Force-field parametrization based on radial and energy distribution functions

We propose a novel force-field-parametrization procedure that fits the parameters of potential functions in a manner that the pair distribution function (DF) of molecules derived from candidate parameters can reproduce the given target DF. Conventionally, approaches to minimize the difference between the candidate and target DFs employ radial DFs (RDF). RDF itself has been reported to be insufficient for uniquely identifying the parameters of a molecule. To overcome the weakness, we introduce energy DF (EDF) as a target DF, which describes the distribution of the pairwise energy of molecules. We found that the EDF responds more sensitively to a small perturbation in the pairwise potential parameters and provides better fitting accuracy compared to that of RDF. These findings provide valuable insights into a wide range of coarse graining methods, which determine parameters using information obtained from a higher-level calculation than that of the developed force field. © 2019 The Authors. Journal of Computational Chemistry published by Wiley Periodicals, Inc.     

Curdlan as a Polymeric Starting Material to Access C6-Modified Glucose Derivatives

We evaluated the potential of a linear β-1,3-glucan (curdlan) as a starting material to access C6-modified glucose derivatives and found that 6-bromo-6-deoxyglucose, 6-azide-6-deoxyglucose, and 6-acetamido-6-deoxyglucose could be readily prepared from curdlan through its C6-selective and quantitative modifications and subsequent acid-catalyzed hydrolysis.     

An improved catalyst for the asymmetric arylation of ketone enolates

A new catalyst system for the enantioselective alpha-arylation of ketones is reported. This catalyst, prepared from Pd(2)(dba)(3) and a bulky dialkylphosphino-binaphthyl ligand, is able to effect the asymmetric arylation of ketone enolates with aryl bromides utilizing NaO(t)()Bu as base. These new catalysts enjoy much higher reactivity than previous systems; arylation reactions could be effected at room temperature with only 2 mol % of the Pd catalyst. The coupling of alpha-alkyl-alpha'-protected cyclopentanones proceeded in high yield, and the resulting quaternary stereogenic center was installed in up to 94% ee.     

Synthesis and Polymerization of (S)-4-Methyl-2-N,N-dimethylaminopentyl Methacrylate

(S)-4-Methyl-2-N,N-dimethylaminopentyl methacrylate (DMAPM) was synthesized from the reaction of N,N-dimethyl-L-leucinol with methacryl chloride, and its radical polymerization was investigated. It was found that DMAPM readily polymerized by α,α¹-azobisisobutyronitrile (AIBN) as an initiator to give poly-DMAPM. The copolymerization of DMAPM(M₁) with styrene(Mz) was also studied in various solvents with AIBN as an initiator at 60°C. From the result obtained in benzene, Q and e values of DMAPM were determined to be 0.64 and -0.04, respectively. Specific rotations of the copolymers of DMAPM with styrene were not proportional to the weight percent of the DMAPM unit incorporated, but the observed relation gave a downward curve. The copolymerizations DMAPM with α, β-disubstituted monomers such as maleic acid, maleimide, and N-phenylmaleimide were carried out in order to induce asymmetric center in the polymer chain. After hydrolysis of the copolymers obtained, the hydrolyzed polymers were found to be optically active, suggesting an induction of asymmetric center into the polymer chain.     

Titanosilicate molecular sieve for size-screening photocatalytic conversion

Titanosilicate molecular sieves, when activated by ultraviolet light irradiation in water in the presence of molecular oxygen, catalyze a conversion of molecules having a size close to the pore of the catalysts but are inactive for molecules having much larger or smaller size. This unprecedented size-screening photocatalytic activity is triggered by a combination of H2O-induced shortened lifetime of active species (charge-transfer excited state of tetrahedrally coordinated titanium oxide) and restricted diffusion of a molecule inside the pore. This catalytic property demonstrates a potential utility of the catalyst for selective transformation of molecules that is associated with a size reduction of molecules, so-labeled "molecular shave" transformation.     

Quantitative estimation of NH3 partial pressure in H2 desorbed from the Li-N-H system by Raman spectroscopy

The partial pressure of NH3 gas estimated by Raman spectroscopy indicates that approximately 0.1% NH3 inevitably contaminates the H2 desorbed from a hydrogen storage material composed of LiH and LiNH2 at any temperature up to 400 degrees C in a closed system.     

Preparation of Sr2CeO4:Eu3+,Dy3+ white luminescence phosphor particles and thin films by using an emulsion liquid membrane system

Sr(2)CeO(4) and Sr(2)CeO(4):Eu(3+),Dy(3+) phosphor particles and thin films were prepared by using an emulsion liquid membrane (ELM, water-in-oil-in-water (W/O/W) emulsion) system, containing VA-10 (2-methyl-2-ethylheptanoic acid) as extractant (cation carrier). A two-step extraction enabled efficient extraction for Sr(3+) and rare earth ions, and the resulting precursor metal oxalate particles produced in the internal water phase of the ELM system were about 60 nm in diameter. Calcination of the oxalate particles in air gave submicrometer-sized Sr(2)CeO(4) and Sr(2)CeO(4):Eu(3+),Dy(3+) particles, which showed blue and white luminescence, respectively, by UV excitation. Blue and white luminescence phosphor thin films were also prepared by soaking alumina substrates into the W/O emulsion containing precursor oxalate particles, followed by calcination in air.