Search

Cobaltabis(dicarbollide) anion ([o-COSAN]- ) is a well-known metallacarborane with multiple applications in a variety of fields. In aqueous solution, the cisoid rotamer is the most stable disposition in the ground state. The present work provides theoretical evidence on the possibility to photoinduce the rotation from the cisoid to the transoid rotamer, a conversion that can be reverted when the ground state is repopulated. The non-radiative decay mechanisms proposed in this work are coherent with the lack of fluorescence observed in 3D fluorescence mapping experiments performed on [o-COSAN]- and its derivatives. This phenomenon induced by light has the potential to destruct the vesicles and micelles cisoid [o-COSAN]- typically forms in aqueous solution, which could lead to promising applications, particularly in the field of nanomedicine., This work was supported by the Generalitat Valenciana (GV, project GV/2020/226), Generalitat de Catalunya (2017 SGR 1720), and the Spanish Ministerio de Ciencia e Innovación (MICINN, projects CTQ2017-87054-C2-2–304-P and PID2019-106832RB-I00). A.M.A.A. is grateful to the Erasmus+ Programme of the European Comission for his Erasmus Mundus TCCM scholarship. A.F.-M. is grateful to the GV and the European Social Fund for the postdoctoral contract APOSTD/2019/149 and to the MICINN for the Juan de la Cierva contract IJC2019-039297-I. D.R.-S. is grateful to the MICINN for the “Ramón y Cajal” grant (RYC-2015–19234). “Severo Ochoa” Program for Centers of Excellence in R&D 234 (SEV-2015-0496) is appreciated. J. A. M. Xavier acknowledges DOC-FAM programme under the Marie Sklodowska-Curie grant agreement No. 754397 and is enrolled in the PhD program of the UAB. Computations have been conducted at the local QCEXVAL and the LluisVives and Tirant III clusters of the Servei d'Informàtica (University of Valencia). We thank Dr. Jordi Faraudo (ICMAB-CSIC) for the scientific discussions., With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).

Post-synthetic modification of a dynamic carborane-based soft porous crystal (1 * DMF) by in situ polymerization of pyrrole to polypyrrole (PPy) provided a permanently porous MOF/polypyrrole hybrid composite material that did not show the dynamic behavior of the mother MOF. Apart from stability, the introduction of conductive PPy in the composite material brings new properties to the otherwise non-conductive MOF., This work was financially supported by MINECO (CTQ2016-75150-R, PID2019-106832RB-I00) and the Generalitat de Catalunya (2017/SGR/1720). ICMAB acknowledges the support of the Spanish MINECO (Grant SEV-2015-0496). Z. Li is enrolled in the UAB PhD program and acknowledges the China Scholarship Council (CSC) for his PhD grants (201808310071). Z. Li thanks Fangchang Tan and Lei Gan for their assistance with the synthesis of 1 ⊃ DMF. The present publication is dedicated to Prof. Alan Welch on the occasion of his retirement from Heriot-Watt University.

Monovalent cations, Cs+, and alkylammonium ([NR4]+) salts have traditionally been used to precipitate the anions of boranes, carborane and metallocarborane clusters. In contrast, in the body and in living organisms in general, divalent cations have a special relevance. In this work, we isolate for the first time the cobaltabis(dicarbollide) salts of the biocompatible divalent cations of biological importance that can have application both in biology and in materials science. The preparation of Ca2+, Mg2+ and Fe2+ salts of anionic iodinated nido-[C2B9H12]− and cobaltabis(dicarbollide) as well as its di-, tetra- and octa-iodinated derivatives are reported. Ca2+ and Mg2+ are hard Lewis acids and thus forms aqua ions if water is present in the synthetic process. All solid Ca2+ and Mg2+ salts studied in this work contained water molecules coordinated that have been detected by IR and TGA/DSC. Fe2+ is a medium hard Lewis acid and Fe3+ is a hard one. In acetone they do not coordinate to cobaltabis(dicarbollide) anion, but are solvated by acetone. The studied Ca2+ salts of iodinated cobaltabis(dicarbollide) are basically inorganic small molecules that provide at once the biocompatible divalent Ca2+ cation and and iodinated anions thus simultaneously providing an X-ray contrast agent and/or bone defect repairing agent in regenerative medicine., This work has been supported by the Spanish Ministerio de Economía y Competitividad (CTQ2016-75150-R) and the Generalitat de Catalunya (2017SGR1720). Miquel Nuez is enrolled in the PhD program of the UAB.

This work was financially supported by MICINN (PID2019-106832RB-I00, PGC2018-093863-B-C21), MICINN through the Severo Ochoa Program for Centers of Excellence for the FUNFUTURE (CEX2019-000917-S and MDM-2017-0767 projects) and the Generalitat de Catalunya (2017/SGR/1720 and SGR2017-1289). D. Ch.-L. acknowledges funding by project no. PGC2018-102047-B-I00 (MCIU/AEI/FEDER, UE). J. Soldevila-Sanmartin is enrolled in the UAB PhD program and acknowledges the PIF pre-doctoral Fellowship from the UAB for his pre-doctoral grant (no. 19032/2). E. R. acknowledges computer resources, technical expertise and assistance provided by the CSUC. We thank Prof. D. Ruiz and Dr C. Roscini for the quantum yield measurements. The present publication is dedicated to Prof. Elena Shubina on the occasion of her 70th birthday., Incorporation of one or two o-carborane moieties at the backbone of the pyrazole ring was achieved by lithiation and nucleophilic addition onto the corresponding 3,5-dimethyl-1-(2-toluene-p-sulfonyloxyethyl)pyrazole. Two monosubstituted carboranyl pyrazoles (L2 and L3) and one disubstituted carboranyl pyrazole (L4) were synthesized and fully characterized. All new compounds, and the corresponding monosubstituted phenylderivative (L1) behave as N-type ligands upon coordination with CuI to afford different polynuclear Cu(I) compounds 1-4. Compounds 1-4 were fully characterized and their molecular structures were determined by X-ray diffraction. It is noteworthy that whereas the pyrazolylphenyl ligand L1, without o-carborane, provides a 1D coordination polymer (1), ligands containing carborane, L2-L3, affords 0D coordination compounds 2 and 3, and disubstituted carboranyl pyrazole ligand L4 gives rise to a 3D coordination polymer. The photoluminescence behaviour of compounds 1-4 has been investigated in the solid state and by TDDFT calculations for molecular compounds 2 and 3. Complex 2 exhibits blue emission with a maximum at 483 nm and a high fluorescence quantum yield of 66.5%. According to TDDFT calculations the emission occurs from LUMO to HOMO-1 and HOMO-2 and deexcitation could be described as cluster-centred excited state of d-s transition in origin. This result contradicts previous studies of scarce tri-coordinated rhombohedral Cu(I) clusters, where it was assumed the origin of their emissions is (X + M)LCT in nature by analogy with tetra-coordinated rhombohedral Cu(I) clusters. Complex 3 exhibits very weak emission (Phi(F) of 5%) in the green region with a maximum at 517 nm, which according to TDDFT is through a (CC)-C-3 state. Calculations also show that, upon excitation, 3 suffers a notable distortion resulting in the total cleavage of the Cu4I4 framework. This cleavage could be the cause of the relatively large Stokes shift observed for 3. To the best of our knowledge, this is the first time that such behaviour is observed for this type of octahedral compounds. Additionally, the 1D polymer 1 exhibits weak fluorescence emission in the orange range with a maximum at 609 nm and a remarkable Stokes shift, whereas the 3D polymer 4 exhibits a similar emission to compound 2, with a moderate quantum yield (FF of 13.7%)., Spanish Government European Commission PID2019-106832RB-I00 PGC2018-093863-B-C21, MICINN through the Severo Ochoa Program for Centers of Excellence for the FUNFUTURE CEX2019-000917-S MDM-2017-0767, Generalitat de Catalunya 2017/SGR/1720 SGR2017-1289, MCIU/AEI/FEDER, UE PGC2018-102047-B-I00, UAB 19032/2

