Based on the structure-properties relationship, novel benzenoid and hetero π-electron systems were investigated. Since cyclooligomerization and homo- and cross-couplings catalyzed by transition metals can produce unique π-electron systems with high symmetry in one- or short-step procedure, these reactions have been employed for the synthesis of novel benzenoid and hetero π-electron systems. We investigated the following molecules with novel structures and properties: (1) highly symmetric π-electron systems with unique electronic and photoelectronic properties; (2) novel organic π-donors and their charge transfer (CT)-complexes and radical salts having high electric conductivities; (3) diads and triads composed of organic π-donor and Cu(II) complex for ferromagnetic interaction; (4) novel π-electron systems with long alkyl chains for the nanostructure formation. This presentation will be mainly focused on topics (1) and (4).

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Hypercoordinate silicon complexes are highly flexible and versatile compounds: 1) Hexacoordinate complexes (1) undergo both ionic (2) and non-ionic (3) dissociation to pentacoordinate species, in a pattern modeling the SN2 reaction coordinate. 2) Subtle changes in donor strength have dramatic effect on complex geometry: octahedral vs. tetrahedral. 3) Different molecular geometries of pentacoordinate compounds in the solid state trace a complete reaction coordinate for the Berry pseudorotation reaction, in the Buergi-Dunitz sense. 4) Complete ligand crossover readily takes place between complex and differently substituted precursors, as well as between two complexes.

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Synthesis and optical properties of hetero-p-conjugated molecules containing boron and other main group elements such as N, P, O, S, and Se, which have azobenzene skeleton or diheteroanthracene and heteroacene frameworks, will be presented. On one hand, we achieved the photocontrol of Lewis acidity of 2-(catecholboryl)azobenzene by photoisomerization of the azobenzene moiety. Introduction of bis(pentafluorophenyl)boryl group to the 2-position of azobenzene was found to provide the molecule with fluorescence, whose property has been hindered by photoisomerization of azobenzenes. The most intensely fluorescent azobenzene was successfully synthesized. On the other hand, we designed and synthesized diheteroanthracenes and heteroacenes containing boron as an electron acceptor and N, P, O, S, or Se as an electron donor in one molecule. Most of these compounds showed a variety of colors and different colored fluorescence. Phosphoniaboraanthracenes were shown to have strong Lewis acidity and transfer fluoride ion from aqueous phase to organic phase. Multi-sensing of fluoride ion, selective cyanide ion sensing in water, and light-harvesting function using diheteroanthracenes or heteroacenes will also be presented.

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A very extensive matter, which is lacking from any current theory in organic reactions, is a comprehensive understanding of the role of solvents. We therefore placed gas-phase chemical reactivity in the center of our projects because gas-phase reactivity is intrinsic. Comparison of reactivity of the same reaction taking place in solution and in the gas phase allowed us to quantify the influence of solvation. These data were found to be particularly fruitful in developing an essential structure-reactivity relationship, because although such relationships have become a powerful tool for the assignment and interpretation of reaction mechanisms, difficulties in the analysis of some effects frequently arise from the involvement of solvent. Furthermore, intrinsic properties of isolated ions provided useful information on reactive intermediates, which are unstable in solution, and metal ion-molecule complexes in the gas phase also provided intrinsic nature of the binding interaction in these complexes.

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Electrocatalytic formal [2+2] cycloaddition between anodically activated aliphatic enol ethers and unactivated olefins possessing an alkoxyphenyl group was observed. Based on cyclic voltammetric studies and B3LYP/6-31G(d) calculations, it is proposed that the alkoxyphenyl group regulates the electron transfer, which operates as an electron donor during the formation of the cyclobutane ring, and as an electron acceptor from the anode to give the final product.

