Search Results (23)

New derivatives of the closo-decaborate anion [B₁₀H₉–O(CH₂)₂O(CH₂)₃C(O)–L–OCH₃]²⁻ (An) (1: L = Trp; 2: L = His; 3: L = Met; 4: L = Ala(2-oxopyrrolidin-3-yl) (Pld) were synthesized and isolated as tetraphenylphosphonium salts (Ph₄P)₂An. Anions 1²⁻; 2²⁻; 3²⁻, and 4²⁻ contain a pendant functional group from the L-tryptophan methyl ester, L-histidine methyl ester, L-methionine methyl ester, or methyl 2-amino-3-(2-oxopyrrolidin-3-yl)propanoate (-Trp–OCH₃, -His–OCH₃, -Met–OCH₃, or -Pld–OCH₃) residue, respectively, bonded with the boron cluster anion through the oxybis[(ethane-2,1-diyl)oxy] spacer. This pacer is formed as a result of the nucleophilic opening of the attached dioxane molecule in the [B₁₀H₉O(CH₂)₄O]⁻ starting derivative. Sodium salts of the target compounds were isolated and used in biological experiments. It was established that among compounds Na₂An (An = 1–4), not all are capable of inhibiting the cytopathic effect of the virus in vitro. Sodium salts Na₂An have a low toxic effect on a monolayer of continuous canine embryonic kidney (MDCK) cell line. Compounds Na₂1 and Na₂2 had IC₅₀ of 5.0 and 20.0 μg/mL, respectively, while for compounds Na₂3 and Na₂4, IC₅₀ values could not be achieved at the concentrations studied. The studies performed for molecular docking of the anionic part of 1²⁻ and 2²⁻ with the transmembrane domain of viroporin M2 show some differences in the location of these two ligands inside the M2 canal pore. Full article

Anionic boron clusters, such as [B₁₂X₁₂]²⁻ (X = Cl, Br, I), have attracted attention in pharmaceuticals due to their unique superchaotropic properties. In particular, [B₁₂Br₁₂]²⁻ (1) has demonstrated strong interactions with biomolecules, facilitating cargo translocation across plasma membranes. In this study, we investigated the effect of covalently attaching chlorinated dodecaborate moiety [B₁₂Cl₁₁O-]²⁻ to 6-carboxyfluorescein (6-FAM) (3) via a PEG3 linker to form conjugate (4). We compared the membrane permeability of this covalent conjugate with that of non-covalent interactions between 6-FAM (3) and [B₁₂Cl₁₂]²⁻ (2). Live-cell fluorescence imaging revealed that the covalent conjugate exhibited enhanced membrane permeability and water solubility while maintaining low cytotoxicity. These results highlight the potential of covalent conjugation with boron clusters for improving the cellular uptake of hydrophilic cargos. Full article

A new synthetic method for the synthesis of C-substituted [RC(O)CH₂-CB₁₁H₁₁]⁻ carborate anions has been developed. The reaction of [closo-B₁₁H₁₁]²⁻ with terminal alkynes in the presence of a copper catalyst leads to insertion into the boron cluster, and C-substituted [RC(O)CH₂-CB₁₁H₁₁]⁻ carborate anions are formed. These reactions are strongly dependent on the reaction conditions, the solvents, and the alkynes used. The alkynes HCCCO₂Et, HCCCO₂Me, and HCCCONH₂ lead to the formation of [NH₂C(O)CH₂-CB₁₁H₁₁]⁻ as the final product in aqueous ammonia solution. In contrast, the reaction using the alkyne HCCCOMe yields [MeC(O)CH₂-CB₁₁H₁₁]⁻. The products have been fully characterized by multinuclear NMR and IR spectroscopy as well as mass spectrometry. The crystal structures of K[NH₂C(O)CH₂-CB₁₁H₁₁] and [NEt₃CH₂Cl][NH₂C(O)CH₂-CB₁₁H₁₁] have been determined. Full article

