TY - JOUR T1 - Carborane-thiol protected copper nanoclusters: Stimuli-responsive materials with tunable phosphorescence JF - Chemical Science Y1 - 2023 A1 - Arijit Jana A1 - Madhuri Jash A1 - Wakeel Ahmed Dar A1 - Jayoti Roy A1 - Papri Chakraborty A1 - Paramasivam Ganesan A1 - Sergei Lebedkin A1 - Kaplan Kirakci A1 - Sujan Manna A1 - P. K. Sudhadevi Antharjanam A1 - Jan Machacek A1 - Monika Kucerakova A1 - Sundargopal Ghosh A1 - Kamil Lang A1 - Manfred Kappes A1 - Tomas Base A1 - T. Pradeep KW - boron KW - Cluster KW - Copper KW - Cu4L4 KW - Phosphorescence KW - Responsive AB -

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’t show mechonoresponsive luminescence in contrast to other clusters, having bent Cu4S4 structures. Cu4@oCBT and Cu4@mCBT are thermally stable up to 400 °C. The Cu4@oCBT retained green emission even upon heating to 200 °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.

VL - 14 UR - https://pubs.rsc.org/en/content/articlelanding/2023/sc/d2sc06578a ER - TY - JOUR T1 - Macropolyhedral syn-B18H22, the “Forgotten” Isomer JF - Journal of the American Chemical Society Y1 - 2023 A1 - Deepak Kumar Patel A1 - B. S. Sooraj A1 - Kaplan Kirakci A1 - Jan Machacek A1 - Monika Kucerakova A1 - Jonathan Bould A1 - Michal Dusek A1 - Martha Frey A1 - Christof Neumann A1 - Sundargopal Ghosh A1 - Andrey Turchanin A1 - Thalappil Pradeep A1 - Tomas Base KW - boron KW - boron hydride KW - Cluster KW - luminescence KW - macropolyhedral KW - NMR KW - PXRD KW - SAM KW - self-assembly KW - single crystal KW - solid state KW - syn-B18H22 KW - XPS AB -

The chemistry and physics of macropolyhedral B18H22 clusters have attracted significant attention due to the interesting photophysical properties of anti-B18H22 (blue emission, laser properties) and related potential applications. We have focused our attention on the “forgotten” syn-B18H22 isomer, which has received very little attention since its discovery compared to its anti-B18H22 isomer, presumably because numerous studies have reported this isomer as nonluminescent. In our study, we show that in crystalline form, syn-B18H22 exhibits blue fluorescence and becomes phosphorescent when substituted at various positions on the cluster, associated with peculiar microstructural-dependent effects. This work is a combined theoretical and experimental investigation that includes the synthesis, separation, structural characterization, and first elucidation of the photophysical properties of three different monothiol-substituted cluster isomers, [1-HS-syn-B18H21] 1, [3-HS-syn-B18H21] 3, and [4-HS-syn-B18H21] 4, of which isomers 1 and 4 have been proved to exist in two different polymorphic forms. All of these newly substituted macropolyhedral cluster derivatives (1, 3, and 4) have been fully characterized by NMR spectroscopy, mass spectrometry, single-crystal X-ray diffraction, IR spectroscopy, and luminescence spectroscopy. This study also presents the first report on the mechanochromic shift in the luminescence of a borane cluster and generally enriches the area of rather rare boron-based luminescent materials. In addition, we present the first results proving that they are useful constituents of carbon-free self-assembled monolayers.

VL - 145 UR - https://pubs.acs.org/doi/10.1021/jacs.3c05530 ER - TY - JOUR T1 - The Au25(SR)18 cluster carrying icosahedral dodecaborate and glutathione ligands: A spectroscopic view JF - Journal of Physics and Chemistry of Solids Y1 - 2020 A1 - Eva Valusova A1 - Maria Kanuchova A1 - Tomas Base A1 - Viktor Viglasky A1 - Marian Antalik KW - Chirality KW - Coating KW - Optoelectronic nanomaterials KW - Spectroscopy AB -

The functionality of Au25(S-glutathione)18 clusters change when some of the ligands in the cluster shell are replaced for other species. In this study we report on the synthesis and characterisation of a new cluster in which undecahydro-closo-dodecaborate thiolates are introduced as constituents of the shell surrounding the gold core. This is the first reported example in which the Au13 core of the Au25(S-glutathione)18 cluster is covered with an Au–S–B linkage instead of an Au–S–C on the dimeric shell units using a ligand exchange reaction. The spectra of the new cluster species clearly indicate a successful ligand exchange while retaining the gold core with undisrupted semirings containing both thiolate species. The resulting clusters were identified as Au25 [(S-glutathione)18-x (S-closo-borate)x-)] (x = 3, 4). Despite the achiral character of the closo-borate thiolates entering the semiring, increased chirality traces were observed in the high-energy region. Circular dichroism (CD) responses are ligand dependent and provide a fingerprint characteristic of the ligands present in the cluster. The next generation of such surface functionalized clusters provides unique base for computational and application studies.

