorophosphonate (DFP), 2-chloroethylethylsulfide (2CEES), cyanogen chloride (CNCl), and hydrogen cyanide (HCN). The type of chemical warfare agents, specifically, whether it was a nerve agent, blister agent, blood agent, or choking agent, could be determined by measuring the quantities of the monatomic ions or CN(+) using mass spectrometry. It was possible to detect gaseous CWAs that could not be detected by a conventional mass spectrometer. The distribution of electron temperature in the plasma could be closely controlled by adjusting the input power of the microwaves used to generate the electron cyclotron resonance plasma, and the target compounds could be detected as molecular ions or fragment ions, enabling identification of the target agents.