In this paper the results of dynamic NMR studies on ethylmethylamino-tertiary-butyl-phenylborane (EMABPB) with or without light are reported. The NMR data were recorded on a Bruker 400 MHz NMR equipped with our custom...In this paper the results of dynamic NMR studies on ethylmethylamino-tertiary-butyl-phenylborane (EMABPB) with or without light are reported. The NMR data were recorded on a Bruker 400 MHz NMR equipped with our custom-made optical probe and with our custom-made 450 watts (W) monochromatic light sources. The molecular photochemistry including twisted intramolecular charge-transfer-excited-state (TICT) of the EMABPB in several solvents has been investigated. These results indicate that the aminoborane demonstrates multiple configurations in CD3Cl and CD2Cl2 resulting in the shifts of the signals of the alkyl groups on the nitrogen and boron. This indicates that there are some time-dependent changes at constant temperature over the irradiation interval. At ﹣60°C and the presence of light (λ = 265 nm), we observed a large change in the populations of the two sites, and this by itself indicates a modification in the rotation around the boron nitrogen bond in the excited state. By considering the existence of the TICT state, many important energy technologies may be developed with higher efficiency by controlling the back-electron transfer processes.展开更多
The motion of the atoms in a molecule may be described as a superposition of translational motion of the molecular center-of-mass,rotational motion about the principal molecular axes,and an intramolecular motion that ...The motion of the atoms in a molecule may be described as a superposition of translational motion of the molecular center-of-mass,rotational motion about the principal molecular axes,and an intramolecular motion that may be associated with vibrations and librations as well as molecular conformational changes.We have constructed projection operators that use the atomic coordinates and velocities at any two times,t=0 and a later time t,to determine the molecular center-of-mass,rotational,and intramolecular motions in a molecular dynamics simulation.This model-independent technique facilitates characterization of the atomic motions within a system of complex molecules and is important for the interpretation of experiments that rely on time correlation functions of atomic and molecular positions and velocities.The application of the projection operator technique is illustrated for the inelastic neutron scattering functions and for the translational and rotational velocity autocorrelation functions.展开更多
Six styryl pyrazine compounds, in which some are streically hindered rotation and some are freely rotated, have been sythesized in this work. The effects of temperature and solvent polarity on the photophysics and lum...Six styryl pyrazine compounds, in which some are streically hindered rotation and some are freely rotated, have been sythesized in this work. The effects of temperature and solvent polarity on the photophysics and luminescence behavior of these compounds were studied in detail. Results indicated that blocking of the double bond twist by a sufficiently rigid bridge increases fluorescence quantum yields dramatically and the single bond connecting the double bond twisted is favorable to the formation of T state (radiation decay). One of the resons for distyryl pyrazines having higher fluorescence quantum yields may be due to the less probability of transformation from E* state to P* state.展开更多
Inspired by nature’s molecular machines,the scientific research on solid-state molecular rotors is of great interest yet remains largely unexplored.Herein,we report a unique example of a thermal energydriven stimuli-...Inspired by nature’s molecular machines,the scientific research on solid-state molecular rotors is of great interest yet remains largely unexplored.Herein,we report a unique example of a thermal energydriven stimuli-responsive solid-state molecular rotor,which features an o-carborane moiety as a rotor that directly transduces the surrounding thermal energy into molecular rotations in the crystalline state.Its rotation is confirmed by X-ray diffraction.展开更多
文摘In this paper the results of dynamic NMR studies on ethylmethylamino-tertiary-butyl-phenylborane (EMABPB) with or without light are reported. The NMR data were recorded on a Bruker 400 MHz NMR equipped with our custom-made optical probe and with our custom-made 450 watts (W) monochromatic light sources. The molecular photochemistry including twisted intramolecular charge-transfer-excited-state (TICT) of the EMABPB in several solvents has been investigated. These results indicate that the aminoborane demonstrates multiple configurations in CD3Cl and CD2Cl2 resulting in the shifts of the signals of the alkyl groups on the nitrogen and boron. This indicates that there are some time-dependent changes at constant temperature over the irradiation interval. At ﹣60°C and the presence of light (λ = 265 nm), we observed a large change in the populations of the two sites, and this by itself indicates a modification in the rotation around the boron nitrogen bond in the excited state. By considering the existence of the TICT state, many important energy technologies may be developed with higher efficiency by controlling the back-electron transfer processes.
基金This work was supported by the U.S.National Science Foundation under Grants DMR-0411748 and DMR-0705974the U.S.Department of Energy through grant No.DEFG02-01ER45912.
文摘The motion of the atoms in a molecule may be described as a superposition of translational motion of the molecular center-of-mass,rotational motion about the principal molecular axes,and an intramolecular motion that may be associated with vibrations and librations as well as molecular conformational changes.We have constructed projection operators that use the atomic coordinates and velocities at any two times,t=0 and a later time t,to determine the molecular center-of-mass,rotational,and intramolecular motions in a molecular dynamics simulation.This model-independent technique facilitates characterization of the atomic motions within a system of complex molecules and is important for the interpretation of experiments that rely on time correlation functions of atomic and molecular positions and velocities.The application of the projection operator technique is illustrated for the inelastic neutron scattering functions and for the translational and rotational velocity autocorrelation functions.
文摘Six styryl pyrazine compounds, in which some are streically hindered rotation and some are freely rotated, have been sythesized in this work. The effects of temperature and solvent polarity on the photophysics and luminescence behavior of these compounds were studied in detail. Results indicated that blocking of the double bond twist by a sufficiently rigid bridge increases fluorescence quantum yields dramatically and the single bond connecting the double bond twisted is favorable to the formation of T state (radiation decay). One of the resons for distyryl pyrazines having higher fluorescence quantum yields may be due to the less probability of transformation from E* state to P* state.
基金support from National Natural Science Foundation of China(nos.21975130,21835003,21404059,21674050,91833304,and 21422402)the National Basic Research Program of China(nos.2017 YFB0404501 and 2014CB648300)+7 种基金the Natural Science Foundation of Jiangsu Province(no.BE2019120)the Six Talent Peaks Project of Jiangsu Province(no.TDXCL-009)the 333 Project of Jiangsu Province(no.BRA2017402)the Leading Talent of Technological Innovation of National Ten-Thousands Talents Program of Chinathe Excellent Scientific and Technological Innovative Teams of Jiangsu Higher Education Institutions(no.TJ217038)Scientific Research Foundation of Nanjing University of Posts&Telecommunications(no.NY219060)the Fundamental Research Funds for the Central Universitiesthe open research fund of Key Laboratory of MEMS of Ministry of Education,Southeast University and the Big Data Center of Southeast University.
文摘Inspired by nature’s molecular machines,the scientific research on solid-state molecular rotors is of great interest yet remains largely unexplored.Herein,we report a unique example of a thermal energydriven stimuli-responsive solid-state molecular rotor,which features an o-carborane moiety as a rotor that directly transduces the surrounding thermal energy into molecular rotations in the crystalline state.Its rotation is confirmed by X-ray diffraction.