UR - https://www.sciencedirect.com/science/article/pii/S0022369720307411?via%3Dihub ER - TY - JOUR T1 - Influence of Terminal Carboxyl Group on Structure and Reactivity of Functionalized m-Carboranethiolate Self-Assembled Monolayers JF - Chemistry of Materials Y1 - 2020 A1 - Dominic P Goronzy A1 - Jan Stanek A1 - Erin Avery A1 - Han Guo A1 - Zdenek Bastl A1 - Michal Dusek A1 - Nathan M Gallup A1 - Saliha Gun A1 - Monika Kucerakova A1 - Brian J Levandowski A1 - Jan Machacek A1 - Vaclav Sicha A1 - John C Thomas A1 - Adem Yavuz A1 - K N Houk A1 - M Fatih Danisman A1 - Ersen Mete A1 - Anastassia N Alexandrova A1 - Tomas Base A1 - Paul S Weiss KW - acidity KW - carborane KW - carboxyl KW - monolayer KW - SAM KW - self-assembly AB -

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.

VL - 32 UR - https://pubs.acs.org/doi/10.1021/acs.chemmater.0c02722 ER - TY - JOUR T1 - 10-vertex closo-carborane: a unique ligand platform for porous coordination polymers JF - CrystEngComm Y1 - 2016 A1 - Ishtvan Boldog A1 - Pablo J Bereciartua A1 - Roman Bulanek A1 - Monika Kucerakova A1 - Marketa Tomandlova A1 - Michal Dusek A1 - Jan Machacek A1 - Dirk De Vos A1 - Tomas Base KW - 10 vertex KW - carborane KW - Co KW - crystallography KW - Cu KW - MOF KW - porous coordination polymers KW - Zn AB -

1,10-dicarboxy-1,10-dicarba-closo-decaborane, a classical dicarboxylate spacer ligand type similar to the prototypal terephthalic acid, proved to be different not only from the latter, but also the closest relative, the 1,12-dicarboxy-closo-1,12-dicarbadecaborane regarding topology of the derived PCPs. Highly porous and robust compounds of zinc (rob net) and cobalt ('quasi' pcu) as well as a topologically unexpected copper compound (lvt) define the individuality of the 10-vertex carborane cage as a new fundamental spacer type in PCP chemistry. A combination of smaller sterics compared to the 12-vertex analogue, 45° preferred-orientation angle between the carboxylate planes and moderately low rotation barrier are held responsible for the uniqueness.

VL - 18 UR - http://pubs.rsc.org/en/content/articlelanding/2016/ce/c5ce02501j#!divAbstract IS - 12 ER - TY - JOUR T1 - Thermal isomerizations of monothiolated carboranes (HS)C2B10H11 and the solid-state investigation of 9-(HS)-1,2-C2B10H11 and 9-(HS)-1,7-C2B10H11 JF - Journal of Organometallic Chemistry Y1 - 2015 A1 - Tomas Base A1 - Jan Machacek A1 - Zuzana Hajkova A1 - Jens Langecker A1 - John D Kennedy A1 - Michael J Carr KW - carborane KW - Carboranethiol KW - closo-dicarbadodecaborane thiol KW - closo-dicarbadodecaboranes KW - Cluster KW - Dipole KW - Isomer KW - Isomerisation KW - Thermal Stability AB -

At 300-500 C, three C-thiolated closo-dicarbadodecaborane isomers 1-(HS)-1,2-C2B10H11 (1-o), 1-(HS)-1,7-C2B10H11 (1-m), and 1-(HS)-1,12-C2B10H11 (1-p), and two B-thiolated isomers 9-(HS)-1,7-C2B10H11 (9-m) and 9-(HS)-1,2-C2B10H11 (9-o) show two types of reaction: first, removal of an SH group from the closo-dicarbadodecaborane skeleton, and second, skeletal isomerizations from ortho to meta to para that lead to new isomers. A previously unreported SH skip from carbon-to-boron is also observed. The effect of the thiol group on the skeletal rearrangement is discussed. The isomerisation products are assigned on the basis of correlation of their computationally obtained dipole moments with their gas-chromatographic retention times. Computational results on molecular energies for the mono-thiolated species show good agreement between the calculated relative stabilities and the incidence and relative quantities of the isomerization products. Two of the starting B-thiolated isomers, 9-o and 9-m, were characterized using single-crystal X-ray diffraction analyses and their crystallographic packings as well as some selected structural parameters are discussed. All starting compounds were characterized using multinuclear NMR spectroscopy.

