Lörtscher Emanuel, Elbing Mark, Tschudy Meinrad, von Hänisch Carsten, Weber Heiko B, Mayor Marcel, Riel Heike
IBM Research GmbH, Säumerstrasse 4, CH-8803 Rüschlikon, Switzerland.
Chemphyschem. 2008 Oct 24;9(15):2252-8. doi: 10.1002/cphc.200800388.
A series of oligophenylene rods of increasing lengths is synthesized to investigate the charge-transport mechanisms. Methyl groups are attached to the phenyl rings to weaken the electronic overlap of the pi-subsystems along the molecular backbones. Out-of-plane rotation of the phenyl rings is confirmed in the solid state by means of X-ray analysis and in solution by using UV/Vis spectroscopy. The influence of the reduced pi-conjugation on the resonant charge transport is studied at the single-molecule level by using the mechanically controllable break-junction technique. Experiments are performed under ultra-high-vacuum conditions at low temperature (50 K). A linear increase of the conductance gap with increasing number of phenyl rings (from 260 meV for one ring to 580 meV for four rings) is revealed. In addition, the absolute conductance of the first resonant peaks does not depend on the length of the molecular wire. Resonant transport through the first molecular orbital is found to be dominated by charge-carrier injection into the molecule, rather than by the intrinsic resistance of the molecular wire length.
合成了一系列长度递增的寡聚亚苯基棒，以研究电荷传输机制。甲基连接到苯环上，以削弱沿分子主链的π子系统的电子重叠。通过X射线分析在固态下以及使用紫外/可见光谱在溶液中证实了苯环的面外旋转。利用机械可控断裂结技术在单分子水平上研究了降低的π共轭对共振电荷传输的影响。实验在超真空条件下于低温（50K）进行。结果表明，随着苯环数量的增加（从一个环的260毫电子伏到四个环的580毫电子伏），电导间隙呈线性增加。此外，第一个共振峰的绝对电导不取决于分子线的长度。发现通过第一个分子轨道的共振传输主要由电荷载流子注入分子主导，而不是由分子线长度的固有电阻主导。
