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971.
On-chip fuel cell: micro direct methanol fuel cell of an air-breathing, membraneless, and monolithic design 总被引:1,自引:0,他引:1
Tominaka S Ohta S Obata H Momma T Osaka T 《Journal of the American Chemical Society》2008,130(32):10456-10457
This paper proposes a novel design for a microfuel cell as an on-chip power source and demonstrates its fabrication and operation to prove the concept. Its simple design is important from the viewpoints of fabrication (e.g., replication), integration, and compatibility with other microdevices. In testing, the prototype cell was able to generate electric power (maximum: ca. 1.4 microW) on methanol without pumps under both neutral and acidic conditions. As for the size, the electrode part of the cell (two cathodes and one anode) is 400 microns in width and 6 mm in length. The evaluation demonstrated that the proposed design is a promising on-chip power source for miniature devices. 相似文献
972.
Dr. Yoshio Ando Daichi Ogawa Prof. Dr. Ken Ohmori Prof. Dr. Keisuke Suzuki 《Angewandte Chemie (International ed. in English)》2023,62(5):e202213682
We report the enantioselective total syntheses of preussomerins EG1, EG2, and EG3. The key transformation is a stereospecific photochemical reaction involving 1,6-hydrogen atom transfer to achieve retentive replacement of a C−H with a C−O bond, enabling otherwise-difficult control of the spiroacetal stereogenic center. 相似文献
973.
Rempei Ando Dr. Ayana Sato-Tomita Prof.Dr. Hajime Ito Prof.Dr. Mingoo Jin 《Angewandte Chemie (International ed. in English)》2023,62(47):e202309694
Molecular motion in the solid state is typically precluded by the highly dense environment, and only molecules with a limited range of sizes show such dynamics. Here, we demonstrate the solid-state rotational motion of two giant molecules, i.e., triptycene and pentiptycene, by encapsulating a bulky N-heterocyclic carbene (NHC) Au(I) complex in the crystalline media. To date, triptycene is the largest molecule (surface area: 245 Å2; volume: 219 Å3) for which rotation has been reported in the solid state, with the largest rotational diameter among reported solid-state molecular rotors (9.5 Å). However, the pentiptycene rotator that is the subject of this study (surface area: 392 Å2; volume: 361 Å3; rotational diameter: 13.0 Å) surpasses this record. Single-crystal X-ray diffraction analyses of both the developed rotors revealed that these possess sufficient free volume around the rotator. The molecular motion in the solid state was confirmed using variable-temperature solid-state 2H spin-echo NMR studies. The triptycene rotor exhibited three-fold rotation, while temperature-dependent changes of the rotational angle were observed for the pentiptycene rotor. 相似文献
974.
Frustrated Lewis pairs (FLPs) have been widely investigated as promising catalysts due to their metal-free feature and ability to activate small molecules. Since their discovery, many works have been investigating how these Lewis pairs (intermolecular pairs) are held together in an encounter complex. This prompted several studies based on theoretical investigations, but experimental ones are limited yet. In this communication we show evidence of weak intermolecular interactions between Lewis acids and Lewis bases, distinguishing the Lewis adduct from FLPs, by probing fluorine-carbon vibrational modes using infrared spectroscopy. The main evidence is based on the band shifts occurring in FLPs due to weak hydrogen bonds between the hydrogen atoms of the Lewis base and the fluorine atoms of Lewis acid. 相似文献
975.
976.
Ando K 《The journal of physical chemistry. B》2008,112(2):250-256
Equilibrium and nonequilibrium dynamics of a blue copper protein plastocyanin in an oxidized state are studied by molecular dynamics (MD) simulation. Potential energy functions of the lowest seven electronic states, including ligand-to-metal charge-transfer (LMCT) and copper d --> d excited states, were taken from our previous work (Ando, K. J. Phys. Chem. B 2004, 108, 3940), which employed ab initio molecular orbital and density functional calculations on the active-site model. The equilibrium MD simulations in the ground state indicate that ligand motions coupled to transition from the ground state to the LMCT state are mostly represented by stretching and bending vibrations of the Cu-S(Cys) distance, Ndelta(His)-Cu-Ndelta(His) angle, and S(Cys)-Cu-[Ndelta(His)]2 trigonal pyramid structure. The nonequilibrium dynamics on the LMCT potential exhibit rapid decays in which surface crossings to the d --> d and the first excited states occur in 70-80 fs. The crossing dynamics mostly correlate with cleavage of the Cu-S(Cys) bond and the associated response in the Ndelta(His)-Cu-Ndelta(His) moiety. The average dynamics of the vertical energy gap coordinates exhibit an overdamped decay with a recurrence oscillation in 500 fs, which shows clear coherence surviving after the ensemble averaging. This oscillation stems mostly from the recoiling motion of the Ndelta(His)-Cu-Ndelta(His) part. The dynamics of the energy gaps after this coherent oscillation are randomized such that the ensemble average yields flat profiles along time, although each single trajectory exhibits fluctuations with amplitudes large enough to reach surface crossings. These indicate that the relaxation from the LMCT state first occurs via ballistic and coherent potential crossings in 70-80 and 500 fs, followed by thermally activated random transitions. 相似文献
977.
The palladium-catalyzed oxidative vinylation of indole-3-carboxylic acids with alkenes effectively proceeds via directed C-H functionalization and decarboxylation to produce the corresponding 2-vinylated indoles. Similarly, pyrrole-, furan-, and thiophenecarboxylic acids also undergo decarboxylative vinylation. 相似文献
978.
Ge Z Hayakawa T Ando S Ueda M Akiike T Miyamoto H Kajita T Kakimoto MA 《Organic letters》2008,10(3):421-424
The electronic structures of eight bathophenanthroline derivatives were elucidated by DFT calculations, and four representatives of which CZBP, m-CZBP, m-TPAP, and BPABP were synthesized and employed as the hosts to afford highly efficient phosphorescent OLEDs. The calculated molecular orbital energies agree well with the experimental results, which further demonstrates that the localization of HOMO and LUMO at the respective hole- and electron-transporting moieties is desirable in bipolar molecular designs. 相似文献
979.
Reaction mechanisms for the isomerization of prostaglandin H2 to thromboxane A2, and degradation to 12‐L‐hydroxy‐5,8,10‐heptadecatrienoic acid (HHT) and malondialdehyde (MDA), catalyzed by thromboxane synthase, were investigated using the unrestricted Becke‐three‐parameter plus Lee–Yang–Parr (UB3LYP) density functional level theory. In addition to the reaction pathway through FeIV‐porphyrin intermediates, a new reaction pathway through FeIII‐porphyrin π‐cation radical intermediates was found. Both reactions proceed with the homolytic cleavage of endoperoxide O? O to give an alkoxy radical. This intermediate converts into an allyl radical intermediate by a C? C homolytic cleavage, followed by the formation of thromboxane A2 having a 6‐membered ring through a one electron transfer, or the degradation into HHT and MDA. The proposed mechanism shows that an iron(III)‐containing system having electron acceptor ability is essential for the 6‐membered ring formation leading to thromboxane A2. Our results suggest that the step of the endoperoxide O? O homolytic bond cleavage has the highest activation energy following the binding of prostaglandin H2 to thromboxane synthase. 相似文献
980.
We present a norm estimate for the partial transpose map Θ on the tensor product
with respect to a unitarily invariant norm. This is related to the norm estimates of the following maps on Mm,n in terms of the spectral norm of
:
We show further that in the special case of
as well as AX + XB and AX + XBT those estimates are much improved and that
for certain Schatten p-norms.
Dedicated to the memory of late Professor Helmut H. Schaefer 相似文献