Hapticity-Dependent Charge Transport through Carbodithioate-Terminated [5,15-Bis(phenylethynyl)porphinato]zinc(II) Complexes in Metal鈥揗olecule鈥揗etal Junctions
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- 作者：Zhihai Li ; Manuel Smeu ; Tae-Hong Park ; Jeff Rawson ; Yangjun Xing ; Michael J. Therien ; Mark A. Ratner ; Eric Borguet
- 刊名：Nano Letters
- 出版年：2014
- 出版时间：October 8, 2014
- 年：2014
- 卷：14
- 期：10
- 页码：5493-5499
- 全文大小：429K
- ISSN：1530-6992
文摘
Single molecule break junction experiments and nonequilibrium Green鈥檚 function calculations using density functional theory (NEGF-DFT) of carbodithioate- and thiol-terminated [5,15-bis(phenylethynyl)-10,20-diarylporphinato]zinc(II) complexes reveal the impact of the electrode-linker coordination mode on charge transport at the single-molecule level. Replacement of thiolate (鈭扴鈥?/sup>) by the carbodithioate (鈭扖S2鈥?/sup>) anchoring motif leads to an order of magnitude increase of single molecule conductance. In contrast to thiolate-terminated structures, metal鈥搈olecule鈥搈etal junctions that exploit the carbodithioate linker manifest three distinct conductance values. We hypothesize that the magnitudes of these conductances depend upon carbodithoate linker hapticity with measured conductances across Au-[5,15-bis(4鈥?(dithiocarboxylate)phenylethynyl)-10,20-diarylporphinato]zinc(II)-Au junctions the greatest when both anchoring groups attach to the metal surface in a bidentate fashion. We support this hypothesis with NEGF-DFT calculations, which consider the electron transport properties for specific binding geometries. These results provide new insights into the origin of molecule-to-molecule conductance heterogeneity in molecular charge transport measurements and the factors that optimize electrode鈥搈olecule鈥揺lectrode electronic coupling and maximize the conductance for charge transport.