Pulse radiolysis of aqueous solutions of sodium tetraphenylborate

Crawford, Charles L.; Gholami, Mohammad Reza; Bhave, R. N.; Hanrahan, Robert J.

doi:10.1016/0969-806x(94)90009-4

Cited by 5 publications

(5 citation statements)

References 22 publications

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“…In the literature of boron compound photochemistry, several authors have reported phenyl radicals and boroxyl radicals as products of photolysis, for example the effect of oxidizing agents that can generate other products. [26][27][28][29][30][31][32][33][34] However, the use of spin traps was not properly performed to elucidate the first radicals generated after photolysis of trigonal and tetrahedral boron compounds.…”

Section: Electronic Paramagnetic Resonance Measurementsmentioning

confidence: 99%

“…Several previous reports regarding the photochemistry of trigonal and tetrahedral arylboron compounds have detailed the photoproducts of the reactions, but very few have provided experimental measurements related to the excited-states and/ or transition states involved. [26][27][28][29][30][31][32][33][34][35][36] It is possible that an intramolecular charge transfer (ICT) process between the central boron atom and attached aryl groups may explain this difference, as observed for several organic and hybrid molecules. [37][38][39][40][41][42][43][44] The existence of twisted intramolecular charge transfer (TICT) and localized excited (LE) states is usually proposed to rationalize the dual emission observed in arylboron compounds and some other organic molecules.…”

Section: Introductionmentioning

confidence: 99%

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New insight into the photophysics and reactivity of trigonal and tetrahedral arylboron compounds

Santos

Pina

Burrows

et al. 2016

Photochem Photobiol Sci

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The photophysics and reactivity of two tetraphenylborate salts and triphenylborane have been studied using ultrafast transient absorption, steady-state fluorescence, electron paramagnetic resonance with spin trapping, and DFT calculations. The singlet excited state of tetraarylborates exhibit extended π-orbital coupling between two adjacent aryl groups. The maximum fluorescence band, as well as the transient absorption bands centered at 560 nm (τ = 1.05 ns) and 680 nm (τ = 4.35 ns) are influenced by solvent viscosity and polarity, indicative of a twisted intramolecular charge transfer (TICT) state. Orbital contour plots of the HOMO and LUMO orbitals of the tetraarylboron compounds support the existence of electron delocalization between two aryl groups in the LUMO. This TICT-state and aryl-aryl electron extension is not observed for the trigonal arylboron compound, in which excited π-orbital coupling only occurs between the boron atom and one aryl group, which restricts the twist motion of the aryl-boron bond. The excited triplet state is deactivated primarily through aryl-boron bond cleavage, yielding aryl and diphenylboryl radicals. In the presence of oxygen, this photochemistry results in phenoxyl and diphenylboroxyl radicals, as confirmed by EPR spectroscopy of spin trapped radical adducts. The TICT transition and radical generation is not expected for BoDIPY molecules where the rotational vibration of the B-aryl bond is rigid, restricting changes in the geometric structure. In this sense, this work contributes to the development of new BoDIPY derivatives where the TICT transition may be observed for aryl ligands with free rotational vibrations in the BoDIPY structure.

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Section: Electronic Paramagnetic Resonance Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

New insight into the photophysics and reactivity of trigonal and tetrahedral arylboron compounds

Santos

Pina

Burrows

et al. 2016

Photochem Photobiol Sci

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“…However, filtration of such large volumes requires thousands of hours, and during this time the tetraphenlyborate (TPB) anion decomposes to form benzene and tri-, bi-, and monophenylboron . While TPB was apparently believed to be stable in the approximately 2 M NaOH waste mixture, , prior work shows that TPB decomposes in even less basic solutions . In addition, TPB is also subject to decomposition by radiolysis.…”

Section: Introductionmentioning

confidence: 99%

Continuous-Flow Process for the Separation of Cesium from Complex Waste Mixtures

Ponder

Helkowski

2001

Ind. Eng. Chem. Res.

