A Comprehensive Study of Extended Tetrathiafulvalene Cruciform Molecules for Molecular Electronics: Synthesis and Electrical Transport Measurements

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• 作者：Christian R. Parker ; Edmund Leary ; Riccardo Frisenda ; Zhongming Wei ; Karsten S. Jennum ; Emil Glibstrup ; Peter B忙ch Abrahamsen ; Marco Santella ; Mikkel A. Christensen ; Eduardo Antonio Della Pia ; Tao Li ; Maria Teresa Gonzalez ; Xingbin Jiang ; Thorbj酶rn J. Morsing ; Gabino Rubio-Bollinger ; Bo W. Laursen ; Kasper N酶rgaard ; Herre van der Zant ; Nicolas Agrait ; Mogens Br酶ndsted Nielsen
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：November 26, 2014
• 年：2014
• 卷：136
• 期：47
• 页码：16497-16507
• 全文大小：676K
• ISSN：1520-5126

文摘

Cruciform-like molecules with two orthogonally placed 蟺-conjugated systems have in recent years attracted significant interest for their potential use as molecular wires in molecular electronics. Here we present synthetic protocols for a large selection of cruciform molecules based on oligo(phenyleneethynylene) (OPE) and tetrathiafulvalene (TTF) scaffolds, end-capped with acetyl-protected thiolates as electrode anchoring groups. The molecules were subjected to a comprehensive study of their conducting properties as well as their photophysical and electrochemical properties in solution. The complex nature of the molecules and their possible binding in different configurations in junctions called for different techniques of conductance measurements: (1) conducting-probe atomic force microscopy (CP-AFM) measurements on self-assembled monolayers (SAMs), (2) mechanically controlled break-junction (MCBJ) measurements, and (3) scanning tunneling microscopy break-junction (STM-BJ) measurements. The CP-AFM measurements showed structure鈥損roperty relationships from SAMs of series of OPE3 and OPE5 cruciform molecules; the conductance of the SAM increased with the number of dithiafulvene (DTF) units (0, 1, 2) along the wire, and it increased when substituting two arylethynyl end groups of the OPE3 backbone with two DTF units. The MCBJ and STM-BJ studies on single molecules both showed that DTFs decreased the junction formation probability, but, in contrast, no significant influence on the single-molecule conductance was observed. We suggest that the origins of the difference between SAM and single-molecule measurements lie in the nature of the molecule鈥揺lectrode interface as well as in effects arising from molecular packing in the SAMs. This comprehensive study shows that for complex molecules care should be taken when directly comparing single-molecule measurements and measurements of SAMs and solid-state devices thereof.