Hideo Yamakado

Preparation and properties of two-legged ladder polymers based on polydiacetylenes

A novel diacetylene derivative, N,N′-bis[5-(3-tolylaminocarbonyloxy)-1,3-pentadiynyl]-N,N′-diphenyl-1,4-phenylenediamine (1), was prepared, where two diacetylene groups were connected by a 1,4-phenylenediamine moiety. The molecules stacked one-dimensionally and showed solid-state-polymerization reactivity above 80 °C. The decay of the monomers at 100 °C proceeded gradually without a marked induction period and was fully completed after 400 h. The obtained polymer was a crystalline solid judged by powder X-ray diffraction (PXRD) patterns and SEM imaging. The conjugated π-system of the obtained polymer was classified as a two-legged conjugated ladder. The polymer showed a broad absorption from the visible to the near IR region, indicating a decrease in the optical band gap of ca. 1.0 eV, because of the expansion of the π-conjugated system from a one-dimensional system to a ladder. The ladder polymer showed high conductivity after I2 doping from σ293K = 5 × 10−12 S cm−1 to 1.2 × 10−5 S cm−1. The conductivity depended heavily on the pressure of iodine and reached σ373K = 2.3 × 10−1 S cm−1. The activation energy of the ladder polymer was also estimated as 360 meV.

COLLISION ENERGY RESOLVED PENNING IONIZATION ELECTRON SPECTRA OF POLYCYCLIC AROMATIC HYDROCARBONS

Abstract Penning ionization of naphthalene and anthracene with He*(23S) atoms has been studied by means of simultaneous detection of collision energy and electron energy. The anisotropy of interaction potentials between He*(23S) atoms and the target molecules has been found on the basis of the collision energy dependences of partial Penning ionization cross-sections. Based on the analyses of collision energy dependences and electron correlation calculations, assignments of ultraviolet photoelectron spectra are discussed.

Contact and channel resistances of organic field-effect transistors based on benzodithiophene-dimer films deposited on pentacene crystallinity control layers

We have investigated contact and channel resistances of organic field-effect transistors (FETs) based on benzodithiophene (BDT)-dimer films deposited on thin pentacene layers used as crystallinity control layers (CCLs). The contact resistance of source/drain electrodes made of conductive organic films instead of Au films has been reduced for pentacene-CCL/BDT-dimer FETs; the carrier mobility has been improved to 1.2u2002cm2u2009V−1u2009s−1 at maximum. Because the channel resistance of the pentacene-CCL/BDT-dimer FETs is found to be lower than that of reference pentacene FETs, the carrier transport in the BDT-dimer layers is more important than that in the pentacene CCLs for the high mobility.

Penning ionization of cobaltocene by collision with He*(23S) metastable atoms

Abstract Penning ionization of cobaltocene (C 5 H 5 ) 2 CO upon collision with He * (2 3 S) metastable atoms was studied by two-dimensional Penning ionization electron spectroscopy (2D-PIES). In the studied collision energy range (80–180 meV), the interaction potentials around cyclopentadienyl rings were found to be strongly attractive in the normal direction of the ring plane and were found to be repulsive around C H bonds. Assignments of the photoelectron bands of cobaltocene were discussed in detail by using 2D-PIES and the density functional theory (DFT).

Study of polycyclic aromatic hydrocarbons in the solid state by collision energy resolved Penning ionization electron spectroscopy

Abstract He * (2 3 S) Penning ionization electron spectra (PIES) of chrysene (C 18 H 12 ), perylene (C 20 H 12 ), and coronene (C 24 H 12 ) in the solid state were studied. Collision energy dependence of partial ionization cross-sections (CEDPICS) of solid state samples was measured for the first time. The CEDPICS of those samples shows positive and negative slopes depending on the final ionic states. As common features, negative CEDPICS for π bands and positive CEDPICS for ρ bands were observed. This indicates that the interactions between He * (2 3 S) and those aromatic hydrocarbons are attractive in the region where π orbitals extend and are repulsive around the hydrogen atoms.

Exploration of Carbon Allotropes with Four-membered Ring Structures on Quantum Chemical Potential Energy Surfaces: Exploration of Carbon Allotropes with Four-membered Ring Structures on Quantum Chemical Potential Energy Surfaces

The existence of a new carbon allotrope family with four‐membered rings as a key unit has been recently predicted with quantum chemical calculations. This family includes carbon allotropes in prism‐, polymerized prism‐, sheet‐, tube‐, and wavy‐forms. An atypical bond property has been observed in this series of carbon structures, which differs from the typical sp3, sp2, and sp hybridizations. The lowest energy barrier from some of the equilibrium states of the carbon structures has been determined with the SHS‐ADDF (scaled‐hypersphere‐search combined with the anharmonic downward distortion following) method within the GRRM software program package. The height of the barriers indicates that the well is deep enough for the carbon structures to exist. This class of carbon allotropes is expected to be energy‐reservoirs with extra energy of 100–350 kJ mol−1 per one carbon atom. This article presents the structures, energies and reactivity of the carbon allotropes with four‐membered ring structures as well as the background of the findings in the context of the global exploration of potential energy surfaces.

Quantum chemical exploration of formaldehyde clusters (H2CO) n (n = 2-4)

Global exploration of equilibrium structures and interconversion pathways on the quantum chemical potential energy surface (PES) is performed for (H2CO)n (nu2009=u20092–4) by using the Scaled Hypersphere Search‐Anharmonic Downward Distortion Following (SHS‐ADDF) method. Density functional theoretical (DFT) calculations with empirical dispersion corrections (D3) yielded comparable results for formaldehyde dimer in comparison with recent detailed studies at CCSD(T) levels. Based on DFT‐D3 calculations, trimer and tetramer structures and their stabilities were studied. For tetramer, a highly symmetrical S4 structure was found as the most stable form in good accordance with experimentally determined tetramer unit in the formaldehyde crystal.