Takashi Nakanishi

Molecular bilayer-based superstructures of a fullerene-carrying ammonium amphiphile: structure and electrochemistry.

The synthesis of a water-soluble C60-carrying single-chain ammonium amphiphile, 10- (N-methyl-2-fulleropyrrolidyl)decyltrimethylammonium bromide (1) as well as the characterization of aqueous solutions and cast films of 1 are described. X-ray diffraction study suggests that cast films of 1 form a multilayer structure based on biomembrane-like molecular bilayers. Electron microscopy has revealed that 1 produces both fibrous and disk-like aggregates with 10-12 nm of thickness through self-organization of 1 in aqueous solution. Differential scanning calorimetry, dynamic light scattering, FTIR, and UV-visible absorption studies were also carried out to characterize aqueous solutions and cast films of 1. Electrochemistry for an aqueous solution and for cast films of just 1 and 1 incorporated in lipid films on electrodes was conducted. It was found that films of just 1 and of 1/lipid cast on electrodes showed electron transfer reactions leading to the generation of the fullerene dianion or trianion. In contrast, electrochemistry of aqueous solution of 1 at a bare electrode gives a cathodic current near -0.5 to -0.6 V against SCE; however, an anodic current for the solution did not appear.

Electrochemical and spectroscopic investigation of neutral, oxidized and reduced double-decker lutetium(III) phthalocyanines

The double-decker lutetium(III) phthalocyanine [(C6H13S)8Pc]2Lu was investigated by electrochemical and spectroelectrochemical methods and comparisons made to previously investigated [(C12H25S)4Pc]2Lu and (Pc)2Lu under the some experimental conditions. All three compounds undergo a single reversible one-electron oxidation and up to four reversible one-electron reductions in CH2Cl2 containing 0.1 M tetra-n-butylammonium perchlorate (TBAP). The octa- and tetra substituted phthalocyanine derivatives exhibit one oxidation and three or four reductions in solution while five reductions can be detected for the two compounds in a gel-like cast film membrane of tetraoctylphosphonium bromide (4C8P+Br−) at a basal plane pyrolytic graphite electrode which was immersed in aqueous 0.5 M KCl. The half-wave potentials of these SR substituted complexes in CH2Cl2 are negatively shifted by 210-490 mV from E1/2 values for the same compounds in the aqueous 4C8P+Br− matrix and five reductions of these compounds are observed un...

Structure and Electrochemistry of Self-Organized Fullerene–Lipid Bilayer Films

The unique properties of C(60)-bearing artificial lipids with three C(16) (lipid 1), C(14) (lipid 2), or C(12) (lipid 3) alkyl chains have been characterized by a variety of techniques, including (13)C NMR, UV/Vis, and FT-IR spectroscopies, differential scanning calorimetry (DSC), X-ray diffraction, and electrochemistry. The (13)C NMR and UV/Vis spectra show that the lipids 1-3 have a closed aziridine structure at a 6/6-ring junction of C(60). The DSC data reveal that cast films of 1 exhibit two endothermic peaks at temperature ranges of 35-40 degrees C (main transition) and 47-49 degrees C (subtransition) in air, water, and 0.5 M aqueous tetraethylammonium chloride solution, while cast films of 2 and 3 each display one endothermic peak at 50-57 degrees C. The results of temperature-dependent FT-IR and UV/Vis studies of cast films of 1-3, together with the above data, reveal that the main peak in the DSC thermogram of a film of 1 can be attributed to a typical phase transition as seen in lipid bilayer membranes, while the sub-endothermic peak seen with 1 and the peaks for 2 and 3 stem from a change in the orientation of the C(60) moieties. X-ray diffraction patterns of each of the cast films of 1-3 show a diffraction peak corresponding to the (001) plane, suggesting the formation of molecular bilayer membrane structures. Cyclic voltammograms and Osteryoung square-wave voltammograms obtained from cast films of 1-3 on basal plane pyrolytic graphite (BPG) electrodes show strong temperature dependences. Finally, the thermodynamics of the binding of nine different alkylammonium ions and two alkylphosphonium ions to the electrogenerated radical monoanions and dianions of 1-3 cast on electrodes is described.

A Fullerene/Lipid Electrode Device: Reversible Electron Transfer Reaction of C60 Embedded in a Cast Film of an Artificial Ammonium Lipid on an Electrode in Aqueous Solution

Two reversible one-electron transfers are observed for an electrode device made from C60 and an artificial lipid (see schematic drawing). Cyclic voltammetric studies reveal that the redox couples are unchanged even after 50 cycles, thus indicating that the C60 radical monoanion and the C60 dianion generated in aqueous solution are very stable.

A star polymer with a metallo-phthalocyanine core as a tunable charge storage material for nonvolatile transistor memory devices

We present a strategy for controlling the device performance of organic field effect transistor (OFET) memory devices by using a metallo-phthalocyanine (MPc)-cored star-shaped polystyrene as a charge storage material. MPc-cored four-armed star polymers (M = Cu or Zn) with polystyrene arms of three different number-average molecular weights were prepared by atom transfer radical polymerization and cyclization reactions with metal ions; the density of the MPc cores dispersed in the polymer matrix was dependent on the lengths of polymer arms. The charge carrier mobility of pentacene-based OFET memory devices containing the star polymer varied with the nature of the MPc-cored star polymer layer owing to the presence of the MPc core unit as well as the nanostructures of the polymer thin films. Application of an external gate bias to the OFET device caused significant reversible shifts in the threshold voltage, and the magnitude of the memory shifts was proportional to the weight percentage of MPc cores in the star polymer matrix. The memory device showed a high memory on/off current ratio (>105) and long retention characteristics (>105 s), permitting it to be characterized as a nonvolatile organic memory device; the retention time extended upon increasing the Mn of the star polymer. The MPc-cored star polymer is a promising material designed as a charge storage layer for controlling the performance of organic flash memory devices.

Eine Fulleren/Lipid-Elektrode: reversible Elektronentransferreaktion zwischen C60 in einem synthetischen Lipidfilm und einer Elektrode in wäßriger Lösung

Zwei reversible Einelektronen-Transferreaktionen werden fur eine Elektrode erhalten, auf der sich ein Film aus C60 und einem synthetischen Lipid befindet (siehe schematische Darstellung). Bei cyclovoltammetrischen Messungen in wasriger Losung blieben die Redoxpaare selbst nach 50 Potentialdurchlaufen unverandert, was auf eine grose Stabilitat des dabei gebildeten Radikalmonoanions und des Dianions von C60 hinweist.

Chapter 9:Nanoscopic Organisation of Fullerenes

The topics covered in this chapter discuss the recent developments in the area of supramolecular fullerene assemblies at nano- and macroscopic scales. The control over dimension and morphology is the key challenge in constructing functional fullerene assemblies with their materials applications in mainly organic electronics.