Shinsuke Nishida

Organic tailored batteries materials using stable open-shell molecules with degenerate frontier orbitals

Secondary batteries using organic electrode-active materials promise to surpass present Li-ion batteries in terms of safety and resource price. The use of organic polymers for cathode-active materials has already achieved a high voltage and cycle performance comparable to those of Li-ion batteries. It is therefore timely to develop approaches for high-capacity organic materials-based battery applications. Here we demonstrate organic tailored batteries with high capacity by using organic molecules with degenerate molecular orbitals (MOs) as electrode-active materials. Trioxotriangulene (TOT), an organic open-shell molecule, with a singly occupied MO (SOMO) and two degenerate lowest-unoccupied MOs (LUMOs) was investigated. A tri-tert-butylated derivative ((t-Bu)(3)TOT)exhibited a high discharge capacity of more than 300 A h kg(-1), exceeding those delivered by Li-ion batteries. A tribrominated derivative (Br(3)TOT) was also shown to increase the output voltage and cycle performance up to 85% after 100 cycles of the charge-discharge processes.

Molecular electron-spin quantum computers and quantum information processing: pulse-based electron magnetic resonance spin technology applied to matter spin-qubits

Pulse-based Electron–Nuclear and ELectron–electron DOuble Resonance (ENDOR/ELDOR) techniques have been applied to molecular spins in order to implement ensemble electron spin-qubit based quantum computers/computing (QC) and quantum information processing (QIP) in the solid state. Pulsed ENDOR-based QC/QIP experiments for super dense coding (SDC) have for the first time been carried out by the use of molecular electron- and nuclear-spin entities such as the stable malonyl radical as matter spin-qubits. The spin-qubit manipulation technology for quantum gate operations in this work is based on the time-proportional-phase-increment (TPPI) technique, enabling us to distinguish between the phases of spin-qubit based entangled states. The TPPI technique, as firstly applied by Mehring et al. (M. Mehring, J. Mende and W. Scherer, Phys. Rev. Lett., 2003, 90, 153001), has illustrated the establishment of quantum entanglement between electron- and nuclear-spin states and mutual interconversion between the electron–nuclear Bell states. The electron-spin 4π-periodicity in phase shows up in the QC/QIP experiments, explicitly and experimentally illustrating the electron-spin spinor nature for the first time. Tripartite QC experiments have been made, showing the occurrence of separable states. Also, the development of novel electron-spin technology to manipulate multi-electron spin-qubits is described. In this work, the pulsed coherent-dual ELDOR for QC/QIP has for the first time been implemented by invoking a novel microwave dual phase-rotation technique. Thus, applications of the coherent-dual ELDOR to molecular electron spin-qubit systems are also discussed, emphasising designing the molecular two electron-qubit systems appropriate for QC/QIP. g- and/or hyperfine A-tensor engineering approaches give us the two- and multi-electron-qubit systems, which have been a materials challenge to implement matter spin-qubit based QC/QIP. The targeted matter spin-qubits can be used to facilitate selective resonant microwave excitations achieved by the pulsed ELDOR technique. In addition to DiVincenzos five criteria, general requisites for scalable electron spin-qubit systems as 1D periodic robust spin structures are described. According to the requisites, double- or triple-stranded helicates embedding open-shell metal cations are proposed instead of organic molecular spin-qubits.

A Synthetic Two-Spin Quantum Bit: g-Engineered Exchange-Coupled Biradical Designed for Controlled-NOT Gate Operations†

A quantum gate: A system of two coupled electron spins that is useful for simple quantum computing operations has been prepared by synthesis of a biradical 1 and co-crystallization with an isomorphous host molecule. The two weakly exchange-coupled quantum bits (target qubit blue and control qubit red) span four electron spin states. The electron spin transition is denoted by two black arrows.

