Department of Applied Physics and Chemistry, Columbia University, New York, NY, 10027, USA.
Institute of Theoretical Physics, University of Regensburg, 93040, Regensburg, Germany.
Angew Chem Int Ed Engl. 2017 Nov 6;56(45):14145-14148. doi: 10.1002/anie.201708524. Epub 2017 Oct 6.
We report that the single-molecule junction conductance of thiol-terminated silanes with Ag electrodes are higher than the conductance of those formed with Au electrodes. These results are in contrast to the trends in the metal work function Φ(Ag)<Φ(Au). As such, a better alignment of the Au Fermi level to the molecular orbital of silane that mediates charge transport would be expected. This conductance trend is reversed when we replace the thiols with amines, highlighting the impact of metal-S covalent and metal-NH dative bonds in controlling the molecular conductance. Density functional theory calculations elucidate the crucial role of the chemical linkers in determining the level alignment when molecules are attached to different metal contacts. We also demonstrate that conductance of thiol-terminated silanes with Pt electrodes is lower than the ones formed with Au and Ag electrodes, again in contrast to the trends in the metal work-functions.
我们报告称，与金电极相比，硫醇封端的硅烷与银电极形成的单分子结电导率更高。这些结果与金属功函数 Φ(Ag)<Φ(Au)的趋势相反。因此，人们预计 Au 费米能级与介导电荷输运的硅烷分子轨道之间的排列会更好。当我们用胺取代硫醇时，这种电导率趋势会发生反转，这突出了金属-S 共价键和金属-NH 配位键在控制分子电导率方面的作用。密度泛函理论计算阐明了化学连接体在确定分子与不同金属接触时的能级排列时的关键作用。我们还证明，与 Au 和 Ag 电极形成的单分子结相比，硫醇封端的硅烷与 Pt 电极形成的单分子结的电导率更低，这再次与金属功函数的趋势相反。
