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931.
Hideaki Takahashi Hajime Ohno Ryohei Kishi Masayoshi Nakano Nobuyuki Matubayasi 《Chemical physics letters》2008,456(4-6):176-180
In a recent development we proposed a quantum chemical approach to compute free energy change for chemical reactions in condensed phases by combining the QM/MM method with the theory of energy representation (QM/MM-ER). We extend in this Letter the novel approach to compute reduction free energy of isoalloxazine ring of FAD (flavin adenine dinucleotide) immersed in water within the framework of the QM/MM-ER method. The characteristic feature of our approach is that the excess electron to be attached on the FAD is identified as a solute. The reduction free energy has been obtained as −80.1 kcal/mol in the aqueous solution. 相似文献
932.
Inoue Y Kogure M Matsumoto K Hamashima H Tsukada M Endo K Tanaka T 《Chemical & pharmaceutical bulletin》2008,56(5):692-694
Silver loaded zeolite (Ag-Z) was previously found to have effective bactericidal activity against Escherichia coli. To understand the mechanisms of bactericidal activity of Ag-Z, role of light irradiation was focused and investigated in this study. In this study, we focused on light irradiation. Antibacterial assay and spectroscopic study revealed that light irradiation enabled Ag-Z to reduce dioxygen to form a reactive oxygen species, which led to bactericidal activity. These results indicate that the onset of bactericidal activity can be controlled by light irradiation. 相似文献
933.
Caetano EW Freire VN Dos Santos SG Galvão DS Sato F 《The Journal of chemical physics》2008,128(16):164719
Results of classical force field geometry optimizations for twisted graphene nanoribbons with a number of twists N(t) varying from 0 to 7 (the case N(t)=1 corresponds to a half-twist M?bius nanoribbon) are presented in this work. Their structural stability was investigated using the Brenner reactive force field. The best classical molecular geometries were used as input for semiempirical calculations, from which the electronic properties (energy levels, HOMO, LUMO orbitals) were computed for each structure. CI wavefunctions were also calculated in the complete active space framework taking into account eigenstates from HOMO-4 to LUMO+4, as well as the oscillator strengths corresponding to the first optical transitions in the UV-VIS range. The lowest energy molecules were found less symmetric than initial configurations, and the HOMO-LUMO energy gaps are larger than the value found for the nanographene used to build them due to electronic localization effects created by the twisting. A high number of twists leads to a sharp increase of the HOMO-->LUMO transition energy. We suggest that some twisted nanoribbons could form crystals stabilized by dipolar interactions. 相似文献
934.
Heteroleptic and homoleptic iron(III) complexes supported by a tris(N-heterocyclic carbene) borate ligand have been prepared and crystallographically characterized. The strong electron-donating character of the tris(carbene) donor was revealed by UV-vis absorption spectroscopy and electrochemical measurements combined with quantum chemical calculations. The catalytic activity of each complex was evaluated in cyclohexane oxidation reaction using meta-chloroperoxybenzoic acid (=mCPBA) as an oxidant, and both complexes show high catalytic activity and selectivity with TON=∼350 and A/(K+L)=8–10. Mechanistic studies suggested that radical-chain processes are involved in the reaction due to mCPBA acting as a one-electron oxidant, concomitant with the pathway of metal-based reactive species. Moreover, it was found that the homoleptic and heteroleptic complexes differed significantly in the involvement of metal-based active species, with the homoleptic complex exhibiting more metal-based reactions. 相似文献
935.
Prof. Dr. Mingoo Jin Satsuki Matsuura Hikaru Yamamoto Prof. Dr. Motohiro Mizuno Prof. Dr. Hajime Ito 《European journal of organic chemistry》2023,26(12):e202201468
We report multidynamic molecular rotations in crystals using a concave-shape N-heterocyclic carbene (NHC) binuclear Au(I) complex rotor bearing pyrazine and tetrahydrofuran (THF) molecules as multicomponent rotators. Single-crystal X-ray diffraction (XRD) measurements revealed that two THF molecules are located near the central pyrazine encapsulated by two bulky NHC ligands. From 2H solid-state NMR analysis, it was observed that the pyrazine rotated in a 2-fold site exchange with a 180° rotational angle and a 31 kJ mol−1 energy barrier, while the THF molecules showed a 23°-38° libration with a lower energy barrier (14 kJ mol−1). Interestingly, the pyrazine rotation was accelerated when the THF molecules rotated in fast site exchange with a large angle of libration, suggesting that the rotators exhibit multidynamics in a correlated manner. 相似文献
936.
