Microscopic evidence of a metallic state in the one‐pot organic conductor ammonium tetrathiapentalene carboxylate

¹H NMR (nuclear magnetic resonance) and high‐field ESR (electron spin resonance) measurements were carried out for self‐doped organic conductors in the ammonium tetrathiapentalene carboxylate (TTPCOO)₂[(NH₄¹⁺)_1–x(NH₃⁰)_x ] system. While the pristine TTPCOOH molecule is closed‐shell, self‐doped carriers are generated by substitution of the carboxyl proton by (NH₃⁰) and (NH₄¹⁺), which can be regarded as a charge reservoir. The π‐extended system TTPCOO has a uniaxial g ‐tensor, indicating a 2D isotropic structure such as a herring‐bone‐like or parallel cross donor arrangement. The NMR‐relaxation rate indicated the Korringa relation in the temperature dependence, and the ESR linewidth followed the Elliot mechanism. Both of these observations provide supporting evidence for a stable metallic state. In this paper, we introduce self‐doped organic conductors as a branch of materials design, and emphasize that advanced magnetic resonance measurements are powerful tools for developing functional materials. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Polysulfoximine: A Novel Sulfur-Based Polymer for High Performance Engineering Plastics

First polysulfoximine was synthesized and characterized. 4-Phenoxybenzenesulfonimidoyl chloride was prepared by the reaction of 4-phenoxybenzenesulfinyl chloride with anhydrous chloramine T. Acid-catalyzed polycondensation of the sulfonimidoyl chloride with 10% of anhydrous ferric chloride in nitrobenzene at 120°C for 48 h afforded 80% yield of polysulfoximine having tosyl group at the nitrogen atom (NTs derivative). The spectral characteristics of the NTs derivative suggested occurrence of the regioselective polycondenstion. The NTs derivative was treated with conc. sulfuric acid followed by neutralization with sodium hydroxide to give corresponding “free” polysulfoximine having hydrogen atom at the nitrogen atom (NH derivative) in 80% conversion. Benzylated derivative (NBz derivative) was obtained by benzylation of the NH derivative with benzyl chloride. Thermal properties of these polysulfoximines were examined.     

Preparation and Properties of Aliphatic Polybenzoxazoles from 4,4′-Diamino-3,3′-Dihydroxybiphenyl and Aliphatic Dicarboxylic Acid Chlorides by the Silylation Method

Abstract

A series of aliphatic polybenzoxazoles of high molecular weights was prepared in three steps by the low-temperature solution polycondensation of tetrakis(trimethylsilyl)-substituted 4,4′-diamino-3,3′-dihydroxy-biphenyl with aliphatic diacid chlorides with 7 to 12 methylene units yielding trimethylsilyl-substituted poly(o-hydroxysamide) precursor polymers, which were subjected to desilylation with methanol giving the poly(o-hydroxyamide)s, followed by thermal cyclodehydration. The aliphatic polybenzoxazoles had melting points in the 172 to 246 °C range with glass transition temperatures of 55-97°C. They were stable in the melt state up to 400 °C in nitrogen. These polybenzoxazoles and the corresponding bisbenzoxazole model compounds exhibited no liquid crystallinity.     

Unusual catalytic effect of the two-dimensional molecular space with regular triphenylphosphine groups

A novel organic-inorganic hybrid 2D molecular space with regular triphenylphosphine groups (triphenylphosphineamidephenylsilica, PPh(3)APhS) was successfully synthesized through grafting triphenylphosphine groups in the 2D structure of layered aminophenylsilica dodecyl sulfate (APhTMS-DS), which was developed in our previous research, with regular ammonium groups. The 2D structures were kept after the grafting reaction of triphenylphosphine groups in PPh(3)APhS. The catalytic potentials of 2D molecular space with regular triphenylphosphine groups were investigated. An unusual catalytic effect was found in a carbon-phosphorus ylide reaction. The PPh(3)-catalyzed reaction of modified allylic compounds, including bromides and chlorides with tropone yielded a [3 + 6] annulation product. However, an unusual [8 + 3] cycloadduct was obtained in the reaction of modified allylic compounds, including bromides and chlorides with tropone catalyzed by PPh(3)APhS. Otherwise, the stable catalytic intermediate was successfully separated, and the reaction activity of the catalytic intermediate was confirmed in the reaction of modified allylic compounds with tropone catalyzed by PPh(3)APhS. This research is the first successful example of directly influencing catalytic reaction processes and product structures by utilizing the chemical and geometrical limits of 2D molecular spaces with regular catalyst molecules and affords a novel method for controlling catalytic reaction processes and catalyst design.     

