Theoretical Calculation of Electron Spin Resonance Parameters for Some Organic and Inorganic Compounds Using Density Functional Theory

Abstract

Computation of electron spin resonance parameters (Hyper Fine Coupling Constant and gtensor) by Density Functional Theory using the gauge-including projector augmented wave (GIPAW) method, and Gaussian09 program were conducted for 1,1-Diphenyl-2-picrylhydrazyl ( DPPH, C18H12N5O6), Copper Oxide (CuO), anhydrous copper sulphate (CuSO4) and 2,4-Dinitrophenylhydrazine (DNPH C6H3(NO2)2NHNH2) . DPPH free radical were selected due its stability and the presence of an unpaired valence electron at the nitrogen bridge . The results were compared with practical determined values using ESR technique . Calculations based on two methods proved to be in good agreement with the experimental data. The results were found to be: DPPH : GIPAW gxx = 2.0023106 gyy = 2.0023175 gzz =2.0023189 Gaussian09 gxx = 2.0038201 gyy =2.0080622 gzz = 2.0048070 ESR (experimental) g-tensor = 2.090344. The hyperfine interaction of the unpaired electron was different for nitrogen bridge, the ratio of the coupling constants being nearly 0.98. Isotropic hyperfine splitting value (MHz) of ranges : Carbon Hydrogen Oxygen GIPAW -0.09 to 0.4 -0.1 to 0.1 -0.2 to 0.1 Gaussian09 -61 to 60 -21 to 8 -10 to 5 CuO: GIPAW gxx =2.11789636 gyy = 2.13202641 gzz =2.40888875 Gaussian09 gxx =2.0652326 gyy = 2.0186791 gzz = 2.3558106 ESR (experimental) g-tensor = 2.05304 Isotropic hyperfine splitting value (MHz): Copper Oxygen GIPAW - 879.2 - 34.3 Gaussian09 - 683.0 - 33.1 CuSO4 : GIPAW gxx = 2.02757602 gyy = 2.0190584 gzz =2.01940798 Gaussian09 gxx = 2.0153756 gyy = 1.9934088 gzz2.0509791. ESR (experimental) g-tensor = 2.3330 Isotropic hyperfine splitting value (MHz): Copper Oxygen Sulpher GIPAW -1050.0 - 60 to -13 - 66.4 Gaussian09 1761.6 -121 to 53 94.7 DNPH: GIPAW gxx = 2.004411 gyy= 2.00741 gzz = 2.002319 Gaussian09 gxx = 2.0023193 gyy = 2.0023193 gzz = 2.0023193 ESR (experimental) g-tensor = 4.740 To establish the accuracy of methods used the results obtain were compared with published data. Results computed by the two method, were in good agreement and also show good agreement with the published data.