Ikutaro Hamada

Strongest π–metal orbital coupling in a porphyrin/gold cluster system

Face-on and close configuration of a π-conjugated molecule on an Au cluster generates a strong π–metal coupling between the π and metal orbitals. We successfully synthesized porphyrin-coordinated Au clusters in face-on configuration at the closest distance. The interaction between the Au cluster and porphyrin was investigated by UV-vis-NIR and transient absorption measurement.

Determination of geometric and electronic structures of organic crystals from first principles: Role of the molecular configuration on the electronic structure

We present a van der Waals density functional and many-body perturbation theory based study for accurate prediction of geometric and electronic structures of organic crystals. In addition to the determination of the crystal geometry and the quasiparticle energy, we demonstrate the role of the molecular configuration in organic crystals, which affects the transfer integrals between the frontier orbitals and the dynamical screening effect upon the injected charge. The result highlights the importance of obtaining accurate crystal geometry to elucidate the nature of the electronic state.

Photoelectron Holographic Atomic Arrangement Imaging of Cleaved Bimetal-intercalated Graphite Superconductor Surface.

From the C 1s and K 2p photoelectron holograms, we directly reconstructed atomic images of the cleaved surface of a bimetal-intercalated graphite superconductor, (Ca, K)C8, which differed substantially from the expected bulk crystal structure based on x-ray diffraction (XRD) measurements. Graphene atomic images were collected in the in-plane cross sections of the layers 3.3u2009Å and 5.7u2009Å above the photoelectron emitter C atom and the stacking structures were determined as AB- and AA-type, respectively. The intercalant metal atom layer was found between two AA-stacked graphenes. The K atomic image revealing 2u2009×u20092 periodicity, occupying every second centre site of C hexagonal columns, was reconstructed, and the Ca 2p peak intensity in the photoelectron spectra of (Ca, K)C8 from the cleaved surface was less than a few hundredths of the K 2p peak intensity. These observations indicated that cleavage preferentially occurs at the KC8 layers containing no Ca atoms.

Search for a Self-Regenerating Perovskite Catalyst with Ab Initio Thermodynamics II: Cu-Doped Layered Perovskites with K 2 NiF 4 Structure

These years, an “intelligent” automotive catalyst has been proposed and used in practical applications, which self-regenerates its precious metal nanoparticles during the redox cycles in automotive engines (Nishihata et al. Nature 418:164, 2002). In eliminating the use of expensive precious metals, a self-regenerating catalyst using non-precious metals such as Cu and Fe is necessary. We investigated the self-regeneration properties of Cu dissolved in layered perovskites with K2NiF4 structure under redox conditions of exhaust gas. Using ab initio thermodynamics calculations, we show that the self-regeneration of Cu on LaCuO3 may be hampered by the formation of La2CuO4, a well-known stable layered perovskite. Next, using the same calculation method, we examined the self-regeneration of Cu on a variety of layered perovskites, and proposed some layered perovskites as potential materials of the self-regenerating catalyst.Graphical Abstract