A set of mesomorphic materials in which the o-carborane cluster is covalently bonded to a cholesteryl benzoate moiety (mesogen group) through a suitably designed linker is described. The olefin cross-metathesis between appropriately functionalized styrenyl-o-carborane derivatives and a terminal alkenyl cholesteryl benzoate mesogen (all type I terminal olefins) leads to the desired trans-regioisomer, which is the best-suited configuration to obtain mesomorphic properties in the final materials. The introduction of different substituents (R = H (M2), Me (M3), or Ph (M4)) to one of the carbon atoms of the o-carborane cluster (Ccluster) enables the tailoring of liquid crystalline properties. Compounds M2 and M3 show the chiral nematic (N*) phase, whereas M4 do not show liquid crystal behavior. Weaker intermolecular interactions in the solid M3 with respect to those in M2 may allow the liquid crystallinity in M3 to be expressed as enantiotropic behavior, whereas breaking the stronger intermolecular interaction in the solid state of M2 leads directly to the isotropic state, resulting in monotropic behavior. Remarkably, M3 also displays the blue phase, which was observed neither in the chiral nematic precursor nor in the styrenyl-cholesterol model (M5) without an o-carborane cluster, which suggests that the presence of the cluster plays a role in stabilizing this highly twisted chiral phase. In the carborane-containing mesogens (M2 and M3), the o-carborane cluster can be incorporated without destroying the helical organization of the mesophase., This research was funded by MICINN grants (PID2019-106832RB-100 and CEX2019-000917-S) and Generalitat de Catalunya (2017/SGR/1720).

Malignant gliomas are the most common malignant and aggressive primary brain tumors in adults, the prognosis being&mdash, especially for glioblastomas&mdash, extremely poor. There are no effective treatments yet. However, tyrosine kinase receptor (TKR) inhibitors and boron neutron capture therapy (BNCT), together, have been proposed as future therapeutic strategies. In this sense in our ongoing project of developing new anti-glioblastoma drugs, we identified a sunitinib-carborane hybrid agent, 1, with both in vitro selective cytotoxicity and excellent BNCT-behavior. Consequently, we studied the ability of compound 1 to inhibit TKRs, its promotion of cellular death processes, and its effects on the cell cycle. Moreover, we analyzed some relevant drug-like properties of 1, i.e., mutagenicity and ability to cross the blood&ndash, brain barrier. These results encouraged us to perform an in vivo anti-glioblastoma proof of concept assay. It turned out to be a selective FLT3, KIT, and PDGFR-&beta, inhibitor and increased the apoptotic glioma-cell numbers and arrested sub-G1-phase cell cycle. Its in vivo activity in immunosuppressed mice bearing U87 MG human glioblastoma evidenced excellent anti-tumor behavior.

An electrophilic substitution on metallacarboranes by using a stabilized carbocation that can be made in situ is reported for the first time. This new synthetic methodology provides a new perspective on easy metallacarborane derivatization with organic fragments, which enhances the properties of both fragments and widens their possible applications., This work has been supported by the Spanish Ministerio de Economía y Competitividad (CTQ2016-75150-R), the Generalitat de Catalunya (2017SGR1720) and European Union’s Horizon 2020 Marie Skłodowska-Curie grant agreement MSCA-IF-2016-751587. A. B. Buades is enrolled in the PhD program of UAB.

o-C2B10H12 isomerizes to m-C2B10H12 upon heating at 400 °C. Deboronation in o-C2B10H12 is a relatively easy process, whereas it is more difficult in m-C2B10H12. These two experimental facts indicate that m-C2B10H12 is thermodynamically more stable than o-C2B10H12. On the other hand, it is widely accepted that closo-boranes and -carboranes are aromatic compounds. In this work, we relate the difficulty in the deboronation of the carboranes with their stability and aromaticity. We do this by combining lab work and DFT calculations. Computationally, our results show that the higher thermodynamic stability of m-C2B10H12 is not related to aromaticity differences but to the location of the C atoms in the carborane structure. It is also demonstrated that the aromaticity observed in closo-boranes and -carboranes is also present in their nido counterparts, and consequently, we conclude that aromaticity in boron clusters survives radical structural changes. Further, sandwich metallocenes (e.g., ferrocene) and sandwich metallabis(dicarbollides) (e.g., [Co(C2B9H11)2]−) have traditionally been considered to be similar. Here it is shown that they are not. Metallabis(dicarbollides) display global aromaticity, whereas metallocenes present local aromaticity in the ligands. Remarkable and unique is the double probe given by 1H and 11B NMR tracing the reciprocally antipodal endocyclic open face Hec and B1. These magnetic studies have permitted one to correlate both nuclei and relate them to a diatropic current in the plane at the middle of the nido-[C2B9H12]−. This observation is the first unique evidence that proves experimentally the existence of diatropic currents, and thence aromaticity, in clusters and is comparable to the existence of diatropic currents in planar aromatic compounds. Additionally, heteroboranes with two carbon atoms have been compared to heterocycles with two nitrogen or boron atoms, e.g., C2B10H12 carboranes versus planar N2C4H4 diazines or [B2C4H4]2– diboratabenzenes, thereby proving the higher persistence of the aromaticity of the tridimensional compounds in heteroatom-substituted species. This research accounts very well for the “paradigm for the electron requirements of clusters”, in which a closo-cluster that is aromatic upon addition of 2e– becomes also an aromatic nido-species, and explains the informative schemes by Rudolph and Williams., This work has been supported by the Ministerio de Economía y Competitividad (MINECO) of Spain (Projects CTQ2017-85341-P, CTQ2016-75150-R, CTQ2016-77558-R, and MDM-2017-0767) and the Generalitat de Catalunya (projects 2017SGR39, 2017SGR1720, and 2017SGR348). Excellent service by the Supercomputer center of the Consorci de Serveis Universitaris de Catalunya (CSUC) is gratefully acknowledged. Dedicated to Prof. Alan Welch.

© 2020 by the authors., Closo m-C2B10H12 can perform as a novel core of globular periphery-decorated macromolecules. To do this, a new class of di and tetrabranched m-carborane derivatives has been synthesized by a judicious choice of the synthetic procedure, starting with 9,10-I2-1,7-closo-C2B10H10. The 2a-NPA (sum of the natural charges of the two bonded atoms) value for a bond, which is defined as the sum of the NPA charges of the two bonded atoms, matches the order of electrophilic reaction at the different cluster bonds of the icosahedral o-and m- carboranes that lead to the formation of B-I bonds. As for m-carborane, most of the 2a-NPA values of B-H vertexes are positive, and their functionalization is more challenging. The synthesis and full characterization of dibranched 9,10-R2-1,7-closo-carborane (R = CH2CHCH2, HO(CH2)3, Cl(CH2)3, TsO(CH2)3, C6H5COO(CH2)3, C6H5COO(CH2)3, N3(CH2)3, CH3CHCH, and C6H5C2N3(CH2)3) compounds as well as the tetrabranched 9,10-R2-1,7-R2-closo-C2B10H8 (R = CH2CHCH2, HO(CH2)3) are presented. The X-ray diffraction of 9,10-(HO(CH2)3)2-1,7-closo-C2B10H10 and 9,10-(CH3CHCH)2-1,7-closo-C2B10H10, as well as their Hirshfeld surface analysis and decomposed fingerprint plots, are described. These new reported tetrabranched m-carborane derivatives provide a sort of novel core for the synthesis of 3D radially grown periphery-decorated macromolecules that are different to the 2D radially grown core of the tetrabranched o-carborane framework., This research was funded by the Spanish MINECO, grant number CTQ2016-75150-R, and Generalitat de Catalunya, grant number 2017 SGR 1720. C.V. and Z.K. thanks European Union’s Horizon 2020 Marie Skłodowska-Curie grant agreement MSCA-IF-2016-751587.

