A theoretical study on magneto-structural correlation for binuclear Cu(II) complexes bridged by single N-N group from diazine has been investigated by using broken-symmetry approach within the framework of density functional theory. Calculated results show that antiferromagnetic coupling interaction gradually reduces, and finally turns into ferromagnetic coupling interaction with the decrease of rotation angle θ around N-N bond from 150°to 65°, which is in agreement with the experimental facts. The variation of molecular energy has a reversion with rotation angle θ passing through 140 °. The linear relationship between J and (ε_1-ε_2)~2 is broken with the reversion of the energy of broken-symmetry state from decrease to increase. This reversion of the energy of broken-symmetry state also affects the relationship between (ε_1-ε_2)~2 and θ. The figure for the relationship between J and θ is similar to that for the relationship between (ε_1-ε_2)~2 and θ in the angle range θ = 65° ～ 140°where no reversion of the energy of broken-symmetry state occurs. So in this angle range, (ε_1-ε_2)~2 can replace J to explore the relationship between structure and magnetic properties. The reversion of the energy of broken-symmetry state has little influence on the variation of J values, and rotation angle θ is a key factor influencing the magnitude of magnetic coupling interaction.

Key words: COPPER COMPLEX, magnetic coupling interaction, DINUCLEAR COMPLEX