Takayuki Fueno

Bio: Takayuki Fueno is an academic researcher from Osaka University. The author has contributed to research in topics: Reactivity (chemistry) & Ab initio. The author has an hindex of 32, co-authored 294 publications receiving 4869 citations.

Distribution of odd electrons in ground-state molecules

Abstract: A density function D(r) = 2γ(r, r) − tSγ(r, r′)γ(r′, r) dr′, where γ(r, r′) is a spinless first-order density matrix, has been proposed as fundamental formula representing the spatial distribution of odd electrons in molecules. The bonding properties of π electrons in some representative triatomic species have been examined in the light of D(r). The density function can also be used successfully to assess the diradical character of unstable singlet ground-state molecules.

Extended Hartree-Fock (EHF) theory in chemical reactions

Abstract: The roles of orbital, spin and permutation symmetries in the extended Hartree-Fock (EHF) wavefunction are investigated in relation to the applications of group theory to chemical reactions. The utility of the magnetically ordered set for an extended HF calculation is pointed out. The relative stabilities among linear Huckel and Mobius three-center three-electron (3,3) systems are investigated by the generalized Hartree-Fock (GHF) and EHF methods in order to confirm the reliability of the valence-bond (VB) selection rule for free radical reactions.

Ab Initio MO Calculations of Effective Exchange Integrals between Transition-Metal Ions via Oxygen Dianions: Nature of the Copper-Oxygen Bonds and Superconductivity

Abstract: The superexchange interaction between transition-metal ions via oxygen dianion was investigated by the ab initio molecular orbital (MO) method. It is found that the magnitude of the effective exchange integral (Jab) for the CuOCu unit is far larger than those of the NiONi, CrOCr and FeOFe units. Implications of this result are discussed in relation to the high Tc superconductivity for Ba-La-Cu-O and R-Ba-Cu-O (R=Y, etc.).

Molecular orbital (mo) theory for magnetically interacting organic compounds. ab-initio mo calculations of the effective exchange integrals for cyclophane-type carbene dimers

Abstract: A generalized molecular orbital (GMO) theory for magnetically interacting organic compounds has been presented. The theory is applied to the calculations of the effective exchange integrals (Jab) for the cyclophane-type carbene dimers whose para and ortho-isomers have the high-spin ground state. The calculated Jab-values are consistent with observations.

Density functional theory for transition metals and transition metal chemistry

Abstract: We introduce density functional theory and review recent progress in its application to transition metal chemistry. Topics covered include local, meta, hybrid, hybrid meta, and range-separated functionals, band theory, software, validation tests, and applications to spin states, magnetic exchange coupling, spectra, structure, reactivity, and catalysis, including molecules, clusters, nanoparticles, surfaces, and solids.

Mechanistic Aspects of Diels‐Alder Reactions: A Critical Survey

Abstract: The question of concerted or consecutive bond formation arises in all types of cycloaddition reactions. Stereochemical investigations and studies of regiospecificity as well as intensive kinetic investigations with regard to substituent and solvent effects, and the dependence of the reaction on temperature and pressure permit in many cases mechanistic conclusions concerning the Diels-Alder reaction. Efforts towards a theoretical interpretation, ab initio and semiempirical calculations, the application of frontier molecular orbital theory (FMO) as well as thermochemical measurements permit a description of the energy hypersurface of these [4+2]-cycloadditions. An attempt is made here to draw a line of distinction between the mechanistic alternatives—one-step reaction versus two-step reaction—considering all experimental and theoretical criteria.

New Concepts in Tetrathiafulvalene Chemistry.

Abstract: Tetrathiafulvalene (TTF) and its derivatives were originally prepared as strong electron-donor molecules for the development of electrically conducting materials. This Review emphasizes how TTF and its derivatives offer new and in some cases little-exploited possibilities at the molecular to the supramolecular levels, as well as in macromolecular aspects. TTF is a well-established molecule whose interest goes beyond the field of materials chemistry to be considered an important building block in supramolecular chemistry, crystal engineering, and in systems able to operate as machines. At the molecular level, TTF is a readily available molecule which displays a strong electron-donor ability. However, its use as a catalyst for radical-polar crossover reactions, thus mimicking samarium iodide chemistry, has only recently been addressed. Important goals have been achieved in the use of TTF at the macromolecular level where TTF-containing oligomers, polymers, and dendrimers have allowed the preparation of new materials that integrate the unique properties of TTF with the processability and stability that macromolecules display. The TTF molecule has also been successfully used in the construction of redox-active supramolecular systems. Thus, chemical sensors and redox-switchable ligands have been prepared from TTF while molecular shuttles and molecular switches have been prepared from TTF-containing rotaxanes and catenanes. A large synthetic effort has been devoted to the preparation of the so-called organic ferromagnets, many of which are derived from TTF. The main task in these systems is the introduction of ferromagnetic coupling between the conduction electrons and localized electrons. TTF has also played a prominent role in molecular electronics where TTF-containing D-sigma-A molecules have allowed the preparation of the first confirmed unimolecular rectifier. Recently, it has been confirmed that TTF can display efficient nonlinear optic (NLO) responses in the second and third harmonic generation as well as a good thermal stability. These findings can be combined with the redox ability of TTF as an external stimuli to provide a promising strategy for the molecular engineering of switchable NLO materials. Fullerenes endowed with TTF exhibit outstanding photophysical properties leading to charge-separated (CS) states that show remarkable lifetimes.