@article {164, title = {Competing Intermolecular and Molecule{\textendash}Surface Interactions: Dipole{\textendash}Dipole-Driven Patterns in Mixed Carborane Self-Assembled Monolayers}, journal = {Chemistry of Materials}, volume = {36}, year = {2024}, month = {February 8, 2024}, pages = {2085-2095}, type = {Article}, chapter = {2085}, abstract = {

Carboranedithiol isomers adsorbing with opposite orientations of their dipoles on surfaces are self-assembled together to form mixed monolayers where both lateral dipole{\textendash}dipole and lateral thiol{\textendash}thiolate (S{\textendash}H{\textperiodcentered}{\textperiodcentered}{\textperiodcentered}S) interactions provide enhanced stability over single-component monolayers. We demonstrate the first instance of the ability to map individual isomers in a mixed monolayer using the model system carboranedithiols on Au{111}. The addition of methyl groups to one isomer provides both an enhanced dipole moment and extra apparent height for differentiation via scanning tunneling microscopy (STM). Associated computational investigations rationalize favorable interactions of mixed pairs and the associated stability changes that arise from these interactions. Both STM images and Monte Carlo simulations yield similarly structured mixed monolayers, where approximately 10\% of the molecules have reversed dipole moment orientations but no direct chemical attachment to the surface, leading to homogeneous monolayers with no apparent phase separation. Deprotonating the thiols by depositing the molecules under basic conditions eliminates the lateral S{\textendash}H{\textperiodcentered}{\textperiodcentered}{\textperiodcentered}S interactions while accentuating the dipole{\textendash}dipole forces. The molecular system investigated is composed of isomeric molecules with opposite orientations of dipoles and identical surface packing, which enables the mapping of individual molecules within the mixed monolayers and enables analyses of the contributions of the relatively weak lateral interactions to the overall stability of the assemblies.

}, keywords = {2D assembly, boron, carborane, Cluster Molecules, Dipole-dipole, Molecular interactions, Molecular structure, scanning tunneling microscopy, Supramolecular chemistry}, doi = {https://doi.org/10.1021/acs.chemmater.3c03210}, url = {https://pubs.acs.org/doi/10.1021/acs.chemmater.3c03210}, author = {Katherine E. White and Erin M. Avery and Edison Cummings and Zixiang Hong and Jens Langecker and Aliaksei Vetushka and Michal Dusek and Jan Machacek and Jakub Vi{\v s}n{\'a}k and Jan Endres and Zdenek Bastl and Ersen Mete and Anastassia N. Alexandrova and Tomas Base and Paul S. Weiss} } @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 = {

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.

}, 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 {141, title = {Adsorption of oriented carborane dipoles on a silver surface}, journal = {Physica Status Solidi B}, volume = {253}, year = {2016}, month = {10 DEC 2015}, pages = {591-600}, abstract = {

Modification of surfaces with self-assembled mono-layers (SAMs) represents a powerful and innovative tool for adjusting physical and chemical properties of surfaces. The adsorption of isomeric molecules with relatively strong and oppositely oriented molecular dipoles, 1,2-(HS)2-1,2-C2B10H10 and 9,12-(HS)2-1,2-C2B10H10, on a flat silver surface is investigated in order to adjust its work function in a desired way. Time-offlight secondary ion mass spectroscopy (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) are used to prove that both isomers (i) chemisorb on a silver surface as thiolates and (ii) exhibit comparable surface densities. Densely packed surfaces of both SAMs are additionally investigated by electrochemical impedance spectroscopy, and effective surface passivation is observed. Co-deposition of both derivatives is shown to enable effective and fine adjustment of the surface work function value within a range of 1V, which is confirmed by Kelvin probe force microscopy (KPFM). Experimental data indicate faster SAM formation for the former isomer. Contribution of the interface Ag{\textendash}S bonds to the work function changes is quantified.

