Asymmetric μ2-1,1-azido bridged copper(II) complex: Synthesis, X-ray structure, magnetic study and DFT calculations

A new rare variety asymmetric μ2-1,1-azido bridged copper(II) complex has been synthesized and characterized structurally and magnetically. The complex [Cu2L2(μ2-1,1-N3)2] · H2O · CH3OH (L = 1-(N-ortho-hydroxyacetophenimine)-2-aminoethane) (1), crystallizes in monoclinic space group, P21/n, with a = 9.469(4) Å, b = 12.526(8) Å, c = 12.899(10) Å, β = 105.79(6)°, V = 1472.2(16) Å3. X-ray study reveals that he Cu–N(azide)–Cu angles in this complex is 90.4°. This is unusually low in comparison to that of the same angle in other end-on azido-bridged binuclear complexes. Though a strong ferromagnetic interaction between the metal centers is expected in the complex, the coupling has actually been found to be antiferromagnetic (J = −4.2 cm−1), instead. To rationalize this paradoxical magnetic behavior, DFT calculation of this and other four complexes with very similar structure have been performed within broken symmetry framework. The calculated magnetic coupling constants (J) are in excellent agreement, both in sign and in the magnitude of the exchange interaction, with the experimental data, and the spin density map is correctly reproduced.