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A continuous-flow process is proposed for the separation of Cs from complex, strongly alkaline, aqueous mixtures. This process, which includes the use of tetraphenylborate (TPB) anions to precipitate cesium from the bulk waste, minimizes the exposure time of TPB to the alkaline mixture by injecting TPB as a countercurrent into a small stream of the bulk waste and immediately following with filtration. The recovered solids are dissolved in propylene carbonate, and cesium is then extracted into an aqueous solution, to be later recovered as CsNO3, in a three-phase liquid−liquid−liquid extraction. Minimizing the time of exposure of TPB to strong (2 M) sodium hydroxide avoids the decomposition of TPB and subsequent release of benzene into the atmosphere above the reaction vessel.

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“…The process subsequently blends the resulting waste slurry, containing radioactive cesium and less than 10 percent of the original organic compounds, with high level radioactive sludge and transfers the mixture to a vitrification facility for processing into borosilicate glass for long-term storage. Other studies investigated tetraphenylborate decomposition using chemical oxidation [13][14][15], photolytic [16][17][18], electrochemical [19][20][21] and radiolytic processes [22][23][24][25]. Decomposition products identified in these studies include diphenylborinic acid, phenylboronic acid, biphenyl, benzene and phenol.…”

Section: Phenylborate Decomposition: Hydrolysis and Reactions Involvimentioning

confidence: 99%

“…Several authors report decomposition schemes involving oxidation of tetraphenylborate by chemical [13][14][15], photolytic [16][17][18], electrolytic [19][20][21], and radiolytic [22][23][24][25] techniques to produce the tetraphenylboron radical. All of these studies show predominately both biphenyl and diphenylborinic acid as products.…”

Section: Wsrc-ms-98-00876 Rev 0 Page 5 Of 35mentioning

confidence: 99%

Copper-catalyzed sodium tetraphenylborate, triphenylborane, diphenylborinic acid and phenylboronic acid decomposition kinetic studies in aqueous alkaline solutions

Crawford

Barnes

Peterson

et al. 1999

Journal of Organometallic Chemistry

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This work studied the kinetics of copper-catalyzed decomposition of tetraphenylborate, triphenylborane, diphenylborinic acid and phenylboronic acid (NaTPB, 3PB, 2PB and 1PB, respectively) in aqueous alkaline solution over the temperature range of 25 to 70 °C. The statistically designed test matrices added copper sulfate to maximum concentrations of 10 mg/L. The relative rates of decomposition increase in the order of NaTPB < 1PB ~ 3PB < 2PB. Dependence of decomposition on the amount of added copper increases in the order of 3PB ~ 2PB < 1PB ~ NaTPB. Activation energies ranged from 82 to 143 kJ/mole over the temperature range studied. Final decomposition products predominately involved benzene and phenol. All 3PB, 2PB and 1PB intermediate phenylborate species proved relatively stable (< 8% decomposition ) thermal hydrolysis of the phenylborate species occurs at 55 to 70° C in alkaline (0.6-2.3 M OH -, 2-4.7 M Na + ) solution with no added copper. The experiments suggest an important role for oxygen in copper-catalyzed phenylborate decomposition. NaTPB decomposes promptly under anoxic conditions while 3PB, 2PB and 1PB decompose faster in aerobic solutions. Benzene and phenol form as the predominant end-products from alkaline copper catalysis in static systems sealed under air. Both 2PB and 1PB decompose with near equal rates and quantitatively produce phenol under flowing air-purge conditions at 25 to 60 °C. Mechanisms for copper-catalyzed phenylborate decomposition likely involve a redox process giving loss of a phenyl group from the phenylborate with reduction of cupric ion, or dephenylation by reduced cuprous ion involving a phenylated copper intermediate.

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Pulse radiolysis of aqueous solutions of sodium tetraphenylborate

Cited by 5 publications

References 22 publications

New insight into the photophysics and reactivity of trigonal and tetrahedral arylboron compounds

New insight into the photophysics and reactivity of trigonal and tetrahedral arylboron compounds

Continuous-Flow Process for the Separation of Cesium from Complex Waste Mixtures

Copper-catalyzed sodium tetraphenylborate, triphenylborane, diphenylborinic acid and phenylboronic acid decomposition kinetic studies in aqueous alkaline solutions

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