}, keywords = {carborane, Kelvin probe force microscopy, self-assembled monolayers, silver, time-of-flight secondary ion mass spectrometry, X-ray photoelectron spectroscopy}, doi = {10.1002/pssb.201552446}, author = {Aliaksei Vetushka and Laetitia Bernard and Olga Guseva and Zdenek Bastl and Ji{\v r}{\'\i} Plocek and Ivo Tomandl and Antonin Fejfar and Tomas Base and Patrik Schmutz} } @article {139, title = {Self-Assembled p-Carborane Analog of p-Mercaptobenzoic Acid on Au{111}}, journal = {Chemistry of Materials}, year = {2015}, month = {06/2015}, type = {Article}, abstract = {

Thep-carborane cluster analog of p-mercaptobenzoic acid, 1

}, keywords = {boron compounds, carborane, crystallography, scanning tunneling microscopy, self-assembly}, doi = {10.1021/acs.chemmater.5b02263}, url = {http://pubs.acs.org/doi/pdf/10.1021/acs.chemmater.5b02263}, author = {John C Thomas and Ishtvan Boldog and Harsharn S Auluck and Pablo J Bereciartua and Michal Dusek and Jan Machacek and Zdenek Bastl and Paul S Weiss and Tomas Base} } @article {122, title = {Carboranedithiols: Building Blocks for Self-Assembled Monolayers on Copper Surfaces}, journal = {Langmuir}, volume = {28}, year = {2012}, chapter = {12518}, abstract = {

Two different positional isomers of 1,2-dicarbacloso-dodecaboranedithiols, 1,2-(HS)2-1,2-C2B10H10 (1) and 9,12-(HS)2-1,2-C2B10H10 (2), have been investigated as cluster building blocks for self-assembled monolayers (SAMs) on copper surfaces. These two isomers represent a convenient system in which the attachment of SH groups at different positions on the skeleton affects their acidic character and thus also determines their reactivity with a copper surface. Isomer 1 exhibited etching of polycrystalline Cu films, and a detailed investigation of the experimental conditions showed that both the acidic character of SH groups and the presence of oxygen at the copper surface play crucial roles in how the surface reaction proceeds: whether toward a self-assembled monolayer or toward copper film etching. We found that each positional isomer requires completely different conditions for the preparation of a SAM on copper surfaces. Optimized conditions for the former isomer required the exposure of a freshly prepared Cu surface to vapor of 1 in vacuum, which avoided the presence of oxygen and moisture. Adsorption from a dichloromethane solution afforded a sparsely covered Cu(0) surface; isomer 1 effectively removes the surface copper(I) oxide, forming a soluble product, but apparently binds only weakly to the clean Cu(0) surface. In contrast, adsorption of the latter, less volatile isomer proceeded better from a dichloromethane solution than from the vapor phase. Isomer 2 was even able to densely cover the copper surface cleaned up by the dichloromethane solution of 1. Both isomers exhibited high capacity to remove oxygen atoms from the surface copper(I) oxide that forms immediately after the exposure of freshly prepared copper films to ambient atmosphere. Isomer 2 showed suppression of Cu film oxidation. A number of methods including X-ray photoelectron spectroscopy (XPS), X-ray Rutherford back scattering (RBS), proton-induced X-ray emission (PIXE) analysis, atomic force microscopy (AFM), cyclic voltammetry, and contact angle measurements were used to investigate the experimental conditions for the preparation of SAMs of both positional isomers on copper surfaces and to shed light on the interaction between these molecules and a polycrystalline copper surface.

}, doi = {10.1021/la302334x}, url = {http://pubs.acs.org/doi/abs/10.1021\%2Fla302334x}, author = {Tomas Base and Zdenek Bastl and Vladimir Havranek and Jan Machacek and Jens Langecker and Vaclav Malina} } @proceedings {136, title = {Carboranethiols: Building Blocks for Self-Assembled Monolayers on Copper Surfaces, or a Novel Class of Etchants?}, journal = {European Materials Research Society, Spring Meeting}, year = {2012}, publisher = {E-MRS}, address = {Strasbourg, France, 2012 May 14-18}, abstract = {

This contribution aims at showing an unprecedented behavior of carboranedithiols on copper surfaces. Two different positional isomers of 1,2-dicarba-closo-dodecaborane-dithiol, 1,2-(HS)2-1,2-C2B10H10 (1) and 9,12-(HS)2-1,2-C2B10H10 (2), have been used as a convenient molecular system in which the attachment of -SH groups at different positions on the skeleton affects their acidic character and thus determines their reactivity with a copper surface. While the latter isomer represents a weak acid and forms a self-assembled monolayer (SAM) similarly to various aliphatic and aromatic thiols reported previously, the former isomer shows etching of copper leading to a complete dissolution of the films used in our experiments at a rate of approx. 70 nm per hour (in 7.5 mM EtOH solution of 1 at 20 C). A detailed investigation of the experimental conditions showed that the acidic character of -SH groups and the presence of oxygen at the copper surface play crucial role in how the surface reaction proceeds: whether towards the formation of a 1-SAM or towards etching and dissolution of a copper film. Reaction between 1 and a freshly prepared copper surface in vacuum or in a dry and oxygen-free solvent such as toluene, or dichloromethane yields a 1-SAM. This study shows the first thiol derivative that possesses the ability to etch copper films. A number of methods including XPS, RBS, PIXE have been used and the results will be presented and discussed. Acknowledgement: P205/10/0348, GACR

