“Click” Incorporation of Radical/Ionic Sites into a Reactive Block Copolymer: A Facile and On‐Demand Domain Functionalization Approach toward Organic Resistive Memory

Reversible addition‐fragmentation chain transfer polymerization yields reactive block copolymers bearing the pentafluorophenyl ester (PFPA) group, and subsequent Click amidation using 2,2,6,6‐tetramethylpiperidine‐N‐oxyl‐ and imidazolium‐functionalized primary amines produces the corresponding functional block copolymers, leading to installation of statistical radical‐ and ionic sites into the PFPA segment. The monolayered thin film devices fabricated using the obtained block copolymers exhibit repeatable switching of electric conductivity (on/off ratio > 10³) under a bias voltage, which reveals that the coexistence of radicals and ions in the same spherical domain of the copolymer layer is a prerequisite for repeatable switching memory.

     

A Supramolecular Polymer of Nitroxide Radicals via Hydrogen Bonding

Summary: 2,2,6,6-Tetramethylpiperidinyl-N-oxy (TEMPO) is a robust nitroxide radical molecule under ambient conditions. We found that the TEMPO derivatives act as a proton acceptor to form an intermolecular hydrogen-bonding complex with many kinds of phenol or urea derivatives. ORTEP analysis of the crystals of TEMPO with the phenol derivatives indicated that hydrogen bonding could be formed between the oxygen of the nitroxide and the phenolic proton and the N O bond of the hydrogen-bonded TEMPO was lengthened in comparison to that of the free N O bond. The formation constant of the hydrogen-bonding complex of TEMPO with the phenol or urea derivatives in a chloroform solution was spectroscopically determined by IR to be 10–100 M⁻¹. Hydrogen bonding of the thelechelic bis-TEMPO derivatives with thelechelic bis-phenol or bis-urea derivatives provided a supramolecular structure. The estimated molecular weights of the supramolecules in the chloroform solution, based on DOSY-NMR spectroscopy, were 3000–4000. The potential of the nitroxide radical's supramolecule as a new functional material is also described.     

Temperature programmed desorption of F-doped SnO<Subscript>2</Subscript> films deposited by inverted pyrosol technique

Fluorine-doped tin dioxide (FTO) films were deposited on silicon wafers by inverted pyrosol technique using solutions with different doping concentration (F/Sn=0.00, 0.12, 0.75 and 2.50). The physical and electrical properties of the deposited films were analyzed by SEM, XRF, resistivity measurement by four-point-probe method and Hall coefficient measurement by van der Pauw method. The electrical properties showed that the FTO film deposited using the solution with F/Sn=0.75 gave a lowest resistivity of 3.2·10^–4 ohm cm. The FTO films were analyzed by temperature programmed desorption (TPD). Evolved gases from the heated specimens were detected using a quadruple mass analyzer for mass fragments m/z, 1(H⁺), 2(H₂ ⁺), 12(C⁺), 14(N⁺), 15(CH₃ ⁺), 16(O⁺), 17(OH⁺ or NH₃ ⁺), 18(H₂O⁺ or NH₄ ⁺), 19(F⁺), 20(HF⁺), 28(CO⁺ or N₂ ⁺), 32(O₂ ⁺), 37(NH₄F⁺), 44(CO₂ ⁺), 120(Sn⁺), 136(SnO⁺) and 152(SnO₂ ⁺). The majority of evolved gases from all FTO films were water vapor, carbon monoxide and carbon dioxide. Fluorine (m/z 19) was detected only in doped films and its intensity was very strong for highly-doped films at temperature above 400°C.     

Biomimetic synthesis of (+/-)-galanthamine and asymmetric synthesis of (-)-galanthamine using remote asymmetric induction

(+/-)-Galanthamine (1) was synthesized in excellent yield by applying PIFA-mediated oxidative phenol coupling of N-(4-hydroxy)phenethyl-N-(3',4',5'-trialkoxy)benzyl formamide (15b) as a key step. Because of the symmetrical characteristics of the pyrogallol moiety in the substrate (15b), the phenol coupling resulted in a sole coupling product except for volatile components from the oxidizing agent. On the basis of the successful results of the above strategy, (-)-galanthamine (1) was synthesized by employing a novel remote asymmetric induction, where conformation of the seven-membered ring in the product of the phenol coupling was restricted by forming a fused-chiral imidazolidinone ring with D-phenylalanine on the benzylic C-N bond of the tri-O-alkylated gallyl amino moiety. The conformational restriction and successive debenzylation of the protected hydroxyl groups on the pyrogallol ring caused diastereoselective cyclization to yield a cyclic ether having the desired stereochemistry for the synthesis of (-)-1.     

A nanometer-sized high-spin polyradical: poly(4-phenoxyl-1,2-phenylenevinylene) planarily extended in a non-Kekulé fashion and its magnetic force microscopic images.

A pi-conjugated, but non-Kekulé- and nondisjoint-type poly(1,2-phenylenevinylene) network bearing 4-substituted di-tert-butylphenoxyls was synthesized through a one-pot polycondensation of the star-shaped subpart and the subsequent oxidation, which was persistent even at room temperature. The polyphenoxyl radical with a spin concentration of 0.4 displayed an average S of 10/2. The polyradical with the molecular weight of 3.2 x 10(4) gave a disklike image of ca. 35 x 0.6 nm with both an atomic and a magnetic force microscopy: the molecular image was examined as a nanoscale and single-molecular-based magnetic dot.     

