Department of Chemistry, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK.
Nanoscale. 2016 Dec 7;8(45):19004-19013. doi: 10.1039/c6nr06527a. Epub 2016 Nov 3.
Organic charge transfer (CT) complexes obtained by combining molecular electron donors and acceptors have attracted much interest due to their potential applications in organic opto-electronic devices. In order to work, these systems must have an electronic matching - the highest occupied molecular orbital (HOMO) of the donor must couple with the lowest unoccupied molecular orbital (LUMO) of the acceptor - and a structural matching, so as to allow direct intermolecular CT. Here it is shown that, when molecules are adsorbed on a metal surface, novel molecular organizations driven by surface-mediated CT can appear that have no counterpart in condensed phase non-covalent assemblies of donor and acceptor molecules. By means of scanning tunneling microscopy and spectroscopy it is demonstrated that the electronic and self-assembly properties of an electron acceptor molecule can change dramatically in the presence of an additional molecular species with marked electron donor character, leading to the formation of unprecedented core-shell assemblies. DFT and classical force-field simulations reveal that this is a consequence of charge transfer from the donor to the acceptor molecules mediated by the metallic substrate.
有机电荷转移 (CT) 配合物是通过将分子电子供体和受体结合而获得的，由于它们在有机光电设备中的潜在应用而引起了广泛关注。为了发挥作用，这些系统必须具有电子匹配 - 供体的最高占据分子轨道 (HOMO) 必须与受体的最低未占据分子轨道 (LUMO) 耦合 - 以及结构匹配，以便允许直接的分子间 CT。在这里表明，当分子吸附在金属表面上时，由表面介导的 CT 驱动的新型分子组织可能会出现，而在凝聚相非共价供体和受体分子组装中没有对应的结构。通过扫描隧道显微镜和光谱学证明，在存在具有明显电子供体性质的额外分子物种的情况下，电子受体分子的电子和自组装性质会发生剧烈变化，从而形成前所未有的核壳组装。DFT 和经典力场模拟表明，这是由于金属基底介导的从供体到受体分子的电荷转移所致。