Three‐Dimensional Intramolecular Exchange Interaction in a Curved and Nonalternant π‐Conjugated System: Corannulene with Two Phenoxyl Radicals

In recent years, curved p-conjugated molecules such as fullerenes and carbon nanotubes have attracted much attention not only in chemistry but also in materials science. Their intra/intermolecular interactions within/between threedimensional (3D) curved p-electron networks play intrinsically vital roles in their unique properties and functionalities. Among them, intramolecular magnetic interaction between electronic spins on a curved p surface was extensively studied for ionic species of C60 such as C60 2 and C60 3 . Their electronic structures are greatly influenced by not only the dynamic spin polarization of electrons but also the negative charges on the spherical p-conjugated system and the countercation. Thus, we have focused on neutral diradical systems, which are known to be the most useful probes for studying intramolecular magnetic interactions in organic molecules. While many neutral diradical derivatives relevant to planar pconjugated systems have so far been investigated, studies on curved p-conjugated neutral diradicals are limited to a single C60-based system in which [60]fullerene is linked to two nitroxide radicals. However, their intramolecular exchange interaction J through the C60 skeleton was very weak (j Jk 1 B j < 0.1 K) because of the small spin delocalization onto the C60 p network from the nitroxide radicals with spin-localized nature on the NO moieties. Therefore, in order to evaluate an intramolecular exchange interaction in a curved p-conjugated system in a quantitative manner, synthesis and isolation of a stable neutral diradical derivative with extensively spindelocalized nature on its curved p-conjugated system have been the focus of current attention in molecular magnetism and open-shell chemistry. 5] Recently, we studied corannulene-based stable neutral monoradical systems, such as a phenoxyl radical derivative 1 with highly spin-delocalized nature on the intrinsically 3D bowl-shaped and nonalternant p-conjugated network. These

Curve-Structured Phenalenyl Chemistry : Synthesis, Electronic Structure, and Bowl-Inversion Barrier of a Phenalenyl-Fused Corannulene Anion

We have demonstrated the features of curve-structured phenalenyl chemistry, for the first time. A phenalenyl-fused corannulene anion has been designed by the annelation of a six-memberd ring across peri-positions of corannulene and generated as a stable species in a degassed solution. The 1H and 13C NMR spectra have shown the highly symmetrical structure and high-field shifts of protons and carbons at the asterisked positions in the chemical structure, indicating the occurrence of large negative charge densities at these positions. These results well agree with the HOMO picture and the electrostatic potential surface, demonstrating the phenalenyl anion-type electronic structure is retained in the curved-surface pi-system. The calculated bowl-inversion barrier of the anion (11.3 kcal/mol) is larger than that of corannulene (9.2 kcal/mol) because of peri-annelation of the corannulene skeleton. The calculations of the barriers of the neutral radical (12.6 kcal/mol), radical dianion (8.1 kcal/mol), and trianion (5.4 kcal/mol) of the phenalenyl-fused corannulene have exhibited a stepwise flattening of the curvature with increase in negative charge. Therefore, we have revealed that the bowl-inversion barrier of the anion is governed by the setoff of the peri-annelation and negative charge effects.

Curved aromaticity of a corannulene-based neutral radical: crystal structure and 3 d unbalanced delocalization of spin.

2. 2002–2003年大阪大学英文研究年報(Annual Report)論文100選 受 賞 題 目 : A New Trend in Phenalenyl Chemistry: A Persistent Neutral Radical, 2,5,8-Tri-tert-butyl-1,3-Diazaphenalenyl, and the Excited Triplet State of the Gable syn-Dimer in the Crystal of Column Motif Morita, Y.; Aoki, T.; Fukui, K.; Nakazawa, S.; Tamaki, K.; Suzuki, S.; Fuyuhiro, A.; Yamamoto, K.; Sato, K.; Shiomi, D.; Naito, A.; Takui, T.; Nakasuji, K. Angew. Chem. Int. Ed. (Hot Paper) 2002, 41, 1793–1796.

Organic Rechargeable Batteries with Tailored Voltage and Cycle Performance

Made to order: Rechargeable batteries are fabricated by using organic electron acceptors and donors as active cathode materials. Their output voltage and cycle performance can be tuned by organic chemistry techniques. The output voltages are linked to both the redox potentials and the energy levels of the frontier molecular orbitals of the cathode materials, enabling to predict the output voltage at an early stage of the design.

