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981.
Chatterjee PB Abtab SM Bhattacharya K Endo A Shotton EJ Teat SJ Chaudhury M 《Inorganic chemistry》2008,47(19):8830-8838
Heterobimetallic complexes of a vanadium(V) and rhenium(VII) combination connected by a mu-oxido bridge [LVO(mu-O)ReO 3].H 2O [H 2L = N, N'-ethylene bis(salicylideneimine) (H 2salen) and its methoxy derivative] ( 1, 2) are reported. The compounds have been prepared by a single-pot synthesis in which the precursor [V (IV)OL] complexes are allowed to be oxidized aerially in the presence of added perrhenate. The oxidized [V (V)OL] (+) species accommodate the ReO 4 (-) anion in their vacant coordination site, trans to the terminal oxido group, providing the complexes 1 and 2. The later generates a binuclear oxovanadium(V) compound [H 2en][(TBC)VO(mu-TBC) 2OV(TBC)].5H 2O ( 3) when treated with tetrabromocatechol. Single crystal X-ray diffraction analysis and (1)H NMR spectroscopy have been used to establish their identities. In compound 2, the Re(1)-O(11)-V(1) bridge angle is barely linear [170.2(3) degrees ] with a Re...V separation of 3.9647(9) A. The redox behavior of 1 and 2 are quite interesting, each undergoing two reductions both in the positive potential range at E 1/2 = 0.59 (process I) and E 1/2 = 0.16 V (process II) versus Ag/AgCl reference (corresponding potentials are 0.59 and 0.18 V for 2). Process I has a single-electron stoichiometry involving the [VO(salen)] part of the complexes as established by combined coulometry-Electron Paramagnetic Resonance (EPR) experiments which provide an eight-line isotropic EPR pattern at room temperature ( = 1.967; = 87 x 10 (-4) cm (-1)), characteristic of an unpaired electron being coupled to a vanadium nuclear spin ( (51)V, I = 7/2). The almost linear V-O-Re bridge in 1 and 2 allows this unpaired electron to interact effectively with the neighboring Re nuclear spin, leading to familiar " two-line pattern" superhyperfine coupling ( A ( (185,187)Re) = 20.7 x 10 (-4) cm (-1)). Process II, on the other hand, is based on a Re(VII/VI) electron transfer as confirmed by differential pulse and normal pulse voltammetric experiments. 相似文献
982.
Time-resolved Raman spectroscopy has been applied to the hydrogen-abstraction reaction of decafluorobenzophenone (DFBP) from 2-propanol in temperatures ranging from room to supercritical temperature (520 K) at 31 MPa. The Raman bands of the intermediate ketyl radical (DFBPK) were identified. The Raman bands assigned to the C=C stretching mode (1639 cm-1) and the C-O stretching modes (1274 cm-1) shift to lower frequencies with increasing temperature. The corresponding Raman bands of stable molecules (reference molecules), benzhydrol, decafluorobenzhydrol, and benzophenone (BP), which all have similar molecular structures to those of DFBP or DFBPK, were also investigated at the same range of temperatures. Assignments of the Raman bands were performed with the help of density functional theoretical calculations and the isotopic exchange method. By comparing the Raman peak shifts of the radical with those of the reference molecules, the shift of the C=C stretching mode with increasing temperature (or decrease in the solvent density) is considered to be primarily due to the decrease in the repulsive interaction between the solute and the solvent. On the other hand, the shift of the C-O stretching mode of the radical reflects the decrease in the solvent Lewis acidity or its hydrogen-bonding donating ability, which is clearly illustrated by the shifts of the C=O stretching mode of BP and the C-O stretching mode of 2-propanol. The frequency of the C-O stretching mode of DFBPK was relatively sensitive to the surrounding environment. It was observed that the bandwidth of the radical was generally large, and this observation supports the previous report by Terazima and Hamaguchi (Terazima, M.; Hamaguchi, H. J. Chem. Phys. 1995, 99, 7891). Additionally, the sensitivity and the deformability of the radical structure due to the change of the solvent temperature and density were revealed in our studies. 相似文献
983.
