Transition-Metal-Free Synthesis of Unsymmetrical Diaryl Tellurides via SH2 Reaction of Aryl Radicals on Tellurium

Although diaryl tellurides are parent organotellurium compounds, their synthesis methods, especially for unsymmetrical ones, are limited. This may be due to the instability of diaryl tellurides and their synthesis intermediates under reaction conditions. Radical reactions are known to exhibit excellent functional group selectivity; therefore, we focused on a bimolecular homolytic substitution (S_H2) reaction between the aryl radical and diaryl ditelluride. Aryl radicals are generated from arylhydrazines in air and captured by diaryl ditellurides, resulting in a selective formation of unsymmetrical diaryl tellurides with high yields. The electronic effects of the substituents on both arylhydrazines and diaryl ditellurides on the S_H2 reaction of tellurium are also discussed in detail.     

Synthesis of polyester by means of polycondensation of diol ester and dicarboxylic acid ester through ester–ester exchange reaction

Based on our finding that the ester-ester exchange reaction between butyl benzoate and ethyl 4-phenylbenzoate in the presence of a metal alkoxide is faster than the ester-alcohol exchange reaction of butyl benzoate and ethanol, we investigated the synthesis of polyester through ester-ester exchange reaction under various conditions. The polycondensation of diol formate and methyl dicarboxylate in the presence of a catalytic amount of potassium tert-butoxide (^tBuOK) in diglyme at 120 °C under reduced pressure (90–100 Torr) afforded high-molecular-weight polyesters. Methyl dicarboxylate containing an amino group could be used for this polycondensation, although the corresponding diacid chloride containing an amino group was not isolable. The ester-ester exchange reaction could proceed even at the polyester backbone, and the reaction of poly(1,12-dodecamethylene isophthalate) ( PEs ₁ ) with poly(ε-caprolactone) (PCL) in the presence of ^tBuOK at 140 °C afforded a copolymer PEs ₁ -stat-PCL, the structure of which was confirmed by ¹³C NMR spectroscopy and DSC thermal analysis. A similar copolymer was also obtained by the polycondensation of dodecane-1,12-diol formate and dimethyl isophthalate in the presence of PCL and ^tBuOK at 120 °C under reduced pressure.     

Photoinduced selective hydrophosphinylation of allylic compounds with diphenylphosphine oxide leading to γ-functionalized P-ligand precursors

A series of bifunctional phosphine compounds promising as γ-functionalized phosphine ligand precursors are conveniently synthesized by the radical addition of diphenylphosphine oxide (Ph₂P(O)H) to allylic compounds under photoirradiation. The photoinduced addition proceeds regioselectively in an anti-Markovnikov manner, and phosphines having hydroxy, alkoxy, aryloxy, acyloxy, and thio groups at the γ-position can be prepared by simple operation. Interestingly, novel continuous addition of Ph₂P(O)H to two molecules of allylic ethers and related compounds is also observed, although their yields are moderate. The substituent and steric effects of the allylic substituents on the radical addition are discussed in detail.

     

Stable Singlet Biradicals of Rare-Earth-Fused Diporphyrin-Triple-Decker Complexes with Low Energy Gaps and Multi-Redox States

Dinuclear rare-earth (Tb^III, Y^III) triple-decker complexes with a fused diporphyrin (FP) and two tetraphenylporphyrin (TPP) ligands were synthesized in neutral, dianionic, and diprotonated forms. The neutral forms have large open shell biradical character, as determined from the temperature dependency of the magnetic susceptibility measurements and theoretical calculations. The coupling value (J=−1.4 kcal mol⁻¹, −487 cm⁻¹) of the radical centers in the neutral form of the Y^III complex indicates weak pairing interactions. Theoretical calculations on the neutral form reveal a significant biradical character (y=68 %). Furthermore, the Tb^III complex exhibits multi-redox states, having more than eight clear peaks in the voltammetry curves. The optical (3700 nm, 0.33 eV) and electrochemical measurements (3400 nm, 0.36 eV) indicate that the neutral form has very small HOMO–LUMO energy gap. Despite the large biradical character, the neutral complexes are thermally stable and do not decompose on heating at 120 °C. These complexes with unique characteristics are promising candidates for use in molecular electronics, optics, and spintronics.     

