@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 {163, title = {Macropolyhedral syn-B18H22, the {\textquotedblleft}Forgotten{\textquotedblright} Isomer}, journal = {Journal of the American Chemical Society}, volume = {145}, year = {2023}, month = {August 2, 2023}, pages = {17975-17986}, chapter = {17975}, abstract = {

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 {\textquotedblleft}forgotten{\textquotedblright} 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.

}, keywords = {boron, boron hydride, Cluster, luminescence, macropolyhedral, NMR, PXRD, SAM, self-assembly, single crystal, solid state, syn-B18H22, XPS}, doi = {https://doi.org/10.1021/jacs.3c05530}, url = {https://pubs.acs.org/doi/10.1021/jacs.3c05530}, author = {Deepak Kumar Patel and B. S. Sooraj and Kaplan Kirakci and Jan Machacek and Monika Kucerakova and Jonathan Bould and Michal Dusek and Martha Frey and Christof Neumann and Sundargopal Ghosh and Andrey Turchanin and Thalappil Pradeep and Tomas Base} } @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 {142, title = {10-vertex closo-carborane: a unique ligand platform for porous coordination polymers}, journal = {CrystEngComm}, volume = {18}, year = {2016}, month = {06/2016}, pages = {2036-2040}, chapter = {2036}, abstract = {

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 ({\textquoteright}quasi{\textquoteright} 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{\textdegree} preferred-orientation angle between the carboxylate planes and moderately low rotation barrier are held responsible for the uniqueness.

}, keywords = {10 vertex, carborane, Co, crystallography, Cu, MOF, porous coordination polymers, Zn}, doi = {10.1039/C5CE02501J}, url = {http://pubs.rsc.org/en/content/articlelanding/2016/ce/c5ce02501j$\#$!divAbstract}, author = {Ishtvan Boldog and Pablo J Bereciartua and Roman Bulanek and Monika Kucerakova and Marketa Tomandlova and Michal Dusek and Jan Machacek and Dirk De Vos and Tomas Base} } @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} }