Simultaneous electrochemical/electron paramagnetic

SIMULTANEOUS ELECTROCHEMICAL/ELECTRON PARAMAGNETIC RESONANCE (SEEPR) TECHNIQUES... 

Jeevarajan, A. S., M. Khaled et al. (1994a). Simultaneous electrochemical and electron paramagnetic resonance studies of keto and hydroxyl carotenoids. Chem Phys. Lett. 225 340-345. 

The first mechanism is often found in the electrochemical reduction and oxidation of quinones and flavins in aprotic media.Using cyclic voltammetry (CV) and simultaneous electrochemistry and electron paramagnetic resonance (SEEPR),... 

Jeevarajan AS, Khaled M and Kispert LD (1994c) Simultaneous electrochemical and electron paramagnetic resonance studies of carotenoids Effect of electron donating and accepting substituents. J Phys Chem 98 7777-7781 Jeevarajan JA, Jeevarajan AS and Kispert LD (1996a) Electrochemical EPR and AM 1 studies of acetylenic and ethylenic carotenoids. J Chem Soc Faraday Trans 92 1757-1765... 

Electron paramagnetic resonance (EPR) spectroscopy has also been coupled with electrochemical measurements where radical species are involved in the electrochemical reactions. Figure 2.18 shows a cell for simultaneous electrochanical-EPR studies. The EPR measurements can be ex situ where the radicals are formed outside of the spectrometer (Figure 2.19). In addition, in combination with the flow cell design described above, one can also use electrochanical-EPR technique to monitor the generation of free radicals in a continuous stream of solutions (Figure 2.20). 

Of the several less common spectroscopic methods to combine with electrochemical intermediate generation such as luminescence, Raman, NMR, or X-ray absorption spectroscopy, the EPR method is presented here because of its relative simplicity and pronounced selectivity. Only paramagnetic compounds with a certain, not too rapid relaxation rate from the spin-excited state give detectable signals for EPR spectroscopy, which helps to disregard many simultaneously present species. On the other hand, the rather slow time frame (At 10 s) and the sensitivity of the EPR method to electronic influences from the participating atoms via g-factor shift and hyperfine interaction can render EPR a very valuable method to determine the site of electron transfer (ligand or metal) as well as the spin and thus valence distribution. 

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