UR - http://www.sciencedirect.com/science/article/pii/S0022328X15300462 ER - TY - JOUR T1 - Decaborane Thiols as Building Blocks for Self-Assembled Monolayers on Metal Surfaces JF - Inorganic Chemistry Y1 - 2012 A1 - Jonathan Bould A1 - Jan Machacek A1 - Michael G S Londesborough A1 - Ramon Macias A1 - John D Kennedy A1 - Zdenek Bastl A1 - Patrik Rupper A1 - Tomas Base AB -

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 VL - 51 ER - TY - JOUR T1 - Reversible Capture of Small Molecules On Bimetallaborane Clusters: Synthesis, Structural Characterization, and Photophysical Aspects JF - Inorganic Chemistry Y1 - 2011 A1 - Jonathan Bould A1 - Tomas Base A1 - Michael G S Londesborough A1 - Luis A Oro A1 - Ramon Macias A1 - John D Kennedy A1 - Pavel Kubat A1 - Marcel Fuciman A1 - Tomas Polivka A1 - Kamil Lang VL - 50 UR - http://pubs.acs.org/doi/abs/10.1021%2Fic200374k ER - TY - JOUR T1 - Tuning the surface potential of Ag surfaces by chemisorption of oppositely-oriented thiolated carborane dipoles JF - Journal of Colloid and Interface Science Y1 - 2011 A1 - Jorn F Lubben A1 - Tomas Base A1 - Patrick Rupper A1 - Tina Kunniger A1 - Jan Machacek A1 - Sebastien Guimond AB -

Two selected carboranethiol isomers were used to modify flat silver surfaces. Both isomers, 1,2-(HS)2 VL - 354 UR - http://www.sciencedirect.com/science/article/pii/S0021979710012385 ER - TY - JOUR T1 - An Experimental Solution to the "Missing Hydrogens" Question Surrounding the Macropolyhedral 19-Vertex Boron Hydride Monoanion [B19H22](-), a Simplification of Its Synthesis, and Its Use As an Intermediate in the First Example of syn-B18H22 to anti-B18H22 JF - Inorganic Chemistry Y1 - 2010 A1 - Michael G S Londesborough A1 - Jonathan Bould A1 - Tomas Base A1 - Drahomir Hnyk A1 - Mario Bakardjiev A1 - Josef Holub A1 - Ivana Cisarova A1 - John D Kennedy VL - 49 UR - http://pubs.acs.org/doi/abs/10.1021/ic901976y IS - 9 ER - TY - JOUR T1 - Gold Micrometer Crystals Modified with Carboranethiol Derivatives JF - J. Phys. Chem. C Y1 - 2008 A1 - Tomas Base A1 - Zdenek Bastl A1 - Miroslav Slouf A1 - Mariana Klementova A1 - Jan Subrt A1 - Aliaksei Vetushka A1 - Martin Ledinsky A1 - Antonin Fejfar A1 - Jan Machacek A1 - Michael J Carr A1 - Michael G S Londesborough AB -

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.

VL - 112 UR - http://pubs.acs.org/doi/abs/10.1021/jp802281s IS - 37 ER - TY - JOUR T1 - Carboranethiol-Modified Gold Surfaces. A Study and Comparison of Modified Cluster and Flat Surfaces JF - Langmuir Y1 - 2005 A1 - Tomas Base A1 - Zdenek Bastl A1 - Zbynek Plzak A1 - Tomas Grygar A1 - Jaromir Plesek A1 - Michael J Carr A1 - Vaclav Malina A1 - Jan Subrt A1 - Jaroslav Bohacek A1 - Eva Vecernikova A1 - Otomar Kriz AB -

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 VL - 21 UR - http://pubs.acs.org/doi/abs/10.1021/la051122d IS - 17 ER - TY - JOUR T1 - Synthesis and catalytic activity of spaced ferrocene oxazolines JF - Collection of Czechoslovak Chemical Communications Y1 - 2003 A1 - Petr Stepnicka A1 - Tomas Base A1 - Ivana Cisarova A1 - Jiri Kubista A1 - Stepan Vyskocil A1 - Martin Sticha VL - 68 UR - http://cccc.uochb.cas.cz/68/7/1206/ IS - 7 ER - TY - JOUR T1 - Carborane-thiol protected copper nanoclusters: Stimuli-responsive materials with tunable phosphorescence JF - Chemical Science Y1 - 0 A1 - Arijit Jana A1 - Madhuri Jash A1 - Wakeel A Dar A1 - Jayoti Roy A1 - Papri Chakraborty A1 - Paramasivam Ganesan A1 - Sergei Lebedkin A1 - Kaplan Kirakci A1 - Sujan Manna A1 - P. K. Sudhadevi Antharjanam A1 - Jan Machacek A1 - Monika Kucerakova A1 - Sundargopal Ghosh A1 - Kamil Lang A1 - Manfred Kappes A1 - Tomas Base A1 - T. Pradeep KW - boron KW - carborane KW - Cluster KW - Copper KW - Phosphorescence KW - Responsive KW - thiol AB -

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’t show mechonoresponsive luminescence in contrast to other clusters, having bent Cu4S4 structures. Cu4@oCBT and Cu4@mCBT are thermally stable up to 400 °C. The Cu4@oCBT retained green emission even upon heating to 200 °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.

UR - https://pubs.rsc.org/en/content/articlelanding/2023/sc/d2sc06578a ER -