A small library of carborane-BODIPY/aza-BODIPY dyads were efficiently synthesized by means of a novel convergent synthetic approach, the key step of which is a Pd-catalyzed Heck coupling reaction. The structural characterization and photoluminescence properties of the newly synthesized dyads were evaluated. The presence of the carborane did not significantly alter the photophysical patterns of the BODIPY or aza-BODIPY in the final fluorophores, but it produced a decrease of the emission fluorescent quantum yields that was in the range from 1.4 % for aza-BODIPY to 48 % for BODIPY-dyads. The carborane-BODIPY dyads were successfully incorporated into cells, especially compounds 2, 4 and 13, demonstrating their cytoplasmic localization. The fluorescent and biocompatibility properties make these compounds good candidates for in vitro cell tracking.

A set of distyrylbenzene, distyrylbiphenyl and distyrylanthracene end-substituted with carborane clusters is introduced herein. All these compounds have been prepared from the corresponding styrene-containing carborane derivatives via Heck coupling reaction. High regioselectivity has been achieved yielding exclusively E isomers. All compounds have been fully characterized and the crystal structure of the distyrylbiphenyl end-substituted with Methyl-o-carborane was analyzed by X-ray diffraction. The absorption properties of compounds were elucidated by TD-DFT calculations, highlighting the importance of the aromatic core and π-conjugation. It is worth noting that the luminescence properties of these systems depend on the aromatic core; in solution, benzene and biphenyl derivatives showed higher fluorescence emission than the anthracene ones and the presence of the carborane clusters does not induce any major change in fluorescence as compared to the pristine non-carborane containing partners. Nevertheless, all compounds exhibited low fluorescence quantum yields in aggregation state, which gives clear evidence of considerable intermolecular interactions between aggregates that could be the reason of the fluorescence quenching.

In this communication, we report the first evidence of slow-spin relaxation of a low-spin FeIII carborane complex. Iron S = 1/2 complexes showing such behaviour are particularly appealing as qubit candidates because they fulfil some of the main requirements to reach long decoherence times, such as moderate magnetic anisotropy, small spin, metal element mainly with zero-nuclear spin and furthermore, large versatility to introduce chemical modifications.

By minor structure modification of spherical carborane ligands, in a similar synthetic procedure, large morphological changes are produced in Quantum Nanocrystals (QNCs). The spheres are icosahedral C2B10H12 molecules with binding sites on the carbon, and the QNCs produced are Quantum Dots, Rods, Rings and Tetrapods. These QNCs demonstrated high stability and impeccable emissive properties for more than a year., This work has been supported by the Spanish Ministerio de Economia y Competitividad (CTQ2016-75150-R) and Generalitat de Catalunya (2014/SGR/149). A. Saha thanks Generalitat de Catalunya for FPI predoctoral grant (2016FI_B 00214). A. Saini and A. Saha are enrolled in the PhD in Chemistry program of UAB, We acknowledge support of the publication fee by the CSIC Open Access Support Initiative through its Unit of Information Resources for Research (URICI)

Efficient monosubstitution of the non-iodinated, mono-iodinated and di-iodinated m-carborane cluster at one Ccluster has led to the preparation of three single organic molecule-carborane dyads (4–6), which exhibited exceptional fluorescence properties with quantum yield values of 100% in solution, for all of them, with maxima around 415 nm, which correspond to the locally excited state (LE) emission. These results suggest that simply linking the m-carborane fragment to one anthracene unit through a CH2 spacer produces a significant enhancement of the fluorescence in the final fluorophore, probably due to the free rotation of the anthracene linked to the Ccluster. Besides, the presence of one or two iodine atoms linked to boron atoms does not cause any influence on the photophysical properties of the dyads, as it is confirmed by TD-DFT calculations. Notably, the three conjugates show good fluorescence efficiency in the aggregate state with quantum yields in the range of 19–23%, which could be ascribed to the presence of CH2, particularly for 4, and the iodine atoms in 5 and 6, which prevent π–π stacking. All these results indicate that our dyads are extremely good emitters in solution while maintaining the emission properties in the aggregate state. Crystal packing, fingerprint plot analysis, and TD-DFT calculations for the three compounds support these results. Confocal microscopy studies show that 6 is the best-internalized compound by HeLa cells via endocytosis, although 4 and 5 also presented a high fluorescence intensity emission. Moreover, due to the blue emission, this compound is an excellent candidate to be applied as a fluorescent dye in bioimaging studies., The work was supported by the Spanish Ministerio de Economía y Competitividad, MINECO (CTQ2016-75150-R, MAT2017-86357-C3-3-R and “Severo Ochoa” Program for Centers of Excellence in R&D SEV-2015-0496) and Generalitat de Catalunya (2017/SGR/1720, 2017/SGR/503). Z. K. is grateful for the general support of the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement MSCA-IF-2016-751587. D. Ch.-L. acknowledges funding from the Intramural CSIC (201730I019) project. Theoretical calculations have been achieved using computers from the Supercomputing Centre of Catalonia (CESCA). The authors would like to thank the staff at the Servei de Microscòpia de la Universitat Autònoma de Barcelona., We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI).

A set of triads in which o- and m-carborane clusters are bonded to two stilbene units through Ccluster -CH2 bonds was synthesized, and their structures were confirmed by X-ray diffraction. A study on the influence of the o- and m- isomers on the absorption and photoluminescence properties of the stilbene units in solution revealed no charge-transfer contributions in the lowest excited state, as confirmed by (TD)DFT calculations. The presence of one or two B-I groups in m-carborane derivatives does not affect the emission properties of the stilbenes in solution, probably due to the rather large distance between the iodo substituents and the fluorophore. Nevertheless, a significant redshift of the photoluminescence (PL) emission maximum in the solid state (thin films and powder samples) compared to solution was observed; this can be traced back to PL sensitization, most probably due to more densely packed stilbene moieties. Remarkably, the PL absolute quantum yields of powder samples are significantly higher than those in solution, and this was attributed to the restricted environment and the aforementioned sensitization. Thus, the bonding of the carborane clusters to two stilbene units preserves their PL behavior in solution, but produces significant changes in the solid state. Furthermore, iodinated species can be considered to be promising precursors for theranostic agents in which both imaging and therapeutic functions could possibly be combined.

The preparation of Cc-monosubstituted closo and nido carborane derivatives, mono-, di and tetraiodinated is reported. Some of these mono-to poly-iodinated nido carboranes are studied in terms of the acidity of the open face bridging proton, their chemical shift position in the 1H NMR, and the lesser tendency to η5-coordination in parallel to a larger number of iodo groups.

The flexibility and unexpected dynamic behavior of a third-generation metal- organic framework are described for the first time. The synthetic strategy is based on the flexibility and spherical shape of dipyridyl-based carborane linkers that act as pillars between rigid Co/BTB (BTB: 1,3,5-benzenetricarboxylate) layers, providing a 3D porous structure (1). A phase transition of the solid can be induced to generate a new, nonporous 2D structure (2) without any loss of the carborane linkers. The structural transformation is visualized by snapshots of the multistep single-crystal-to-single-crystal transformation by single-crystal and powder X-ray diffraction. Poor hydrogen bond acceptors such as MeOH, CHCl3 or supercritical CO2 induce such a 3D to 2D transformation. Remarkably, the transformation is reversible and the 2D phase 2 is further converted back into 1 by heating in dimethylformamide. The energy requirements involved in such processes are investigated using periodic density functional theory calculations. As a proof of concept for potential applications, encapsulation of C60 is achieved by trapping this molecule during the reversible 2D to 3D phase transition, whereas no adsorption is observed by straight solvent diffusion into the pores of the 3D phase.