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The generation of a tetramethylenethane (TME)-type radical cation and biradical can be triggered by photoinduced electron-transfer (PET). Under PET conditions with an electron-accepting sensitizer, 5,5-dimethyl-2,3-bis(alpha-styryl)cyclopentadiene (4) converts into 4 radical cation, which undergoes facile cyclization to give a TME-type radical cation 5 radical cation. Successive back electron transfer (BET) from sensitizer radical anion to 5 radical cation finally gives the corresponding TME-type biradical 5 biradical. In this work, we have succeeded in observing 5 radical cation and 5 biradical with nanosecond absorption spectroscopy on laser flash photolysis. Radical cation 5 radical cation was observed at 494 nm in CH₂Cl₂ under conditions with a cationic sensitizer and a cosensitizer, where BET is retarded. In contrast, under conditions with a neutral sensitizer, the singlet biradical ¹5 biradical was observed at 370 nm because of facile BET. Calculation with time-dependent density functional theory also supports this conclusion.

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Combined computational and experimental studies were performed to understand substituent-effect on the ground state spin-multiplicity in localized tetraradical species. The singlet ground state of tetramethoxy-substituted tetraradical TR2b' was confirmed by the spectroscopic analysis, which is consistent with a computational prediction that was calculated at the CASPT2//CASSCF method.

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We report the effects of metal and non-metallic salts on the solvolysis reaction rates of 1-adamantyl halides (SN1) and hexyl halides (SN2) in DMA–H2O mixed solvents. The exponential increase in solvolysis rates of typical SN1 substrates in the presence of alkali metal and alkaline earth metal perchlorates have been explained by the direct chemical interaction between the metal cations and the halide ions from the substrates at the activated states. Contrastingly, non-metallic salts (e.g. Et4NClO4) caused decreases in the SN1 solvolysis rates in a good accordance with the distortion of water structure. For SN1-SN2 borderline substrates (benzyl halides), as well as the typical SN2 substrates, the anion exchange between the leaving group of a substrate and the anion of an added salt was observed when Et4NX (X = Cl and Br) was added. A linear relation was observed between the stabilities of carbocations and the changes by LiClO4 of solvolysis rate constants of various substrates.

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Substituent effects on the acetolysis rates of a-CN-a-CF₃-phenylethyl triflates (1), b-CN-b-CF₃-phenylethyl triflates (2), and a-CN-b-CF₃-phenylethyl triflates (3) were analyzed by using LArSR equation. The rho values obtained were -2.76 to -3.48, suggesting that these acetolyses undergo by k_delta mechanisms. The obtained r⁺ values of 0.93 to 1.06, on the other hand, were much larger than those of the typical k_delta solvolyses, and were rather close to those of the benzylic k_c solvolyses.

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Reaction of acyloxyalkene with iodosylbenzene in the presence of BF3•OEt2 gave acyloxytetrahydrofuran product via a 1,3-dioxan-2-yl cation intermediate. The reaction may be initiated by electrophilic addition of iodine(III) reagent toward alkene, followed by nucleophilic participation of the internal acyloxy group. Stereoselective formation of tetrahydrofuran product was achieved. Cyclic structure of the dioxanyl cation generated may control stereoselectivity of the formation of tetrahydrofuran product.

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[3,3]-Sigmatropic rearrangements of allyl aryl (or vinyl) ethers reported by L. Claisen helped spur the development of various other reactions. The Claisen rearrangement proceeds through a six-membered transition state by a supra-supra reaction following Woodward-Hoffmann rules and frontier orbital theory. However, its mechanism has remained controversial. In this work, observation of a molecular structural change in the [3,3]-Sigmatropic rearrangements process of allyl vinyl ether enabled us to elucidate the 3-step reaction mechanism.

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Metastable ion spectra for electron ionized molecular ions for titled system gave multiple hydrogen transferred ions by a four sector tandem mass spectrometer. Deuterium labeling has been done in order to elucidate the origin for transferred hydrogen atoms. Thus, a new system could be found for very rare triple hydrogen transfer on the competitive channels of stepwise double-single hydrogen transfer.

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Computational investigations have been made on a model reaction sequence for the title [6+2] cycloaddition reaction. B3LYP and MP2 calculations suggest a stepwise mechanism via a zwitterionic intermediate and [1,5] sigmatropic rearrangement processes connecting the cycloaddition products.