A rational design for the directed helicity change of polyacetylene using dynamic rotaxane mobility by means of through-space chirality transfer

Directed helicity control of a polyacetylene dynamic helix was achieved by hybridization with a rotaxane skeleton placed on the side chain. Rotaxane-tethering phenylacetylene monomers were synthesized in good yields by the ester end-capping of pseudorotaxanes that consisted of optically active crown ethers and sec-ammonium salts with an ethynyl benzoic acid. The monomers were polymerized with [{RhCl(nbd)}(2)] (nbd=norbornadiene) to give the corresponding polyacetylenes in high yields. Polymers with optically active wheel components that are far from the main chain show no Cotton effect, thereby indicating the formation of racemic helices. Our proposal that N-acylative neutralization of the sec-ammonium moieties of the side-chain rotaxane moieties enables asymmetric induction of a one-handed helix as the wheel components approach the main chain is strongly supported by observation of the Cotton effect around the main-chain absorption region. A polyacetylene with a side-chain rotaxane that has a shorter axle component shows a Cotton effect despite the ammonium structure of the side-chain rotaxane moiety, thereby suggesting the importance of proximity between the wheel and the main chain for the formation of a one-handed helix. Through-space chirality induction in the present systems proved to be as powerful as through-bond chirality induction for formation of a one-handed helix, as demonstrated in an experiment using non-rotaxane-based polyacetylene that had an optically active binaphthyl group. The present protocol for controlling the helical structure of polyacetylene therefore provides the basis for the rational design of one-handed helical polyacetylenes.     

The discovery of Hepatocyte Growth Factor (HGF) and its significance for cell biology,life sciences and clinical medicine

It has been more than 25 years since HGF was discovered as a mitogen of hepatocytes. HGF is produced by stromal cells, and stimulates epithelial cell proliferation, motility, morphogenesis and angiogenesis in various organs via tyrosine phosphorylation of its receptor, c-Met. In fetal stages, HGF-neutralization, or c-Met gene destruction, leads to hypoplasia of many organs, indicating that HGF signals are essential for organ development. Endogenous HGF is required for self-repair of injured livers, kidneys, lungs and so on. In addition, HGF exerts protective effects on epithelial and non-epithelial organs (including the heart and brain) via anti-apoptotic and anti-inflammatory signals. During organ diseases, plasma HGF levels significantly increased, while anti-HGF antibody infusion accelerated tissue destruction in rodents. Thus, endogenous HGF is required for minimization of diseases, while insufficient production of HGF leads to organ failure. This is the reason why HGF supplementation produces therapeutic outcomes under pathological conditions. Moreover, emerging studies delineated key roles of HGF during tumor metastasis, while HGF-antagonism leads to anti-tumor outcomes. Taken together, HGF-based molecules, including HGF-variants, HGF-fragments and c-Met-binders are available as regenerative or anti-tumor drugs. Molecular analysis of the HGF-c-Met system could provide bridges between basic biology and clinical medicine.     

Lewis-Pairing-Induced Electrochemiluminescence Enhancement from Electron Donor-Acceptor Diads Decorated with Tris(pentafluorophenyl)borane as an Electrochemical Protector

This study reports an effective peripheral decoration of organic donor-acceptor diads with B(C₆F₅)₃ for stabilizing electrogenerated radical ions. By employing a common p-type organic semiconductor benzothienobenzothiophene (BTBT) as the donor, tetracoordinate boron complexes showed improved solution electrochemiluminescence (ECL) intensity, reaching a 156-fold increase compared to that of the parent diad. The unprecedented Lewis-pairing-induced ECL enhancement is attributed to the multiple roles of B(C₆F₅)₃: 1) redistributing frontier orbitals, 2) facilitating electrochemical excitation, and 3) restricting molecular motions. Furthermore, B(C₆F₅)₃ converted the molecular arrangement of BTBT from conventional 2D herringbones into 1D π-stacks. This robust, highly ordered columnar nanostructure allowed red-shifting of the crystalline film ECL with electrochemical doping through the electronic coupling pathways of BTBT. Our approach will facilitate the development of elaborate metal-free ECL systems.     

Conjugated complex system composed of quinonediimine unit

A combination of transition metals and π-conjugated molecules or polymers as redox-active ligands affords the hybrid conjugated complexes. A variety of structural design is possible based on the coordination number and geometry to construct an efficient multi-redox system.     

Efficient Transformation of Polymer Main Chain Catalyzed by Macrocycle Metal Complexes via Pseudorotaxane Intermediate

Post-synthesis modification of polymers streamlines the synthesis of functionalized polymers, but is often incomplete due to the negative polymer effects. Developing efficient polymer reactions in artificial systems thus represents a long-standing objective in the fields of polymer and material science. Here, we show unprecedented macrocycle-metal-complex-catalyzed systems for efficient polymer reaction that result in 100 % transformation of the main chain functional groups presumably via a processive mode reaction. The complete polymer reactions were confirmed in not only intramolecular reaction (hydroamination) but also intermolecular reaction (hydrosilylation) by using Pd- and Pt-macrocycle-catalyzed systems. The most fascinating feature of the both reactions is that higher-molecular-weight polymers reach completion faster. Various studies suggested that the reactions occur in the catalyst cavity via the formation of a supramolecular complex between the macrocycle catalyst and polymer substrate like pseudorotaxane, which should be of characteristic of the efficient polymer reactions progressing in a processive mode.