Room temperature hyperpolarization of nuclear spins in bulk

Significance Nuclear spins are only slightly aligned even in the strong magnetic fields of superconducting magnets because the magnetic energy of nuclear spin is much smaller than thermal energy. This is the major reason for the low sensitivity of NMR spectroscopy. Using electron spins in thermal equilibrium, which have 660 times higher magnetic energy, the sensitivity can be enhanced by at most this factor through a method called dynamic nuclear polarization. Utilizing photo-excited nonthermalized electrons instead, we demonstrate an enhancement factor of 250,000 at room temperature, which can be applied to a wide range of fields including NMR, MRI, and physics. Dynamic nuclear polarization (DNP), a means of transferring spin polarization from electrons to nuclei, can enhance the nuclear spin polarization (hence the NMR sensitivity) in bulk materials at most 660 times for 1H spins, using electron spins in thermal equilibrium as polarizing agents. By using electron spins in photo-excited triplet states instead, DNP can overcome the above limit. We demonstrate a 1H spin polarization of 34%, which gives an enhancement factor of 250,000 in 0.40 T, while maintaining a bulk sample (∼0.6 mg, ∼0.7 × 0.7 × 1 mm3) containing >1019 1H spins at room temperature. Room temperature hyperpolarization achieved with DNP using photo-excited triplet electrons has potentials to be applied to a wide range of fields, including NMR spectroscopy and MRI as well as fundamental physics.

Oxophenalenoxyl: Novel stable neutral radicals with a unique spin-delocalized nature depending on topological symmetries and redox states

Stable organic open-shell systems have attracted much attention in the field of molecule-based magnetism. We have been exploring novel stable neutral radicals based on a phenalenyl system known as an odd-alternant hydrocarbon π-radical with a highly spin-delocalized nature. Recently, we have designed and synthesized novel oxophenalenoxyl neutral radical systems possessing two oxygen atoms on the phenalenyl skeleton. These systems are unique in comprising some topological isomers depending on the positions of oxygen substituents on the phenalenyl skeleton. The isomers exhibit different topological symmetries of spin density distributions (spin topological symmetry control). In addition, two-stage one-electron reductions of these systems give the corresponding radical dianions, which show remarkably different topological symmetries of a spin-delocalized nature from those of the neutral radical systems (redox-based spin diversity). In this paper, we discuss the unique spin-delocalized nature of 3-, 4-, and 6-oxophenalenoxyl systems in view of the topological symmetry and redox ability, emphasizing the results from the radical dianion of 4-oxophenalenoxyl system from both experimental and theoretical sides.

A Bowl-Shaped ortho-Semiquinone Radical Anion: Quantitative Evaluation of the Dynamic Behavior of Structural and Electronic Features†

Organic radical ions play increasingly important roles in a wide range of research fields from biochemistry to materials science. o-Semiquinone is a typical organic radical anion with multistage redox ability that can form chelate salts and complexes with many kinds of metal cations. Investigation of a variety of transition-metal complexes of o-semiquinone radical could help not only to increase general knowledge of their fundamental chemistry but also to develop functional materials based on valence tautomerism phenomena. 3] In contrast, the alkali-metal salts have been extensively studied, and much attention has been focused on the dynamic behavior of their structure and of the electronic features of the ion pair in solution. 5] Solution-phase ESR spectroscopy measurements of some alkali-metal salts show significant temperature dependence in their hyperfine coupling constants (hfccs). The origin of this behavior has been only qualitatively interpreted as temperature-dependent positional change or migration of the alkali-metal cation to the oxygen atoms of the o-semiquinone radical. A quantitative discussion of such dynamic behavior has not been carried out to date. Recently, we synthesized and isolated corannulene (1)based stable neutral monoand diradical derivatives with bowl-shaped non-alternant p-conjugated systems. Their three-dimensional spin-delocalized nature and intraand intermolecular magnetic interactions were experimentally illustrated in terms of geometrical and topological aspects. These studies have inspired us to design a novel bowl-shaped radical anion system 2C based on corannulene with the o-