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

2016 ◽  
Vol 15 (9) ◽  
pp. 1124-1137 ◽  
Author(s):  
Willy G. Santos ◽  
João Pina ◽  
Douglas H. Burrows ◽  
Malcolm D. E. Forbes ◽  
Daniel R. Cardoso
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Steady State ◽  
Dft Calculations ◽  
Transient Absorption ◽  
Spin Trapping ◽  
Paramagnetic Resonance ◽  
Steady State Fluorescence ◽  
Ultrafast Transient Absorption ◽  
Electron Paramagnetic ◽  
Insight Into

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.

scholarly journals Electron Paramagnetic Resonance - A Powerful Tool of Medical Biochemistry in Discovering Mechanisms of Disease and Treatment Prospects

2010 ◽  
Vol 29 (3) ◽  
pp. 175-188 ◽  
Author(s):  
Ivan Spasojević
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Epr Spectroscopy ◽  
Human Organism ◽  
Efficient Tool ◽  
Paramagnetic Resonance ◽  
Beneficial Effects ◽  
Ascorbyl Radical ◽  
Antioxidative Therapy ◽  
Electron Paramagnetic ◽  
Insight Into

Electron Paramagnetic Resonance - A Powerful Tool of Medical Biochemistry in Discovering Mechanisms of Disease and Treatment ProspectsIn pathophysiological conditions related to oxidative stress, the application of selected antioxidants could have beneficial effects on human health. Electron paramagnetic resonance (EPR) spectroscopy is a technique that provides unique insight into the redox biochemistry, due to its ability to: (i) distinguish and quantify different reactive species, such as hydroxyl radical, superoxide, carbon centered radicals, hydrogen atom, nitric oxide, ascorbyl radical, melanin, and others; (ii) evaluate the antioxidative capacity of various compounds, extracts and foods; (iii) provide information on other important parameters of biological systems. A combination of EPR spectroscopy and traditional biochemical methods represents an efficient tool in the studies of disease mechanisms and antioxidative therapy prospects, providing a more complete view into the redox processes in the human organism.

Quantitative Electron Paramagnetic Resonance: The Importance of Matching the Q-Factor of Standards and Samples

2001 ◽  
Vol 55 (10) ◽  
pp. 1375-1381 ◽  
Author(s):  
Richard L. Blakley ◽  
Dwight D. Henry ◽  
Walter T. Morgan ◽  
William L. Clapp ◽  
Carr J. Smith ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Free Radicals ◽  
Free Radical ◽  
Spin Trapping ◽  
Microwave Energy ◽  
Q Factor ◽  
Paramagnetic Resonance ◽  
Tert Butyl ◽  
Electron Paramagnetic ◽  
Stable Free Radicals

Electron paramagnetic resonance (EPR) quantification of free radicals from different samples facilitates comparison of free radical concentrations. Stable free radicals, such as 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), in a suitable solvent (e.g., benzene) can be used as a quantification standard. Free radicals found in samples can be shorter lived than radicals in prepared standards and require stabilizing spin-trapping agents such as N-tert-butyl-α-phenylnitrone (PBN) in an appropriate solvent (e.g., benzene). Analysis in our laboratory showed that free radicals from spin-trapped samples quantified against a standard of TEMPO in benzene displayed large differences among identical samples measured on either a Micro-Now 8300, Micro-Now 8400, or Bruker EMX EPR instrument. The Bruker instrument reported that the typical TEMPO in benzene standard had a Q-factor of ∼4400 while the Q-factor of our PBN-containing samples was ∼2500. (The Q-factor is inversely proportional to the amount of dissipated microwave energy in an EPR cavity.) By placing the TEMPO standard in a PBN/benzene solvent matrix we were able to match the Q-factor of our standards and samples, resulting in each of the three EPR instruments giving the same quantified free radical yields for the samples. This result points out the importance of matching the Q-factor between samples and standards for any quantitative EPR measurement.

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