萘二酰亚胺同分异构体化合物的设计合成及其单分子导电性能研究

Design, synthesis and single-molecular conductivity of isomeric naphthalene diimides

本文设计合成了两个4-甲硫基苯乙炔基取代的1,4,5,8-萘二酰亚胺(1,4,5,8-NDI)和1,2,5,6-萘二酰亚胺(1,2,5,6-NDI)同分异构体化合物1和2,并用紫外-可见吸收光谱、电化学等手段研究了其物理化学性质.化合物1和2结构上的差异导致其物理化学性质以及单分子器件性能表现出差异.密度泛函理论(DFT)计算表明,基于1,4,5,8-NDI的化合物1具有更低的最高已占轨道(HOMO)/最低未占轨道(LUMO)能级,更有利于电子的传输.利用扫描隧道显微镜裂结技术(STM-BJ)技术制备了化合物1和2的单分子结,并研究了其导电行为.在离子液体1-丁基-3-甲基咪唑六氟磷酸盐(BMIPF_(6))中施加0.1 V电位,化合物1和2的电导值分别为10^(−3.70)G_(0)(15.5 nS,1G_(0)=77.5μS)和10^(−3.90)G_(0)(9.8 nS),表明化合物1具有更好的导电能力.

Two isomeric 4-methylthiophenylethynyl-substituted 1,4,5,8-naphthalene diimide(1,4,5,8-NDI)and 1,2,5,6-naphthalene diimide(1,2,5,6-NDI)derivatives 1 and 2 were designed and synthesized.The physicochemical properties of 1 and 2 were studied by means of ultraviolet-visible(UV-vis)spectra,electrochemical measurements and density functional theory(DFT)calculations.The structural differences between 1 and 2 led to their different physicochemical properties and single-molecule device performance.Compound 1 based on 1,4,5,8-NDI that has lower highest occupied molecular orbital(HOMO)/lowest unoccupied molecular orbital(LUMO)energy levels and narrower band gap is more conducive to electron transport relative to compound 2 with 1,2,5,6-NDI core.The single-molecular junctions of 1 and 2 were prepared by scanning tunneling microscope-break junctions(STM-BJ)technique,and their conductive behaviors were studied.When the potential of 0.1 V was applied in the ionic liquid BMIPF_(6),the conductance of single-molecular junctions of 1 and 2 was 10^(−3.70) G_(0)(15.5 nS,1G_(0)=77.5μS)and 10^(−3.90) G_(0)(9.8 nS),respectively,and the single-molecule device based on 1 has a better conductivity.