Orbital redistribution in molecular nanostructures mediated by metal-organic bonds.
Orbital redistribution in molecular nanostructures mediated by metal-organic bonds.
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DOI：
10.1021/nn504431e
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发表时间：
2014-09
期刊：
影响因子：
17.1
通讯作者：
Zechao Yang;M. Corso;R. Robles;C. Lotze;R. Fitzner;E. Mena‐Osteritz;P. Bäuerle;K. Franke;J. Pascual
中科院分区：
文献类型：
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作者：
Zechao Yang;M. Corso;R. Robles;C. Lotze;R. Fitzner;E. Mena‐Osteritz;P. Bäuerle;K. Franke;J. Pascual
二氰基乙烯基喹硫醚（DCV 5 T-Me 2）是一种用于高效有机太阳能电池的原型共轭低聚物。这类低聚噻吩由富电子供体（D）主链和末端缺电子受体（A）部分构成。本文利用低温扫描隧道显微镜/光谱（STM/STS）和原子力显微镜（AFM）研究了它吸附在Au（111）表面时的结构和电子性质。我们发现，DCV 5 T-Me 2自组装在延长链，稳定的插入Au原子。与Au吸附原子的金属-配体杂化的效果导致DCV 5 T-Me 2最低未占分子轨道（LUMO）相对于表面上的未配位分子的能量下移。金原子与仅一个分子端基的不对称配位导致LUMO和LUMO+1态在相对侧的不对称定位。使用模型密度泛函理论（DFT）计算，我们解释了这样的轨道重塑的结果，原来的LUMO和LUMO+1轨道的线性组合，混合的连接的桥接Au吸附原子。我们的研究表明，分子轨道的排列和它们在单个分子中的分布可以通过将它们与特定位点的金属原子接触来改变。
Dicyanovinyl-quinquethiophene (DCV5T-Me2) is a prototype conjugated oligomer for highly efficient organic solar cells. This class of oligothiophenes are built up by an electron-rich donor (D) backbone and terminal electron-deficient acceptor (A) moieties. Here, we investigated its structural and electronic properties when it is adsorbed on a Au(111) surface using low temperature scanning tunneling microscopy/spectroscopy (STM/STS) and atomic force microscopy (AFM). We find that DCV5T-Me2 self-assembles in extended chains, stabilized by intercalated Au atoms. The effect of metal-ligand hybridization with Au adatoms causes an energetic downshift of the DCV5T-Me2 lowest unoccupied molecular orbital (LUMO) with respect to the uncoordinated molecules on the surface. The asymmetric coordination of a gold atom to only one molecular end group leads to an asymmetric localization of the LUMO and LUMO+1 states at opposite sides. Using model density functional theory (DFT) calculations, we explain such orbital reshaping as a consequence of linear combinations of the original LUMO and LUMO+1 orbitals, mixed by the attachment of a bridging Au adatom. Our study shows that the alignment of molecular orbitals and their distribution within individual molecules can be modified by contacting them to metal atoms in specific sites.