Facile one-pot preparation of gold nanoparticles in the presence of fluoroalkyl end-capped oligomers,fluoroalkyl end-capped oligomers/silica nanocomposites,and fluoroalkyl end-capped oligomers/polyaniline nanocomposites

A variety of fluoroalkyl end-capped oligomers, such as fluoroalkyl end-capped acrylic acid oligomer [R_F-(ACA) _n -R_F], acryloylmorpholine oligomer [R_F-(ACMO) _n -R_F], 2-acrylamido-2-methylpropanesulfonic acid oligomer [R_F-(AMPS) _n -R_F], 2-(methacryloyloxy)ethanesulfonic acid oligomer [R_F-(MES) _n -R_F], and N,N-dimethylacrylamide oligomer [R_F-(DMAA) _n -R_F], were applied to the autoreduction of gold ions to give the corresponding oligomers/gold nanocomposites, of whose sharp plasmon absorption bands are observed around 535 nm. In these fluorinated oligomers, R_F-(ACA) _n -R_F oligomer and R_F-(ACMO) _n -R_F were effective for the one-pot preparation of the gold nanoparticles under very mild conditions; although the other fluorinated oligomers and the corresponding non-fluorinated–(ACMO) _n -oligomer were unable to afford the gold nanoparticles. R_F-(ACA) _n -R_F/SiO₂ nanocomposites and R_F-(ACMO) _n -R_F/SiO₂ nanocomposites, which were prepared by the sol–gel reactions of tetraethoxysilane in the presence of silica nanoparticles and the corresponding oligomers under alkaline conditions, were also applied to the encapsulation of gold nanoparticles into these fluorinated nanocomposite cores through the autoreduction of gold ions at room temperature. Interestingly, these fluorinated oligomers/silica nanocomposite-encapsulated gold nanocomposites before and after calcination at 800 °C were found to exhibit the same plasmon absorption band around 525 nm. R_F-(MES) _n -R_F oligomer and R_F-(AMPS) _n -R_F oligomer are not suitable for the autoreduction of gold ions; however, R_F-(MES)_n-R_F[or R_F-(AMPS) _n -R_F]/polyaniline [PAn] nanocomposites, which were prepared by the polymerization of aniline initiated by ammonium persulfate in the presence of the corresponding oligomer, enabled the formation of gold nanoparticles through the oxidation of PAn in the composites at room temperature. The reversible conformational change of PAn in the nanocomposites from the polyemeraldine salt to the oxidized pernigraniline base was observed during such oxidation process. Graphical abstract

?     

Syntheses,Crystal Structures and Ligand Field Properties of Iron(II) Complexes with PNP Ligands: Origin of Large Ligand Field by a Phosphorous Donor Atom

New iron(II) complexes were synthesized with two tridentate hybrid ligands having phosphorous and nitrogen donor sites, in order to quantitatively estimate the difference of the ligand-field strengths of phosphorous and nitrogen donor sites in cationic metal complexes. Iron(II) complexes with bis(dimethylphosphinoethyl)amine (PNP) and 2,6-bis(diphenylphosphinomethyl)pyridine (PpyP) ligands crystallized as un-symmetric facial-[Fe(PNP)₂](PF₆)₂·CH₃NO₂ and mer-[Fe(PpyP)₂](CF₃SO₃)₂, respectively, as expected from the steric congestion and from the tendency to avoid the mutual trans influence between two phosphorous donor sites. Both complexes are in the low-spin electronic state up to 400 K. The pseudo-D _4h coordination geometry of the PpyP complex made it possible to separate axial (2 × N) and equatorial (4 × P) contributions to the overall ligand-field by means of a spectrometric method: the difference in the ligand-field strengths by the equatorial Ph₂P-donor sites and by the axial 2,6-disubstituted pyridine donor sites is ca. 13,200 cm^?1. A significantly reduced inter-electronic repulsion parameter (425 cm^?1 for both PNP and PpyP complexes) from the value of the free ion (1,060 cm^?1) indicates covalent interaction between the Fe(II) and P atoms even in these cationic metal complexes. It is shown that the degree of covalency as well as the coordination bond strengths between various metal ions and phosphorous/nitrogen donor atoms is successfully explained by the relative energy levels of interacting atomic orbitals calculated on the basis of the Thomas–Fermi–Dirac potential.     