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We examined the mechanism of an enantiodivergent asymmetric cyclization of N-Boc-alpha-amino acid derivatives via memory of chirality by DFT calculations. With potassium amide bases in DMF, cyclization proceeds with retention of configuration, while inversion of configuration was observed with lithium amide bases in THF. We focused on the deprotonation process of the substrate because it gives a long-lived axially chiral enolate. The present calculations agree well with the experimental results. In the case of a lithium amide base, deprotonation proceeds via the inversion pathway predominantly; the TS of deprotonation was stabilized by coordination of Li to the carbonyl oxygen atom of the carbamate group. On the contrary, deprotonation proceeds via retention pathway predominantly in the case of a potassium amide base. And the substrate conformer 4a was more stable than 4b in DMF, which is also consistent with the observed retention of configuration.

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Interaction energies for fucose-phenol and fucose-indole clusters were calculated by ab initio molecular orbital method. The calculations show that significant attraction exists between the nonpolar surface of fucose and the aromatic rings. The dispersion interaction is the major source of the attraction in the clusters. The interaction of indole with fucose is substantially larger than that of benzene due to the large polarizability of indole.

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As the first step to understand the reaction mechanism and diastereoselectivity of sodium borohydride reduction of ketones, ab initio Car-Parrinello molecular dynamics simulation has been performed on a solution of NaBH₄ in methanol. According to pointwise thermodynamic integration involving constrained molecular dynamics simulations, it was strongly suggested that Na⁺ and BH₄^- are associated in the solvent forming contact ion pairs. Thus we propose a new transition state structure model that contains complexation of the carbonyl oxygen with sodium cation. Predicted diastereoselectivity of the reduction of some substituted cyclohexanones applying this novel transition state model is in good agreement with experimental data, showing its validity and effectiveness to investigate the diastereoselectivity of NaBH₄ reduction of other ketones.

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MO theory is constructed based on Born-Oppenheimer Approximation of original Schrodinger equation. However, it should be considered that there are some limitations in its application for the molecules in the midway state of chemical reactions, because their structures incessantly change with time t. The author propose the dynamic correlation diagram method, where the molecular orbital patterns (symmetry and phase or shape) of reactants are conserved in those of products with a minimum deformation.

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FMO-MD simulations for amination of formaldehyde with ammonia in aqueous solution are reported. Preliminary MO calculations of NH₃ + H₂CO + nH₂O (n = 0 - 2) to form carbinolamine NH₂CH₂OH at HF/6-31G** in vacuo and in water by using PCM showed the concerted and the two-stage mechanism, respectively. Very high activation barriers (20 - 40 kcal/mol with respect to the reaction complexes) make the amination reactions in the free MD simulations rare to occur. In our FMO-MD simulations, Blue Moon sampling, one of the efficient MD methods which can treat rare events, was used. FMO-MD simulations at HF/6-31G** were carried out on the systems constituted substrates and about 150 water molecules, where R_NC - R_NH was selected as a reaction coordinate. The results from the simulations clearly revealed that amination of formaldehyde with ammonia at neutral pH proceed by the two-stage mechanism via the zwitterionic intermediate.

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One of the isomers of hexafluoropropen trimers, perfluoro-3-isopropyl-4-methyl-2-pentene (T-2) was investigated on the trifluoromethylation by Ruppert-Prakash reagent under various solvents, such as DMF, DMA, NMP, CH3CN, DME, Diglyme, Triglyme, and DMI. In the cases of DMF, DMA, NMP, and CH3CN, bis-adduct of perfluoro-3-isopropyl-2,4,4-trimethyl-2-pentene was accompanied as a by-product to the main mono-trifluoromethylated product, perfluoro-3-isopropyl-2,4-dimethyl-2-pentene. However, In the Triglyme case, bis-adduct formation was remarkably suppressed and in the case of DMI, total selective mono-trifluoromethylation occurred to give the desired olefin as a sole product in very high yields. This unexpected solvent effect of DMI on the trifluoromethylation of highly-branched perfluoroolefin by Ruppert-Prakash reagent is discussed.

