Nonuniform STM Contrast of Self-Assembled Tri-<i>n</i>-octyl-triazatriangulenium Tetrafluoroborate on HOPG

Snegir, Sergii; Dappe, Yannick J.; Sysoiev, Dmytro; Huhn, Thomas; Scheer, Elke

doi:10.1021/acsomega.3c06454

Cited by 2 publications

(1 citation statement)

References 30 publications

(84 reference statements)

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“…For example, XPS and scanning tunneling microscopy (STM) studies of SAMs comprising TATA-based carbocation components have shown these can lose BF4ions upon surface adsorption. 6,74,75 In these reports it was noted that the loss of counterions implied a significant charge transfer to the substrate, 6 and that ion dissociation may be favored by the electric field generated at an STM tip. 75 Supporting computational experiments revealed that while a TATA + -BF4ion pair is stabilized by adsorption on a gold surface, the cohesive energy of the system is reduced by addition of an electron (as we also show above).…”

Section: Additional Discussionmentioning

confidence: 99%

Counterion loss from charged surface-bound complexes drives the formation of loosely packed monolayers

Trang,

Mora Perez,

Ran

et al. 2024

Preprint

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The functionality of multicomponent self-assembled monolayers (SAMs) can be severely diminished by the segregation of like components into nanoscale domains, a process that maximizes favorable short-range intermolecular interactions. Here, we explore the use of a modular family of sulfur-functionalized metal bis(terpyridine) complexes ([M(tpy-R)2]2+(PF6–)2) to prepare mixed SAMs, considering that the comparable structure, dimensions, and ionic composition of these species should render them interchangeable within the adsorbed surface layer. While surface voltammetry experiments show these SAMs do exhibit compositions representative of their assembly solutions, they also suggest, in line with previous reports, that adjacent complexes in the monolayer are separated by a gap of ~1 nm. Remarkably, X-ray photoelectron spectroscopy studies reveal no F 1s peak features that would confirm the proliferation of PF6− counterions on the surface. We propose that the loose packed structure of these SAMs results from the loss or exchange of PF6– counterions which introduces significant repulsive Coulomb interactions between the adsorbed 2+ charged complexes. The hypothesis is supported by an electrostatic model which indicates these complexes should form close packed SAMs if mobile counterions are present. First-principles calculations demonstrate that complex-counterion binding interactions are weakened by charge transfer to the gold substrate, suggesting this may play an important role in the formation of such low coverage SAMs. Together, this study raises important questions regarding the assembly, organization, and composition of charged SAMs, and highlights new opportunities in the design of multicomponent monolayer assemblies with free volume, for example, to facilitate surface-based reactions or support molecular switches.

show abstract

Section: Additional Discussionmentioning

confidence: 99%

Counterion loss from charged surface-bound complexes drives the formation of loosely packed monolayers

Trang,

Mora Perez,

Ran

et al. 2024

Preprint

View full text Add to dashboard Cite

show abstract

Counterion Loss from Charged Surface-Bound Complexes Drives the Formation of Loosely Packed Monolayers

Trang,

Mora Perez,

Ran

et al. 2024

J. Am. Chem. Soc.

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The functionality of multicomponent self-assembled monolayers (SAMs) can be severely diminished by the segregation of like components into nanoscale domains, a process that maximizes favorable short-range intermolecular interactions. Here, we explore the use of a modular family of sulfur-functionalized metal bis(terpyridine) complexes ([M(tpy-R) 2 ] 2+ (PF 6 – ) 2 ) to prepare mixed SAMs, considering that the comparable structure, dimensions, and ionic composition of these species should render them interchangeable within the adsorbed surface layer. While surface voltammetry experiments show that these SAMs do exhibit compositions representative of their assembly solutions, they also suggest, in line with previous reports, that adjacent complexes in the monolayer are separated by a gap of ∼ 1 nm. Remarkably, X-ray photoelectron spectroscopy studies reveal no F 1s peak features that would confirm the proliferation of PF 6 – counterions on the surface. We propose that the loosely packed structure of these SAMs results from the loss or exchange of PF 6 – counterions, which introduces significant repulsive Coulomb interactions between the adsorbed 2+ charged complexes. The hypothesis is supported by an electrostatic model which indicates that these complexes should form close-packed SAMs if mobile counterions are present. First-principles calculations demonstrate that complex–counterion binding interactions are weakened by charge transfer to the gold substrate, suggesting that this may play an important role in the formation of such low-coverage SAMs. Together, this study raises important questions regarding the assembly, organization, and composition of charged SAMs and highlights new opportunities in the design of multicomponent monolayer assemblies with free volume, for example, to facilitate surface-based reactions or support molecular switches.

show abstract

Nonuniform STM Contrast of Self-Assembled Tri-n-octyl-triazatriangulenium Tetrafluoroborate on HOPG

Cited by 2 publications

References 30 publications

Counterion loss from charged surface-bound complexes drives the formation of loosely packed monolayers

Counterion loss from charged surface-bound complexes drives the formation of loosely packed monolayers

Counterion Loss from Charged Surface-Bound Complexes Drives the Formation of Loosely Packed Monolayers

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