@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 {161, title = {Carborane-thiol protected copper nanoclusters: Stimuli-responsive materials with tunable phosphorescence}, journal = {Chemical Science}, volume = {14}, year = {2023}, month = {12/2023}, pages = {1613-1626}, type = {Article}, chapter = {1613}, abstract = {

Atomically precise nanomaterials with tunable solid-state luminescence attract global interest. In this work, we present a new class of thermally stable isostructural tetranuclear copper nanoclusters (NCs), shortly Cu4@oCBT, Cu4@mCBT and Cu4@ICBT, protected by nearly isomeric carborane thiols: ortho-carborane-9-thiol, meta-carborane-9-thiol and ortho-carborane 12-iodo 9-thiol, respectively. They have a square planar Cu4 core and a butterfly-shaped Cu4S4 staple, which is appended with four respective carboranes. For Cu4@ICBT, strain generated by the bulky iodine substituents on the carboranes makes the Cu4S4 staple flatter in comparison to other clusters. High-resolution electrospray ionization mass spectrometry (HR ESI-MS) and collision energy-dependent fragmentation, along with other spectroscopic and microscopic studies confirm their molecular structure. Although none of these clusters show any visible luminescence in solution, bright μs-long phosphorescence is observed in their crystalline forms. The Cu4@oCBT and Cu4@mCBT NCs are green emitting with quantum yields (Ф) of 81 and 59 \%, respectively, whereas Cu4@ICBT is orange emitting with a Φ of 18 \%. Density functional theory (DFT) calculations reveal the nature of their respective electronic transitions. The green luminescence of Cu4@oCBT and Cu4@mCBT clusters get shifted to yellow after mechanical grinding, but it is regenerated after exposure to solvent vapour, whereas the orange emission of Cu4@ICBT is not affected by mechanical grinding. Structurally flatten Cu4@ICBT didn{\textquoteright}t show mechonoresponsive luminescence in contrast to other clusters, having bent Cu4S4 structures. Cu4@oCBT and Cu4@mCBT are thermally stable up to 400 {\textdegree}C. The Cu4@oCBT retained green emission even upon heating to 200 {\textdegree}C under ambient conditions, while Cu4@mCBT changed from green to yellow in the same window. This is the first report on structurally flexible carborane thiol appended Cu4 NCs having stimuli-responsive tunable solid-state phosphorescence.

}, keywords = {boron, Cluster, Copper, Cu4L4, Phosphorescence, Responsive}, doi = {https://doi.org/10.1039/D2SC06578A}, url = {https://pubs.rsc.org/en/content/articlelanding/2023/sc/d2sc06578a}, author = {Arijit Jana and Madhuri Jash and Wakeel Ahmed Dar and Jayoti Roy and Papri Chakraborty and Paramasivam Ganesan and Sergei Lebedkin and Kaplan Kirakci and Sujan Manna and P. K. Sudhadevi Antharjanam and Jan Machacek and Monika Kucerakova and Sundargopal Ghosh and Kamil Lang and Manfred Kappes and Tomas Base and T. Pradeep} } @article {158, title = {Carboranethiol-Protected Propeller-Shaped Photoresponsive Silver Nanomolecule}, journal = {Inorganic Chemistry}, volume = {61}, year = {2022}, month = {May 27, 2022}, pages = {8593-8603}, type = {Article}, chapter = {8593}, abstract = {

We report the synthesis, structural characterization, and photophysical properties of a propeller-shaped Ag21 nano-molecule with six rotary arms, protected with m-carborane-9-thiol (MCT) and triphenylphosphine (TPP) ligands. Structural analysis reveals that the nanomolecule has an Ag13 central icosahedral core with six directly connected silver atoms and two more silver atoms connected through three Ag-S-Ag bridging motifs. While 12 MCT ligands protect the core through metal-thiolate bonds in a 3-6-3-layered fashion, two TPP ligands solely protect the two bridging silver atoms. Interestingly, the rotational orientation of a silver sulfide staple motif is opposite to the orientation of carborane ligands, resembling the existence of a bidirectional rotational orientation in the nanomolecule. Careful analysis reveals that the orientation of carborane ligands on the cluster{\textquoteright}s surface resembles an assembly of double rotors. The zero circular dichroism signal indicates its achiral nature in solution. There are multiple absorption peaks in its UV-vis absorption spectrum, characteristic of a quantized electronic structure. The spectrum appears as a fingerprint for the cluster. High-resolution electrospray ionization
mass spectrometry proves the structure and composition of the nanocluster in solution, and systematic fragmentation of the molecular ion starts with the loss of surface-bound ligands with increasing collision energy. Its multiple optical absorption features are in good agreement with the theoretically calculated spectrum. The cluster shows a narrow near-IR emission at 814 nm with a Stokes shift of 355 nm. The Ag21 nanomolecule is thermally stable at ambient conditions up to 100 {\textdegree}C. However, white-light illumination (lamp power = 120-160 W) shows photosensitivity, and this induces structural distortion, as confirmed by changes in the Raman and electronic absorption spectra. Femtosecond and nanosecond transient absorption studies reveal an exceptionally stable excited state having a lifetime of 3.26 {\textpm} 0.02 μs for the carriers, spread over a broad wavelength region of 500-650 nm. The formation of core-centered long-lived carriers in the excited state is responsible for the observed light-activated structural distortion.

