@article {155,
	title = {Influence of Terminal Carboxyl Group on Structure and Reactivity of Functionalized m-Carboranethiolate Self-Assembled Monolayers},
	journal = {Chemistry of Materials},
	volume = {32},
	year = {2020},
	month = {07/2020},
	pages = {6800-6809},
	type = {Article},
	chapter = {6800},
	abstract = {<p>The structure and function of self-assembled monolayers (SAMs) at the nanoscale are determined by the steric and electronic effects of their building blocks. Carboranethiol molecules form pristine monolayers that provide tunable two-dimensional systems to probe lateral and interfacial interactions. Additional ω-functionality, such as carboxyl groups, can be introduced to change the properties of the exposed surfaces. Here, two geometrically similar isomeric m-carborane analogs of m-mercaptobenzoic acid, 1 COOH-7-SH-1,7-C2B10H10 and racem-1-COOH-9-SH-1,7-C2B10H10, are characterized and their SAMs on Au{111} are examined. The latter isomer belongs to the rare group of chiral cage molecules and becomes, to our knowledge, the first example assembled on Au{111}. Although different in symmetry, molecules of both isomers assemble into similar hexagonal surface patterns. The nearest neighbor spacing of 8.4 {\textpm} 0.4 {\r A} is larger than that of non-carboxylated isomers, consistent with the increased steric demands of the carboxyl groups. Computational modeling reproduced this spacing and suggests a tilt relative to the surface normal. However, tilt domains are not observed experimentally, suggesting the presence of strong lateral interactions. Analyses of the influence of the functional groups through the pseudo-aromatic m carborane skeleton showed that the thiol group attached to either carbon or boron atoms increases the carboxyl group acidity in solution. In contrast, the acidity of the exposed carboxyl group in the SAMs decreases upon surface attachment; computational analyses suggest that the driving force of this shift is the dielectric of the environment in the monolayer as a result of confined intermolecular interactions, proximity to the Au surface, and partial desolvation.</p>},
	keywords = {acidity, carborane, carboxyl, monolayer, SAM, self-assembly},
	doi = {https://doi.org/10.1021/acs.chemmater.0c02722},
	url = {https://pubs.acs.org/doi/10.1021/acs.chemmater.0c02722},
	author = {Dominic P Goronzy and Jan Stanek and Erin Avery and Han Guo and Zdenek Bastl and Michal Dusek and Nathan M Gallup and Saliha Gun and Monika Kucerakova and Brian J Levandowski and Jan Machacek and Vaclav Sicha and John C Thomas and Adem Yavuz and K N Houk and M Fatih Danisman and Ersen Mete and Anastassia N Alexandrova and Tomas Base and Paul S Weiss}
}
@article {149,
	title = {Acid-Base Control of Valency within Carboranedithiol Self-Assembled Monolayers: Molecules Do the Can-Can},
	journal = {ACS Nano},
	volume = {12},
	year = {2018},
	month = {02/2018},
	pages = {2211{\textendash}2221},
	type = {Full paper},
	chapter = {2211},
	abstract = {<p>We use simple acid-base chemistry to control the valency in self-assembled monolayers of two different carboranedithiol isomers on Au{111}. Monolayer formation proceeds via Au-S bonding, where manipulation of pH prior to or during deposition enables the assembly of dithiolate species, monothiol/monothiolate species, or combination. Scanning tunneling microscopy (STM) images identify two distinct binding modes in each unmodified monolayer, where simultaneous spectroscopic imaging confirms different dipole offsets for each binding mode. Density functional theory calculations and STM image simulations yield detailed understanding of molecular chemisorption modes and their relation with the STM images, including inverted contrast with respect to the geometric differences found for one isomer. Deposition conditions are modified with controlled equivalents of either acid or base, where the coordination of the molecules in the monolayers is controlled by protonating or deprotonating the second thiol/thiolate on each molecule. This control can be exercised during deposition to change the valency of the molecules in the monolayers, a process that we affectionately refer to as the {\textquotedblleft}can-can.{\textquotedblright} This control enables us to vary the density of molecule-substrate bonds by a factor of two without changing the molecular density of the monolayer.</p>},
	keywords = {carborane, dipoles, molecules switch, nanoscience, scanning tunneling microscopy, self-assembled monolayer, self-assembly, two dimensional},
	doi = {10.1021/acsnano.7b09011},
	url = {https://pubs.acs.org/doi/10.1021/acsnano.7b09011},
	author = {John C Thomas and Dominic P. Goronzy and Andrew C Serino and Harsharn S Auluck and Olivia R Irving and Elisa Jimenez-Izal and Jacqueline M Deirmenjian and Jan Machacek and Philippe Sautet and Anastassia N Alexandrova and Tomas Base and Paul S Weiss}
}