In this work, we studied lead(II) and cobalt(II) complexation of derivatives [2-B₁₀H₉O(CH₂)₂O(CH₂)₂N₃]²⁻ and [2-B₁₀H₉O(CH₂)₅N₃]²⁻ of the closo-decaborate anion containing pendant azido groups in the presence of 1,10-phenanthroline and 2,2′-bipyridyl. Mononuclear [PbL₂{An}] and binuclear [Pb₂L₄(NO₃)₂{An}] lead complexes (where {An} is the N₃-substituted boron cluster) were isolated and studied by IR spectroscopy and elemental analysis. The mononuclear lead(II) complex [Pb(phen)₂[B₁₀H₉O(CH₂)₂O(CH₂)₂N₃] and the binuclear lead(II) complex [Pb₂(phen)₄(NO₃)₂[B₁₀H₉O(CH₂)₅)N₃] were determined by single-crystal X-ray diffraction. In complex [Pb₂(phen)₄(NO₃)₂[B₁₀H₉O(CH₂)₅)N₃], the boron cluster is coordinated by the metal atom only via the 3c2e MHB bonds. In complex [Pb(phen)₂[B₁₀H₉O(CH₂)₂O(CH₂)₂N₃], the coordination environment of the metal includes BH groups of the boron cluster and the oxygen atom of the exo-polyhedral substituent. When the reaction was performed in a CH₃CN/water mixture, the binuclear lead(II) complex [(Pb(bipy)NO₃)(Pb(bipy)₂NO₃)(B₁₀H₉O(CH₂)₂O(CH₂)₂N₃)]·CH₃CN·H₂O was isolated, where the boron cluster acts as a bridging ligand between lead atoms coordinated by the boron cage via the O atoms of the substituent and/or the BH groups. In the course of cobalt(II) complexation, the starting compound (Ph₄P)₂[B₁₀H₉O(CH₂)₅N₃] was isolated and its structure was also determined by X-ray diffraction. Although a number of lead(II) complexes with coordinated N₃ are known from the literature, no complexes with the boron cluster coordinated by the pendant N₃ group involved in the metal coordination have been isolated. Full article

The functionalization of copolyfluorenes containing dicyanophenanthrene units by closo-decaborate anion is described. Target copolyfluorenes were analyzed using SEM, UV-vis, luminescence, NMR, and Fourier-transform infrared (FTIR) spectroscopy. The effect of complexation with the closo-decaborate anion on the photophysical properties was studied both experimentally and theoretically. The PL data indicate an efficient charge transfer from fluorene to the dicyanophenanthrene units coordinated to the closo-decaborate. The coordination of closo-decaborate clusters to the nitrile groups of copolyfluorenes provides an important route to new materials for sensors and light-emitting devices while, at the same time, serving as a platform for further study of the nature of boron clusters. Full article

Here, we present composites and materials that can be prepared starting with boron hydride cluster compounds (decaborane, decahydro-closo-decaborate and dodecahydro-closo-dodecaborate anions and carboranes). Recent examples of their utilization as boron protective coatings including using them to synthesize boron carbide, boron nitride, metal borides, metal-containing composites, and neutron shielding materials are discussed. The data are generalized demonstrate the versatile application of materials based on boron cluster anions and carboranes in various fields. Full article

A theoretical modelling of the interaction process between a protonated complex of carboxonium derivative [2,6-B₁₀H₈O₂CCH₃*H^fac]⁰ and acetonitrile molecule CH₃CN was carried out. As a result of the process, a trisubstituted [B₁₀H₇O₂CCH₃(NCCH₃)]⁰ derivative was formed. This reaction has an electrophile-induced nucleophilic substitution (EINS) mechanism. The main intermediates and transition states of the substitution process were established. As in the case of all previously investigated EINS processes, the key intermediate was an anion with a dihydrogen H₂ fragment attached to one boron atom (B(H₂) structure motif). The process of nucleophilic substitution can proceed on a different position of the cluster cage. The main potential pathways were assessed. It was established that substitution on the B₄ position of the cluster cage was the most energetically favourable, and the [2,4,6-B₁₀H₇O₂CCH₃(NCCH₃)]⁰ isomer was formed. Full article

Mixed-ligand lead(II) complexes with 2,2′-bipyridyl and [B₁₀H₉OH]²⁻ or monosubstituted hydroxy-substituted closo-decaborate anions with a pendant hydroxy group, separated from the boron cage by an alkoxylic spacer of different lengths [B₁₀H₉O(CH₂)_xO(CH₂)₂OH]]²⁻ (x = 2 or 5) have been synthesized. Compounds have been characterized by IR and multinuclear NMR spectroscopies. The structures of binuclear complex [Pb(bipy)₂[B₁₀H₉OH]]₂·CH₃CN (1·CH₃CN), mononuclear complex [Pb(bipy)₂[B₁₀H₉O(CH₂)₂O(CH₂)₂OH]]·0.5bipy·CH₃CN (2·0.5bipy·CH₃CN), and polymeric complex [Pb(bipy)[B₁₀H₉O(CH₂)₅O(CH₂)₂OH]]_n (3) have been determined by single-crystal X-ray diffraction. In all three compounds, the co-ordination polyhedra of lead(II) are formed by N atoms from two bipy molecules, O atoms of the substituent attached to the boron cage, and BH groups of the boron cage. Full article