New hybrids synthesized by linking two anthracenyl units to the Ccluster atoms of a non- (4), a mono- (5) and a di-iodinated (6) m-carborane fragment through CH2 spacers, along with their full characterization, are reported. Noticeably, bonding the m-carborane fragment to the anthracene moieties produces a significant increase of more than two-fold in the intrinsic fluorescence quantum yield (ϕF) of the anthracene itself, with values of ϕF > 60% in THF and ϕF > 48% in toluene, although it does not alter the absorption and emission patterns of the fluorophore in solution. A red-shift of the emission maximum with respect to the solution is observed in the aggregate state (THF/H2O, 1 : 99 v/v), along with moderate quantum yields; compounds 4 and 5 show ϕF = 22 and 19%, respectively, whereas 6 has a lower value (ϕF = 8%). The difference between the ϕF values in the aggregate state has been attributed to the arrangement of dimers for each compound in the solid state structures. X-ray crystal structures of compounds 4 and 5 show the anthracene units to be roughly parallel, whereas such an arrangement is clearly disrupted in compound 6. Such differences have been analyzed by Hirshfeld surfaces, decomposed fingerprint plots for the three compounds and DFT calculations. The combined results from the supramolecular analyses and DFT studies support the idea that a less delocalized system in the case of 6 can be explained by the different packing in the aggregate or solid state for this di-iodo derivative. The observed arrangement of molecules of 6 seems to be related to a larger number of H⋯I contacts, with respect to the non-iodinated or mono-iodinated compounds, 4 or 5. According to this assumption, there is a direct relationship between the structure in the solid state and the PL properties; in the m-carborane derivatives, small changes in their structures have caused variations in the photophysical properties, especially in the quantum efficiency., The work was supported by the Spanish Ministerio de Economı´a y Competitividad, MINEICO (CTQ2016-75150-R and ‘‘Severo Ochoa’’ Program for Centers of Excellence in R&D SEV-2015-0496) and the Generalitat de Catalunya (2017/SGR/1720). ZK is grateful for the general support of the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement MSCA-IF-2016-751587. Theoretical calculations have been achieved using computers from the Supercomputing Centre of Catalonia (CESCA).

A synthetic strategy for functionalization of the three vertices of o-carborane and the attachment of the obtained triped to the solid support was developed. Further functionalization of the triped with short DNA sequences by automated DNA synthesis was achieved. The proposed methodology is a first example of boron cluster chemistry on a solid support opening new perspectives in boron cluster functionalization.

A new class of globular polybranched macromolecules that contain multiple anionic metallacarborane clusters at the o-carborane periphery is reported. The water soluble high boron rich containing molecules could be of interest for boron neutron capture therapy (BNCT) as well as for drug delivery. The reinforced electrostatic noncovalent interactions between anionic polyethylene glycol cobaltabisdicarbollide (PEG-COSAN) branches and the ammonium cation have been shown using ESI-MS.

Because of their amphiphilic structure, surfactants adsorb at the water-air interface with their hydrophobic tails pointing out of the water and their polar heads plunging into the liquid phase. Unlike classical surfactants, metallabisdicarbollides (MCs) do not have a well-defined amphiphilic structure. They are nanometer-sized inorganic anions with an ellipsoidal shape composed of two carborane semicages sandwiching a metal ion. However, MCs have been shown to share many properties with surfactants, such as self-assembly in water (formation of micelles and vesicles), formation of lamellar lyotropic phases, and surface activity. By combining second harmonic generation and surface tension measurement, we show here that cobaltabis(dicarbollide) anion {[(C2B9H11)2Co](-) also named [COSAN](-)} with H(+) as a counterion, the most representative metallacarborane, adsorbs vertically at the water surface with its long axis normal to the surface. This vertical molecular orientation facilitates the formation of intermolecular and nonconventional dihydrogen bonds such as the B-H(δ-)···(δ+)H-C bond that has recently been proven to be at the origin of the self-assembly of MCs in water. Therefore, it appears here that lateral dihydrogen bonds are also involved in the surface activity of MCs.

Ten structurally related racemic 2-pyridylmethyl alcohols containing an o-carborane core (1,2-closo-C2B10H10; rac-1a) or m-carborane (1,7-closo-C2B10H10; rac-2a) or p-carborane (1,7-closo-C2B10H10; rac-3a) and their enantiopure forms (R- and S-1a or R- and S-2a or R- and S-3a), as well as an iodo derivative of rac-3a (rac-4a) and a non-carborane derivative (C6H5; rac-5) have been studied by single crystal X-ray crystallography. All racemic and enantiopure structures show O-H⋯N hydrogen bonded homochiral 21-helical networks, except that for rac-3a, which forms O-H⋯N hydrogen bonded trimers. A comparison of these X-ray structures with that for others found in the Cambridge Structural Database for chiral 2-pyridyl alcohols-either in racemic or enantiopure forms-that form O-H⋯N hydrogen bonded homochiral 21-helical networks reveals a possible relationship between the torsion angle of the hydrogen bond donor and acceptor groups in these molecules and the hydrogen bonded supramolecular helices formed in the solid state. Fil: Tsang, Min Ying. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia de Los Materiales de Barcelona; España Fil: Di Salvo, Florencia. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia de Los Materiales de Barcelona; España. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina Fil: Teixidor, Francesc. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia de Los Materiales de Barcelona; España Fil: Viñas, Clara. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia de Los Materiales de Barcelona; España Fil: Planas, José Giner. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia de Los Materiales de Barcelona; España Fil: Choquesillo Lazarte, Duane. Universidad de Granada; España. Consejo Superior de Investigaciones Científicas; España Fil: Vanthuyne, Nicolas. Aix Marseille Universite; Francia

A new neutral host PdL metallacycle, featuring a bulky bis[3-pyridyl(hydroxy)methyl]-1,2-dicarba-closo-dodecaborane, is synthesized, and seven crystalline inclusion compounds are obtained from DMF, DMSO, EtOAc, and THF, with the last four acting as guest solvents. Single-crystal X-ray diffraction structural analysis shows the formation of 1:n (n = 6–8) host/guest crystals, indicating a high stoichiometric ratio of included solvent. Single-crystal X-ray diffraction analyses of all structures reveal a supramolecular ordering of the palladacycles in the solid state, through extensive hydrogen bonding or intermolecular contacts, mainly between the host and the guest molecules., We thank the Ministerio de Educación y Ciencia (MEC) grant CTQ2013-44670-R and the Generalitat de Catalunya (2014/SGR/ 149) for financial support. The project “Factoría de Cristalización, CONSOLIDER INGENIO-2010” provided X-ray structure facilities for this work. ICMAB acknowledges the support of the Ministerio de Economía y Competitividad (MINECO), Spain through the Severo Ochoa Centers of Excellence Program, under grant SEV-2015-0496

We report the synthesis and characterization of six novel coordination polymers (CPs) based on M(II) (M: Zn and Co), di-, tri-, and tetracarboxylate linkers and two novel bis-pyridylalcohol 1,7-bis{(pyridin-n′-yl)methanol}-1,7-dicarba-closo-dodecaboranes (n′ = 3, L1; n′ = 4, L2) ligands. The polycarboxylates are terephthalic acid (H2BDC), 1,3,5-benzenetricarboxylic acid (H3BTB), and 1,2,4,5-tetrakis(4-carboxyphenyl)benzene (H4TCPB). Structural description of CPs reveals the flexibility of the carborane ligands and their ability to construct extended structures. The CP containing Co(II), BTB, and L2 behaves as a crystalline sponge for a variety of guests, showing a higher affinity for aromatic guest molecules. Single-crystal nanoindentation experiments indicate that a high number of specific interactions between the guests and the CP framework result in a high elastic modulus and hardness values., This work was supported by the EU FP7 ERC-Co 615954. M.Y.T., T.F., F.T., C.V. and J.G.P. acknowledge MEC grants CTQ2013-44670-R and the Generalitat de Catalunya (2014/ SGR/149) for financial support. J.S. thanks the Generalitat de Catalunya 2014/SGR/1015 for financial support and MAT2014-57960-C3-1-R for partial financial support and associated FEDER is acknowledged. The Intramural CSIC (201530E011) provided X-ray structural facilities for this work. ICMAB and ICN2 acknowledge the support of the Spanish MINECO through the Severo Ochoa Centers of Excellence Program, under Grants SEV-2015-0496 and SEV-2013-0295. F.T. is enrolled in the UAB Ph.D. program and acknowledges the China Scholarship Council (CSC) for her Ph.D. grant (201506060171).

