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Open AccessArticle

Neutral Rhenadicarbaboranes with Re(CO)₂(NO) Vertices: A Theoretical Study of Building Blocks for Rhenacarborane-Based Drug Delivery Agents

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Amr A. A. Attia

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Alexandru Lupan

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Radu Silaghi-Dumitrescu

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R. Bruce King

Molecules 2020, 25(1), 110; https://doi.org/10.3390/molecules25010110 - 27 Dec 2019

Cited by 1 | Viewed by 1900

Abstract

The rhenadicarbaborane carbonyl nitrosyls (C₂B_n₋₃H_n₋₁)Re(CO)₂(NO), (n = 8 to 12), of interest in drug delivery agents based on the experimentally known C₂B₉H₁₁Re(CO)₂(NO) and related [...] Read more.

The rhenadicarbaborane carbonyl nitrosyls (C₂B_n₋₃H_n₋₁)Re(CO)₂(NO), (n = 8 to 12), of interest in drug delivery agents based on the experimentally known C₂B₉H₁₁Re(CO)₂(NO) and related species, have been investigated by density functional theory. The lowest energy structures of these rhenadicarbaboranes are all found to have central ReC₂B_n₋₃ most spherical closo deltahedra in accord with their 2n + 2 Wadean skeletal electrons. Carbon atoms are found to be located preferentially at degree 4 vertices in such structures. Furthermore, rhenium atoms are preferentially located at a highest degree vertex, typically a vertex of degree 5. Only for the 9-vertex C₂B₆H₈Re(CO)₂(NO) system are alternative isocloso deltahedral isomers found within ~8 kcal/mol of the lowest energy closo isomer. Such 9-vertex isocloso structures provide a degree 6 vertex for the rhenium atom flanked by degree 4 vertices for each carbon atom. Full article

(This article belongs to the Special Issue Advances in Materials Derived from Polyhedral Boron Clusters)

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Open AccessArticle

Gold Nanoparticles as Boron Carriers for Boron Neutron Capture Therapy: Synthesis, Radiolabelling and In Vivo Evaluation

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Krishna R. Pulagam

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Kiran B. Gona

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Vanessa Gómez-Vallejo

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Molecules 2019, 24(19), 3609; https://doi.org/10.3390/molecules24193609 - 07 Oct 2019

Cited by 28 | Viewed by 3537

Abstract

Background: Boron Neutron Capture Therapy (BNCT) is a binary approach to cancer therapy that requires accumulation of boron atoms preferentially in tumour cells. This can be achieved by using nanoparticles as boron carriers and taking advantage of the enhanced permeability and retention [...] Read more.

Background: Boron Neutron Capture Therapy (BNCT) is a binary approach to cancer therapy that requires accumulation of boron atoms preferentially in tumour cells. This can be achieved by using nanoparticles as boron carriers and taking advantage of the enhanced permeability and retention (EPR) effect. Here, we present the preparation and characterization of size and shape-tuned gold NPs (AuNPs) stabilised with polyethylene glycol (PEG) and functionalized with the boron-rich anion cobalt bis(dicarbollide), commonly known as COSAN. The resulting NPs were radiolabelled with ¹²⁴I both at the core and the shell, and were evaluated in vivo in a mouse model of human fibrosarcoma (HT1080 cells) using positron emission tomography (PET). Methods: The thiolated COSAN derivatives for subsequent attachment to the gold surface were synthesized by reaction of COSAN with tetrahydropyran (THP) followed by ring opening using potassium thioacetate (KSAc). Iodination on one of the boron atoms of the cluster was also carried out to enable subsequent radiolabelling of the boron cage. AuNPs grafted with mPEG-SH (5 Kda) and thiolated COSAN were prepared by ligand displacement. Radiolabelling was carried out both at the shell (isotopic exchange) and at the core (anionic absorption) of the NPs using ¹²⁴I to enable PET imaging. Results: Stable gold nanoparticles simultaneously functionalised with PEG and COSAN ([email protected][4]⁻) with hydrodynamic diameter of 37.8 ± 0.5 nm, core diameter of 19.2 ± 1.4 nm and ξ-potential of −18.0 ± 0.7 mV were obtained. The presence of the COSAN on the surface of the NPs was confirmed by Raman Spectroscopy and UV-Vis spectrophotometry. [email protected][4]⁻ could be efficiently labelled with ¹²⁴I both at the core and the shell. Biodistribution studies in a xenograft mouse model of human fibrosarcoma showed major accumulation in liver, lungs and spleen, and poor accumulation in the tumour. The dual labelling approach confirmed the in vivo stability of the [email protected][4]⁻. Conclusions: PEG stabilized, COSAN-functionalised AuNPs could be synthesized, radiolabelled and evaluated in vivo using PET. The low tumour accumulation in the animal model assayed points to the need of tuning the size and geometry of the gold core for future studies. Full article

