Masahiko Iyoda

Giant thienylene-acetylene-ethylene macrocycles with large two-photon absorption cross section and semishape-persistence.

Giant π-conjugated macrocycles composed of thiophene, acetylene, and ethylene subunits arranged as 72π, 108π, 144π, and 180π electron systems were synthesized and analyzed for their one- and two-photon absorbance properties. Increasing π-conjugation showed an increase in the two-photon absorption cross section with magnitudes as high as 100u2009000 GM in the visible spectral region.

Dynamic Molecular Tweezers Composed of Dibenzocyclooctatetraene Units: Synthesis, Properties, and Thermochromism in Host–Guest Complexes

Novel dynamic molecular tweezers (DMTs) 3 a, 3 b, 4 a, 4 b, and 5 b, composed of two tub-shaped dibenzocyclooctatetraene (DBCOT) units, were designed and synthesized. The cyclooctatetraene (COT) rings of these DMTs readily invert in solution, and the molecular structure shows rigid syn and anti forms in an equilibrium mixture in solution. The syn and anti conformers can be observed by NMR. The isomerization barriers of 3 a, 3 b, 4 a, 4 b, and 5 b are in the range of 16.5-21.3 kcal mol(-1), depending on steric repulsion between substituents of the COT rings and protons of the central benzene ring. These DMTs form complexes with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and 1,2,4,5-tetracyano-benzene (TCNB) in solution and in the solid state. The binding abilities of these DMTs increase with electron-donating substituents on COT, which increase the electron densities of the cavity of the syn form, as supported by theoretical calculations. In addition, elongation of the terminal alkoxy chains of the DMTs was found to cause the enhancement of van der Waals contact with guest molecules. Therefore, 5 b, which has CH(2)OMe groups on the COT rings and longer ethoxy groups on the terminal benzene rings, showed the highest electron density of the cavity and hence the highest binding ability with the electron-deficient guest molecules. Interestingly, solutions of 3 b, 4 b, and 5 b show thermochromism in the presence of DDQ. A solution of 3 b or 4 b with DDQ in CHCl(3) is green due to charge-transfer interaction at room temperature and the color changes from green to yellow upon heating to 60 degrees C and from green to blue upon cooling to -40 degrees C, whereas the high complexation ability of 5 b with DDQ only shows a change in the shade of blue.

Synthesis of Nonaphenylenes and Dodecaphenylenes Using Electron-Transfer Oxidation of Lipshutz Cuprates and Formation of Nanostructural Materials from Hexadodecyloxynonaphenylene

Nonaphenylenes and dodecaphenylenes have been synthesized by using electron-transfer oxidation of Lipshutz cuprates with duroquinone. Oxidation of the Lipshutz cuprate derived from 4,4-dibromo-o-terphenyl 3a in THF produced nonaphenylene 1a in 46% yield, whereas the similar oxidation of the Lipshutz cuprates derived from 4,4-diiodo-4,5-dialkyl-o-terphenyls 3b-d in ether afforded the corresponding nonaphenylenes 1b-d and dodecaphenylenes 2b-d in moderate total yields. In the case of 4,4-diiodo-4,5-didodecyloxy-o-terphenyl 3e as the starting material, oxidation of the corresponding Lipshutz cuprate in ether or THF only led to the formation of nonaphenylene 1e. Both nonaphenylenes 1a-e and dodecaphenylenes 2b-d are unreactive to light, atmospheric oxygen, and prolonged heating. These oligophenylenes showed strong UV absorption and fluorescent emission and exhibited some redox properties on CV analysis. Moreover, hexadodecyloxynonaphenylene 1e exhibits different nanostructures on the surface and in solution to form a film by casting a solution of 1e in cyclohexane, benzene, chloroform, THF, or diisopropyl ether (IPE) and nanofibers from IPE-MeOH (1:1), indicating different absorption and emission spectra and XRD patterns. The absorption maxima of THF solution, fiber, and film are in the order of 1e film (315 nm) > fiber (302 nm) > solution (295 nm), whereas the emission maxima are in the order of 1e fiber (425 m) > solution (418 nm) > film (401 nm). XRD analysis revealed that 1e aligns laterally on a glass or silicon surface to form a thin film with a lamella structure; however, it forms a nanofiber with a Lego-like stacking structure without pi-pi stacking interaction of the aromatic rings. Reflecting the different nanostructures of the 1e film and fiber, a spin-coated 1e film is found to be effective in detecting the vapor of explosives due to the intercalation of nitroaromatics to the cracked surface of the loosely stacked 1e. In contrast, the 1e fiber is not effective in detection of nitroaromatics but exhibits fluorescence anisotropy. The maximum fluorescence intensity is obtained in a direction perpendicular to the longitudinal axis of the fiber, indicating the stacking direction to be parallel to the longitudinal axis of the fiber.