Effects of phosphatidylserine and phosphatidylethanolamine content on partitioning of triflupromazine and chlorpromazine between phosphatidylcholine-aminophospholipid bilayer vesicles and water studied by second-derivative spectrophotometry

To assess the affinity of psychotropic phenothiazine drugs, triflupromazine (TFZ) and chlorpromazine (CPZ), for the membranes of central nervous system and the other organs in the body, the partition coefficients (Kps) of these drugs to phosphatidylcholine (PC)-phosphatidylserine (PS) and PC-phosphatidylethanolamine (PE) small and large unilamellar vesicles (SUV, LUV) were examined by a second-derivative spectrophotometric method, since PS is abundantly contained in the membranes of the central nervous system and PE is distributed widely in the membranes of the organs in the body. Size and preparation methods of the vesicles did not affect the Kp values at each aminophospholipid content suggesting that the partition of the phenothiazine drugs was not affected by the structural differences in the vesicles such as their curvature or asymmetric distribution of the phospholipids between the outer and inner layers of the bilayer membranes. However, the Kp values of both drugs increased remarkably according to the PS content in the bilayer membranes, i.e., the Kp values for the vesicles of 30 mol% PS content were about 3 times of that for the vesicles of PC alone, while both Kp values slightly reduced with the increase in the content of PE in the bilayer membranes of PC-PE vesicles. The results indicate that both drugs have higher affinity for the PC-PS bilayer membranes than for the PC and PC-PE membranes, which can offer an evidence for the fact that TFZ and CPZ are predominantly distributed and accumulated in the brain and nerve cell membranes that contain PS abundantly.     

Ladderlike ferromagnetic spin coupling network on a pi-conjugated pendant polyradical

A poly(9,10-anthryleneethynylene)-based polyradical with two pendant stable phenoxyls in one anthracene skeleton was newly synthesized via polymerization of the corresponding bromoethynylanthracene monomer using a Pd(0) catalyst. The average molecular weight of the polymer reached M(n) = 5 x 10(3) and was soluble in common organic solvents. The polyradical was prepared from the corresponding hydroxyl precursor polymer and was appropriately stable at room temperature. The ESR spectrum of the corresponding monomeric radical suggested an effectively delocalized spin density distribution on the backbone anthracene. The magnetization and the static magnetic susceptibility of the polyradical were measured using a SQUID magnetometer. The large average spin quantum number (S = (5)/(2)) of the polyradical indicated that the ferromagnetic spin coupling network of the polyradical had spread throughout the pi-conjugated chain and that it was considerably insensitive to spin defects.     

Relationship of stereochemical and skeletal diversity of small molecules to cellular measurement space

Systematic and quantitative measurements of the roles of stereochemistry and skeleton-dependent conformational restriction were made using multidimensional screening. We first used diversity-oriented synthesis to synthesize the same number (122) of [10.4.0] bicyclic products (B) and their corresponding monocyclic precursors (M). We measured the ability of these compounds to modulate a broad swath of biology using 40 parallel cell-based assays. We analyzed the results using statistical methods that revealed illuminating relationships between stereochemistry, ring number, and assay outcomes. Conformational restriction by ring-closing metathesis increased the specificity of responses among active compounds and was the dominant factor in global activity patterns. Hierarchical clustering also revealed that stereochemistry was a second dominant factor; whereas the stereochemistry of macrocyclic appendages was a determinant for bicyclic compounds, the stereochemistry of the carbohydrates was a determinant for the monocyclic compounds of global activity patterns. These studies illustrate a quantitative method for measuring stereochemical and skeletal diversity of small molecules and their cellular consequences.     

Gomadalactones A, B, and C: novel 3-oxabicyclo[3.3.0]octane compounds in the contact sex pheromone of the white-spotted longicorn beetle, Anoplophora malasiaca

The ether extract of the females of white-spotted longicorn beetle Anoplophora malasiaca showed activity as contact sex pheromone to males. The extract was fractionated, and a pheromonal activity was revealed only when three fractions; n-hexane, n-hexane/EtOAc 9:1, and EtOAc were blended. The relative structures of gomadalactone A, B, and C, three active components isolated from the EtOAc fraction, were determined by spectroscopic studies to be (1S^∗,4R^∗,5S^∗)-5-hydroxy-4-[(E)-7-hydroxy-4-methylhept-3-enyl]-4,8-dimethyl-3-oxabicyclo[3.3.0]octan-7-en-2,6-dione, (1R^∗,4R^∗,5R^∗)-5-hydroxy-4-[(E)-7-hydroxy-4-methylhept-3-enyl]-4,8-dimethyl-3-oxabicyclo[3.3.0]octan-7-en-2,6-dione, and (1S^∗,4R^∗,5S^∗,8S^∗)-5-hydroxy-4-[(E)-7-hydroxy-4-methylhept-3-enyl]-4,8-dimethyl-3-oxabicyclo[3.3.0]octan-2,6-dione, respectively.     

Adsorption of metal ions on crosslinked poly(4-vinylpyridine) resins prepared with a metal ion as template

Poly(4-vinylpyridine) (PVP) was crosslinked with 1,4-dibromobutane with a metal ion as template. The adsorption behavior of copper, cobalt, zinc, and cadmium ions on the obtained resin (DBQP) was studied. The DBQP resin prepared with a metal ion as template preferentially adsorbed the metal ion used as template. The stability constant of the copper complex of DBQP was largest for the DBQP resin prepared with a copper ion as template, which was due to its large entropy change for the complexation.