Yamaguchi Y Shimoi Y Ochi T Wakamiya T Matsubara Y Yoshida Z 《The journal of physical chemistry. A》2008,112(23):5074-5084
To create highly fluorescent organic compounds in longer wavelength regions, and to gain physical chemistry insight into the photophysical characteristics, we investigated photophysical properties (Phi(f), lambda(em), tau, lambda(abs), epsilon, k(r), and k(d)) and their controlling factor dependence of the following pi-conjugated molecular rods consisting of p-phenyleneethynylene units modified by donor (OMe) and/or acceptor (CN): (1) side-donor modification systems (SD systems), (2) side-acceptor modification systems (SA systems), and (3) systems consisting of donor block and acceptor block (BL systems). As a result, very high Phi(f) values (>0.95) were obtained for BL systems. Bathochromic shifts of lambd(em) in the same pi conjugation length were largest for BL systems. Thus we succeeded in the creation of highly efficient light emitters in the longer wavelength region by block modification (e.g., Phi(f) = 0.97, lambda(em) = 464 nm for BL-9), contrary to expectation from energy gap law. Considerably intense solid emission (Phi(f) approximately 0.5) in the longer wavelength region (500-560 nm) was also found for BL systems, presumably because of molecular orientation that hinders the self-quenching of fluorescence in solids. From (1) a Lippert-Mataga plot, (2) density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations, and (3) the positive linear relationship between the optical transition energy (nu(em)) and the difference between the highest occupied molecular orbital of the donor and the lowest unoccupied molecular orbital of the acceptor (HOMO(D)-LUMO(A) difference), it is elucidated that the excited singlet (S1) state of BL systems has a high charge transfer nature. The number (n) of energetically equivalent dipolar structure (EEDS) units in the oligoarylene ethynylenes is shown to be a measure of the effective pi conjugation length in the S1 state. The S1 state planarity increases with n values of EEDS units and by the introduction of donor and/or acceptor groups. It is worth noting that the Phi(f) values increase linearly with the n values of EEDS units. 相似文献
984.
This paper is a revised version of my previous paper [4]. Main purpose is to give a right proof for non-archimedean Hartogs theorem(Stawski’s theorem) in case when the value group of the field K is discrete. 相似文献
985.
986.
Dr. Yohei Adachi Takanori Nomura Prof. Dr. Joji Ohshita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(19):4974-4983
Dithienogermole (DTG) has been applied as a useful building unit of optical/semiconducting materials for organic optoelectronic devices because of its extended conjugation, high chemical stability, and good emissive properties. Although DTG has two substituents on the Ge atom, the substituents have been limited to simple alkyl and aryl groups in previous work. In this work, to further uncover the new functionalities of this useful building unit, various π-conjugated groups were introduced on Ge of DTG. It was expected that the introduction of π-conjugated groups would give rise to efficient energy transfer between the substituents and the DTG core, which are in proximity and linked by a Ge atom. The thus-prepared DTG compounds with fluorene, terthiophene, and pyrene units on Ge possessed well-separated frontier orbitals on the substituents and the DTG core, as proved by the absorption spectra and DFT calculations. The substituted DTG derivatives showed clear emission only from the energy acceptor even though the energy donor was photoexcited. This indicated the highly efficient energy transfer in these compounds. We also prepared more π-extended compound DTGFl2-Ph with phenyl groups on the DTG thiophene rings. DTGFl2-Ph showed strong emission in the visible region with efficient energy transfer properties. These results clearly indicate the potential application of the present DTG system as optical functional materials. 相似文献
987.
Masahiro Komeda Shintaro Nagayama Yoshiaki Yoshida Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2019,57(21):2175-2180
1‐Benzocyclobutenyl methacrylate‐bearing methacrylate (BCBMA) backbone has been synthesized, and radical polymerization of the monomer was performed by utilizing 2, 2′‐azobisisobutyronitrile (AIBN) as initiator to result poly‐BCBMA. Differential scanning calorimetry (DSC) measurement of the derived poly‐BCBMA revealed the lowering of thermal isomerization temperature from that of nonsubstituted benzocyclobutene. The thermal decomposition temperature of BCBMA before and after thermal treatment was confirmed by thermogravimetric analysis (TGA). The results of the TGA observation did not show significant difference in both 5% and 10% weight loss temperature (Td5 and Td10). This result suggests that the thermal conversion of the poly‐BCBMA to the networked polymer take place without thermal decomposition of the main chain based on the methacrylate framework. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2175–2180 相似文献
988.
Guoliang Zhong Yukinori Kobayashi Yohei Hoshino Takanori Emaru 《Nonlinear dynamics》2013,73(1-2):167-182
Trajectory tracking of a mobile manipulator is a challenging research because of its complex nonlinearity and dynamics. This paper presents an adaptive control strategy for trajectory tracking of a mobile manipulator system that consists of a wheeled platform and a modular manipulator. When a robot system moves in the presence of sliding, it is difficult to accurately track its trajectory by applying the backstepping approach, even if we employ a non-ideal kinematic model. To address this problem, we propose using a combination of adaptive fuzzy control and backstepping approach based on a dynamic model. The proposed control scheme considers the dynamic interaction between the platform and manipulator. To accurately track the trajectory, we propose a fuzzy compensator in order to compensate for modeling uncertainties such as friction and external disturbances. Moreover, to reduce approximation errors and ensure system stability, we include a robust term to the adaptive control law. Simulation results obtained by comparing several cases reveal the presence of the dynamic interaction and confirm the robustness of the designed controller. Finally, we demonstrate the effectiveness and merits of the proposed control strategy to counteract the modeling uncertainties and accurately track the trajectory. 相似文献
989.
Optical Review - This paper describes a novel image filter with superior performance on detail-preserving removal of random-valued impulse noise superimposed on natural gray-scale images. The... 相似文献
990.
Optical Review - High performance of color quantization processing is very important for obtaining limited-color images with good quality. The median cut algorithm (MCA) is a typical color... 相似文献