Solution Deposition of Self-Assembled Benzoate Monolayers on Rutile (110): Effect of π–π Interactions on Monolayer Structure

Abstract

High-quality, self-assembled benzoate monolayers were synthesized on rutile (110) using simple aqueous reactions. Sputtering and annealing cycles, which create surface and subsurface defects, were not needed. The monolayers were hydrophobic and remained largely contaminant free during exposures to laboratory air for tens of minutes. During this period, infrared spectroscopy showed that the monolayers did not spontaneously adsorb airborne hydrocarbons or other adventitious aliphatic species. Scanning tunneling microscopy (STM) images, infrared and X-ray photoemission spectra, Monte Carlo simulations, and ab initio calculations were all consistent with benzoate molecules adopting an edge-to-face ring geometry with their four nearest neighborsa tetrameric bonding geometry. This bonding is further stabilized by a pairing interaction between adjacent benzoate molecules, a pairing that has previously been interpreted as dimerization. The coexistence of paired and unpaired regions of the monolayer is consistent with the relatively small additional energy gained by pairing and the cooperative nature of the pairing interaction. Monolayer stability is driven both by the strong bidentate bonding to unsaturated Ti atoms on the surface as well as by π–π interactions between adsorbates.

Breaking π–π Interactions in Carboxylic Acid Monolayers on Rutile TiO2(110) Leads to Unexpected Long-Range Ordering

“…This replacement reduced intermolecular interactions modestly, which suggests that the long-range ordering is not primarily due to the aromatic head group. Consistent with this calculation, previous researchers have noted the surprising regularity (i.e., (2 × 1) structure) of formate monolayers on rutile (110). , This same (2 × 1) structure is also observed in adventitious carboxylate monolayers formed from ppb levels of carboxylic acids in air. − Ordered carboxylic acid monolayers have been observed on TiO 2 surfaces prepared in solution , and by vapor deposition in air and in ultrahigh vacuum, , which suggests that the ordering is not a consequence of exposure to air or solution. This inference is further supported by the nearly identical energetics of the p- and m- fluorobenzoate grain boundaries.…”

Self-assembly of 1,3,5-benzenetribenzoic acid on Ag and Cu at the liquid/solid interface

“…The large majority of studies have been performed on conducting substrates, mostly coinage metals and graphite, and, to a lesser extent, on semiconducting supports. 11,[24][25][26][27][28][29][30] Recently, the range of substrates has been extended to dielectrics. [31][32][33][34][35] and various two-dimensional (2D) materials.…”

Inhibiting Reductive Elimination as an Intramolecular Disulfide Dramatically Enhances the Thermal Stability of SAMs on Gold Derived from Bidentate Adsorbents

“…Nevertheless, it is reasonable to assume that the aromatic ring in the R1ArmDT SAMs aligns with an upright orientation similar to the structurally analogous R1ArDT SAMs, where such orientation accommodates the closest packing of the aromatic adlayer and affords optimized π–π stacking interactions. , When comparing the dithiolate headgroups for these two adsorbates, it is notable that R1ArmDT has a longer intramolecular S···S distance than that of R1ArDT ; specifically, the calculated distances between the sulfur atoms in the dithiolate headgroups of R1ArmDT and R1ArDT are 4.90 and 3.50 Å, respectively . Correspondingly, the R1ArmDT footprint is larger than the R1ArDT footprint, and R1ArmDT molecules would occupy a larger surface area and create a larger spacing between alkyl chains above the aromatic ring in a SAM derived from R1ArmDT .…”