}, author = {Tomas Base and Zdenek Bastl and Vladimir Havranek and Jan Machacek and Vaclav Malina} } @article {119, title = {Decaborane Thiols as Building Blocks for Self-Assembled Monolayers on Metal Surfaces}, journal = {Inorganic Chemistry}, volume = {51}, year = {2012}, chapter = {1685}, abstract = {

Three nido-decaborane thiol cluster compounds, [1-(HS)-nido-B10H13] 1, [2-(HS)-nido-B10H13] 2, and [1,2-(HS)2-nido-B10H12] 3 have been characterized using NMR spectroscopy, single-crystal X-ray diffraction analysis, and quantum-chemical calculations. In the solid state, 1, 2, and 3 feature weak intermolecular hydrogen bonding between the sulfur atom and the relatively positive bridging hydrogen atoms on the open face of an adjacent cluster. Density functional theory (DFT) calculations show that the value of the interaction energy is approximately proportional to the number of hydrogen atoms involved in the interaction and that these values are consistent with a related bridging-hydrogen atom interaction calculated for a B18H22 C6H6 solvate. Self-assembled monolayers (SAMs) of 1, 2, and 3 on gold and silver surfaces have been prepared and characterized using X-ray photoelectron spectroscopy. The variations in the measured sulfur binding energies, as thiolates on the surface, correlate with the (CC2) calculated atomic charge for the relevant boron vertices and for the associated sulfur substituents for the parent B10H13(SH) compounds. The calculated charges also correlate with the measured and DFT-calculated thiol 1H chemical shifts. Wetting-angle measurements indicate that the hydrophilic open face of the cluster is directed upward from the substrate surface, allowing the bridging hydrogen atoms to exhibit a similar reactivity to that of the bulk compound. Thus, [PtMe2(PMe2Ph)2] reacts with the exposed and acidic B }, doi = {10.1021/ic202000b}, author = {Jonathan Bould and Jan Machacek and Michael G S Londesborough and Ramon Macias and John D Kennedy and Zdenek Bastl and Patrik Rupper and Tomas Base} } @article {117, title = {Carborane-thiol-silver interactions. A comparative study of the molecular protection of silver surfaces}, journal = {Surface and Coatings Technology}, volume = {204}, year = {2010}, chapter = {2639}, abstract = {

The interaction between flat silver surfaces and carboranethiol derivatives, and its relevance regarding the molecular protection of silver against corrosion by hydrogen sulphide, are reported here. A comparison of the protective qualities of four carboranethiols (1-HS-1,2-C2B10H11, 1,2-(HS)2-1,2-C2B10H10, 9,12-(HS)2-1,2-C2B10H10, and 1,12-(HS)2-1,2-C2B10H10) with several organic thiols (1-butanethiol, 1-octanethiol, 1-dodecanethiol, benzene-1,2-dithiol, benzenethiol, and sodium 2-mercaptoethanesulphonate) is provided. All these derivatives are categorized according to their capacity to inhibit the interaction of silver with H2S in the presence of water molecules in the gas phase. We found that significantly better molecular protection for silver surfaces is afforded by the carboranethiol derivatives, and, of these, 9,12-(HS)2-1,2-C2B10H10 proved to be particularly effective. The corrosion of silver by H2S is accompanied by well-defined colour changes from lustrous silver, through yellow, violet, blue, and finally to grey. This sequence has not been reported before and it is used in this study as a qualitative indicator of the extent of silver corrosion. Our results are supported by reflectance UV