In the course of the study, nanocrystalline cobalt monoboride was prepared by thermal decomposition of precursors [Co(DMF)₆][An], where [An] = [B₁₂H₁₂]²⁻ (1), [trans-B₂₀H₁₈]²⁻ (2) or [B₁₀Cl₁₀]²⁻ (3) in an argon atmosphere. Three new salt-like compounds 1–3 were prepared when Co(NO₃)₂ was allowed to react with (Et₃NH)₂[An]. Compound 1 is new; the structures of compounds 2 and 3 have been previously reported. Samples 1–3 were annealed at 900 °C in argon to form samples 1a–3a, which were characterized by single crystal XRD for 1 and powder XRD for 1–3. Powder XRD on the products showed the formation of BN and CoB for 1a in a 1:1 ratio; 2a gave a higher CoB:BN ratio but an overall decreased crystallinity. For 3a, only CoB was found. IR spectra of samples 1a–3a as well as X-ray spectral fluorescence analysis for 3a confirmed these results. The nanoparticular character of the decomposition products 1a–3a was shown using TEM; quite small particle sizes of about 10–15 nm and a quite normal size distribution were found for 1a and 2a, while the decomposition of 3 gave large particles with 200–350 nm and a broad distribution. Full article

This review systematizes data on the coordination ability of mono- and disubstituted derivatives of boron cluster anions and carboranes in complexation with transition metals. Boron clusters anions [B_nH_n]^2–, monocarborane anions [CB_nH_n–1]^–, and dicarboranes [C₂B_nH_n–2] (with non-functionalized carbon atoms) (n = 10, 12) containing the B–X exo-polyhedral bonds (X = N, O, S, Hal) are discussed. Synthesis and structural features of complexes known to date are described. The effect of complexing metal and substituent attached to the boron cage on the composition and structures of the final complexes is analyzed. It has been established that substituted derivatives of boron cluster anions and carboranes can act as both ligands and counterions. A complexing agent can coordinate substituted derivatives of the boron cluster anions due to three-center two-electron 3c2e MHB bonds, by the substituent functional groups, or a mixed type of coordination can be realized, through the BH groups of the boron cage and the substituent. As for B-substituted carboranes, complexes with coordinated substituents or salts with non-coordinated carborane derivatives have been isolated; compounds with MHB bonding are not characteristic of carboranes. Full article

This work is a mini-review highlighting the relevance of the θ metallabis(dicarbollide) [3,3′-Co(1,2-C₂B₉H₁₁)₂]⁻ with its peculiar and differentiating characteristics, among them the capacity to generate hydrogen and dihydrogen bonds, to generate micelles and vesicles, to be able to be dissolved in water or benzene, to have a wide range of redox reversible couples and many more, and to use these properties, in this case, for producing potentiometric membrane sensors to monitor amine-containing drugs or other nitrogen-containing molecules. Sensors have been produced with this monoanionic cluster [3,3′-Co(1,2-C₂B₉H₁₁)₂]⁻. Other monoanionic boron clusters are also discussed, but they are much fewer. It is noteworthy that most of the electrochemical sensor species incorporate an ammonium cation and that this cation is the species to be detected. Alternatively, the detection of the borate anion itself has also been studied, but with significantly fewer examples. The functions of the borate anion in the membrane are different, even as a doping agent for polypyrrole which was the conductive ground on which the PVC membrane was deposited. Apart from these cases related to closo borates, the bulk of the work has been devoted to sensors in which the θ metallabis (dicarbollide) [3,3′-Co(1,2-C₂B₉H₁₁)₂]⁻ is the key element. The metallabis (dicarbollide) anion, [3,3′-Co(1,2-C₂B₉H₁₁)₂]⁻, has many applications; one of these is as new material used to prepare an ion-pair complex with bioactive protonable nitrogen containing compounds, [YH]_x[3,3′-Co(1,2-C₂B₉H₁₁)₂]_y as an active part of PVC membrane potentiometric sensors. The developed electrodes have Nernstian responses for target analytes, i.e., antibiotics, amino acids, neurotransmitters, analgesics, for some decades of concentrations, with a short response time, around 5 s, a good stability of membrane over 45 days, and an optimal selectivity, even for optical isomers, to be used also for real sample analysis and environmental, clinical, pharmaceutical and food analysis. Full article