Prof. Takayuki Nakajima Mizuki Takubo Yurika Komura Yuki Maeda Miwa Sato Maki Zouda Prof. Tomoaki Tanase 《欧洲无机化学杂志》2023,26(9):e202200648
A new series of cationic heterodinuclear complexes, [M1M2Cl2(meso-dpmppp)(RNC)2]PF6 (M1=Ni, M2=Rh, R=tBu ( 1 a ); M1=Pd, M2=Rh, R=tBu ( 2 a ), Xyl ( 2 b ); M1=Pt, M2=Rh, R=tBu ( 3 a ), Xyl ( 3 b ); M1=Pd, M2=Ir, R=tBu ( 4 a )), supported by a tetradentate phosphine ligand, meso-Ph2PCH2P(Ph)(CH2)3P(Ph)CH2PPh2 (meso-dpmppp), were synthesized by stepwise reactions of meso-dpmppp with NiCl2 ⋅ 6H2O or MCl2(cod) (M=Pd, Pt), forming mononuclear metalloligands of [M1Cl2(meso-dpmppp)], and with [M2Cl(cod)]2 (M2=Rh, Ir) and RNC (R=tBu, Xyl) in the presence of [NH4][PF6]. The related neutral PdRh complex, [PdRhCl3(meso-dpmppp)(XylNC)] ( 5 ), was also prepared. The structures of 1 – 5 were determined by X-ray analyses to contain two square planar d8 metal centers with face-to-face arrangement, where meso-dpmppp supports M1 and M2 metal ions in cis/trans-P,P coordination mode, combining cis-{M1P2Cl2} and trans-{M2P2(CNR)2} units. Complexes 1 – 4 showed an intence characteristic absorption around 422–464 nm derived from RhI→RNC MLCT transition (HOMO→LUMO+1), which are influenced by changing M1 (NiII, PdII, PtII) metal ions since HOMO composed of dσ* orbitals appreciably destabilized by changing M1 from Ni to Pd, and Pt. The electronic structures of 1 a – 4 a were investigated on the basis of DFT calculations and NBO analyses to show weak but noticeable d8–d8 metallophilic interaction as empirical dispersion energy of 0.9–1.5 kcal/mol without M1–M2 covalent bonding interaction. In addition, 1 – 5 were utilized as catalysts for hydrosilylation of styrene, and the NiRh complex 1 a was found to show higher activity and chemo- and regioselectivity compared with 2 – 5 . 相似文献
937.
We refine the computation of the d? ? ū flavor asymmetry in the proton sea with a complementary effort to reveal the dynamics of pion exchange in high-energy processes. In particular, we discuss the efficacy of pion exchange models to simultaneously describe leading neutron electroproduction at HERA along with the d? ? ū flavor asymmetry in the proton. A detailed \({\chi^{2}}\) analysis of the ZEUS and H1 data, when combined with constraints on the pion flux from Drell-Yan data, allows regions of applicability of one-pion exchange to be delineated. Based on the fit results, we also address a possible estimate for leading proton structure functions in upcoming tagged deep-inelastic scattering experiments at Jefferson Lab on the deuteron with forward protons. 相似文献
938.
Direct Observation of Ordered High‐Spin–Low‐Spin Intermediate States of an Iron(III) Three‐Step Spin‐Crossover Complex
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Dr. Zhao‐Yang Li Dr. Hiroyoshi Ohtsu Dr. Tatsuhiro Kojima Dr. Jing‐Wei Dai Takefumi Yoshida Dr. Brian K. Breedlove Dr. Wei‐Xiong Zhang Dr. Hiroaki Iguchi Prof. Osamu Sato Prof. Masaki Kawano Prof. Masahiro Yamashita 《Angewandte Chemie (International ed. in English)》2016,55(17):5184-5189
A neutral mononuclear FeIII complex [FeIII(H‐5‐Br‐thsa‐Me)(5‐Br‐thsa‐Me)]?H2O ( 1 ; H2‐5‐Br‐thsa‐Me=5‐bromosalicylaldehyde methylthiosemicarbazone) was prepared that exhibited a three‐step spin‐crossover (SCO) with symmetry breaking and a 14 K hysteresis loop owing to strong cooperativity. Two ordered intermediate states of 1 were observed, 4HS–2LS and 2HS–4LS, which exhibited reentrant phase‐transition behavior. This study provides a new platform for examining multistability in SCO complexes. 相似文献
939.
Dr. Kuirun Zhang Dr. Soonchul Kang Dr. Zi‐shuo Yao Kazusa Nakamura Dr. Takashi Yamamoto Prof. Dr. Yasuaki Einaga Nobuaki Azuma Dr. Yuji Miyazaki Prof. Dr. Motohiro Nakano Dr. Shinji Kanegawa Prof. Dr. Osamu Sato 《Angewandte Chemie (International ed. in English)》2016,55(20):6047-6050
Heterometallic Prussian blue analogues are known to exhibit thermally induced charge transfer, resulting in switching of optical and magnetic properties. However, charge‐transfer phase transitions have not been reported for the simplest FeFe cyanide‐bridged systems. A mixed‐valence FeII/FeIII cyanide‐bridged coordination polymer, {[Fe(Tp)(CN)3]2Fe(bpe)?5 H2O}n, which demonstrates a thermally induced charge‐transfer phase transition, is described. As a result of the charge transfer during this phase transition, the high‐spin state of the whole system does not change to a low‐spin state. This result is in contrast to FeCo cyanide‐bridged systems that exhibit charge‐transfer‐induced spin transitions. 相似文献
940.
Theoretical Modelling and Facile Synthesis of a Highly Active Boron‐Doped Palladium Catalyst for the Oxygen Reduction Reaction
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Tat Thang Vo Doan Jingbo Wang Kee Chun Poon Desmond C. L. Tan Bahareh Khezri Prof. Richard D. Webster Prof. Haibin Su Prof. Hirotaka Sato 《Angewandte Chemie (International ed. in English)》2016,55(24):6842-6847
A highly active alternative to Pt electrocatalysts for the oxygen reduction reaction (ORR), which is the cathode‐electrode reaction of fuel cells, is sought for higher fuel‐cell performance. Our theoretical modelling reveals that B‐doped Pd (Pd‐B) weakens the absorption of ORR intermediates with nearly optimal binding energy by lowering the barrier associated with O2 dissociation, suggesting Pd‐B should be highly active for ORR. In fact, Pd‐B, facile synthesized by an electroless deposition process, exhibits 2.2 times and 8.8 times higher specific activity and 14 times and 35 times less costly than commercial pure Pd and Pt catalysts, respectively. Another computational result is that the surface core level of Pd is negatively shifted by B doping, as confirmed by XPS, and implies that filling the density of states related to the anti‐bonding of oxygen to Pd surfaces with excess electrons from B doping, weakens the O bonding to Pd and boosts the catalytic activity. 相似文献