Multicolor photoluminescence of Cu clusters modulated using surface ligands.

Copper nanoclusters exhibit unique structural features and their molecular assembly results in diverse photoluminescence properties. In this study, we present ligand-dependent multicolor luminescence observed in a Cu cluster, primarily protected by -carborane-9,12-dithiol (-CBDT), featuring an octahedral Cu inner kernel enveloped by eight isolated copper atoms. The outer layer of the metal kernel consists of six bidentate -CBDT ligands, in which carborane backbones are connected through μ-sulphide linkages.

Macropolyhedral -BH, the "Forgotten" Isomer.

The chemistry and physics of macropolyhedral BH clusters have attracted significant attention due to the interesting photophysical properties of -BH (blue emission, laser properties) and related potential applications. We have focused our attention on the "forgotten" -BH isomer, which has received very little attention since its discovery compared to its -BH isomer, presumably because numerous studies have reported this isomer as nonluminescent. In our study, we show that in crystalline form, -BH exhibits blue fluorescence and becomes phosphorescent when substituted at various positions on the cluster, associated with peculiar microstructural-dependent effects.

Carborane-thiol protected copper nanoclusters: stimuli-responsive materials with tunable phosphorescence.

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 Cu@oCBT, Cu@mCBT and Cu@ICBT, protected by nearly isomeric carborane thiols: -carborane-9-thiol, -carborane-9-thiol and -carborane 12-iodo 9-thiol, respectively. They have a square planar Cu core and a butterfly-shaped CuS staple, which is appended with four respective carboranes.

The Livelihood of Artisanal and Small-Scale Miners and Awareness of the Use of 3T Minerals in Rwanda-A Case Study in the Rutsiro District: A Qualitative Assessment.

This article examines the impact of artisanal and small-scale mining (ASM) on livelihood in mining communities in Rwanda (Rutsiro) where wolframite and coltan are mined. The paper discusses the development of ASM and other entrepreneur activities, in particular agriculture. With ASM activities, there is environmental degradation on the one hand but also an improvement in the well-being of the local population on the other.

Carboranethiol-Protected Propeller-Shaped Photoresponsive Silver Nanomolecule.

We report the synthesis, structural characterization, and photophysical properties of a propeller-shaped Ag nanomolecule with six rotary arms, protected with -carborane-9-thiol (MCT) and triphenylphosphine (TPP) ligands. Structural analysis reveals that the nanomolecule has an Ag 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.

Light-Activated Intercluster Conversion of an Atomically Precise Silver Nanocluster.

Noble metal nanoclusters protected with carboranes, a 12-vertex, nearly icosahedral boron-carbon framework system, have received immense attention due to their different physicochemical properties. We have synthesized -carborane-1,2-dithiol (CBDT) and triphenylphosphine (TPP) coprotected [Ag(CBDT)(TPP)] (shortly Ag) using a ligand-exchange induced structural transformation reaction starting from [AgH(TPP)] (shortly Ag). The formation of Ag was confirmed using UV-vis absorption spectroscopy, mass spectrometry, transmission electron microscopy, X-ray photoelectron spectroscopy, infrared spectroscopy, and multinuclear magnetic resonance spectroscopy.

Lewis Superacidic Tellurenyl Cation-Induced Electrophilic Activation of an Inert Carborane.

The aryltellurenyl cation [2-(tBuNCH)C H Te] , a Lewis super acid, and the weakly coordinating carborane anion [CB H ] , an extremely weak Brønsted acid (pK =131.0 in MeCN), form an isolable ion pair complex [2-(tBuNCH)C H Te][CB H ], in which the Brønsted acidity (pK 7.4 in MeCN) of the formally hydridic B-H bonds is dramatically increased by more than 120 orders of magnitude.

Navigational Needs and Preferences of Hospital Patients and Visitors: What Prospects for Smart Technologies?

In this paper, we map navigational needs and preferences of patients and visitors to evaluate the appropriateness of a smartphone navigation application in the hospital in contrast to other, more traditional navigational cues. We test the effects of sociodemographic variables (age, gender, education) on wayfinding strategies and preferences of respondents (using chi2 tests). Empirical research is based on the survey among 928 patients/visitors of the Vítkovice Hospital in Ostrava, Czechia.