Two sets of o-carborane derivatives incorporating fluorene and anthracene fragments as fluorophore groups have been successfully synthesized and characterized, and their photophysical properties studied. The first set, comprising fluorene-containing carboranes 6-9, was prepared by catalyzed hydrosilylation reactions of ethynylfluorene with appropriate carboranylsilanes. The compound 1-[(9,9-dioctyl-fluorene-2-yl)ethynyl]carborane (11) was synthesized by the reaction of 9,9-dioctyl-2-ethynylfluorene and decaborane (B10H14). Furthermore, reactions of the lithium salt of 11 with 1 equivalent of 4-(chloromethyl)styrene or 9-(chloromethyl)anthracene yielded compounds 12 and 13. Members of the second set of derivatives, comprising anthracene-containing carboranes, were synthesized by reactions of monolithium or dilithium salts of 1-Me-1,2-C2B10H 11, 1-Ph-1,2-C2B10H11, and 1,2-C2B10H12 with 1 or 2 equivalents of 9-(chloromethyl)anthracene, respectively, to produce compounds 14-16. In addition, 2 equivalents of the monolithium salts of 1-Me-1,2-C2B 10H11 (Me-o-carborane) and 1-Ph-1,2-C2B 10H11 (Ph-o-carborane) were reacted with 9,10-bis(chloromethyl)anthracene to produce compounds 17 and 18, respectively. Fluorene derivatives 6-9 exhibit moderate fluorescence quantum yields (32-44 %), whereas 11-13, in which the fluorophore is bonded to the Ccluster (Cc), show very low emission intensity (6 %) or complete fluorescence quenching. The anthracenyl derivatives containing the Me-o-carborane moiety exhibit notably high fluorescence emissions, with φF=82 and 94 %, whereas their Ph-o-carborane analogues are not fluorescent at all. For these compounds, we have observed a correlation between the Cc - C c bond length and the fluorescence intensity in CH2Cl 2 solution, comparable to that observed for previously reported styrene-containing carboranes. Thus, our hypothesis is that for systems of this type the fluorescence may be tuned and even predicted by changing the substituent on the adjacent Cc. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The accurate selection of a ligand for a metal-catalyzed homogeneous reaction can be as decisive as the selection of the metal. Incorporating a carborane cage as a backbone to produce new phosphines often leads to remarkable properties, which are not accessible employing conventional organic entities. The synergy effects between the o-carborane cluster and the P atom in these closo- and nido-carboranylphosphines is observed from two points of view: the cluster and the P atom. The P atoms in the closo-carboranylmonophosphines grant to the cluster a unique plasticity on the Ccluster Ccluster distance. The cooperation between the carboranyl moiety and the P atom may result in mono-, di- and tridendicity according to the necessities of the metal, not an ever-available property for organic phosphines.

[3,3′-Co(1,2-C2B9H11)2]−, [1]−, and its chloroderivatives have been described as displaying surfactant/aggregation properties. We have studied their behaviour as electrolytes in the water electrolysis process. The electrolysis experiments support the surfactant behaviour of these compounds. These conclusions have been drawn on the grounds of the intensity/voltage (I/V) curves of water splitting into H2 and O2 of aqueous solutions in which the electrolytes have been tested at the same concentration. The I/V curves have permitted us to map and group the different electrolytes studied in this work. Three differentiated zones have been observed: one for true electrolytes, NO3− and ClO4−; a second one for intermediate electrolytes, BF4− and p-toluenesulfonate (PTS); and a third having the surfactant dodecylbenzenesulfonate (DBS), [1]− and its chloroderivatives. The incorporation into the study of the chloroderivatives of [1]− has allowed us to correlate molecular structure features with aqueous performance. The studied chloroderivatives perform better as electrolytes in accordance with the descending order of available B–H groups. This comes from the higher capacity to generate B–H⋯H–Cc dihydrogen bonds in the non- or less-halogenated molecules, considered one of the main reasons for the generation of the aggregates. In order to generate B–H⋯H–Cc dihydrogen bonds the H–Cc from the carborane cluster is needed. [B12H12]2− was chosen to prove the hypothesis as it has B–H units but lacks H–Cc units. Consequently, it should not produce self-assembling motifs, as is the case. [B12H12]2− has an aqueous behaviour similar to SO42−. MICINN (CTQ2010-16237), CSIC (I3P grant to P.G.), MEC (FPU grant to M.T.) and the Generalitat de Catalunya 2009/SGR/00279. peer-reviewed

This review includes a compilation of different types of star-shaped molecules and dendrimers decorated with boron clusters, carboranes or metallacarboranes, at their periphery. Dendrimeric platforms, such as PAMAM, carbosilane, poly(aryl-ether), among others, have been functionalized with a different number of small metallacarboranes, nido-carboranes or cobaltabisdicarbollide clusters following diverse methodologies. In general, all these structures are high-boron content molecules, and for those that carry nido-carboranes and alkaline metals, are also soluble in water. Most of these compounds have been proposed as highly promising boron delivery agents for the BNCT of tumors, particularly for malignant brain tumors. Nevertheless, other applications such as catalysts, optoelectronic devices, drug delivery systems, and others can be envisaged.

Materials that combine flexibility and open metal sites are crucial for myriad applications. In this article, we report a 2D coordination polymer (CP) assembled from CuII ions and a flexible meta-carborane-based linker [Cu2(L1)2(Solv)2]&bull, xSolv (1-DMA, 1-DMF, and 1-MeOH, L1: 1,7-di(4-carboxyphenyl)-1,7-dicarba-closo-dodecaborane). 1-DMF undergoes an unusual example of reversible phase transition on solvent treatment (i.e., MeOH and CH2Cl2). Solvent exchange, followed by thermal activation provided a new porous phase that exhibits an estimated Brunauer-Emmett-Teller (BET) surface area of 301 m2 g&minus, 1 and is capable of a CO2 uptake of 41 cm3 g&minus, 1. The transformation is reversible and 1-DMF is reformed on addition of DMF to the porous phase. We provide evidence for the reversible process being the result of the formation/cleavage of weak but attractive B&ndash, H∙∙∙Cu interactions by a combination of single-crystal (SCXRD), powder (PXRD) X-ray diffraction, Raman spectroscopy, and DFT calculations.

Preferential chlorination sites resulting from sequential substitution reactions in the representative metallacarborane [3,3′-Co(1,2-C2B9H11)2]− have been studied by combining experimental and computational methods. Similarly to aromatic substitution, the preferential chlorination sites in metallacarborane and carborane anions are of kinetic origin. There is no site preference in thermodynamic terms; however, there are sites on which the reaction takes place more rapidly. Preferential chlorination numbers have been proven experimentally by mixing the substrate with incremental ratios of N-chlorosuccinimide at 194 ± 6 °C and analyzing the resulting samples by negative MALDI-TOF-MS. Two parameters Δy and πy have been developed which are indicators of the ease of synthesis of species with y chlorine substituents, relative to the species with y + 1 substituents, and the persistence of the y species, relative to that with y + 1, in excess of chlorinating agent. These parameters have been used to account for the rates of the reaction. They explain the largely known stability of the hexachlorinated cobaltabisdicarbollide anion along with the mono, and dichlorinated species, but strongly support the stability of the octachlorinated cobaltabisdicarbollide anion, a species never previously reported. An excellent correlation for the relative reaction rates has been found with the 2a-NPA charges on the non-chlorinated starting material. The 2a-NPA value for a bond is defined as the sum of the NPA charges of the two bonded atoms (e.g. B–H or C–H). 2a-NPA charges match the order of attack on the bonds.

