Home – Home – Jornals – Journal of Structural Chemistry 2009 number 2

The thermodynamic activation parameters of hindered rotation of the CF₃ group in the 4-nitrophenyltrifluoromethylsulfone radical anion in DMF were determined from the temperature dependence of the EPR line widths and spin density distributions calculated by the U-B3LYP method in the 6-31+G* basis set. In the range 293 > T > 199 K, the activation energy of hindered rotation E_F depends on the temperature and changes in the range 9.67 < E_F < 18.95 kJ·mol^-1; the changes in the activation enthalpy and entropy are 7.23 < ΔH^≠ < 17.30 kJ·mol^-1 and −53.45 < ΔS^≠ < -11.37 J·(mol·K)^-1, respectively. Based on the suggested method for evaluating the inner product of the g tensor and the tensor of anisotropic hfi with the ¹⁴N nucleus for nitrobenzene radical anions in the liquid state we calculated the correlation time and determined the activation energy of rotational diffusion of the 4-nitrophenyltrifluoromethylsulfone radical anion in DMF, E_r = 20.175±0.54 kJ·mol⁻¹.