A theoretical analysis of the structure and properties of BH isomers. Consequences to the laser and semiconductor doping capabilities of large borane clusters.

Decaborane(14), nido-BH, is the major commercially available molecular building block in boron cluster chemistry. The condensation of two such {nido-B} blocks gives the known isomers of BH- a molecule used in the fabrication of p-type semiconductors and capable of blue laser emission. Here, we computationally determine the structures and thermodynamic stabilities of 20 possible BH regioisomers constructed from the fusion of three {nido-B} blocks with the three subclusters conjoined by two-boron atom shared edges.

Acid-Base Control of Valency within Carboranedithiol Self-Assembled Monolayers: Molecules Do the Can-Can.

We use simple acid-base chemistry to control the valency in self-assembled monolayers of two different carboranedithiol isomers on Au{111}. Monolayer formation proceeds via Au-S bonding, where manipulation of pH prior to or during deposition enables the assembly of dithiolate species, monothiol/monothiolate species, or combination. Scanning tunneling microscopy (STM) images identify two distinct binding modes in each unmodified monolayer, where simultaneous spectroscopic imaging confirms different dipole offsets for each binding mode.

Nuclear Magnetic Shielding of Monoboranes: Calculation and Assessment of B NMR Chemical Shifts in Planar BX and in Tetrahedral [BX] Systems.

B NMR chemical shifts of tricoordinated BX and tetracoordinated BX compounds (X = H, CH, F, Cl, Br, I, OH, SH, NH, and CH═CH) were computed, and the shielding tensors were explored not only within the nonrelativistic GIAO approach but also by application of both relativistic ZORA computations including spin-orbit coupling as well as scalar nonrelativistic ZORA computations (BP86 level of density functional theory). The contributions of the spin-orbit coupling to the overall shieldings are decisive for X = Br and I in both series. No relationship was found between the 2p orbital occupancies or 1/ΔE (difference between LUMO and suitably occupied MO that can be coupled with LUMO) with the shielding tensors (or their principal values) in the BX series.

Unique stereocontrol in carborane chemistry: skeletal alkylcarbonation (SAC) versus exoskeletal alkylmethylation (EAM) reactions.

Reactions between the arachno-6,9-C2B8H14 (1) dicarbaborane and acyl chlorides, RCOCl (2), are subject to stereocontrol that completely changes the nature of the reaction products. While most chlorides produce the 8-R-nido-7,8,9-C3B8H11 (3) tricarbollides (by skeletal alkylcarbonation=SAC), bulky RCOCls (2; where R=1-adamantyl, 2 a; 1-mesityl, 2 b; 9-anthranyl, 2 c; 1-naphthyl, 2 d) in 1,2-dichloroethane (DCE) in the presence of triethylamine at 40-60 °C gave a series of entirely different 1-R-2-CH3-closo-1,6-C2B8H8 (4) dicarbaboranes upon acidification with conc. H2SO4 (by exosleletal alkylmehylation=EAM).

The dominant role of chalcogen bonding in the crystal packing of 2D/3D aromatics.

The chalcogen bond is a nonclassical σ-hole-based noncovalent interaction with emerging applications in medicinal chemistry and material science. It is found in organic compounds, including 2D aromatics, but has so far never been observed in 3D aromatic inorganic boron hydrides. Thiaboranes, harboring a sulfur heteroatom in the icosahedral cage, are candidates for the formation of chalcogen bonds.

Carboranedithiols: building blocks for self-assembled monolayers on copper surfaces.

Two different positional isomers of 1,2-dicarba-closo-dodecaboranedithiols, 1,2-(HS)(2)-1,2-C(2)B(10)H(10) (1) and 9,12-(HS)(2)-1,2-C(2)B(10)H(10) (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.

Decaborane thiols as building blocks for self-assembled monolayers on metal surfaces.

Three nido-decaborane thiol cluster compounds, [1-(HS)-nido-B(10)H(13)] 1, [2-(HS)-nido-B(10)H(13)] 2, and [1,2-(HS)(2)-nido-B(10)H(12)] 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 B(18)H(22)·C(6)H(6) solvate.

Tuning the surface potential of Ag surfaces by chemisorption of oppositely-oriented thiolated carborane dipoles.

