Effects of Azido Bridge on Magnetic Properties of Dinuclear Nickel Complexes: Density Functional Theory Studies

The magnetic properties of the antiferromagnetic complex mu-1,3-N-3-Ni(II)[LNi2(N-3)](ClO4)(2) (L=pyrazolate) were investigated using density functional theory (DFT) calculations combined with the broken symmetry approach. The calculation results obtained using the hybrid density functional theory (HDFT) agree well with the experimental data, and accurately describe the magnetic properties of complex. The large energy splitting, 0.93-0.99 eV, between singly occupied molecular orbitals indicates that there is strong non-degeneracy between them, and the two coupling paths (azido and pyrazolate) in the complex show that there is overlap between the p orbitals of the N atoms. All these factors contribute to the antiferromagnetism of the complex. The magnetic properties of the complex are also closely related to the dihedral angle tau of Ni-N-N-N-Ni. The antiferromagnetism of the complex increases as tau decreases from -55.38 degrees to -1.5 degrees the maximum absolute value of magnetic coupling constant (J(ab)) occurs at -11.95 degrees (J(ab)=-151.02 cm(-1)). During this process, the coplanarity of the seven-membered ring, which consists of two Ni(II), one azido, and two bridging nitrogen atoms (N(4) and N(5)), is enhanced, i.e., coplanarity increases the antiferromagnetism of the complex.