ab initio Study of Electronic Structure and Magnetic Properties of a Novel Two-Dimensional Copper(II)-Radical Complex [Cu(NTTmPy)2(N3)2]n

The full-potential linearized augmented plane wave (FPLAPW)method with the generalized gradient approximations (GGA) is applied tostudy the compound [Cu(NTTmPy)₂(N₃)₂]_n(NITmPy=2-(3'-Pyridy1)-4, 4, 5,5-tetramethylimidazolin-1-oxy1-3-oxide).The total density of states (DOS) and the partial density of states(pDOS) are calculated to explain the electronic and the magneticproperties of [Cu(NTTmPy)₂(N₃)₂]_n. It is found that[Cu(NTTmPy)₂(N₃)₂]_n is stable in the ferromagnetic state andthe magnetic moment of the molecule mainly comes from the Cu atoms(0.518 μ_B) with partial contributionfrom N, O atoms of nitronyl nitroxide radicals. There exist orbitalhybridization between 3d orbital of Cu and p orbitals of N(1)(from pyridyl rings of the NITmPy ligands) and N(4) (from azido group)and the weak direct exchange interactions between Cu and O atoms ofnitronyl nitroxides. In addition, the bridging carbon atom (C(6)) carriesa significant negative spin density (-0.019μ_B).The sign alternation of the magnetic moment alongthe pyridyl ring is obtained, which agrees withexperiments.