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Reaction of 2-aryl-1,3-dithiolanes with vinylcarbenoid formed by decomposition of Vinyldiazo compounds yielded vinylsulfonium ylides, which underwent ring expansion to produced 1,4-dithiacyclohexane derivertives and 1,4-dithia-5-cyclooctene derivetives. Effects of substituents on aromatic ring of 2-aryl-1,3-dithiolanes on product distribution will be also duscussed.

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It is essentially important to understand fundamental concept of electronic effects from substituents to ionic centers for both controlling reactions and designing molecules. Aromatic carbocations are first stabilized or destabilized by inductive effects of every substituents, followed by stabilization by resonance effect of para-pi-electron-releasing substituents. These behaviors of ring substituents are well described by the Yukawa-Tsuno equation. In this paper, substituent effects on the gas phase stabilities of benzylic anions were investigated in order to make clear the intrinsic effects of the substituents in anionic systems. We used proton transfer equilibria to determine the relative stabilities of ring substituted benzylic anions. Energies of species in these reactions were calculated by means of DFT method. We compared substituent effects of various benzylic anions with one another, to discuss what kind of electronic effects contribute to the gas phase stabilities in anionic systems.

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Microheterogeneous structures in solutions, formed through halogen-bonding and hydrogen-bonding interactions were studied by the mass spectrometric analysis of clusters isolated from solutions. These microscopic structures were found to be controlled by Lewis and Bronsted acid-base interactions. For the halogen-bonding system, iodopentafluorobenzene-pyridine clustering and iodopentafluorobenzene-pyrazine clustering were measured. For the hydrogen-bonding system, phenol-pyridine clustering and phenol-pyrazine clustering were measured. Pyridine and pyrazine were used as relatively strong and weak base, respectively. The halogen-bonding interactions with base molecules were decreased with the decrease of their Lewis acid-base interactions. In case of the hydrogen-bonding system, the phenol self-association clusters were increased with the decrease of Bronsted acid-base interaction.

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The experimental and computational studies on the gas-phase acidities of some hydrofluorocarbon(HFC) compounds and their hydroxy derivatives with chain, cyclic, and cage structures are done to reveal the importance of negative hyperconjugation in the stabilization of conjugate base anions of these compounds by C-F and C-CF₃ bonds at beta-positions.

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Reactions of substituted phenylketenes generated by light irradiation of the corresponding 2-diazoacetylbenzene with amines in MeCN were investigated by the time-resolved infrared detection (TRIR). Detailed analysis of the substituent effect for a process of formation of an intermediate (amide enol) showed curved correlations with reactivity. The degree of curvature was found to change with nucleophilicity of amines, suggesting a change of transition structure.

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The thermal reaction of a hydrido(selenolato) Pt(II) complex bearing a dibenzobarrelenyl group gave novel 4-membered selenaplatinacycles and and 5-membered one. The thermal reaction of one of the 4-membered selenaplatinacycles 1 with DMAD yielded the carboselenation adduct (diester 2), the structure of which was determined by NMR spectroscopy and X-ray crystallography. The UV/vis spectrum of 2 in CH2Cl2 showed the longest absorption maxima at 370 nm, attributable to the HOMO-LUMO transition of the 3-methylene-2,3-dihydroselenophene part. In the fluorescence spectrum, an intense emission was observed at 494 nm with the quantum yield of 0.66. The diester 2 was hydrolyzed in aq. NaOH to give the corresponding dicarboxylic acid 3, and refluxing a solution of 3 in Ac2O provided the corresponding acid anhydride 4 in good yield. In fluorescence spectra of 3 and 4, the emission maxima were observed at 507 and 517 nm, respectively, which are red-shifted compared with 2.