Two selected carboranethiol isomers were used to modify flat silver surfaces. Both isomers, 1,2-(HS)(2)-1,2-C(2)B(10)H(10) (a) and 9,12-(HS)(2)-1,2-C(2)B(10)H(10) (b), are relatively strong dipoles with two SH groups per molecule. They are both anchored to the surface via two SH groups per molecule.

Ferrocene-like iron bis(dicarbollide), [3-Fe(III)-(1,2-C(2)B(9)H(11))(2)](-). The first experimental and theoretical refinement of a paramagnetic (11)B NMR spectrum.

Nuclear magnetic resonance (NMR) of paramagnetic molecules (pNMR) provides detailed information on the structure and bonding of metallo-organic systems. The physical mechanisms underlying chemical shifts are considerably more complicated in the presence of unpaired electrons than in the case of diamagnetic compounds. We report for the first time a combined first-principles theoretical as well as experimental liquid-state (11)B NMR study of a paramagnetic compound, applied on the [3-Fe(III)-(1,2-C(2)B(9)H(11))(2)](-) metallaborane, which is an electronically open-shell structure where the iron centre binds two hemispherical boron-carbon cages.

Computational studies of structures and properties of metallaboranes. Part 3: protonated iron bis(dicarbollide), [3-Fe-(1,2-C2B9H11)2H]-.

On the basis of the energies and 11B NMR chemical shifts computed at the BP86/AE1(*) and GIAO-B3LYP/II' levels of density functional theory, respectively, the structure of the long-known protonated iron(II) bis(dicarbollide) can be assigned to a staggered isomer with a cisoid conformation of the carborane ligands. In the unprotonated species, in contrast, these ligands adopt the usual trans orientation, suggesting that suitable control of protonation/deprotonation equilibria could induce rotary motion at the molecular level.

The first member of the eleven-vertex azadicarbaborane series, 1,6,9-NC2B8H13, and its N-alkyl derivatives.

Reactions between closo-1,2-C(2)B(8)H(10) (1) and amines of general formulation R(1)R(2)NH (where R(1), R(2) = H, H; Me, H; t-Bu, H and Et, Et) resulted in a straightforward cluster expansion and formation of the 11-vertex arachno-azadicarbaboranes of the 1,1-R(1),R(2-)1,6,9-NC(2)B(8)H(11) (2) cluster constitution (where R(1), R(2) = H, H 2a; Me, H 2b; t-Bu, H 2c and Et, Et 2d) in yields 10-75%, depending on the nature of the amine used. The reactions are the first example of a direct closo to arachno transformation in the area of cluster-boron compounds. Compounds 2b and 2c were isolated in two isomeric forms anti- and syn- that differ in the positioning of the t-Bu substituent with respect to the bridging hydrogen site.

New route to 1-thia-closo-dodecaborane(11), closo-1-SB11H11, and its halogenation reactions. The effect of the halogen on the dipole moments and the NMR spectra and the importance of spin-orbit coupling for the 11B chemical shifts.

Reaction between nido-B10H14 (1) and elemental sulfur in CHCl3 in the presence of Et3N at room temperature, followed by treatment with Et3N.BH3 at 170-190 degrees C, resulted in the isolation of closo-1-SB11H11 (2) in 50% yield. Selected electrophilic halogenation reactions of compound led to the isolation of a series of monohalogenated derivatives of general constitution 12-X-closo-1-SB11H10 (12-X-, where X = Cl, Br, and I).

Computational study of structures and properties of metallaboranes: cobalt bis(dicarbollide).

A density functional study at the BP86/AE1 level is presented for the cobalt bis(dicarbollide) ion [3-Co-(1,2-C2B9H11)2]- (1) and selected isomers and rotamers thereof. Rotation of the two dicarbollide moieties with respect to each other is facile, as judged by the small energetic separation of the three rotamers located (within 11 kJ mol(-1)) and by the low barriers for their interconversion (at most 41 kJ mol(-1)). Among the isomers differing in carbon atom positions that contain two equivalent dicarbollide ligands, the 1,7 ("carbon apart") form [2-Co-(1,7-C2B9H11)2]- is the most stable, 121 kJ mol(-1) below 1.