The theoretical calculations on magnetic exchange of the title complex are carried out by using multiconfigurational second-order perturbation theory, CASPT2, and density functional theory combined with broken-symmetry approach, DFT-BS. The CASPT2 calculated quartet ground state, stabilized by 8.02cm −1 compared with the nearest excited doublet state, is close to 5cm −1 of the experimental measurement. The dependence of energy levels on the ratio J 23 /J 12,13 validates occurrence of the spin frustration phenomenon. Both CASPT2 and DFT-BS calculations reproduce well experimentally coupling constants of J 12,13 =−9.35cm −1 , J 23 =−3.95cm −1 , for CASPT2 J 12,13 =−6cm −1 , J 23 =−2cm −1 and for DFT-BS J 12,13 =−11.31cm −1 , J 23 =−4.20m −1 . The methodological comparison is briefly discussed.