Novel polyhedral oligomeric silsesquioxanes (POSS) or octasilses- quioxanes with carboranyl-styrene fragments attached to each corner are described. These compounds have been synthesized by olefin-metathesis reac- tions between octavinylsilsesquioxane and carboranyl-styrene compounds that possess different substituents (Ph, Me, or H). In all cases, these reactions, which were catalyzed by the Grubbs catalyst, are highly regioselective and yield exclusively the E isomers. The ex- istence of the carborane cage in the POSS structure induces a remarkable thermal stability in these compounds. After combustion at 10008C, these car- boranyl-POSS compounds exhibit a mass loss lower than 10 %. The UV/ Vis absorption data of these carboran- yl-POSS compounds shows a slight bathochromic shift with respect to the carboranyl-styrene monomers, with an absorption maximum around 262 nm. Nevertheless, important differences in the emission spectra of the carboranyl- POSS compounds with regard to their carboranyl-styrene precursors are ob- served; the phenyl-o-carborane-con- taining POSS compound exhibits the highest fluorescence intensity (FF = 44 %), whereas for the POSS com- pound bearing the methyl substituent, and for the unsubstituted o-carborane clusters, the fluorescence intensity is much lower (FF = 9 and 2 %, respec- tively). This is precisely the reverse of what occurs with the monomers, in which the unsubstituted o-carboranyl- styrene compound exhibits the highest FF, and a quenching of the fluores- cence is observed in the phenyl-o-car- boranyl-styrene compound. In addi- tion, a large red shift of around 100 nm is observed for the POSS compounds with respect to their precursors. These experimental results can only be ac- counted for by the spatial ordering in- duced by the POSS core that eases in- teractions, which otherwise would not occur. These results have been con- firmed by time-dependent density func- tional theory (TDDFT) calculations that exclude a photoinduced electron transfer (PET) process in the POSS

Materials with surfaces that can be switched from high/superhydrophobicity to superhydrophilicity are useful for myriad applications. Herein, we report a metal–organic framework (MOF) assembled from Zn ions, 1,4-benzenedicarboxylate, and a hydrophobic carborane-based linker. The MOF crystal-surface can be switched between hydrophobic and superhydrophilic through a chemical treatment to remove some of the building blocks., This work was supported by the EU FP7 ERC-Co 615954.M.Y.T., F.T. , C.V., and J.G.P. thank MINECO grants CTQ2013-44670-R and the Generalitat de Catalunya (2014/SGR/149) for financial support. The Intramural CSIC (201530E011) provided X-ray structural facilities for this work. I.I. thanks the MINECO for a RyC fellowship and V. G. is grateful to the Generalitat de Catalunya for a Beatriu de Pinos Fellowship. ICMAB and ICN2 acknowledge the support of the Spanish MINECO through the Severo Ochoa Centers of Excellence Program, under Grant SEV-2015-0496 and SEV-2013-0295

The influence of ethereal solvents (diethyl ether (Et(2)O), tetrahydrofuran (THF) or dimethoxyethane (DME)) on the formation of organolithiated compounds has been studied on the 1,2-C(2)B(10)H(12) platform. This platform is very attractive because it contains two C(c)-H adjacent units ready to be lithiated. On would expect that the closeness of both C(c)-H units would induce a higher resistance of the second C(c)-H unit being lithiated following the first lithiation. However, this is not the case, which makes 1,2-C(2)B(10)H(12) attractive to get a better understanding of the ethereal solvent influence on the lithiation process. The formation of carboranyl disubstituted species has been attributed to the existence of an equilibrium in which the carboranyl monolithiated species disproportionates into dilithium carborane and pristine carborane. The way Li(+) binds to C(c) in the carboranyl fragment and how the solvent stabilizes such a binding is paramount to drive the reaction to the generation of mono- and disubstituted carboranes. In fact, the proportion of mono- and disubstituted species is a consequence of the formation of contact ion pairs and, to a lesser extent, of separated ion pairs in ethereal solvents. All ethereal solvents generate contact ion pairs in which a large degree of covalent C(c)-Li(solvent) bonding can be assumed, according to experimental and theoretical data. Furthermore, Et(2)O tends to produce carboranyllitium ion pairs with a higher degree of contact ion pairs than THF or DME. It has been determined that for a high-yield preparation of monosubstituted 1-R-1,2-C(2)B(10)H(11), in C(c)-R (R=C, S or P) coupling reactions, the reagent type defines which is the most appropriate ethereal solvent. In reactions in which a halide is generated, as with ClPPh(2) or BrCH(2) CH=CH(2), Et(2)O appears to produce the highest degree of monosubstitution. In other situations, such as with S(8), or when no halide is generated, THF or DME facilitate the largest degree of monosubstitution. It has been shown that upon the self reaction of Li[1,2-C(2)B(10)H(11)] to produce [LiC(4)B(20)H(22)](-) the nucleophilicity of the carboranyllithium can even be further enhanced, beyond the ethereal solvent, by synergism with halide salts. The mediation of Li(+) in producing isomerizations on allyl substituents has also been demonstrated, as Et(2)O does not tend to induce isomerization, whereas THF or DME produces the propenyl isomer. The results presented here most probably can be extended to other molecular types to interpret the Li(+) mediation in C-C or other C-X coupling reactions.

A set of neutral and anionic carborane derivatives in which the styrenyl fragment is introduced as a fluorophore group has been successfully synthesized and characterized. The reaction of the monolithium salts of 1-Ph-1,2-C(2)B(10)H(11), 1-Me-1,2-C(2)B(10)H(11) and 1,2-C(2)B(10)H(12) with one equivalent of 4-vinylbenzyl chloride leads to the formation of compounds 1-3, whereas the reaction of the dilithium salt of 1,2-C(2)B(10)H(12) with two equivalents of 4-vinylbenzyl chloride gives disubstituted compound 4. The closo clusters were degraded using the classical method, KOH in EtOH, to afford the corresponding nido species, which were isolated as tetramethylammonium salts. The crystal structure of the four closo compounds 1-4 were analyzed by X-ray diffraction. All compounds, except 1, display emission properties, with quantum yields dependent on the nature of the cluster (closo or nido) and the substituent on the second C(cluster) atom. In general, closo compounds 2-4 exhibit high fluorescence emission, whereas the presence of a nido cluster produces a decrease of the emission intensity. The presence of a phenyl group bonded to the C(cluster) results in an excellent electron-acceptor unit that produces a quenching of the fluorescence. DFT calculations have confirmed the charge-separation state in 1 to explain the quenching of the fluorescence and the key role of the carboranyl fragment in this luminescent process.

A series of new mononuclear and carboranylcarboxylate-bridged dinuclear copper(II) compounds containing the 1-CH3-2-CO2H-1,2- closo-C2B10H10 carborane ligand (LH) has been synthesized. Reaction of different copper salts with LH at room temperature leads to dinuclear compounds of the general formula [Cu2(μ-L) 4(Lt)2] (Lt=thf (1), L t=H2O (1′)). The reaction of 1 and 1′ with different terminal pyridyl (py) ligands leads to the formation of a series of structurally analogous complexes by substitution of the terminal ligand thf or H2O (Lt=py (2), p-CF3-py (3), p-CH 3-py (4), pz (6), and 4,4′-bpy (7)), which maintain the structural Cu2(μ-O2CR)4 core in the majority of the cases except for o-(CH3)2-py, where a mononuclear compound (5) is exclusively obtained. These compounds have been characterized through analytical, spectroscopic (NMR, IR, UV-visible, ESI-MS) and magnetic techniques. X-ray structural analysis revealed a paddle-wheel structure for the dinuclear compounds, with a square-pyramidal geometry around each copper ion and the carboranylcarboxylate ions bridging two copper atoms in syn-syn mode. The mononuclear complex obtained with the o-(CH3)2-py ligand presents a square-planar structure, in which the carboranylcarboxylate ligand adopts a monodentate coordination mode. The magnetic properties of the dinuclear compounds 1, 3, 4, and 6 show a strong antiferromagnetic coupling in all cases (J=-261 (1), -255 (3), -241 (4), -249 cm-1 (6)). Computational studies based on hybrid density functional methods have been used to study the magnetic properties of the complexes and also to evaluate their relative stability on the basis of the strength of the bond between each CuII and the terminal ligand This research has been financed by MEC of Spain through projects CTQ2010-21532-C02-01 and CTQ2010-16237 and Generalitat de Catalunya (2009/SGR/00279). M.F. thanks Generalitat de Catalunya for an FI predoctoral grant and A.R.P. to the Spanish Ministry of Education for the FPU grant. The access to the computational facilities of High Performance Computing Centre of CSIC and Centre de Supercomputaci de Catalunya (CESCA) is gratefully acknowledged. Serveis T cnics de Recerca (STR) from UdG are also acknowledged for technical support. N.A.-A. thanks the Spanish Ministerio de Ciencia e Innovaci n (CTQ2009-06959) and ICREA (Instituci Catalana de Recerca i Estudis Avançats). E.R. thanks to the Ministerio de Ciencia e Innovaci n and the Direcci General de Recerca for the grants CTQ2008-06670-C02-01 and 2009SGR-1459 as well as to the Centre de Supercomputaci de Catalunya (CESCA) for providing computational resources

