Search Results (9)

Boron-containing compounds, known for their high calorific value, can significantly enhance the energy density of traditional liquid propellants. Through precise chemical modification of the C-H bonds in ortho-carborane, a novel liquid cluster material was synthesized: C,C′-Bis(2-ethylhexanoylmethyl)-o-carborane (BEHMC). This compound exhibits excellent stability, density, and energy properties. By combining BEHMC with mixed amine-50, a cluster liquid propellant was formulated, and its key performance metrics such as density, freezing point, mass calorific value, and volumetric calorific value were evaluated. The propellant achieved a density of 0.884 g·cm⁻³, a freezing point below −55 °C, a mass calorific value of 41.13 kJ·g⁻¹, and a volumetric calorific value of 36.36 kJ·cm⁻³. The theoretical specific impulse reached 346 s, and the theoretical density impulse was 2.99 × 10⁶ N·s·m⁻³. Compared to the traditional mixed amine-50/red fuming nitric acid propellant, the cluster liquid propellant developed in this study maintains a similar calorific value while improving the theoretical specific impulse and density impulse by 2.3% and 3.8%, respectively. Full article

The objective of this study is to design and synthesize substituted η⁶-chromium(0) tricarbonyl metal complexes carrying o-carborane units as potential boron neutron capture therapy (BNCT) agents. In this study, 1,2-diphenyl-o-carborane (1) units were used as starting materials to generate biologically active species. We investigated how the structural changes of 1 substituted with chromium(0) tricarbonyl affect the biological properties, and 1-(Phenyl-η⁶-chromium(0) tricarbonyl)-2-phenyl-o-carborane (2) and 1,2-bis(phenyl-η⁶-chromium(0) tricarbonyl)-o-carborane (3) species were produced in moderate yields. The molecular structures of compounds 1–3 were identified and established by infrared (IR); ¹H, ¹¹B, and ¹³C nuclear magnetic resonance (NMR) and X-ray crystallography analyses. Crystal structures of 1,2-diphenyl-o-carborane and the corresponding chromium complexes 1, 2, and 3 were obtained. In an in vitro study using B16 and CT26 cancer cells containing the triphenyl-o-carboranyl chromium(0) complexes Ph3C2BCr2 and Ph3C2BCr3, which we reported previously, compounds 2 and 3 accumulated at higher levels than compounds Ph3C2BCr2 and Ph3C2BCr3. However, the phenylated o-carboranyl chromium complexes have been found to be more cytotoxic than p-boronophenylalanine (BPA). Full article

The efficiency of intramolecular charge transfer (ICT)-based emission on π-aromatic-group-appended closo-ortho-carboranyl luminophores is known to be affected by structural fluctuations and molecular geometry, but investigation of this relationship has been in progress to date. In this study, four naphthyl-based bis-o-carboranyl compounds, in which hydrogen (15CH and 26CH) or trimethysilyl groups (15CS and 26CS) were appended at the o-carborane cage, were synthesized and fully characterized. All the compounds barely displayed an emissive trace in solution at 298 K; however, 15CH and 26CH distinctly exhibited a dual emissive pattern in rigid states (in solution at 77 K and in films), attributed to locally excited (LE) and ICT-based emission, while 15CS and 26CS showed strong ICT-based greenish emission. Intriguingly, the molecular structures of the four compounds, analyzed by single X-ray crystallography, showed that the C-C bond axis of the o-carborane cage in the trimethysilyl group-appended compounds 15CS and 26CS were more orthogonal to the plane of the appended naphthyl group than those in 15CH and 26CH. These features indicate that 15CS and 26CS present an efficient ICT transition based on strong exo-π-interaction, resulting in a higher quantum efficiency (Φ_em) for ICT-based radiative decay than those of 15CH and 26CH. Moreover, the 26CS structure revealed most orthogonal geometry, resulting in the highest Φ_em and lowest k_nr values for the ICT-based emission. Consequently, all the findings verified that efficient ICT-based radiative decay of aromatic group-appended o-carboranyl luminophores could be achieved by the formation of a specific geometry between the o-carborane cage and the aromatic plane. Full article

Bis(carboranyl)amides 1,1′-μ-(CH₂NH(O)C(CH₂)_n-1,2-C₂B₁₀H₁₁)₂ (n = 0, 1) were prepared by the reactions of the corresponding carboranyl acyl chlorides with ethylenediamine. Crystal molecular structure of 1,1′-μ-(CH₂NH(O)C-1,2-C₂B₁₀H₁₁)₂ was determined by single crystal X-ray diffraction. Treatment of bis(carboranyl)amides 1,1′-μ-(CH₂NH(O)C(CH₂)_n-1,2-C₂B₁₀H₁₁)₂ with ammonium or cesium fluoride results in partial deboronation of the ortho-carborane cages to the nido-carborane ones with formation of [7,7′(8′)-μ-(CH₂NH(O)C(CH₂)_n-7,8-C₂B₉H₁₁)₂]²⁻. The attempted reaction of [7,7′(8′)-μ-(CH₂NH(O)CCH₂-7,8-C₂B₉H₁₁)₂]²⁻ with GdCl₃ in 1,2-dimethoxy- ethane did not give the expected metallacarborane. The stability of different conformations of Gd-containing metallacarboranes has been estimated by quantum-chemical calculations using [3,3-μ-DME-3,3′-Gd(1,2-C₂B₉H₁₁)₂]⁻ as a model. It was found that in the most stable conformation the CH groups of the dicarbollide ligands are in anti,anti-orientation with respect to the DME ligand, while any rotation of the dicarbollide ligand reduces the stability of the system. This makes it possible to rationalize the design of carborane ligands for the synthesis of gadolinium metallacarboranes on their base. Full article

