The condensed phases of carboranes

Gamba, Z.; Powell, B. M.

doi:10.1063/1.472111

Cited by 20 publications

(18 citation statements)

References 15 publications

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“…These ligands are anticipated to be much more structurally rigid due to their cage-like nature than the Cu 4 S 4 cores. Importantly, the distance between M9 groups is substantially larger than the molecular distance in m-carborane crystal 17 , indicating that the M9 groups are not in van der Waals (vdW) contact, thus allowing them to move without mutual steric hindrance under compression.…”

Section: Main Textmentioning

confidence: 99%

Sterically controlled mechanochemistry under hydrostatic pressure

Yan

Yang

Pan

et al. 2018

Nature

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Mechanical stimuli can modify the energy landscape of chemical reactions and enable reaction pathways, offering a synthetic strategy that complements conventional chemistry. These mechanochemical mechanisms have been studied extensively in one-dimensional polymers under tensile stress using ring-opening and reorganization, polymer unzipping and disulfide reduction as model reactions. In these systems, the pulling force stretches chemical bonds, initiating the reaction. Additionally, it has been shown that forces orthogonal to the chemical bonds can alter the rate of bond dissociation. However, these bond activation mechanisms have not been possible under isotropic, compressive stress (that is, hydrostatic pressure). Here we show that mechanochemistry through isotropic compression is possible by molecularly engineering structures that can translate macroscopic isotropic stress into molecular-level anisotropic strain. We engineer molecules with mechanically heterogeneous components-a compressible ('soft') mechanophore and incompressible ('hard') ligands. In these 'molecular anvils', isotropic stress leads to relative motions of the rigid ligands, anisotropically deforming the compressible mechanophore and activating bonds. Conversely, rigid ligands in steric contact impede relative motion, blocking reactivity. We combine experiments and computations to demonstrate hydrostatic-pressure-driven redox reactions in metal-organic chalcogenides that incorporate molecular elements that have heterogeneous compressibility, in which bending of bond angles or shearing of adjacent chains activates the metal-chalcogen bonds, leading to the formation of the elemental metal. These results reveal an unexplored reaction mechanism and suggest possible strategies for high-specificity mechanosynthesis.

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Section: Main Textmentioning

confidence: 99%

Sterically controlled mechanochemistry under hydrostatic pressure

Yan

Yang

Pan

et al. 2018

Nature

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“…Our simulations suggest that the reorientational relaxation of the fullerenes is nearly one order of magnitude slower than that of a low molecular-weight nonpolar aromatic molecular crystal such as benzene 36 ͑moment of inertia, I ϳ 14ϫ 10 −46 kg m 2 ͒ in this temperature range ͑ J = 0.5-6.0 ps͒, but somewhat more similar to that of car- boranes ͑I ϳ 5 ϫ 10 −45 kg m 2 ͒, despite the differences between the molecular rotational motions in these crystals. 37,38 It is also interesting to compare the behavior of C 60 in the C 60 -cubane crystal to the dynamics of the crystalline C 60 . Johnson et al 39 have investigated the rotational dynamics of C 60 in the solid state using NMR over the temperature range of 240 up to 331 K. They observed that the reorientational correlation time follows an Arrhenius temperature dependence with activation energy of approximately 1.4 kcal/mol for the rotor phase of crystalline C 60 .…”

Section: A Rotor-stator Phasementioning

confidence: 99%

Rotational dynamics and polymerization of C60 in C60-cubane crystals: A molecular dynamics study

Coluci

Sato

Braga

et al. 2008

The Journal of Chemical Physics

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We report classical and tight-binding molecular dynamics simulations of the C(60) fullerene and cubane molecular crystal in order to investigate the intermolecular dynamics and polymerization processes. Our results show that, for 200 and 400 K, cubane molecules remain basically fixed, presenting only thermal vibrations, while C(60) fullerenes show rotational motions. Fullerenes perform "free" rotational motions at short times (approximately < 1 ps), small amplitude hindered rotational motions (librations) at intermediate times, and rotational diffusive dynamics at long times (approximately > 10 ps). The mechanisms underlying these dynamics are presented. Random copolymerizations among cubanes and fullerenes were observed when temperature is increased, leading to the formation of a disordered structure. Changes in the radial distribution function and electronic density of states indicate the coexistence of amorphous and crystalline phases. The different conformational phases that cubanes and fullerenes undergo during the copolymerization process are discussed.

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“…All simulations were performed on a RHCC-NT- o -carborane (C 2 B 10 H 12 ) complex in which all four cavities were simultaneously occupied by a single carborane molecule. The complex was formed by inserting a modeled structure of an o -carborane molecule into each cavity of the measured structure of an RHCC-NT tetramer (PDB code 1FE6) 13 which was crystallized at T = 298 K. The Amber 99 force field parameters for o -carborane were obtained from literature 23 – 25 . Each RHCC-NT complex was solvated in water and Na + ions to neutralize the system.…”

Section: Methodsmentioning

confidence: 99%

Boron rich nanotube drug carrier system is suited for boron neutron capture therapy

Heide

McDougall

Harder-Viddal

et al. 2021

Sci Rep

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Boron neutron capture therapy (BNCT) is a two-step therapeutic process that utilizes Boron-10 in combination with low energy neutrons to effectively eliminate targeted cells. This therapy is primarily used for difficult to treat head and neck carcinomas; recent advances have expanded this method to cover a broader range of carcinomas. However, it still remains an unconventional therapy where one of the barriers for widespread adoption is the adequate delivery of Boron-10 to target cells. In an effort to address this issue, we examined a unique nanoparticle drug delivery system based on a highly stable and modular proteinaceous nanotube. Initially, we confirmed and structurally analyzed ortho-carborane binding into the cavities of the nanotube. The high ratio of Boron to proteinaceous mass and excellent thermal stability suggest the nanotube system as a suitable candidate for drug delivery into cancer cells. The full physicochemical characterization of the nanotube then allowed for further mechanistic molecular dynamic studies of the ortho-carborane uptake and calculations of corresponding energy profiles. Visualization of the binding event highlighted the protein dynamics and the importance of the interhelical channel formation to allow movement of the boron cluster into the nanotube. Additionally, cell assays showed that the nanotube can penetrate outer membranes of cancer cells followed by localization around the cells’ nuclei. This work uses an integrative approach combining experimental data from structural, molecular dynamics simulations and biological experiments to thoroughly present an alternative drug delivery device for BNCT which offers additional benefits over current delivery methods.

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The condensed phases of carboranes

Cited by 20 publications

References 15 publications

Sterically controlled mechanochemistry under hydrostatic pressure

Sterically controlled mechanochemistry under hydrostatic pressure

Rotational dynamics and polymerization of C60 in C60-cubane crystals: A molecular dynamics study

Boron rich nanotube drug carrier system is suited for boron neutron capture therapy

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