The recently reported crystal structure of [NMe4][1-SiMe2H-3,3′-Co(1,2-C2B9H10)(1′,2′-C2B9H11)] shows short contacts between the Si–H proton acceptor group and the Cc–H proton donor moiety in the dicarbollide ligand. These short contacts were studied within the framework of the Quantum Theory of Atoms in Molecules (QTAIM) at different levels of DFT theory (B3LYP/6-311(d,p) and BP86/TZ2P(+)) that shows the existence of a bifurcated Si–H⋯H–Cc dihydrogen bond. This paper presents the study of an experimental uncommon Si–H group playing as proton acceptor bond in a dihydrogen bond where hydrides like M–H (M, as metal transition), B–H or Al–H usually perform this role. Furthermore, this paper accounts with a new simple method to estimate bonding energies for closed-shell intramolecular interactions in the scheme of Voronoi charge population analysis and Coulomb′s Law.

The synthesis of N,S-heterodisubstituted 1-(2'-pyridyl)-2-SR-1,2-closo-C2B10H10 compounds (R = Et, 2; R = (i)Pr, 3) has been accomplished starting from 1-(2'-pyridyl)-l,2-closo-C2B10H11 (1), and their partial deboronation reaction leading to the structurally chiral [7-(2'-pyridyl)-8-SR-7,8-nido-C2B9H10]-derivatives (R = Et, [4]-; R = (i)Pr, [5]-) has been studied. Capillary electrophoresis combined with the chiral selector alpha-cyclodextrin has permitted the separation of the electrophoretically pure racemic [7-(2'-pyridyl)-8-SR-7,8-nido-C2B9H11]- ions into two peaks each one corresponding to the interaction of one enantiomer with the alpha-cyclodextrin. The N,S-heterodisubstituted o-carborane containing a mercapto group, 1-(2'-pyridyl)-2-SH-1,2-closo-C2B10H10, 1, is one of the two examples of a rigid bidentate chelating (pyridine)N-C-C-C-S(H) motif having been structurally fully characterized. To study the potential of such a binding site, 1 has been tested as a ligand with metal ions requiring different coordination numbers, two (Au(+)) and four (Pd2+ and Rh+). The crystal structures of the Pd(II) and Au(I) complexes are reported. For the Pd(II) complex, 1 acts as a bidentate ligand whereas for Au(I), 1 acts as a monodentate ligand through the thiolate.

Experimental (single-crystal X-ray diffraction) and computational evidence shows that there is short intramolecular distance between two phosphorus atoms in 1,2-(diphenylphosphino)-1,2-dicarba-closo-dodecaborane. In the optimized structure at the B3LYP/6-31G∗ level of theory the interaction was analyzed by quantum theory – atoms-in-molecules and natural bonding orbitals methods. Both methods established the interaction. The former method indicates direct P⋯P interaction, while the latter describes it as donor–acceptor interaction between phosphorus electron lone pair and adjacent antibonding P–C(phenyl) orbital.

New dinuclear carboranylcarboxylate-bridged and mononuclear copper(II) compounds containing the 1-CO2H-2-H-1,2-closo-C2B10H10 carborane ligand (LH) have been synthesized from the previously synthesized dinuclear compound [Cu-2(mu-L)(4)(THF)(2)], 1. Reaction of LH with CuSO4 in THF leads to the dinuclear compound [CCu2(mu-L)(4)(THF)(2)], 1. The reaction of 1 with different terminal pyridyl ligands leads to the formation of a series of structurally analogous complexes by substitution of the terminal ligand THF (L-t = py, 2; p-CF3-py, 3; p-CH3-py, 4), which maintain the structural Cu-2(mu-O2CR)(4) core in most of the cases except for o-(CH3)(2)-py where a mononuclear compound (5) is exclusively obtained. In the case of 2 and 4, other dinuclear compounds [Cu-2(L)(4)(L-t)(4)], 2' and 4' are obtained in lower yield. These compounds have been characterized using analytical, spectroscopic (NMR, IR, UV-visible) and electrochemical techniques (CV, DPV). X-ray analysis revealed a paddle-wheel structure for the main dinuclear compounds with a square-pyramidal geometry around each copper ion and the carboranylcarboxylate ions bridging two copper atoms in syn-syn mode. In the case of 2' and 4' there are two carboranylcarboxylate ions bridging the copper atoms in syn-anti mode whereas the other two adopt a monodentate coordination mode. The mononuclear complex obtained with the o-(CH3)-py ligand presents a square-planar structure, in which the carboranylcarboxylate ligand adoptsmonodentate coordination. The effect of the substituent group on the cluster of the carboranylcarboxylate ligands on the reactivity of compound 1 is also discussed This research was financed by MEC of Spain through projects, CTQ2010-21532-C02-01, CTQ2013-44670-R, European Union (COST Action CM1302-Smart Inorganic Polymers) and the Generalitat de Catalunya (2014 SGR 149)

The influence of weakly coordinating anions with different shapes and substituents has been studied to get the overoxidation resistance limit of the material, ORL. The anions utilized are derivatives of [Co(C2B9H11)2]−, [B12H12]2− and [B12H11NH3]−. The following tendencies have been established (1) boron cluster monoanions are to date the anions that offer the highest stability to overoxidation of PPy doped materials (2) the ORL stability of the material can not be attributed only to the shape of the cluster (3) monoanionic clusters are far superior than dianionic to get an ORL rise (4) cluster charge density reduction results in ORL rise as has been observed in [Co(C2B9H11)2]− after incorporation of electron-withdrawing substituents with no electron back-donation (5) globular, rigid and large monoanions are less suitable for enhanced ORL values than elongated and non-rigid species (6) adequate anion's substitution produce a rise in the ORL of the material, thus polyether side-arms are beneficial with [Co(C2B9H11)2]−, whereas, T-shaped methylaryl groups are appealing in [B12H11NH3]− based materials, respectively, (7) substituents on the anions usually imply higher difficulty in the materials' growth. The high boron contents in these materials has permitted to learn on the fate of the doping anions during the overoxidation process. There is a built-up of the concentration of the doping anion in the electrolyte near surface area, whereas, a depletion is observed in the nearest inner layers.

Neutral and especially dianionic 6- and 12-vertex closo ortho-carboranes (o-carboranes) 1,2-R2-1,2-C2BnHn (R = H, CH3, NH2, OH, F, SiH3, PH2, SH, Cl, as well as e-, CH2-, NH-, O-, SiH2-, PH-, and S- exhibit extremely large variations (over 1 A!) of the cage CC distances, from 1.626 to 2.638 A, at the B3LYP/6-31G//B3LYP/6-31G DFT level. These CC "bond lengths," among the longest ever reported, generally are greater in the icosahedral than those in the corresponding octahedral systems and depend strongly on the substituents. While 1,2-(NH2)2-1,2-C2B10H10 has the longest Cc...Cc separation in neutral species (1.860 A), Cc...Cc distances can be much larger in the corresponding dianions. These range from 1.823 A (R- = e-) to 2.638 A (R- = CH2-) for 1,2-(R-)2-1,2-C2B10H10 and from 1.626 A (R- = SiH2-) to 3.099 A (R- = NH-) for 1,2-(R-)2-1,2-C2B4H4. Remarkably, there is no abrupt discontinuity over the entire range of CC lengths. Consequently, the relationship between the gradual changes in the distances and the nature of the bonding was analyzed by means of the form of the Kohn-Sham orbitals, the Wiberg Cc...Cc bond indices, and Bader AIM method. Cluster carboranes, and possibly other heteroboranes, thus appear to offer unique opportunities for modulating Cc...Cc distances.

