Influence of Terminal Carboxyl Group on Structure and Reactivity of Functionalized m-Carboranethiolate Self-Assembled Monolayers

0525516 - ÚACH 2021 RIV US eng J - Journal Article
Goronzy, D. P. - Staněk, Jan - Avery, E. - Guo, H. - Bastl, Zdeněk - Dušek, Michal - Gallup, N. - Gün, S. - Kučeráková, Monika - Levandowski, B.J. - Macháček, Jan - Šícha, Václav - Thomas, J. C. - Yavuz, A. - Houk, K. - Danişman, M.F. - Mete, E. - Alexandrova, A. N. - Baše, Tomáš - Weiss, P. S.
Influence of Terminal Carboxyl Group on Structure and Reactivity of Functionalized m-Carboranethiolate Self-Assembled Monolayers.
Chemistry of Materials. Roč. 32, č. 15 (2020), s. 6800-6809. ISSN 0897-4756. E-ISSN 1520-5002
R&D Projects: GA MŠMT(CZ) LTAIN19152; GA TA ČR TH02020628; GA ČR(CZ) GA18-10438S
Institutional support: RVO:61388980 ; RVO:61388955 ; RVO:68378271
Keywords : Monolayers * Carboxyls * Thiols * Molecular structure
OECD category: Inorganic and nuclear chemistry; Physical chemistry (UFCH-W); Condensed matter physics (including formerly solid state physics, supercond.) (FZU-D)
Impact factor: 9.811, year: 2020
Method of publishing: Limited access
https://pubs.acs.org/doi/10.1021/acs.chemmater.0c02722

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 ± 0.4 Å 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.
Permanent Link: http://hdl.handle.net/11104/0310677