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Synthesis, structure, and properties of crowded triarylphosphine analogs of triarylamine functional dyes were studied. Crowded triarylphosphines carrying dimesitylboryl or 3.5-thienylene extended dimesitylboryl groups at 4-position were synthesized by using crowded (bromoaryl)phosphines as key synthetic intermediates. Properties of the borylphosphines were studied by UV-Vis and fluorescence spectroscopy, and electrochemical measurement. Cyclic voltammograms of the borylphosphines showed reversible redox waves corresponding to oxidation to a cation radical of triarylphosphine and quasi-reversible redox waves corresponding to reduction to an anion radical of triarylborane. The borylphosphines exhibited absorption and weak fluorescence corresponding to orange color. Introduction of crowded triarylphosphines lead to large Stokes shift and low quantum yield as compared with borylamines known as functional fluorescent dyes.

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It is known that phosphole has a high electron-accepting ability. To construct chemically and thermally stable pi-conjugated phospholes, we designed three types of naphthalene-fused phosphole derivatives, and succeeded in preparing the desired compounds based on a titanacycle methodology. The structure-property relationship will be presented.

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The polarity of a chemical bond is an important factor that affects its reactivity. We report here a method for reversing polarity of a hydrogen atom of water, which meant conversion of a proton (H+) to a hydride (H–), by using a hexacoordinated phosphorus species. Dihydrophosphate 2 was synthesized by the reaction of hydrophosphorane 1 with lithium naphthalenide, quenching with water, and cation exchange, successively. The hydrogen atoms on the phosphorus atom of 2 are not only exchangeable for a proton, but also usable as a hydride ion. The unique reactivity enables umpolung of deuterium of D2O and reductive deuteration of carbonyl compounds. The method is valuable for isotope-labeling of various compounds because the reaction proceeds under mild conditions and does not use transition metal. These results demonstrated the potential utility of non-metallic compounds for umpolung of a hydrogen atom.

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Cyclic compounds have various functions derived from their structures. Especially, heterocyclic compounds have attracted much attention due to unique properties different from those of typical hydrocarbon cyclic compounds. Trivalent phosphorus atom is widely used not only as a ligand for various transition metals but also as a chiral source because of its high inversion barrier. In this work, we report "stereospecific synthesis of trans-1,4-diphosphacyclohexane"and "synthesis of chiral 18-diphosphacrown-6". trans-1,4- Diphosphacyclohexane is important as a useful building block for metal-organic frameworks. Chiral 18-diphosphacrown-6 is the first example of optically active crown ether derivatives possessing chiral hetero atoms in the ring. In addition, we also report the transition metal complex formation of the chiral 18-diphosphacrown-6.

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Carbon is a central element in organic chemistry and it is commonly believed to obey the octet rule. Recently, Akiba et al. predicted and synthesized stable compounds having a penta-coordinate carbon atom, based on the concept of three-center four-electron bond (3c–4e). Kikuchi et al. clarified the existence of hexa-coordinate hypervalent carbon compound analogous to penta-coordinate carbon compound by ab initio calculations. However, the hexa-coordinate carbon compounds have not been synthesized so far. In the present study, we theoretically investigate the stability of hexa-coordinate hypervalent carbon compounds in relation to the substituent effect.

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We have recently reported that a novel silicon-silicon π single bond is present in 1,2,2,3,4,4-hexa-tert-butylbicyclo[1.1.0]tetrasilane. In order to study the conjugation between the silicon-silicon π single bond and a benzene π system, we synthesized 2,2,4,4-tetra-tert-butyl-1,3-diphenylbicyclo[1.1.0]tetrasilane 2. The X-ray analysis of compound 2 showed that the bicyclo[1.1.0]tetrasilane ring has a planar structure and is almost coplanar to the benzene rings. The silicon-silicon π single bond length is 2.7896(6) Å. The UV-visible absorption band of compound 2 shows a bathochromic shift compared with that of 1,2,2,3,4,4-tetra-tert-butylbicyclo[1.1.0]tetrasilane 3 at room temperature. At 77 K, the intensity of the absorption band of compound 2 remarkably increases. This result shows temperature-dependent dynamics of the molecular structure of compound 2 in solution.