Magnetic Alignment in Solid State and Temperature Hysteresis in Aqueous Tetrahydrofuran Solution for Tetrathiafulvaleno[18]annulenes

Tris(tetrathiafulvaleno)dodecadehydro[18]annulene-hexaesters have a multi-functionality that is very sensitive to small differences in the ester side-chain. Self-aggregation of the [18]annulenes in amphiphilic media such as THF-H(2)O (v/v, 1:1) either produce a fibrous structure or result in temperature hysteresis of the color and (1)H NMR signals. This temperature hysteresis in solution is due to both strong self-aggregation behavior and unique cluster formation in a binary solution of THF and water.

Synthesis and electrical conductivity of perchlorate-doped TTF–diamide nanofibers with double and triple helix structures

We synthesized 4,5-bis(octadecylthio)-4′,5′-bis(ethylcarbamoyl)tetrathiafulvalene and measured the electrical conductivity of its perchlorate (ClO4−)-doped nanofibers, which have double and triple helix structures. The nanostructure of the bis(octadecylthio)-TTF–diamide and its ClO4−-doped fibers in a 3u2006:u20061 ratio was deduced in relation to the X-ray crystal structure of bis(methylthio)-TTF–diamide. The doubly coiled nanofibers form when initially formed spiral ribbons of lamellarly arranged TTF–diamide perchlorate split in the middle, and a further split of the double helix produces the triplex structure. Temperature-dependent conductance and current–voltage (I–V) characteristics of the coiled fibers were measured in the temperature (T) range of 70–300 K. The conductance decreased with a decrease in T, and the I–V characteristics were nonlinear over the entire T range. The results were analyzed by using a modified fluctuation-induced tunneling conduction model, where the barrier height and width were linearly dependent on the electric field.

Novel electron-transfer oxidation of Lipshutz cuprates with 1,4-benzoquinones: an efficient homo-coupling reaction of aryl halides and its application to the construction of macrocyclic systems

The electron transfer reaction from Lipshutz cuprates, which can be easily prepared from aryl bromides, to 1,4-benzoquinones was found to proceed smoothly, affording either the corresponding homo-coupling products, in modest to excellent yields, or macrocyclic products selectively.

Synthesis and electrochromic properties of bis(2-tetrathiafulvalenylethynylphenyl)ethynes

Bis(2-tetrathiafulvalenylethynylphenyl)ethynes la and 1b have been synthesized by the Sonogashira coupling reaction of 4-iodotetrathiafulvalenes with bis(2-ethynylphenyl)ethyne. The dimeric TTFs la and 1b form an open-chain anti conformation in the neutral and tetracation states, whereas la and 1b form a helical syn conformation in the mono- and dication states owing to their face-to-face interaction between the two TTF units. Such conformational changes lead to unique electrochromic and on-off switching properties of la and 1b in UV-vis-NIR spectra.

Long-distance ferromagnetic coupling through spin polarization in a linear heterotrinuclear iron(III)–copper(II)–iron(III) complex derived from 5-ferrocenyl-2-aminotropone

A novel hetrotrinuclear complex composed of two ferrocenium-ion moieties and copper complex of 2-aminotropones showed relatively strong intramolecular ferromagnetic coupling in the solid states owing to spin polarization mechanism.

SYNTHESIS AND π-AMPHOTERIC PROPERTIES OF TRIS(TETRATHIAFULVALENO)HEXADEHYDRO[12]ANNULENE

The Sonogashira coupling reaction of the diiodide 6 of 1,2-[4,5-bis(butylthio)tetrathiafulvalenyl]ethyne with 4,5-bis(ethynyl)-4,5-bis-(butylthio)tetrathiafulvanene 5 produced the corresponding tris(tetrathiafulvaleno)hexadehydro[12]annulene 1 in moderate yield. The [12]annulene 1 exhibits multi-redox behavior and solvatochromism in the neutral state.

Supramolecular Structures and Nanoassemblies of Oligothiophenes and Tetrathiafulvalenes

Supramolecular nanostructures derived from self-assembling oligothiophenes and tetrathiafulvalenes are reviewed. The two representative sulfur-containing π-electron systems have been extensively studied for their application in material sciences and have been shown to exhibit their excellent characteristics in conductive and optical properties. In the last decade, several researchers have developed these versatile π-electron systems as soft materials by means of substituents that cause weak intermolecular interactions. As the result, unique nanostructures such as fibers and particles endowed with characteristic conductive and optical properties have been demonstrated. These techniques may offer a bottom-up approach to construct future organic and molecular electronics.