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.