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The CBD analogues consisting of heavier group 14 elements are hitherto unknown. Here we present the synthesis and characterization of the first free CBD silicon analogue (1) stabilized by the bulky EMind group. Treatment of tribromosilane (EMindSiBr3) with 3 equiv. of LiNaph gave diamagnetic tetrasilacyclobutadiene 1 as orange crystals. According to the X-ray analysis, the four-membered ring of 1 is planar and forms a nearly rhombic structure. The Si-Si bond length are 2.2671(9)-2.2927(9) angstrom, being intermediate between the Si-Si single and double bonds. The diagonal Si1 and Si3 atoms are in a distance of 3.5843(8) angstrom and significantly pylamidalized; the sum of the bond angles around Si1 and Si3 are 339 and 336°, respectively. In contrast, the other diagonal Si2 and Si4 atoms are ina distance of 2.8281(9) angstrom and assume an almost planar geometry; the sum of the bond angles around Si2 and Si4 are ca.360°.

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It is well known that alkynyl groups have unique reactivities and are employed as pi-spacers. Although they are expected as an effective substituent for disilenes in terms of molecular transformation or construction of novel pi conjugated system, very few disilenes bearing alkynyl groups have been reported so far. We report here the first syntheses of 1,2-bis(trimethylsilylethynyl)disilenes as stable compounds and their structures and properties. Reduction of dichlorosilanes 2 with lithium naphthalenide in THF at -78 C afforded the corresponding 1,2-bis(trimethylsilyl)ethynyldisilenes 1a and 1b as stable yellow crystals in 18 and 23%, respectively. In their UV-vis spectra, the absorption maxima of 1a and 1b appeared at 434 and 437 nm, respectively, which correspond to the pi-pi* transitions of the disilene moieties. MO calculations of 1 strongly indicated the conjugation between the Si=Si and CC moieties.

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In 2004, we succeeded in synthesizing of the first isolable disilyne 1 {RSiSiR, R = SiⁱPr[CH(SiMe₃)₂]₂}, and we have also investigated the unique reactivity of disilyne 1 toward alcohols, alkenes, alkynes, nitriles, and silylcyanides to understand the nature of the π bonds of the silicon-silicon triple bond. Some reactions gave the compounds containing Si=Si and Si=C double bond, and it was indicated that disilyne 1 could be a good precursor for the synthesis of the unsaturated silicon compounds. Herein we wish to report the recent results on the reactivity of disilyne 1 with secondary amines and hydroboranes, giving amino- and boryl-substituted disilenes, respectively. Their molecular structures were determined by NMR spectroscopy as well as X-ray crystallography, and the conjugation effect of lone-pair electron on nitrogen atom and vacant 2p-orbital on boron atom with π orbital of Si=Si double bond of disilene was also investigated.

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A systematic DFT calculations using the 6-31++G(d,p) basis set for dimethylsilylene (:SiMe₂) insertion into Si-Cl bonds of various chlorosilanes (YR¹R²SiCl) have revealed that the insertion proceeds concertedly via three-membered cyclic transition states (TS) and the activation free energies are affected remarkably by the substituents on chlorosilanes. Effects of in-plane substituents Y located in the three-membered ring plane at TS are mostly electronic. Electron-withdrawing Y accelerates the insertion via enhanced nucleophilic interaction between silylene lone-pair orbital with antibonding sigma(Si-Y) orbital at the TS. The activation free energies correlate with sigmaI constants as a scale of inductive effect of Y. The effects of out-of-plane substituents (R¹, R²) are mainly steric; bulky substituents increase the activation free energy. The good linear correlation of the activation free energies with Taft's steric substituent constants(E_S) was observed. Interestingly, there is no significant difference in the out-of-plane substituent effects between electron-withdrawing Cl and electron donating Me.

