Charge transfer in self-assembled monolayers of molecular conductors containing tripodal anchor and terpyridine-metal redox switching element

Lachmanová, Štěpánka Nováková; Vavrek, F.; Sebechlebská, Táňa; Kolivoška, Viliam; Valášek, Michal; Hromadová, Magdaléna

doi:10.1016/j.electacta.2021.138302

Cited by 5 publications

(8 citation statements)

References 53 publications

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“…We also explicitly report the synthesis and characterization of [Co(tpySH)2](PF6)2 (CoSH) for the first time, and demonstrate this complex is air-sensitive in solution. In line with previous observations for SAMs assembled from polypyridyl complexes (see SI, Table S12), 1,22,31,32,[23][24][25][26][27][28][29][30] surface voltammetric analyses indicate that the surface coverage of MSS (and CoSH) SAMs is lower than expected for a close packed structure. This phenomenon has been attributed to unfavorable electrostatic interactions between charged components on the surface.…”

Section: Introductionsupporting

confidence: 90%

Mixed monolayers formed from methyldisulfide-functionalized metal bis(terpyridine) complexes

Trang

Saal

Inkpen

2022

Preprint

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Multicomponent self-assembled monolayers (SAMs) often suffer from segregation of like components into nanoscale domains. One strategy to form perfectly mixed SAMs is to use a modular series of molecules with similar structures and dimensions, ensuring comparable formation kinetics as well as surface and intermolecular interactions. To help evaluate this concept, we prepared a new family of methyldisulfide-functionalized metal bis(terpyridine) complexes, [M(tpySSMe)2](PF6)2 (M = Fe, Co, Zn), and characterized their single- and multi-component SAMs on gold surfaces. We find these complexes are air-stable in solution for >7 d, in stark contrast to their thiol-functionalized analogues, [M(tpySH)2](PF6)2 (MSH, M = Fe, Co), which decompose in <1 d. Though CoSH has been previously reported, we explicitly detail its synthesis and characterization here for the first time. Solution and surface voltammetry experiments show these complexes can indeed form SAMs with compositions representative of their assembly solutions, a prerequisite for perfect mixing at the molecular scale. However, we find MSS and CoSS SAMs generally exhibit remarkably low saturation surface coverages. This observation agrees with earlier SAM studies involving different polypyridyl-based metal complexes, and is typically attributed to repulsive Coulomb interactions between charged complexes on the surface. Despite their apparent loose packing, we show that purportedly vacant surface sites in MSS SAMs are not readily accessible for coordination by uncharged thiols in solution. X-ray photoelectron spectroscopy studies of CoSS SAMs further reveal clear S 2p (primarily of thiolate character) and N 1s features, but show no F 1s signal attributable to PF6− counterions (either due to their absence or the low surface coverage of MSS). This study raises important new questions regarding the assembly mechanism and nanoscale structure of these and other, structurally-related, charged SAMs, also serving to highlight key challenges in the design and characterization of emerging multi-component monolayer assemblies.

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Section: Introductionsupporting

confidence: 90%

Mixed monolayers formed from methyldisulfide-functionalized metal bis(terpyridine) complexes

Trang

Saal

Inkpen

2022

Preprint

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“…Namely, during the first potential scan in the positive potential direction, two distinct current peaks were observed; the first peak disappeared upon repeated electrode potential cycling between the negative and positive potential directions, leading to a final steady-state CV, shown in the red color. It has characteristics typical of a 1-electron reversible surface-confined redox system with repulsive interactions between the individual redox-active moieties, meaning that the full width at half maximum of the peak current is larger than 90.6 mV, which is theoretically predicted for non-interacting redox centers in the adsorbed state [ 34 ]. Figure 3 shows the same type of the voltammetric experiment for the Ru-tripod SAM.…”

Section: Resultsmentioning

confidence: 99%

“…Thus, the main difference between these two films seems to be the molecular arrangement within the SAM structure. The full electrochemical characterization of the final voltammograms on the gold bead electrode has been provided in our previous publication [ 34 ]. In summary, the surface concentration of the Os-tripod film was found to be higher than that of the Ru-tripod SAM; whereas, from the comparison of the full width at half maximum of the peak current, it was concluded that the repulsion interactions are more pronounced in the Ru-tripod SAMs.…”

Section: Resultsmentioning

confidence: 99%

“…In summary, the surface concentration of the Os-tripod film was found to be higher than that of the Ru-tripod SAM; whereas, from the comparison of the full width at half maximum of the peak current, it was concluded that the repulsion interactions are more pronounced in the Ru-tripod SAMs. This difference in the degree of repulsive interactions was used to explain the higher surface concentration of Os-tripod molecules in the compact SAM, compared with the Ru-tripod SAM [ 34 ].…”

Section: Resultsmentioning

confidence: 99%

“…Such tripodal arrangement should provide better geometry [ 13 , 14 , 29 , 30 , 31 , 32 ] and enhanced electronic coupling between the electrode and redox switching element [ 33 ]. In our previous work [ 34 ], we reported that molecules shown in Figure 1 form SAMs with higher surface coverage for molecule Os-tripod compared with Ru-tripod, with less pronounced mutual interaction between redox centers. Interestingly, surface coverage was higher than that reported by Figgemeier et al [ 28 ] for pyridine-anchored molecules, confirming favorable upright orientation of redox centers due to the presence of covalently bonded tripodal pedestals.…”

Section: Introductionmentioning

confidence: 94%

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Self-Assembled Monolayers of Molecular Conductors with Terpyridine-Metal Redox Switching Elements: A Combined AFM, STM and Electrochemical Study

et al. 2022

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Self-assembled monolayers (SAMs) of terpyridine-based transition metal (ruthenium and osmium) complexes, anchored to gold substrate via tripodal anchoring groups, have been investigated as possible redox switching elements for molecular electronics. An electrochemical study was complemented by atomic force microscopy (AFM) and scanning tunneling microscopy (STM) methods. STM was used for determination of the SAM conductance values, and computation of the attenuation factor β from tunneling current–distance curves. We have shown that SAMs of Os-tripod molecules contain larger adlayer structures compared with SAMs of Ru-tripod molecules, which are characterized by a large number of almost evenly distributed small islands. Furthermore, upon cyclic voltammetric experimentation, Os-tripod films rearrange to form a smaller number of even larger islands, reminiscent of the Ostwald ripening process. Os-tripod SAMs displayed a higher surface concentration of molecules and lower conductance compared with Ru-tripod SAMs. The attenuation factor of Os-tripod films changed dramatically, upon electrochemical cycling, to a higher value. These observations are in accordance with previously reported electron transfer kinetics studies.

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Bifunctional interface of metal–organic framework synergized with bismuth endows high stable zinc anode

He,

Zhou,

et al. 2024

Chemical Engineering Journal

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Charge transfer in self-assembled monolayers of molecular conductors containing tripodal anchor and terpyridine-metal redox switching element

Cited by 5 publications

References 53 publications

Mixed monolayers formed from methyldisulfide-functionalized metal bis(terpyridine) complexes

Mixed monolayers formed from methyldisulfide-functionalized metal bis(terpyridine) complexes

Self-Assembled Monolayers of Molecular Conductors with Terpyridine-Metal Redox Switching Elements: A Combined AFM, STM and Electrochemical Study

Bifunctional interface of metal–organic framework synergized with bismuth endows high stable zinc anode

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