(This article belongs to the Special Issue Advances in Materials Derived from Polyhedral Boron Clusters)

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Open AccessArticle

Effect of Planarity of Aromatic Rings Appended to o-Carborane on Photophysical Properties: A Series of o-Carboranyl Compounds Based on 2-Phenylpyridine- and 2-(Benzo[b]thiophen-2-yl)pyridine

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Molecules 2019, 24(1), 201; https://doi.org/10.3390/molecules24010201 - 07 Jan 2019

Cited by 9 | Viewed by 3633

Abstract

Herein, we investigated the effect of ring planarity by fully characterizing four pyridine-based o-carboranyl compounds. o-Carborane was introduced to the C4 position of the pyridine rings of 2-phenylpyridine and 2-(benzo[b]thiophen-2-yl)pyridine (CB1 and CB2, respectively), and the compounds [...] Read more.

Herein, we investigated the effect of ring planarity by fully characterizing four pyridine-based o-carboranyl compounds. o-Carborane was introduced to the C4 position of the pyridine rings of 2-phenylpyridine and 2-(benzo[b]thiophen-2-yl)pyridine (CB1 and CB2, respectively), and the compounds were subsequently borylated to obtain the corresponding C^∧N-chelated compounds CB1B and CB2B. Single-crystal X-ray diffraction analysis of the molecular structures of CB2 and CB2B confirmed that o-carborane is appended to the aryl moiety. In photoluminescence experiments, CB2, but not CB1, showed an intense emission, assignable to intramolecular charge transfer (ICT) transition between the aryl and o-carborane moieties, in both solution and film states. On the other hand, in both solution and film states, CB1B and CB2B demonstrated a strong emission, originating from π-π * transition in the aryl groups, that tailed off to 650 nm owing to the ICT transition. All intramolecular electronic transitions in these o-carboranyl compounds were verified by theoretical calculations. These results distinctly suggest that the planarity of the aryl groups have a decisive effect on the efficiency of the radiative decay due to the ICT transition. Full article

(This article belongs to the Special Issue Advances in Materials Derived from Polyhedral Boron Clusters)

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Open AccessArticle

Synthesis and Structural Characterization of Amidine, Amide, Urea and Isocyanate Derivatives of the Amino-closo-dodecaborate Anion [B₁₂H₁₁NH₃]⁻

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Molecules 2018, 23(12), 3137; https://doi.org/10.3390/molecules23123137 - 29 Nov 2018

Cited by 14 | Viewed by 3495

Abstract

The synthesis and structural characterization of new derivatives of [B₁₂H₁₂]²⁻ is of fundamental interest and is expected to allow for extended applications. Herein we report on the synthesis of a series of amidine, amide, urea and isocyanate derivatives [...] Read more.

The synthesis and structural characterization of new derivatives of [B₁₂H₁₂]²⁻ is of fundamental interest and is expected to allow for extended applications. Herein we report on the synthesis of a series of amidine, amide, urea and isocyanate derivatives based on the amino-closo-dodecaborate anion [B₁₂H₁₁NH₃]⁻. Their structures have been confirmed by spectroscopic methods, and nine crystal structures are presented. Full article

(This article belongs to the Special Issue Advances in Materials Derived from Polyhedral Boron Clusters)

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Open AccessFeature PaperArticle

Exploiting the Electronic Tuneability of Carboranes as Supports for Frustrated Lewis Pairs

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Molecules 2018, 23(12), 3099; https://doi.org/10.3390/molecules23123099 - 27 Nov 2018

Cited by 7 | Viewed by 2649

Abstract

The first example of a carborane with a catecholborolyl substituent, [1-Bcat-2-Ph-closo-1,2-C₂B₁₀H₁₀] (1), has been prepared and characterized and shown to act as the Lewis acid component of an intermolecular frustrated Lewis pair in [...] Read more.

