Liu peinian of Huali, Lin Nian of HKUST and Chen keqiu of Huda made important progress in the research of surface organic reaction

In recent years, the research group of Professor Liu peinian from the school of chemistry and molecular engineering of East China University of science and technology has made a series of important progress in the field of surface organic reactions Recently, the research group, together with Lin Nian, Professor of the Department of physics, Hong Kong University of science and technology, and Chen keqiu, Professor of the Department of Applied Physics, Hunan University, published the paper "negative differential conductivity in polyporphyrin polymers with nonlinear backbones" (J am Chem SOC 2018, 140, 570 − 573) in the Journal of the American Chemical Society (JACS) Source: the negative differential conductivity (NDC) effect of J am Chem SOC is a phenomenon that the current decreases with the increase of bias voltage Because of its unique properties, it has been widely used in molecular switches, molecular amplifiers, molecular memories, etc In this work, T-type, L-type and linear polyporphyrins were synthesized on the surface of ultra clean Au (111) by surface Ullmann reaction in ultra-high vacuum Then, by means of the tip manipulation of STM, the different shapes of the PPCs are pulled up from the Au (111) surface, which can selectively control the charge transport path in the PPCs of different shapes On this basis, the influence of the configuration, conformation and charge transfer path of the single molecular chain on the negative differential conductance effect is studied It is found that for the T-type porphyrin molecule, the charge passing through the T-type single molecule junction will produce stable and significant NDC effect; for the L-type porphyrin molecule, the charge passing through the 90 ° inflection point will produce bistable NDC effect, but the charge passing through the 120 ° inflection point will not produce NDC effect; for the linear type porphyrin molecule, the charge passing through will not produce NDC effect Through the calculation of the first nonequilibrium Green's function, the charge transfer of metal molecule metal single molecular junction is simulated, and the internal mechanism of NDC effect is revealed: (1) the molecular orbital based on the molecular skeleton determines the resonant charge transfer channel; (2) the coupling strength between the molecular orbital and the electrode is regulated by the external bias voltage, the higher the bias voltage, the weaker the coupling strength The new discovery of the mechanism of NDC effect can provide guidance and theoretical basis for the construction of various molecular junctions with NDC effect, and open up a new path for the design of NDC molecular devices The research was supported by the NSFC innovation research group project and nsfc-rgc joint project led by Professor Long Yitao and academician Tian He Paper link: http://pubs.acs.org/doi/10.1021/jacs.7b11016 profile of Professor Liu peinian: http://chem.security.edu.cn/2014/1113/c6655a50252/page.htm profile of Professor Liu peinian: http://physics.ust.hk/eng/people_detail PHP? Pplcat = 1 & id = 18 profile of Professor Chen keqiu: Http://spe.hnu.edu.cn/index.php/2015-04-27-07-54-54 / 2015-04-15-08-27-28 / 2015-05-15-08-18-39 / 40-c / 2-2015-04-15-08-48-35 Professor Chen keqiu