Yoshinori Yamanoi

Plugging a Molecular Wire into Photosystem I: Reconstitution of the Photoelectric Conversion System on a Gold Electrode

Plug and play: Photoinduced electron transfer occurs from photoexcited P700 in photosystem I (PSI) to a gold surface (see picture). A novel molecular connector system is used, in which an artificial molecular wire, which is assembled on the gold surface, was plugged into PSI by reconstitution. Analysis of the photoelectron transfer kinetics proved both the output of electrons from PSI and the effectiveness of the molecular wire.

Reversible On/Off Conductance Switching of Single Diarylethene Immobilized on a Silicon Surface

The chemical functionalization of hydrogen-terminated silicon(111) surfaces with photochromic diarylethene using an ethylene anchoring group was achieved. Conductive atomic force microscopy measurements showed the current changes on modified silicon electrodes caused by light-induced isomerization of the diarylethene between an open form and a closed form.

Direct and Selective Arylation of Tertiary Silanes with Rhodium Catalyst

We have developed a convenient and efficient approach to the arylation of tertiary silanes under mild conditions. A variety of arylsilanes were synthesized in a one-step process with good to excellent yields in the presence of a rhodium catalyst with a base. The reaction was highly solvent dependent, and amides were the most effective of the various solvents used. This common catalyst system is highly tolerant of the various sensitive functional groups on the substrates, which might be difficult to extract by other methods. The rhodium-promoted silylation of aryl halides with electron-donating groups occurred more efficiently than the silylation of aryl halides substituted with electron-withdrawing groups. Heteroaromatic halides were also found to be readily silylated with tertiary silanes. The successful application of this reaction to the synthesis of a TAC-101 analogue, which is a trialkylsilyl-containing synthetic retinoid benzoic acid derivative with selective binding affinity for retinoic acid receptor-alpha, is also described.

Optical properties of disilane-bridged donor-acceptor architectures: strong effect of substituents on fluorescence and nonlinear optical properties.

A series of disilane-bridged donor-acceptor architectures 1-9 containing strong electron-donating and -withdrawing substituents were designed and synthesized in acceptable yields. The substituents substantially affected the fluorescence and nonlinear optical properties of the compounds. In the solid state, the compounds showed purple-blue fluorescence (λ(em) = 360-420 nm) with high quantum yields (up to 0.81). Compound 3, which had p-N,N-dimethylamino and o-cyano substituents, exhibited optical second harmonic generation (activity 2.9 times that of urea, calculated molecular hyperpolarizability β = 1.6 × 10(-30) esu) in the powder state. Density functional theory calculations for the ground and excited states indicated that both the locally excited state and the intramolecular charge transfer excited state make important contributions to the luminescence behavior.

Integrated Palladium-Catalyzed Arylation of Heavier Group 14 Hydrides

A convenient procedure has been developed for the preparation of Group 14 compounds by integrated palladium-catalyzed cross-coupling of aromatic iodides with the corresponding Group 14 hydrides in the presence of a base. The reaction conditions can be applied to the cross-coupling of tertiary, secondary, and primary Group 14 compounds. In most cases, the desired arylated products were obtained in synthetically useful yields. Even in the case of aryl iodides containing OH, NH(2), CN, or CO(2)R groups, the reactions proceeded with good to high yields with tolerance of these reactive functional groups. A possible application of this method is the unique synthesis of a fungicidal diarylmethyl(1H-1,2,4-triazol-1-ylmethyl)silane derivative.

A New Method To Generate Arene-Terminated Si(111) and Ge(111) Surfaces via a Palladium-Catalyzed Arylation Reaction

Formation of silicon-aryl and germanium-aryl direct bonds on the semiconductor surface is a key issue to realize molecular electronic devices, but the conventional methods based on radical intermediates have problems to accompany the side reactions. We developed the first example of versatile and efficient methods to form clean organic monolayers with Si-aryl and Ge-aryl bonds on hydrogen-terminated silicon and germanium surfaces by applying our original catalytic arylation reactions of hydrosilanes and hydrogermanes using Pd catalyst and base in homogeneous systems. We could immobilize aromatic groups with redox-active and photoluminescent properties, and further applied in the field of rigid π-conjugated redox molecular wire composites, as confirmed by the successive coordination of terpyridine molecules with transition metal ions. The surfaces were characterized using cyclic voltammetry (CV), water contact angle measurements, X-ray photoelectron spectroscopy (XPS), fluorescence spectroscopy, and atomic force microscopy (AFM). Especially, the AFM analysis of 17 nm-long metal complex molecular wires confirmed their vertical connection to the plane surface.

A Cyclic Hexanuclear Heterometalladithiolene Cluster [{(Cp*Rh)2Mo(μ‐CO)2(CO)}2(S2C6H2S2)2] with Two π‐Conjugated S2C6S2 Bridges: Synthesis, Crystal Structure, and Properties

Two dragons playing ball: Direct metal-metal bond formation using a pi-conjugated dinuclear metalladithiolene complex with two electron-deficient metal centers as building blocks led to a cyclic double trinuclear heterometalladithiolene cluster with two parallel plane bridges (see structure; Rh pink, Mo green, S yellow, C gray, O red).

Modification of the luminescence spectra of chloro(tetrapyridylcyclotetramine)europium complexes by fine tuning of the Eu–Cl distance with outer-sphere counterions in the solid state, in a polymer matrix and in solution

Controlling the coordination environments and the luminescence properties of Eu(3+) complexes with outer-sphere counterions was achieved in the solid state, in a polymer matrix and in solution.

Bright Solid‐State Emission of Disilane‐Bridged Donor–Acceptor–Donor and Acceptor–Donor–Acceptor Chromophores

The development of disilane-bridged donor-acceptor-donor (D-Si-Si-A-Si-Si-D) and acceptor-donor-acceptor (A-Si-Si-D-Si-Si-A) compounds is described. Both types of compound showed strong emission (λem =ca. 500 and ca. 400 nm, respectively) in the solid state with high quantum yields (Φ: up to 0.85). Compound 4 exhibited aggregation-induced emission enhancement in solution. X-ray diffraction revealed that the crystal structures of 2, 4, and 12 had no intermolecular π-π interactions to suppress the nonradiative transition in the solid state.

Assembly of nanosize metallic particles and molecular wires on electrode surfaces

This article highlights recent developments in the assembly of nanosize materials on electrode surfaces. A brief historical background of the field is given, followed by a selection of topics of particular current interest. We focus especially on the assembly of nanosize metallic particles and molecular wires on gold and silicon electrode surfaces. The fabrication, properties, and characteristics of functional nanostructured biointerfaces on electrode surfaces are also described.