theoretical study of solvent effect on nmr shielding for pyrazole and pyrazoline

the physical and chemical properties of pyrazole and pyrazoline molecules were theoreticallystudied by gaussian 03, software with nmr and molecular orbital calculations at b3lyp/6-31g andb3lyp/6-31+g(d) levels, in gas phase and solution. in this study a comparison effect of threesolvents with different dielectric constants on pyrazole and pyrazoline molecules in aspect energyinteraction between solute and solvent, and nmr shielding parameters (ppm) such as,
iso (
isotropic),
aniso (
anisotropic), anisotropic magnetic shielding tensor, 
, chemical shift, , totalatomic charge and asymmetry parameter, , were performed. these parameters were calculated byusing the giao method. the results show solvent-induced shielding variation is more stronglyrelated to the intensity of the solvent reaction field rather than on the change of molecular geometryinduced by the solvent.