Gradient-corrected density functional theory applied to 1,2-diphosphino-1,2-dicarba-closo-dodecaborane, 1,2-(PH2)2-1,2-C2B10H10, and its respective PdCl2 complex presents a clear picture of the effect of complexation on the P–Cc–Cc–P fragments (Cc = cage carbon C1 or C2) in the structures. The complexation results in clear closing in the P–Cc–Cc angles and shortening of Cc–Cc bond, but only minor changes take place in the P–Cc–Cc–P torsion angle. Furthermore, complexation brings along shortening of the P–Cc bonds with concomitant increase of covalency, as revealed by atoms-in-molecules calculations. Although there is also change in the Cc–Cc distance in the cage, no significant change is involved in the bonding. These findings are compared with the results obtained by single-crystal X-ray study for [PdCl2(1,2-(PiPr2)2-1,2-C2B10H10)] and additional calculations carried out for [PdCl2(1,2-(PH2)2-C2H4)].

Ruthenium complexes of the type [RuH(η5-CB)(PPh3)2] {CB is a monoanionic charge-compensated carborane ligand such as [9-SR2-7,8-C2B9H10]− and [9-SR2-7-CH3-7,8-C2B9H9]−} efficiently catalyse the Kharasch addition of CCl4 across olefins and, with maximum total turnover numbers of 9000 and initial turnover frequencies of 1900 h−1 at 40°C, highly surpass their Ru–Cp# analogues in these reactions.

Reaction of [RuH(AcO)(PPh 3 ) 3 ] and [NMe 4 ][7,8-(PPh 2 ) 2 -7,8-C 2 B 9 H 10 ] in methanol yields [RuH(7,8-(PPh 2 ) 2 -7,8-C 2 B 9 H 10 )(PPh 3 ) 2 ] (1). The reaction of [RuCl 2 (PPh 3 ) 3 ] and [NMe 4 ][7,8-(PPh 2 ) 2 -7,8-C 2 B 9 H 10 ] in a 1:1 or 1:2 ratio in methanol yields [RuX(7,8-(PPh 2 ) 2 -7,8-C 2 B 9 H 10 )(PPh 3 ) 2 ] (X = Cl, H) (2). NMR spectroscopic analyses of 1 and 2 indicate that the centers have an octahedral geometry and the carborane acts as a tricoordinating ligand to ruthenium(II) by means of P-Ru, B(11)-H→Ru and B(2)-H→Ru agostic bonds. A chloride or hydride and two PPh 3 ligands complete the coordination sphere of the metal. The formation of two B-H→Ru agostic bonds rather than a second P-Ru bond appears to be due to steric factors. Reaction of [NMe 4 ][7,8-(PPh 2 ) 2 -7,8-C 2 B 9 H 10 ] with [RuCl 2 (PMePh 2 ) 4 ] in ratios of 1:1 and 2:1 in methanol yields complexes [Ru(7,8-(PPh 2 ) 2 -7,8-C 2 B 9 H 11 ) 2 ] (3) and [RuH(7,8-(PPh 2 ) 2 -7,8-C 2 B 9 H 11 ) 2 ] (4) respectively, which incorporate two nido-carboranylphosphine ligands.

1,2-Cc-substituted o-carboranes, where Cc represents the cluster carbon atoms, display a range of experimental/computed Cc⋯Cc distances from 1.629/1.624 A for the unsubstituted parent compound 1,2-C2B10H12 (1) to 1.798/1.818 A for l,2-(SPh)2-l,2-C2B10H10 (5) 1 or 1.858(5)/1.826(5) for l,2-μ-SCH2(CH2OCH2)2CH2S-1,2-C2B10H10 (7). Different Cc⋯Cc distances can be achieved by modifying the substituents on the carbon of the cluster compound. The crystal structure of a new disubstituted o-carborane 1,2-(SPh)2-l,2-C2B10H10 (5) was elucidated by single crystal X-ray diffraction. Purely alkyl substituents alter the Cc⋯Cc distance of the parent compound very little, which implies that steric effects, although relevant, are not the major cause of the lengthening. In contrast, substituents with lone pairs alter the Cc⋯Cc distance substantially. Our calculations suggest that the cause of the elongation is the transfer of electron density from the available lone pairs on the substituents to the Ψ* low-lying virtual orbitals mainly distributed around Cc, producing a decrease in the Cc⋯Cc bond order and, thereby, an increase in the Cc⋯Cc distance. A Bader analysis shows that the electron density at the bond-critical point, which is found at the mid-point of the Cc⋯Cc distance, decreases considerably with the presence of lone pairs of the sulfur atoms bound to the Cc atoms of the carborane cage.

The synthesis of new 3-halogeno nido derivatives of o-carborane, [3-X-7-R-7,8-nido-C2B9H10]− (X=Br, I; R=H, CH3, C6H5) is described, through deboronation of the compounds 3-X-1-R-1,2-closo-C2B10H10, previously synthesised in our laboratory. These nido products have been fully characterised using 1H-, 11B- and 13C-NMR spectroscopies, MALDI-TOF and, for [3-I-7,8-nido-C2B9H11]− by an X-ray crystallographic study. The influences of the halogen moiety on both the B(3) resonance and that of the bridge proton are discussed.

The high stability of the closo-carboranylmonophosphines and the low basicity and nucleophilicity are attributed to the electron-withdrawing character of the closo cluster. On the contrary, the nido cluster has an electron-donor character, which induces high electronic density on the phosphorus atom, then increasing the basicity and nucleophilicity of these ligands. In this way, the nido-carboranylmonophosphines react with ethanol to give the tertiary phosphonium salts and are readily oxidized by air in solution. They readily react with transition metals to form the corresponding metallacarboranes. To learn more of the distinct behavior of the closo-and nido-carboranylmonophosphines, the reaction of some of them with the BH3·THF Lewis acid has been carried out. In this communication, we report the reaction of closo- and nido-carboranylmonophosphines with BH3·THF leading to the formation of new phosphine–borane adducts. In the case of the nido-carboranylmonophosphines, all of them have shown a similar behavior irrespective of the nature of the R and R′ groups. However, the closo-carboranylmonophosphines have demonstrated to be less basic and only one of them has been able to form the corresponding phosphine–borane adduct. The crystal structure of [NBu4]+[7-PiPr2·BH3-8-Me-7,8-C2B9H10]− has also been described. The coordination chemical shift (ccs) has been calculated and a relation established between the coupling constants (11B1H and 31P11B) obtained by the 11B{1H}- and 31P{1H}-NMR and the Lewis basicity of the phosphines.

In this paper we report the synthesis of three new carborane derivatives of the series 7,8-R,R′-10-L-7,8-C2B9H9 (R=R′=H, L=SEtPh; R=CH3, R′=H, L=SMe2 and L=SEt2) along with the enhanced characterization of formerly described compounds 7,8-R,R′-10-L-7,8-C2B9H9 (R=R′=H, L=SMe2 (1), L=SEt2 (2) and L=S(CH2)4 (3)). They have been fully characterised using 1H-, 11B- and 13C-NMR spectroscopy. Their bridging proton resonances have been located for the first time. Individual sulfonium substituent contributions have been calculated that have permitted to establish a rule to predict its position in the 1H-NMR spectrum. The crystal structures of 1 and 3 have been resolved for the first time. Thermolysis of 1, 2 and 3 in aromatic solvents at reflux temperature yielded a mixture of the corresponding 9-substituted derivative via isomerisation and 2,3-closo-C2B9H11 via elimination of SR2. This reaction has been demonstrated to be tuneable upon convenient choice of the aromatic solvent, the ligand and the reaction time, leading to a new and more straightforward preparation of the series 9-L-7,8-nido-C2B9H11 and the cluster 2,3-closo-C2B9H11.