}, doi = {10.1016/j.surfcoat.2010.02.019}, url = {http://www.sciencedirect.com/science/article/pii/S0257897210001106}, author = {Tomas Base and Zdenek Bastl and Vladimir Havranek and Kamil Lang and Jonathan Bould and Michael G S Londesborough and Jan Machacek and Jaromir Plesek} } @proceedings {128, title = {A comparison of boron hydride- and hydrocarbon-based thiol derivatives assembled on gold surfaces}, journal = {NSTI Nanotechnology Conference and Trade Show}, volume = {1}, year = {2008}, publisher = {NSTI}, address = {Boston, USA}, issn = {978-1-4200-8503-7}, url = {http://www.nsti.org/procs/Nanotech2008v1/2/T35.902}, author = {Tomas Base and Zdenek Bastl and Michael G S Londesborough and Jan Machacek} } @article {116, title = {Gold Micrometer Crystals Modified with Carboranethiol Derivatives}, journal = {J. Phys. Chem. C}, volume = {112}, year = {2008}, chapter = {14446}, abstract = {

The preparation and characterization of micrometer gold and silver single-crystals of well-defined shapes are reported here. The shapes of the crystals can be described as plates, polyhedra, and wires. The orientation of the crystal faces was studied using electron and X-ray powder diffraction techniques, and a (111) orientation of the large faces of gold plates was experimentally shown. The surface morphology of the crystal faces was studied by atomic force microscopy. Modifications of gold microplates with the thiolated carborane clusters 1,2-(HS)2-1,2-C2B10H10 (1), 9,12-(HS)2-1,2-C2B10H10 (2), and 1,12-(HS)2-1,12-C2B10H10 (3) are described. The carboranethiol molecules 1 and 2 show dipole moments of 4.1 and 5.9 D. In comparison, the thiolate derivative of compound 1 has a dipole moment of 4.7 D in the opposite direction to 1, and the thiolate form of compound 2 has a dipole moment of 16.7 D in the same direction. On the basis of X-ray photoelectron spectroscopy (XPS) analyses and values of work functions, we revealed that the molecules of 1 and 2 attached to the gold surface have similar electron distribution and dipole moments as within the free thiol derivatives. Following the modification of microplate gold crystals with 3, a monolayer of gold nanoparticles was attached on top of the carborane moieties. The composition of the surface species was studied using XPS. Dynamic contact angles of water on the modified gold surfaces are also discussed.

}, doi = {10.1021/jp802281s}, url = {http://pubs.acs.org/doi/abs/10.1021/jp802281s}, author = {Tomas Base and Zdenek Bastl and Miroslav Slouf and Mariana Klementova and Jan Subrt and Aliaksei Vetushka and Martin Ledinsky and Antonin Fejfar and Jan Machacek and Michael J Carr and Michael G S Londesborough} } @proceedings {134, title = {Carborane Thiol-modified Gold Surfaces. A Study and Comparison of Modified Cluster and Flat Surfaces}, journal = {12th International Meeting on Boron Chemistry (IMEBORON-XII)}, year = {2005}, address = {Sendai, Japan, 11 }, author = {Tomas Base and Zdenek Bastl and Zbynek Plzak and Tomas Grygar and Jaromir Plesek and Michael J Carr} } @article {115, title = {Carboranethiol-Modified Gold Surfaces. A Study and Comparison of Modified Cluster and Flat Surfaces}, journal = {Langmuir}, volume = {21}, year = {2005}, chapter = {7776}, abstract = {

Four different carboranethiol derivatives were used to modify the surfaces of gold nanoparticles and flat gold films. The novel materials engendered from these modifications are extraordinarily stable species with surfaces that support self-assembled monolayers of 1-(HS)-1,2-C2B10H11, 1,2-(HS)2-1,2-C2B10H10, 1,12-(HS)2-1,12-C2B10H10, and 9,12-(HS)2-1,2-C2B10H10, respectively. Surprisingly, characterization of these materials revealed that a number of molecules of the carboranethiol derivatives are incorporated inside the nanoparticles. This structural feature was studied using a number of techniques, including X-ray photoelectron spectroscopy (XPS), UV }, doi = {10.1021/la051122d}, url = {http://pubs.acs.org/doi/abs/10.1021/la051122d}, author = {Tomas Base and Zdenek Bastl and Zbynek Plzak and Tomas Grygar and Jaromir Plesek and Michael J Carr and Vaclav Malina and Jan Subrt and Jaroslav Bohacek and Eva Vecernikova and Otomar Kriz} }