}, keywords = {Ag21, boron, carborane, clusters, double rotor, luminescence, silver, thiol}, doi = {https://doi.org/10.1021/acs.inorgchem.2c00186}, url = {https://pubs.acs.org/doi/10.1021/acs.inorgchem.2c00186}, author = {Arijit Jana and Parvathy M Unnikrishnan and Ajay K Poonia and Jayoti Roy and Madhuri Jash and Ganesan Paramasivam and Jan Machacek and Kumaran Nair Valsala Devi Adarsh and Tomas Base and Thalappil Pradeep} } @article {120, title = {Carbon-substituted 9,12-dimercapto-1,2-dicarba-closo-dodecaboranes via a 9,12-bis(methoxy-methylthio)-1,2-dicarba-closo-dodecaborane precursor}, journal = {Polyhedron}, volume = {45}, year = {2012}, chapter = {144}, doi = {10.1016/j.poly.2012.07.067}, url = {http://www.sciencedirect.com/science/article/pii/S0277538712005207}, author = {Jens Langecker and Karla Fejfarova and Michal Dusek and Daniel Rentsch 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 {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} } @article {130, title = {Chemie podivnych tvaru aneb Vylet do rise hydridu boru (in Czech)}, journal = {Vesmir}, volume = {87}, year = {2008}, month = {2008/11}, pages = {748-749}, type = {popular}, keywords = {b{\'o}r, klastr, klec, molekula, monovrstva, nanovrstva, samo-organizace, uhl{\'\i}k}, issn = {1214-4029}, url = {http://casopis.vesmir.cz/clanky/clanek/id/8022}, author = {Tomas Base and Michael G S Londesborough} } @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} } @mastersthesis {131, title = {Carboranethiol-modified surfaces of gold colloids and films}, volume = {Ph.D.}, year = {2007}, month = {2007}, pages = {60}, school = {Institute of Chemical Technology}, address = {Prague}, author = {Tomas Base} } @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} } @article {160, title = {Carborane-thiol protected copper nanoclusters: Stimuli-responsive materials with tunable phosphorescence }, journal = {Chemical Science}, abstract = {

Atomically precise nanomaterials with tunable solid-state luminescence attract global interest. In this work, we present a new class of thermally stable isostructural tetranuclear copper nanoclusters (NCs), shortly Cu4@oCBT, Cu4@mCBT and Cu4@ICBT, protected by nearly isomeric carborane thiols: ortho-carborane-9-thiol, meta-carborane-9-thiol and ortho-carborane 12-iodo 9-thiol, respectively. They have a square planar Cu4 core and a butterfly-shaped Cu4S4 staple, which is appended with four respective carboranes. For Cu4@ICBT, strain generated by the bulky iodine substituents on the carboranes makes the Cu4S4 staple flatter in comparison to other clusters. High-resolution electrospray ionization mass spectrometry (HR ESI-MS) and collision energy-dependent fragmentation, along with other spectroscopic and microscopic studies confirm their molecular structure. Although none of these clusters show any visible luminescence in solution, bright μs-long phosphorescence is observed in their crystalline forms. The Cu4@oCBT and Cu4@mCBT NCs are green emitting with quantum yields (Ф) of 81 and 59 \%, respectively, whereas Cu4@ICBT is orange emitting with a Φ of 18 \%. Density functional theory (DFT) calculations reveal the nature of their respective electronic transitions. The green luminescence of Cu4@oCBT and Cu4@mCBT clusters get shifted to yellow after mechanical grinding, but it is regenerated after exposure to solvent vapour, whereas the orange emission of Cu4@ICBT is not affected by mechanical grinding. Structurally flatten Cu4@ICBT didn{\textquoteright}t show mechonoresponsive luminescence in contrast to other clusters, having bent Cu4S4 structures. Cu4@oCBT and Cu4@mCBT are thermally stable up to 400 {\textdegree}C. The Cu4@oCBT retained green emission even upon heating to 200 {\textdegree}C under ambient conditions, while Cu4@mCBT changed from green to yellow in the same window. This is the first report on structurally flexible carborane thiol appended Cu4 NCs having stimuli-responsive tunable solid-state phosphorescence.

}, keywords = {boron, carborane, Cluster, Copper, Phosphorescence, Responsive, thiol}, doi = {https://doi.org/10.1039/D2SC06578A}, url = {https://pubs.rsc.org/en/content/articlelanding/2023/sc/d2sc06578a}, author = {Arijit Jana and Madhuri Jash and Wakeel A Dar and Jayoti Roy and Papri Chakraborty and Paramasivam Ganesan and Sergei Lebedkin and Kaplan Kirakci and Sujan Manna and P. K. Sudhadevi Antharjanam and Jan Machacek and Monika Kucerakova and Sundargopal Ghosh and Kamil Lang and Manfred Kappes and Tomas Base and T. Pradeep} }