Novel zwitter-ionic nido-carboranyl azide 9-N₃(CH₂)₃Me₂N-nido-7,8-C₂B₉H₁₁ was prepared by the reaction of 9-Cl(CH₂)₃Me₂N-nido-7,8-C₂B₉H₁₁ with NaN₃. The solid-state molecular structure of nido-carboranyl azide was determined by single-crystal X-ray diffraction. 9-N₃(CH₂)₃Me₂N-nido-7,8-C₂B₉H₁₁ was used for the copper(I)-catalyzed azide-alkyne cycloaddition with phenylacetylene, alkynyl-3β-cholesterol and cobalt/iron bis(dicarbollide) terminal alkynes to form the target 1,2,3-triazoles. The nido-carborane-cholesterol conjugate 9-3β-Chol-O(CH₂)C-CH-N₃(CH₂)₃Me₂N-nido-7,8-C₂B₉H₁₁ with charge-compensated group in a linker can be used as a precursor for preparation of liposomes for Boron Neutron Capture Therapy (BNCT). A series of novel zwitter-ionic boron-enriched cluster compounds bearing a 1,2,3-triazol-metallacarborane-carborane conjugated system was synthesized. Prepared conjugates contain a large amount of boron atom in the biomolecule and potentially can be used for BNCT. Full article

The metalation of [Tl]₂[1-(1′-3′,1′,2′-closo-TlC₂B₉H₁₀)-3,1,2-closo-TlC₂B₉H₁₀], with the smaller {Ni(dmpe)} fragment sourced from [Ni(dmpe)Cl₂], is explored. The bis(metalated) products are obtained as a diastereoisomeric mixture. These isomers were separated, fully characterised spectroscopically and crystallographically and identified as rac-[1-(1′-3′-(dmpe)-3′,1′,2′-closo-NiC₂B₉H₁₀)-3-(dmpe)-3,1,2-closo-NiC₂B₉H₁₀] (1) and meso-[1-(1′-3′-(dmpe)-3′,1′,2′-closo-NiC₂B₉H₁₀)-3-(dmpe)-3,1,2-closo-NiC₂B₉H₁₀] (2). Previously, these 3,1,2-NiC₂B₉-3′,1′,2′-NiC₂B₉ architectures (where both cages are not isomerised), were inaccessible, and thus new structures can be achieved during bis(nickelation) with {Ni(dmpe)}. Further, the metalation of the tetra-thallium salt with the bulky {Ni(dppe)} fragment sourced from [Ni(dppe)Cl₂] was also studied. These bis(nickelated) products were also fully characterised and are afforded as the stereospecific species rac-[1-(1′-3′-(dppe)-3′,1′,2′-closo-NiC₂B₉H₁₀)-3-(dppe)-3,1,2-closo-NiC₂B₉H₁₀] (3) and [1-(2′-4′-(dppe)-4′,1′,2′-closo-NiC₂B₉H₁₀)-3-(dppe)-3,1,2-closo-NiC₂B₉H₁₀] (4α). In the latter metalation, compound 3 shows intramolecular dihydrogen bonding, contributing to the stereospecificity, whereas isomerisation from 3,1,2 to 4,1,2- in the 4α is related to steric relief. Full article

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. Full article

9-Dimethyloxonium, 10-dimethyloxonium, 9-methoxy and 10-methoxy derivatives of nido-carborane (9-Me₂O-7,8-C₂B₉H₁₁, 10-Me₂O-7,8-C₂B₉H₁₁, [9-MeO-7,8-C₂B₉H₁₁]⁻, and [10-MeO-7,8-C₂B₉H₁₁]⁻, respectively) were prepared by the reaction of the parent nido-carborane [7,8-C₂B₉H₁₂]⁻ with mercury(II) chloride in a mixture of benzene and dimethoxymethane. Reactions of the 9 and 10-dimethyloxonium derivatives with triethylamine, pyridine, and 3-methyl-6-nitro-1H-indazole result in their N-methylation with the formation of the corresponding salts with 9 and 10-methoxy-nido-carborane anions. The reaction of the symmetrical methoxy derivative [10-MeO-7,8-C₂B₉H₁₁]⁻ with anhydrous FeCl₂ in tetrahydrofuran in the presence of t-BuOK results in the corresponding paramagnetic iron bis(dicarbollide) complex [8,8′-(MeO)₂-3,3′-Fe(1,2-C₂B₉H₁₀)₂]⁻, whereas the similar reactions of the asymmetrical methoxy derivative [9-MeO-7,8-C₂B₉H₁₁]⁻ with FeCl₂ and CoCl₂ presumably produce the 4,7′-isomers [4,7′-(MeO)₂-3,3′-M(1,2-C₂B₉H₁₀)₂]⁻ (M = Fe, Co) rather than a mixture of rac-4,7′- and meso-4,4′-isomers. Full article

Morpholine- and bis(2-methoxyethyl)amine-substituted 1,3,5-triazine derivatives containing an alkoxy-o-carborane in the 6-position of the triazine ring were successfully synthesized. The molecular structures of the methoxy- and ethoxy-o-carboranyl-1,3,5-triazines were established by X-ray crystallography. In vitro studies showed that the methylene bridged morpholine- and bis(2-methoxyethyl)amine-substituted o-carboranyl-1,3,5-triazines accumulated to high levels in B16 melanoma cells and exhibited higher cytotoxicity than p-boronophenylalanine. Full article