A theoretical investigation of mono-methyl derivatives of closo-borate anions of the general form [B_nH_nCH₃]^2– (n = 6, 10, 12) and monocarboranes [HCB_nH_nCH₃]⁻ (n = 5, 9, 11) was carried out. An analysis of the main bonding descriptors of exo-polyhedral B–C bonds was performed using the QTAIM (quantum theory of “Atoms in Molecules”), ELF (electron localisation function), NBOs (natural bond orbitals) analyses and several other approaches for the estimation of B–C bond orders (viz. Laplacian bond order (LBO), fuzzy bond order (FBO) and Mayer and Wiberg formalisms). Based on the data obtained on electron density descriptors, it can be concluded that orbital interaction increases with increasing boron cluster size. The present investigation provides a better understanding of exo-polyhedral B–C bond phenomena in boron cluster systems. The data obtained can be used to estimate B–C bond strength, which can be useful for studies devoted to the synthesis and properties of boron cluster systems. Full article

A new series of compounds based on perbrominated disubstituted sulfonium derivatives of the closo-decaborate anion (n-Bu₄N)[2-B₁₀Br₉SR₂] (R = n-Pr, i-Pr, n-Bu, n-C₈H₁₇, n-C₁₂H₂₅, n-C₁₈H₃₇) was obtained, characterised by modern physicochemical methods of analysis. According to the results of an X-ray diffraction study, some of the anions and solvate molecules were disordered. The cations (n-Bu₄N)⁺ and anions [2-B₁₀Br₉SR₂]⁻ were associated via C-H…Br and H…H contacts. In addition, Br…Br interactions between anions were revealed. The role of these contacts was analysed in terms of Hirshfeld surface analysis, QTAIM theory and the NCI method using quantum chemical calculations. An increase in the size of the alkyl R moiety led to significant strengthening of the total energy of H…H interactions. In the case of R = -n-C₁₈H₃₇, a parallel mutual orientation of alkyl moieties was established that was similar to the packing of salts of fatty acids. The nature of C-H…Br and Br…Br interionic interactions was found to be attractive, in contrast to the repulsive nature of intermolecular Br…Br interactions. Full article

We report a comprehensive theoretical investigation on phosphorus–boron mixed neutral, anionic, and cationic clusters P₂B_n/P₂B_n⁻/P₂B_n⁺ (n = 3–7) with two phosphorus atoms and three to seven boron atoms. We reveal the common character of all the structures (i.e., the phosphorus atoms choose to occupy the peripheral position), whereas the boron atoms tend to be in the central and inside position of the ground state phosphorus—boron mixed clusters at each stoichiometry. Any three atoms preferentially form a stable triangle and grow with zigzag shape in a planar network. Interestingly, a series of planar motifs (including tetra-, penta-, and hexa-coordination) have been discovered in the phosphorus–boron clusters. The large binding energies (3.6 to 4.6 eV/atom) and quite large HOMO–LUMO gaps (5 to 10 eV) indicate the high stability of the clusters. The energy differences Δ₁E, Δ₂E, and energy gaps display oscillating behavior with increasing numbers of boron atoms. The electron affinity (EA) and ionization potential (IP) generally have small variations, with the EA values ranging from 2 to 3 eV, and the IP values ranging from 7 to 9 eV. Chemical bond analysis shows that the existence of multi-center delocalized bonds stabilize the clusters. Full article

Anionic homo- and copolymerization of p-diethynylbenzene in the presence of n-BuLi in polar solvents was carried out. The use of hexamethylphosphortriamide (HMPA) makes it possible to synthesize a completely linear soluble polymer that does not have branching and phenylene fragments. A copolymer of p-diethynylbenzene with diphenyldiacetylene was synthesized. Homo- and copolymers of p-diethynylbenzene have high thermo- and thermo-oxidative stability. By the interaction of side reactive ethynylphenylene groups with various reagents, it is proposed to synthesize clusters along the conducting chain of poly-p-diethynylbenzene. Due to presenting C≡CH side groups, boron, copper, and cobalt derivatives were synthesized. It is shown that not all theoretically possible stereoisomers can be formed as a result of the polymerization. The application of p-diethynylbenzene polymers for the modification of industrial samples of epoxy novolac resin, oligoester acrylates, and carbon fibers has been demonstrated. Full article