Assignment of the Absolute-Handedness Chirality of Single-Walled Carbon Nanotubes by Using Organic Molecule Supramolecular Structures

Supramolecular structures of organic molecules on planar nanocarbon surfaces, such as highly oriented pyrolytic graphite (HOPG), have been extensively studied and the factors that control them are generally well-established. In contrast, the properties of supramolecular structures on curved nanocarbon surfaces like carbon nanotubes remain challenging to predict and/or to understand. This paper reports an investigation into the first study of the supramolecular structures of 5,15-bisdodecylporphyrin (C12P) on chiral, concentrated single-walled carbon nanotubes (SWNTs; with right-handed helix P- and left-handed helix M-) surfaces using STM. Furthermore, the study is the first of its kind to experimentally assign the absolute-handedness chirality of SWNTs, as well as to understand their effect on the supramolecular structures of organic molecules on their surfaces. Interestingly, these SWNT enantiomers resulted in supramolecular structures of opposite chirality based on the handedness chirality. With molecular modelling, we predicted the absolute-handedness chirality of SWNTs, before demonstrating this experimentally.     

Molecular recognition by a novel boronate-containing CTG derivative for hydroxyanthraquinones

C₃-functionalized cyclotriguaiacylene (CTG) derivatives were employed in the development of highly selective recognition compounds due to their unique molecular structures. Here, a novel C₃-functionalized CTG containing boronate (PPB-CTG) was synthesized and its molecular recognition ability for hydroxyanthraquinones was investigated by fluorescence spectroscopy. The addition of the synthesized PPB-CTG led to a large increase in the fluorescence intensity of only alizarin and not 1-hydroxyanthraquinone, 2-hydroxyanthraquinone nor quinizarin. It was, thus, suggested that the cyclotriveratrylene (CTV) structure plays an important role in the recognition ability toward alizarin since the mono-phenyl boronate compound (m-TPBAP) showed poor fluorescence properties toward alizarin. Moreover, it was found that the 1:1 mixture of PPB-CTG and alizarin was effective as a fluorescence-enhanced probe toward fluoride ions.     

Onion (Allium cepa L.)-Derived Nanoparticles Inhibited LPS-Induced Nitrate Production,However, Their Intracellular Incorporation by Endocytosis Was Not Involved in This Effect on RAW264 Cells

The aim of this study was to evaluate the involvement of nanoparticles prepared from Allium cepa L. as anti-inflammatory agents. In the present study, we identified nanoparticles from Allium cepa L. using the ultracentrifugation exosome purification method. The nanoparticles were referred to as 17,000× g and 200,000× g precipitates, and they contained quercetins, proteins, lipids, and small-sized RNA. The nanoparticles inhibited nitric oxide production from lipopolysaccharide (LPS)-stimulated RAW264 cells without cytotoxic properties. Cellular incorporation was confirmed by laser microscopic observation after PKH26 staining. The inhibition of caveolae-dependent endocytosis and macropinocytosis significantly prevented the incorporation of the nanoparticles but had no effect on the inhibition of nitric oxide in RAW264 cells. Collectively, the identified nanoparticles were capable of inhibiting the LPS response via extracellular mechanisms. Taken together, the way of consuming Allium cepa L. without collapsing the nanoparticles is expected to provide an efficient anti-inflammatory effect.     

Abelian Categories from Triangulated Categories via Nakaoka–Palu’s Localization

Applied Categorical Structures - The aim of this paper is to provide an expansion of Abe–Nakaoka’s heart construction to the following two different realizations of the module category...     

Critical dissipative estimate for a heat semigroup with a quadratic singular potential and critical exponent for nonlinear heat equations

We consider a heat semigroup with an inverse square potential and prove critical dissipative estimates including the endpoint case. Some application to a nonlinear heat equation with an inverse square potential is also discussed.