Institut für Physik, Technische Universität Ilmenau , D-98693 Ilmenau, Germany.
Department of Chemistry, UMR ENS-CNRS-UPMC 8640, Ecole Normale Supérieure , F-75005 Paris, France.
ACS Nano. 2016 Feb 23;10(2):2010-6. doi: 10.1021/acsnano.5b06153. Epub 2016 Feb 1.
Single-molecule chemistry with a scanning tunneling microscope has preponderantly been performed on metal surfaces. The molecule-metal hybridization, however, is often detrimental to genuine molecular properties and obscures their changes upon chemical reactions. We used graphene on Ir(111) to reduce the coupling between Ir(111) and adsorbed phthalocyanine molecules. By local electron injection from the tip of a scanning tunneling microscope the two pyrrolic H atoms were removed from single phthalocyanines. The detachment of the H atom pair induced a strong modification of the molecular electronic structure, albeit with no change in the adsorption geometry. Spectra and maps of the differential conductance combined with density functional calculations unveiled the entire depopulation of the highest occupied molecular orbital upon H abstraction. Occupied π states of intact molecules are proposed to be emptied via intramolecular electron transfer to dangling σ states of H-free N atoms.
使用扫描隧道显微镜进行单分子化学实验主要是在金属表面上进行的。然而，分子-金属杂化通常不利于真正的分子性质，并掩盖了它们在化学反应中的变化。我们使用 Ir(111)上的石墨烯来减少 Ir(111)和吸附的酞菁分子之间的耦合。通过扫描隧道显微镜针尖的局部电子注入，从单个酞菁分子中去除了两个吡咯 H 原子。H 原子对的脱附引起了分子电子结构的强烈修饰，尽管吸附几何形状没有变化。微分电导谱和图谱与密度泛函计算相结合，揭示了 H 原子提取后最高占据分子轨道的完全耗尽。据推测，完整分子的占据π态通过分子内电子转移到无 H 的 N 原子的悬空σ态而被排空。