An Anti CuO2‐type Metal Hydride Square Net Structure in Ln2M2As2Hx (Ln=La or Sm,M=Ti,V, Cr,or Mn)

Using a high pressure technique and the strong donating nature of H^?, a new series of tetragonal La₂Fe₂Se₂O₃‐type layered mixed‐anion arsenides, Ln₂M₂As₂H_x, was synthesized (Ln=La or Sm, M=Ti, V, Cr, or Mn; x≈3). In these compounds, an unusual M₂H square net, which has anti CuO₂ square net structures accompanying two As^3? ions, is sandwiched by (LaH)₂ fluorite layers. Notably, strong metal–metal bonding with a distance of 2.80 Å was confirmed in La₂Ti₂As₂H_2.3, which has metallic properties. In fact, these compounds are situated near the boundary between salt‐like ionic hydrides and transition‐metal hydrides with metallic characters.     

Aplysiasecosterol A: A 9,11‐Secosteroid with an Unprecedented Tricyclic γ‐Diketone Structure from the Sea Hare Aplysia kurodai

A new 9,11‐secosteroid having an unprecedented tricyclic γ‐diketone structure, aplysiasecosterol A ( 1 ), was isolated from the sea hare Aplysia kurodai. The structure was determined by one‐ and two‐dimensional NMR spectroscopic analysis, molecular modeling studies, a comparison of experimental and calculated ECD spectra, and a modified Mosher′s method. Aplysiasecosterol A ( 1 ) exhibited cytotoxicity against human myelocytic leukemia HL‐60 cells. A biosynthetic pathway for 1 from a known cholesterol was proposed and includes twice α‐ketol rearrangements and an intramolecular acetalization.     

Functional renormalization group beyond the static approximation and its application to the two-dimensional Hubbard model

While the functional renormalization group is a powerful theoretical method, the static approximation has been usually adopted in which the Matsubara frequency dependence of vertex functions is ignored. We propose a formalism beyond the static approximation with an efficient parameterization in the Matsubara frequency space for the vertex functions to incorporate the self-energy.     

2-Fluoro-3-phenyl-allyltrimethylsilane: A new fluorinated reagent for Hosomi-Sakurai reaction

2-Fluoro-3-phenyl-allyltrimethylsilane, prepared from β-fluorinated allylic acetate via a π-allylpalladium intermediate, reacted with various aldehydes and acetals in the presence of TiCl₄ to afford the corresponding homoallyl alcohols and homoallyl ethers, respectively, in good to moderate yields.     

Genetically-increased taste cell population with Gα-gustducin-coupled sweet receptors is associated with increase of gurmarin-sensitive taste nerve fibers in mice

Background  

The peptide gurmarin is a selective sweet response inhibitor for rodents. In mice, gurmarin sensitivity differs among strains with gurmarin-sensitive C57BL and gurmarin-poorly-sensitive BALB strains. In C57BL mice, sweet-responsive fibers of the chorda tympani (CT) nerve can be divided into two distinct populations, gurmarin-sensitive (GS) and gurmarin-insensitive (GI) types, suggesting the existence of two distinct reception pathways for sweet taste responses. By using the dpa congenic strain (dpa CG) whose genetic background is identical to BALB except that the gene(s) controlling gurmarin sensitivity are derived from C57BL, we previously found that genetically-elevated gurmarin sensitivity in dpa CG mice, confirmed by using behavioral response and whole CT nerve response analyses, was linked to a greater taste cell population co-expressing sweet taste receptors and a Gα protein, Gα-gustducin. However, the formation of neural pathways from the increased taste cell population to nerve fibers has not yet been examined.     

Synthesis of macrocyclic bis(phenylbenzoxazole) derivatives via tandem claisen rearrangement and their fluorescence behavior

Novel macrocyclic bis(phenylbenzoxazole) derivatives were easily synthesized from macrocyclic isobutenyl bis(amide‐ether)s by tandem Claisen rearrangement and subsequent intramolecular cyclization of the amide‐phenol intermediates. The position of substitution of the oligoethylene glycol moiety on the phenylamido groups of the macrocycles did not have a large effect on the yields of the bis(benzoxazole)s for the meta and para derivatives. The fluorescence quantum yields of most of the macrocyclic bis(benzoxa‐zole)s were lower than those of the corresponding nonmacrocyclic bis(benzoxazole) model compounds. The quantum yields of the para‐substituted macrocyclic bis(benzoxazole)s were clearly lower than those of the model compounds and decreased with increasing length of the oligoethylene chain.