Electron paramagnetic resonance calculation

Schreckenbach, G., Ziegler, T., 1997b, Calculation of the g-Tensor of Electron Paramagnetic Resonance Spectroscopy Using Gauge-Including Atomic Orbitals and Density Functional Theory , J. Phys. Chem. A, 101, 3388. 

The description theoretical study of defects frequently refers to some computation of defect electronic structure i.e., a solution of the Schrodin-ger equation (Pantelides, 1978 Bachelet, 1986). The goal of such calculations is normally to complement or guide the corresponding experimental study so that the defect is either properly identified or otherwise better understood. Frequently, the experimental study suffices to identify the basic structure of the defect this is particularly true when the system is EPR (electron paramagnetic resonance) active. However, if the computational method properly simulates the defect, we are provided with a wealth of additional information that can be used to reveal some of the more basic and general features of many-electron defect systems and defect reactions. 

Analysis of antioxidant properties relative to the DPPH" radical involves observation of colour disappearance in the radical solution in the presence of the solution under analysis which contains antioxidants. A solution of extract under analysis is introduced to the environment containing the DPPH radical at a specific concentration. A methanol solution of the DPPH radical is purple, while a reaction with antioxidants turns its colour into yellow. Colorimetric comparison of the absorbance of the radical solution and a solution containing an analysed sample enables one to make calculations and to express activity as the percent of inhibition (IP) or the number of moles of a radical that can be neutralised by a specific amount of the analysed substance (mmol/g). In another approach, a range of assays are conducted with different concentrations of the analysed substance to determine its amount which inactivates half of the radical in the test solution (ECso). The duration of such a test depends on the reaction rate and observations are carried out until the absorbance of the test solution does not change [4]. If the solution contains substances whose absorbance disturbs the measurement, the concentration of DPPH radical is measured directly with the use of electron paramagnetic resonance (EPR) spectroscopy. 

The triplet state of the phenanthrolines has interested several groups, frequently in conjunction with electron paramagnetic resonance (EPR) transitions.22,52-60 Electron spin densities in radical cations and anions of 1,10-phenanthrolines have been calculated.61,62 The binding energies of N-l in salts of 1,10-phenanthroline have been studied using X-ray photoelectron spectroscopy.63... 

A molecular modeling program to calculate electron paramagnetic resonance hyper-fine couplings in semiquinone anion radicals was offered [173b]. 

Recently, approximate MO theories have been applied to a wide range of solid-state phenomena in addition to those reviewed in this paper. A short review of some of these problems indicates its versatility. Messmer and Watkins (3) have used EH to predict the position of N impurity levels in diamond using a 35-atom C lattice. Their calculations indicated the presence of a Jahn-Teller effect in accordance with electron paramagnetic resonance (EPR) experiments. The calculation was successful in explaining the deepening of the N donor level as due to Jahn-Teller distortion. 

The one-electron reduction of phospholium salts llla-c has been studied by electron paramagnetic resonance (EPR) and DFT calculations, which conclude that they are good electron acceptors <2006PCP862>. Their reduction affords neutral radicals where the unpaired electron is mainly delocalized over the carbon skeleton of the P-ring. These compounds have been characterized in the solid state by X-ray diffraction and exhibit metric data that are typical of this type of compound (see Table 11). 

Bors W, Michel C, Stettmaier K, Lu Y, Yeap Foo L. (2003) Pulse radiolysis, electron paramagnetic resonance spectroscopy and theoretical calculations of caffeic acid oligomer radicals. Biochim Biophys Acta 1620 97-107. 

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