Forging Unsupported Metal–Boryl Bonds with Icosahedral Carboranes

Saleh, Liban M. A.; Dziedzic, Rafal M.; Khan, Saeed I.; Spokoyny, Alexander M.

doi:10.1002/chem.201601292

Cited by 54 publications

(22 citation statements)

References 67 publications

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“…Icosahedral carboranes (C 2 B 10 H 12 ) are well-known boron-rich clusters that can be often regarded as 3D analogues of organic aryl derivatives [1]. Among them, organic and organometallic complexes that contain closo - o -carborane ( closo -1,2-C 2 B 10 H 12 ) have been widely investigated as a novel family of optoelectronic materials for various functional and photonic applications [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23] because they definitely possess excellent thermal and electrochemical stabilities. They also realize unique photophysical properties induced by the electron-withdrawing character of the o -carborane unit [24,25,26,27,28].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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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.

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Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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“…To date, closo - ortho -carborane (1,2-C 2 B 10 H 12 ) derivatives, which are well-known icosahedral boron-cluster compounds, have been widely studied for their interesting optoelectronic properties, which are based on a variety of organic/organometallic luminophores [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28]. Indeed, these desirable electronic properties are due to the unique characteristics of the o -carborane unit, such as its strongly electron-deficient nature, as well as its highly polarizable σ-aromaticity.…”

Section: Introductionmentioning

confidence: 99%

Photophysical Properties of Spirobifluorene-Based o-Carboranyl Compounds Altered by Structurally Rotating the Carborane Cages

Kim

Lee

et al. 2019

Molecules

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9,9′-Spirobifluorene-based o-carboranyl compounds C1 and C2 were prepared and fully characterized by multinuclear nuclear magnetic resonance (NMR) spectroscopy and elemental analysis. The solid-state structure of C1 was also determined by single-crystal X-ray diffractometry. The two carboranyl compounds display major absorption bands that are assigned to π−π* transitions involving their spirobifluorene groups, as well as weak intramolecular charge-transfer (ICT) transitions between the o-carboranes and their spirobifluorene groups. While C1 only exhibited high-energy emissions (λem = ca. 350 nm) in THF at 298 K due to locally excited (LE) states assignable to π−π* transitions involving the spirobifluorene group alone, a remarkable emission in the low-energy region was observed in the rigid state, such as in THF at 77 K or the film state. Furthermore, C2 displays intense dual emissive patterns in both high- and low-energy regions in all states. Electronic transitions that were calculated by time-dependent-DFT (TD-DFT) for each compound based on ground (S0) and first-excited (S1) state optimized structures clearly verify that the low-energy emissions are due to ICT-based radiative decays. Calculated energy barriers that are based on the relative energies associated with changes in the dihedral angle around the o-carborane cages in C1 and C2 clearly reveal that the o-carborane cage in C1 rotates more freely than that in C2. All of the molecular features indicate that ICT-based radiative decay is only available to the rigid state in the absence of structural fluctuations, in particular the free-rotation of the o-carborane cage.

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“…Meanwhile, much work has been carried out on graft copolymerization with vinyl monomers using various initiators, such as ammonium persulfate (APS) and potassium persulfate (KPS), free radical active sites were first produced on silk fiber macromolecules, and then functional graft chains were introduced to achieve the purpose of modification. And with the current requirements for green health, other emerging material processing technologies such as electrostatic layer self‐assemble and sol‐gel technology have also been applied to the flame retardancy of silk.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of carborane acrylate and flame retardant modification on silk fabric via graft copolymerization with phosphate‐containing acrylate

You

Liu

et al. 2019

Fire and Materials

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Summary A novel carborane acrylate monomer (1‐acryloyloxyethyl carborane) was synthesized by addition reaction, hydrolysis, and esterification and characterized by proton nuclear magnetic resonance (1H NMR) spectroscopy and Fourier transform infrared spectroscopy (FT‐IR) analysis. Subsequently, the carborane monomer and a phosphate‐containing methacrylate monomer were applied on the modification of a silk fabric. The heat resistance and flame retardancy of the silk fabric before and after modification were compared. Energy‐dispersive X‐ray spectrometer (EDS) and FT‐IR showed that carborane monomer and phosphate‐containing methacrylate were grafted onto the surface of the fibers. The cross‐sectional morphology of silk fabrics after burning was observed by scanning electron microscope (SEM), and the flame‐retardant mechanism was analyzed. Thermal‐gravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis revealed that the thermal stability of the modified silk increased with the increase of the grafting yield. The MCC‐2 microcalorimeter (MCC) test showed that, when using 1‐acryloyloxyethyl carborane as monomer and blending with phosphate‐containing methacrylate, the maximum heat release rate (PHRR) of the modified silk fabric decreased from 97.6 W/g (before grafting) to 51.3 and 45.8 W/g, respectively, and the total heat release (THR) decreased from 10.2 kJ/g (before grafting) to 5.9 and 5.2 kJ/g, respectively. The limiting oxygen index (LOI) test revealed that using 1‐acryloyloxyethyl carborane and phosphate‐containing methacrylate as mixed monomers to modify the silk fabric obtained good flame retardancy, whose LOI value reached 29.8%.

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Forging Unsupported Metal–Boryl Bonds with Icosahedral Carboranes

Cited by 54 publications

References 67 publications

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

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

Photophysical Properties of Spirobifluorene-Based o-Carboranyl Compounds Altered by Structurally Rotating the Carborane Cages

Synthesis of carborane acrylate and flame retardant modification on silk fabric via graft copolymerization with phosphate‐containing acrylate

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