title: Hapticity-dependent charge transport through carbodithioate-terminated [5,15-bis(phenylethynyl)porphinato]zinc(II) complexes in metal-molecule-metal junctions.
abstract: Single molecule break junction experiments and nonequilibrium Green's 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 (-S(-)) by the carbodithioate (-CS2(-)) anchoring motif leads to an order of magnitude increase of single molecule conductance. In contrast to thiolate-terminated structures, metal-molecule-metal 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'-(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-molecule-electrode electronic coupling and maximize the conductance for charge transport.
authors.affiliation: Department of Chemistry, Temple University , Philadelphia, Pennsylvania 19122, United States.
authors.forename: Zhihai
authors.initials: Z
authors.lastname: Li
authors.forename: Manuel
authors.initials: M
authors.lastname: Smeu
authors.forename: Tae-Hong
authors.initials: TH
authors.lastname: Park
authors.forename: Jeff
authors.initials: J
authors.lastname: Rawson
authors.forename: Yangjun
authors.initials: Y
authors.lastname: Xing
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Therien
authors.forename: Mark A
authors.initials: MA
authors.lastname: Ratner
authors.forename: Eric
authors.initials: E
authors.lastname: Borguet
mesh_terms: D056831:Coordination Complexes / Q000737:chemistry*; D004553:Electric Conductivity; D004566:Electrodes; D004581:Electronics / Q000295:instrumentation; D004867:Equipment Design; D008665:Metalloporphyrins / Q000737:chemistry*; D008958:Models, Molecular; D013859:Thiocarbamates / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D008665:Metalloporphyrins; D013859:Thiocarbamates; D015032:Zinc
keywords: Linker hapticity; NEGF-DFT; STM break junction; carbodithioate linker; molecular electronics