Self-Assembly of Di(pyrazol-1-yl)pyridine-benzoic Acid on Underpotentially Deposited Ag from Solution

Abstract

Monolayers of 4-(2,6-di(1 H-pyrazol-1-yl)pyridine-4-yl)benzoic acid (DPP-BA) on Au substrates modified by an underpotential-deposited bilayer of Ag were studied by X-ray photoelectron spectroscopy (XPS), near edge X-ray absorption fine structure spectroscopy, and scanning tunneling microscopy. Highly crystalline layers are formed with molecules coordinatively bonding to the surface through the carboxylate moiety in a bidentate configuration. The molecules assemble to rows characterized by densely packed upright-orientated DPP units occupying an area of 41 Å. The DPP units adopt a trans-trans conformation as inferred from the N 1s XPS spectra taken at different photon energies. Their alignment alternates between adjacent rows, giving rise to a herringbone pattern. The pronouncedly different structure of the weakly commensurate self-assembled monolayer (SAM) of DPP-BA on Ag compared to the commensurate SAM of a DPP thiol on Au is a manifestation of the shift from substrate-directed assembly in the latter case to assembly dominated by intermolecular interactions in the former case.

Spin‐Crossover Grafted Monolayer of a Co(II) Terpyridine Derivative Functionalized with Carboxylic Acid Groups

“…After that, they were washed and rinsed thoroughly with clean DMA to remove any physisorbed material and dried under N 2 stream. Silver was chosen as substrate with the aim of promoting chemisorption of both molecules through the interaction with carboxylate moieties, [ 52 ] which may form large domains of well‐ordered 2D molecular arrays at room temperature within a short time promoted through this kind of interaction. [ 51 ]…”

“…Hereby, we intend to take advantage of the anchoring capabilities of the carboxylic acid group on silver to form grafted monolayers from solution at room temperature of a Co(II) SCO complex. [ 51,52 ]…”

Electron-Induced Modification of Self-Assembled Monolayers of Aromatic Carboxylic Acids

“…Unfortunately, the spectral signature of the free COOH groups masks the changes associated with the anchoring configuration, thus impeding to gather direct spectroscopic evidence. To pinpoint this, experiments with SAMs of molecules geometrically analogous but with only one COOH group (e.g., 1,3-diphenyl-5-(4-carboxyphenyl)benzene or di(1H-pyrazol-1-yl)pyridine-4-yl)benzoic acid 11 ) would be of interest. Second, the rotations of molecules and the subsequent changes create more space between the rows, which allows a reduction in distance between them (see models in bottom rows of Figure 10) and opening a gap between other rows.…”

“…Compared to archetypical self-assembled monolayers (SAMs) with the thiolate docking group, 1,2 carboxylic-acid (CA) based SAMs, specifically those featuring aromatic backbones, have been investigated in detail only more recently. [3][4][5][6][7][8][9][10][11][12][13][14][15] These SAMs can be efficiently assembled from solution on a variety of substrates, including the coinage metals silver and copper. Silver, in particular, has turned out as beneficial for a flexible SAM design, owing to a comparatively weak interaction between the CA docking group and the substrate.…”

“…Compared with archetypical self-assembled monolayers (SAMs) with the thiolate docking group, , carboxylic acid (CA)-based SAMs, specifically those featuring aromatic backbones, have been investigated in detail only more recently. − These SAMs can be efficiently assembled from solution on a variety of substrates, including the coinage metals silver and copper. Silver, in particular, has turned out to be beneficial for a flexible SAM design, owing to a comparatively weak interaction between the CA docking group and the substrate. − ,,, Consequently, the molecular structure and intermolecular interactions become factors for self-assembly, dominating over molecule–substrate interactions, so that the structure and organization of a SAM can be flexibly tuned by the design of its constituents.…”