Chemistry Department, University of Liverpool, Liverpool L69 7ZD, UK.
Nat Nanotechnol. 2011 Jul 31;6(8):517-23. doi: 10.1038/nnano.2011.111.
Short chains of porphyrin molecules can mediate electron transport over distances as long as 5-10 nm with low attenuation. This means that porphyrin-based molecular wires could be useful in nanoelectronic and photovoltaic devices, but the mechanisms responsible for charge transport in single oligo-porphyrin wires have not yet been established. Here, based on electrical measurements of single-molecule junctions, we show that the conductance of the oligo-porphyrin wires has a strong dependence on temperature, and a weak dependence on the length of the wire. Although it is widely accepted that such behaviour is a signature of a thermally assisted incoherent (hopping) mechanism, density functional theory calculations and an accompanying analytical model strongly suggest that the observed temperature and length dependence is consistent with phase-coherent tunnelling through the whole molecular junction.
短链卟啉分子可以在 5-10nm 的长距离内进行电子传输，而且衰减很小。这意味着基于卟啉的分子导线在纳米电子学和光伏器件中可能很有用，但负责单寡聚卟啉导线中电荷传输的机制尚未建立。在这里，我们基于单分子结的电测量结果表明，寡聚卟啉导线的电导对温度有很强的依赖性，对导线的长度有很弱的依赖性。尽管人们普遍认为这种行为是热辅助非相干（跳跃）机制的特征，但密度泛函理论计算和一个伴随的分析模型强烈表明，观察到的温度和长度依赖性与整个分子结的相干隧穿一致。