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An unsymmetrically substituted quaterthiophene and terthiophene with two terminal ferrocenyl groups was prepared as a long conjugated system. Electrochemical and spectroscopic studies were carried out to evaluate the electrical communication between the two terminals. The electrical communication between two terminals was't observed in terthiophene, but it was observed in quaterthiophene.

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Peptide-inspired compounds containing thieno[3,2-b]thiophene moiety, i.e. 1,4-bis(3-ethynylthieno[3,2-b]-thiophen-2-yl)benzene derivatives, 1-(3-ethynylthieno[3,2-b]thiophen-2-yl)-4-(2-ethynyl-3-thienyl)benzene derivative, and 2,5-bis(2-ethynyl-3-thienyl)thieno[3,2-b]thiophene derivative, were prepared and their UV-vis spectra were studied. Extension of pai-system through the central aromatic ring was suggested by the UV-vis spectra.

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We attempt to design of new type of multi-steps reversible redox systems containing organic and organometallic redox active flagments by using ferrocene-thiophene hybrid molecules. We have synthesized tetraferrocenyl-thiophene, -bithiophene, -terthiophene by palladium catalyzed cross-coupling reactions of corresponding tetrabromo-derivatives with ferrocenylzinc chloride. The structure of tetraferrocenylthiophene has been determined by X-ray crystallographic analysis. The electrochemical properties of these compounds were examined by cyclic voltammetry tequnique. The voltammograms of tetraferrocenyl compounds showed multi-steps oxidation process via mixed-valency and one reduction process derived form four ferrocene and origothiophene fragments.

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For the development of molecular electronics, it is of great importance to elucidate the nature of the electric contact between metal electrodes and anchoring groups. Thiols are the most commonly used group to be adsorbed on a gold electrode, while other functional groups have been recently attracting much attention as the candidate of an alternative anchoring group. Here, we present the synthesis of tripodal anchor units bearing pyridyl, amino, and selenol groups and the characterization of their monolayers. The monolayers on a gold surface were prepared by immersing Au/mica substrate in their CH2Cl2 solution for 12 h. These monolayers were characterized by CV and XPS measurements. The conductance measurement of molecules having tripodal anchor units at both terminal positions were investigated by STM break junction.

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Recently, organic field-effect transistors based on organic semiconductors have much interest from viewpoints of application such as a displays and electronic papers. In organic semiconductors, n-type materials have problems of mobility, solubility, and atmosphere stability. We synthesized n-type materials with high mobility and observed ambipolar OFET with a frame of anthracene.

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Recently, functional organic electronic materials have been actively studied. In particular, p-channel organic field-effect transistors (OFETs) have attained high performance and stability under ambient conditions. In contrast, n-channel OFETs suffer from both low performances and poor air-stability. Dicyanomethylene-substituted thienoquinoid derivatives are promising candidates as air-stable n-channel semiconductors, owing to their low-lying LUMO levels. In fact, terthienoquinoide with solubilizing groups were reported to be solution-processable n-channel OFETs materials with high electron mobility up to 0.16 cm2V-1s-1. However, introduction of solublizing groups on the terthienoquinoiod core requires a multiple-step synthesis, which makes it difficult to use it in various applications. In order to develop another soluble n-channel semiconductors with thienoquinoidal cores, we have designed new alkoxycarbonylcyanomethylene-substituted thienoquinoid derivatives e.g. -oligothiophene, benzo[2,3; b]dithiophene, thienoacene. In this presentation, we will report their synthesis, properties, and structures, together with FET characteristics of their OFET devices.

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Phenazasiline derivatives with various degree of polymerization (monomer, dimer, and polymer) and various substituents on the Si atom were prepared for comparison of investigation of transistor properties. The TFT devices using the compounds were fabricated as bottom-contact type by cast or vaccum-depositon. We found that the degree of polymerization of phenazasiline had to be at least over two so that transistor properties of the device could appear. The substituent effect of poly(phenazasiline) was also investigated.

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n-Type semiconductor tri(phenanthreno)- and tri(phenanthrolino)hexaazatriphenylenes were prepared and their self-assembling nature was discussed. The compounds were self-assembled both in solution and film state to form one-dimensional aggregates.

