Polymerization of optically active disubstituted acetylene monomers by Pd catalyst bearing bulky phosphine ligand

Chloro- and aryl-substituted acetylene monomers having an optically active group were polymerized by a Pd catalyst [(^tBu₃P)PdMeCl] bearing a bulky phosphine ligand, and by MoCl₅ for comparison. The corresponding disubstituted acetylene polymers with M_n's = 2000–19,500 and 6900–10,800 were obtained in 29–83% and 11–62% yields when the Pd and Mo catalysts were used, respectively. The formation of polyacetylenes, poly[(R)- 1p ], poly[(R)- 1m ], and poly[(S)- 2p ] were confirmed by SEC and the presence of a Raman scattering peak based on the alternating double bonds of the main chain. Pd-based poly[(R)- 1m ] exhibited CD signals around 350 nm assignable to a certain secondary structure, while Mo-based poly[(R)- 1m ] did not. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3011–3016     

Rapid one-step synthesis, characterization and functionalization of silica coated gold nanoparticles

This paper describes a rapid, simple and one-step method for preparing silica coated gold (Au@SiO₂) nanoparticles with fine tunable silica shell thickness and surface functionalization of the prepared particles with different groups. Monodispersed Au nanoparticles with a mean particle size of 16 nm were prepared by citrate reduction method. Silica coating was carried out by mixing the as prepared Au solution, tetraethoxysilane (TEOS) and ammonia followed by microwave (MW) irradiation. Although there are several ways of coating Au nanoparticles with silica in the literature, each of these needs pre-coating step as well as long reaction duration. The present method is especially useful for giving the opportunity to cover the colloidal Au particles with uniform silica shell within very short time and forgoes the use of a silane coupling agent or pre-coating step before silica coating. Au@SiO₂ nanoparticles with wide range of silica shell thickness (5-105 nm) were prepared within 5 min of MW irradiation by changing the concentration of TEOS only. The size uniformity and monodispersity were found to be better compared to the particles prepared by conventional methods, which were confirmed by dynamic light scattering and transmission electron microscopic techniques. The prepared Au@SiO₂ nanoparticles were further functionalized with amino, carboxylate, alkyl groups to facilitate the rapid translation of the nanoparticles to a wide range of end applications. The functional groups were identified by XPS, and zeta potential measurements.     

Synthesis, structures and ab initio studies of selenium and tellurium bis(carbodithioates and carbothioates)

A series of selenium and tellurium bis(carbodithioates and carbothioates) were synthesized. X-Ray structure analysis revealed that Se(SSCC(6)H(4)OMe-2)(2), Te(SSCC(6)H(4)OMe-2)(2) and Te(SSCC(6)H(4)Me-4)(2) have trapezoidal-planar configuration of ES(4) (E = Se, Te) and despite the larger atomic radii, the C=S···Te distances in Te(SSCC(6)H(4)OMe-2)(2) are comparable to those in the corresponding selenium derivatives Se(SSCC(6)H(4)OMe-2)(2). Molecular-orbital calculations performed on compounds E(E'SCR)(2) (E = S, Se, Te; E' = O, S; R = Me, Ph, C(6)H(4)OMe-2) showed that the syn-conformers of Se(SSCR)(2) and Te(SSCR)(2) are more stable than the corresponding anti-ones, while, in the case of carbothioic acid derivatives, E(SOCR)(2) showed that their anti-conformers are all more stable than the corresponding syn-ones. Natural bond orbital (NBO) analyses of these dithio-compounds revealed that two types of orbital interactions, n(S(1))→σ*(E-S(2)) and n(O)→σ*(E-S(2)), play a role in the bonding of E[S(2)S(1)CC(6)H(4)OMe-2](2) (E = Se, Te) and the former play a particularly predominant role.     

Use of the MALDI BioTyper system with MALDI–TOF mass spectrometry for rapid identification of microorganisms

In a clinical diagnosis microbiology laboratory, the current method of identifying bacterial isolates is based mainly on phenotypic characteristics, for example growth pattern on different media, colony morphology, Gram stain, and various biochemical reactions. These techniques collectively enable great accuracy in identifying most bacterial isolates, but are costly and time-consuming. In our clinical microbiology laboratory, we prospectively assessed the ability of matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI–TOF MS) to identify bacterial strains that were routinely isolated from clinical samples. Bacterial colonies obtained from a total of 468 strains of 92 bacterial species isolated at the Department of Clinical Laboratory at Chiba University were directly placed on target MALDI plates followed by addition of CHCA matrix solution. The plates were then subjected to MALDI–TOF MS measurement and the microorganisms were identified by pattern matching with the libraries in the BioTyper 2.0 software. Identification success at the species and genus levels was 91.7% (429/468) and 97.0% (454/468), respectively. MALDI–TOF MS is a rapid, simple, and high-throughput proteomic technique for identification of a variety of bacterial species. Because colony-to-colony differences and effects of culture duration on the results are minimal, it can be implemented in a conventional laboratory setting. Although for some pathogens, preanalytical processes should be refined, and the current database should be improved to obtain more accurate results, the MALDI–TOF MS based method performs, in general, as well as conventional methods and is a promising technology in clinical laboratories.     

Theoretical study of the inclusion properties of 1,2,4,5-tetra(morpholinocarbonyl)benzene

Molecular inclusion by the new amide host molecule (TMB) has been reconsidered by calculating the crystal stabilization energies for the guest molecules in the TMB + guest system from the simple intermolecular potential functions of Caillet and Claverie. Water, ethylene glycol, methanol, and ethanol have been employed as guest molecules and their relative stabilities have been considered. Water has been found to be the most suitable guest molecule in the TMB + guest system. It also has been found that the guest host interaction is the most important contributor in determining the relative stabilities of the guest molecules in the TMB + guest system, but the guest guest interaction is very important, too. Moreover, the electrostatic interaction has been found to be the most important contributor to the total interaction energy in the TMB + guest system.     

Synthesis and helical conformation of poly(N‐propargylamides) carrying L‐aspartic acid in the side chain

Aspartic acid‐based novel poly(N‐propargylamides), i.e., poly[N‐(α‐tert‐butoxycarbonyl)‐L ‐aspartic acid β‐benzyl ester N′‐propargylamide] [poly( 1 )] and poly[N‐(α‐tert‐butoxycarbonyl)‐L ‐aspartic acid α‐benzyl ester N′‐propargylamide] [poly( 2 )] with moderate molecular weights were synthesized by the polymerization of the corresponding monomers 1 and 2 catalyzed with (nbd)Rh⁺[η⁶‐C₆H₅B^?(C₆H₅)₃] in CHCl₃ at 30 °C for 2 h in high yields. The chiroptical studies revealed that poly( 1 ) took a helical structure in DMF, while poly( 2 ) did not in DMF but did in CH₂Cl₂, CHCl₃, and toluene. The helicity of poly( 1 ) and poly( 2 ) could be tuned by temperature and solvents. Poly( 2 ) underwent solvent‐driven switch of helical sense, accompanying the change of the tightness. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5168–5176, 2005     

Excess enthalpies of binary mixtures of 2-ethyl-1-butanol with hexane isomers

Molar excess enthalpies, measured at 298.15 K in a flow microcalorimeter, are reported for binary mixtures of 2-ethyl-1-butanol with the five isomeric hexanes. The results are compared with previously published excess enthalpies for mixtures of 1-hexanol and 2-methyl-1-pentanol with the same hexane isomers.