A laser desorption ionization mass spectrometry investigation of triarylboranes and tri-9-anthrylborane photolysis products

Ramsey, Brian G.; Bier, Mark E.

doi:10.1016/j.jorganchem.2004.11.002

Cited by 6 publications

(5 citation statements)

References 31 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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“…Several simple free borylenes, such as :B–R for R = H, , F, , Cl, Br, I, and Ph, have been examined extensively, some having been identified decades ago. − “Note on the Spectrum of Boron Fluoride” was published in 1935, for example, and referenced two slightly earlier and less successful (ultraviolet) spectroscopic studies of BF. , Those investigations were motivated in part by the already extensive data available on the isovalent CO and N 2 molecules, but unlike N 2 , BF and other simple :B–R molecules tend to be unstable and have been detected and probed primarily in the gas phase or in inert matrices. − ,− …”

Section: Introductionmentioning

confidence: 99%

On Neutral Unsaturated Ouroboric Borylenes

2022

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The search is on for stable isolated borylenes. Potential roles in modern synthetic chemistry for boron analogues of carbenes continue to motivate interest in locating them. Using density functional and ab initio methods, we posit and examine the thermochemistry, and chemical bonding, including aromaticity, of several classes of 5- and 6-membered borylenic rings. In these systems, cyclization relies on dative bonding (ouroboric coordination) and π donation to a monovalent boron center from an adjacent O center. Certain neutral five-membered rings (heterocyclic cyclopentadienyl analogues) in particular are found to exhibit exceptionally strong preferences for the singlet multiplicity, each with singlet–triplet (S–T) gaps in excess of 40 kcal·mol–1. The singlet five-membered rings with the largest S–T gaps and some of the six-membered rings show evidence of weak aromaticity. Relationships of the form N = A·r –b , in line with Gordy’s and other functions linking bond order, N, and covalent bond length, are identified for dative B←O contacts, r, reinforced in rings by π-delocalization.

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“…In the analysis of low‐molecular‐weight compounds, the presence of matrix‐related ions (so‐called clusters ) in the mass spectrum complicates the application of MALDI‐TOF MS. Therefore, matrices with the matrix‐related ions not shielding the peaks of the analytes can be used, or instead the laser desorption/ionization (LDI) technique can be applied 12, 13…”

Section: Introductionmentioning

confidence: 99%

Mass spectrometric characterization of low‐molecular‐mass color pI markers and their use for direct determination of pI value of proteins

2006

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The use of low-molecular-mass color pI markers for the determination of pI values of proteins in gel isoelectric focusing (IEF) in combination with mass spectrometry is described. Different types of substituted phenols of known pI values within the mass range 250-400 were used here as pI markers. The pure, synthesized pI markers were studied by MALDI-TOF/TOF MS. Fragmentation studies of the pI markers were also performed. Only stable and well-characterized pI markers were used in this work. The selected pI markers were mixed with proteins, deposited on a gel and separated in a pH gradient. Color pI markers enable supervision of progress of the focusing process and also estimation of the position of the invisible focused bands. The separated bands of the pI markers (containing separated proteins) were excised, and the pI markers were eluted from each gel piece by water/ethanol and identified by MALDI-TOF/TOF MS. From the washed gel pieces the remaining carrier ampholytes were then washed out and proteins were in-gel digested with trypsin. The obtained peptides were measured by MALDI-TOF/TOF MS and the proteins identified via a protein database search. This procedure allows avoiding time-consuming protein staining and destaining procedures, which shortens the analysis time roughly by half. For comparison, IEF gels were stained with Coomassie Brilliant Blue R 250 and proteins in the gel bands were identified according to the standard proteomic protocol. This work has confirmed that our approach can give information about the correct pI values of particular proteins and shorten significantly the time of analysis.

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A laser desorption ionization mass spectrometry investigation of triarylboranes and tri-9-anthrylborane photolysis products

Cited by 6 publications

References 31 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

On Neutral Unsaturated Ouroboric Borylenes

Mass spectrometric characterization of low‐molecular‐mass color pI markers and their use for direct determination of pI value of proteins

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