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The photoreactive conductive properties of gold nanoparticle- diarylethene network structure were measured. The gold nanoparticle acted as a Coulomb island and showed Coulomb blockade at 12 K. The current value of the nanostructure was digitally jumped under irradiation with UV light. According to the theory of single-electron transistor, digital-type current jump was turned out to be the potential shift of gold nanoparticle.

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Switchable photocurrent generating devices two outputting responses against two different external stimuli have received considerable attention because they represent current challenges for photoelectronic molecular device applications. One practical problem in such systems was that two functional molecules have a tendency to deactivate each other, leading the decrease performances due to rather complex molecular structure. Herein, rigid and compact tripod [70]fullerene derivatives and metal-complexes were synthesized and employed in co-assembly with a pentapod [60]fullerene derivative to obtain a mixed-component monolayer device showing direction-switchable photocurrent generation.

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Derivatives of Ce@C₈₂ (C_2v) have been synthesized and fully characterized, and their anisotropic magnetism has been observed as paramagnetic shifts in NMR measurements. Carbene addition by photochemical reaction afforded two isomers of Ce@C₈₂(C_2v)Ad (Ad = adamantylidene), 2a and 2b, demonstrating high regioselectivity. The two isomers were characterized using MALDI-TOF mass spectrometry, vis-NIR absorption spectroscopy, ¹H and ¹³C NMR spectroscopy, and electrochemistry. The structure of the minor isomer (2b) was elucidated by single-crystal X-ray structural analysis. ¹³C and ¹H NMR measurements revealed the characteristic anisotropic interaction between the f electron on the Ce atom and nuclear spins of the carbon atoms of the cage and the protons of the Ad group, respectively.

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We will report synthesis, structure, and properties of cobaltadithiolene-TTF-fullerene complexes, which were synthesized from the corresponding dicarbonyl complexes with simple methods. The obtained donor-acceptor arrays exhibited a characteristic absorption in near infrared region by a charge transfer transition between TTF and cobaltadithiolene moieties. They also exhibited reversible multiple redox processes. We will also discuss the structure, time-dependent photophysics, and third-order nonlinearity of them.

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Chiral (S)-s-BuCpFe complex of sumanene (C21H12) was synthesized, where magnetic and optical desymmetrization was exhibited in the sumanene ligand. [CpRu(η6-sumanene)]PF6 was also synthesized. The dynamic bowl-to-bowl inversion behaviour of the Ru complex was studied in solution.

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C3 symmetric cup-shaped syn-tris(norborneno)benzenes have been recently applied for host-guest chemistry as well as synthesis of bowl-shaped buckybowls. We have developed cycloctrimerization reaction of enantiopure iodonorbornene to prepare C3 symmetric homochiral syn-tris(norborneno)benzenes selectively, using palladium nanoclusters conditions. This cyclotrimerization is applicable to prepare C3 symmetric homochiral syn-tris(noborneneo)benzenes selectively possessing silyloxy group, carbonyl group, alkoxycarbonyl group, or amide group. In contrast, cyclotrimerization of enantiopure iodonorbornene diol acetoneide afforded C3v symmetric syn-tris(norborneno)benzene in 47% yield as well as anti-tris(norborneno)benzene in 13% yield. The formation of anti-isomer suggests that the reaction undergoes through Pd(IV) species, possibly palladacycle.

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We previously developed an efficient access to highly oxygenated tricyclobutabenzenes via repeated [2+2] cycloaddition of benzyne and ketene silyl acetal. Based on this knowledge, highly functionalized tricyclobutabenzenes are available via SN2 reaction of trisiodo-tricyclobutabenzene. Moreover, tricyclobutabenzene is cleanly isomerized to the corresponding valence isomer, hexaradialene, under the suitable conditions. By using this ring opening, functionalized triphenylenes are also synthesized via iterative three-fold [4+2] cycloaddition with dienophiles.

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