The first example of a carborane with a catecholborolyl substituent, [1-Bcat-2-Ph-closo-1,2-C₂B₁₀H₁₀] (1), has been prepared and characterized and shown to act as the Lewis acid component of an intermolecular frustrated Lewis pair in catalyzing a Michael addition. In combination with B(C₆F₅)₃ the C-carboranylphosphine [1-PPh₂-closo-1,2-C₂B₁₀H₁₁] (IVa) is found to be comparable with PPh₂(C₆F₅) in its ability to catalyze hydrosilylation, whilst the more strongly basic B-carboranylphosphine [9-PPh₂-closo-1,7-C₂B₁₀H₁₁] (V) is less effective and the very weakly basic species [μ-2,2′-PPh-{1-(1′-1′,2′-closo-C₂B₁₀H₁₀)-1,2-closo-C₂B₁₀H₁₀}] (IX) is completely ineffective. Base strengths are rank-ordered via measurement of the ¹J ³¹P-⁷⁷Se coupling constants of the phosphineselenides [1-SePPh₂-closo-1,2-C₂B₁₀H₁₁] (2), [9-SePPh₂-closo-1,7-C₂B₁₀H₁₁] (3), and [SePPh₂(C₆F₅)] (4). Full article

(This article belongs to the Special Issue Advances in Materials Derived from Polyhedral Boron Clusters)

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Open AccessArticle

Synthesis and Ceramic Conversion of a New Organodecaborane Preceramic Polymer with High-Ceramic-Yield

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Molecules 2018, 23(10), 2461; https://doi.org/10.3390/molecules23102461 - 26 Sep 2018

Cited by 8 | Viewed by 2059

Abstract

Boron carbide is one of the hardest materials known, with diamond-like mechanical properties and excellent chemical stability. It is wildly used in military defense area, nuclear industry, aerospace technology, etc. Precursor-derived ceramics have made it easier to produce pure boron carbide in processed [...] Read more.

Boron carbide is one of the hardest materials known, with diamond-like mechanical properties and excellent chemical stability. It is wildly used in military defense area, nuclear industry, aerospace technology, etc. Precursor-derived ceramics have made it easier to produce pure boron carbide in processed forms and expand its applications. The challenge of this method is the synthesis of precursor polymer with high-ceramic-yield. The aim of the present work is to develop a new poly(6-norbornenyldecaborane-co-decaborane) [P(ND-co-D)] copolymer, which was successfully synthesized via ring-opening metathesis polymerization of 6-norbornenyldecaborane and tandem hydroboration with decaborane. The obtained light-yellow powder displayed good solubility, and was fully characterized by NMR, FT-IR and GPC analysis. Thermogravimetric analysis demonstrated that the char yield was up to 79%. The polymer-to-ceramic transformation process and pyrolysis mechanism has shown that the rearrangement of carbon chains of P(ND-co-D) mainly occurred in the temperature range of 350 °C~470 °C. Furthermore, the crystallization behavior and microstructures of derived ceramics were studied by XRD and SEM. Nano-sized boron carbide powders were prepared by pyrolysis of P(ND-co-D) under argon at 1400 °C for 2 h, while the structure and morphologies of the obtained rhombohedral B₄C were investigated. Full article

(This article belongs to the Special Issue Advances in Materials Derived from Polyhedral Boron Clusters)

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Open AccessArticle

o-Carboranylalkoxy-1,3,5-Triazine Derivatives: Synthesis, Characterization, X-ray Structural Studies, and Biological Activity

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Molecules 2018, 23(9), 2194; https://doi.org/10.3390/molecules23092194 - 30 Aug 2018

Cited by 4 | Viewed by 3733

Abstract

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 [...] Read more.

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

(This article belongs to the Special Issue Advances in Materials Derived from Polyhedral Boron Clusters)

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Review

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Open AccessFeature PaperReview

Ferrocene and Transition Metal Bis(Dicarbollides) as Platform for Design of Rotatory Molecular Switches

by

Igor B. Sivaev

Molecules 2017, 22(12), 2201; https://doi.org/10.3390/molecules22122201 - 11 Dec 2017

Cited by 19 | Viewed by 6493

Abstract

Design of rotatory molecular switches based on extremely stable sandwich organometallic complexes ferrocene and bis(dicarbollide) complexes of transition metals is reviewed. The “on”–“off” switching in these systems can be controlled by various external stimuli such as change of the solution pH, interactions with [...] Read more.

Design of rotatory molecular switches based on extremely stable sandwich organometallic complexes ferrocene and bis(dicarbollide) complexes of transition metals is reviewed. The “on”–“off” switching in these systems can be controlled by various external stimuli such as change of the solution pH, interactions with coordinating species or redox reactions involving the central atom or substituents in the ligands. Full article

(This article belongs to the Special Issue Advances in Materials Derived from Polyhedral Boron Clusters)

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