Synthesis and Single‐Molecule Conductance Study of Redox‐Active Ruthenium Complexes with Pyridyl and Dihydrobenzo[b]thiophene Anchoring Groups

Abstract

The ancillary ligands 4'-(4-pyridyl)-2,2':6',2''-terpyridine and 4'-(2,3-dihydrobenzo[b]thiophene)-2,2'-6',2"-terpyridine were used to synthesize two series of mono- and dinuclear ruthenium complexes differing in their lengths and anchoring groups. The electrochemical and single-molecular conductance properties of these two series of ruthenium complexes were studied experimentally by means of cyclic voltammetry and the scanning tunneling microscopy-break junction technique (STM-BJ) and theoretically by means of density functional theory (DFT). Cyclic voltammetry data showed clear redox peaks corresponding to both the metal- and ligand-related redox reactions. Single-molecular conductance demonstrated an exponential decay of the molecular conductance with the increase in molecular length for both the series of ruthenium complexes, with decay constants of βPY =2.07±0.1 nm(-1) and βBT =2.16±0.1 nm(-1) , respectively. The contact resistance of complexes with 2,3-dihydrobenzo[b]thiophene (BT) anchoring groups is found to be smaller than the contact resistance of ruthenium complexes with pyridine (PY) anchors. DFT calculations support the experimental results and provided additional information on the electronic structure and charge transport properties in those metal|ruthenium complex|metal junctions.

Electronic conductance and thermopower of single-molecule junctions of oligo(phenyleneethynylene) derivatives

“…[23][24][25] The wide agreement between conductance data obtained for OPE3 junctions in different research groups, makes this an excellent candidate for a systematic study on the influence of side and end-groups. We chose the very stable dihydrobenzo[b]thiophene (DHBT) anchor as this group is known to bind efficiently to metal electrodes, with high junction formation probability, [26][27][28] and without the problems associated with thiol anchors, such as oxidation and formation of metal-thiolate clusters. 29 We demonstrate that these molecules possess the highly versatile structural features that are required for thermal conductance studies.…”

CrIII as an alternative to RuII in metallo-supramolecular chemistry

“…Creutz-Taube complex, (b) [(tpy)Ru(L)Ru(tpy)] m+ complexes, [69][70][71] (c) [(tpy)Ru II (L)Co III (tpy)] 5+ complexes displaying directional electron transfer, 72,73 (d) [(tpy)Ru II (L)Os II (tpy)] 4+ complexes displaying directional energy transfer. 74,75 six-coordinate bis-terimine 83,84 and ter-bisimine 46,81,82 Cr III complexes.…”

“…[64][65][66][67][68] When applied to back-to-back bis-terpyridine bridging ligands L in [(tpy)Ru(L)Ru(tpy)] 5+ (Fig. 2b), the associated theories successfully rationalized the exponential decrease of the electronic interaction parameter with increasing intermetallic separations [69][70][71] and the magnification of both through-bond electron transfer (Fig. 2c) 72,73 and energy transfer ( Fig.…”

Quantum Interference Enhanced Chemical Responsivity in Single‐Molecule Dithienoborepin Junctions

“…To wards functionalm olecular electronic devices, intensive studies have been focused on charge transport characterization of single-molecule junctions with functional units to revealt he role of the molecular structure, [1,2,3] anchoring group, [1,4] environment, [5,6] external stimuli, [7,8,9] and electrode materials [10,11,12] in the charget ransport process.R ecently, chemicalr esponsive molecular junctionsh ave received intensive interestf or their potential in the sensing of surrounding environments throught he charge transport characterizationa t the single-molecule scale, such as pH and ions. Scullion et al have reportedac onductancec hangeo f1 7t imes in peptide single-molecule junctions triggered by pH change.…”