Abstract: Adopting ligand occupation strategy and the principle of molecular self-assembly, a mononuclear cobalt(Ⅲ) complex [Co^Ⅲ(DIEN)(N₃)₃] (1, DIEN=diethylenetriamine) was synthesized by solution method using diethylenetriamine as the organic ligand and Co³⁺ as the central metal ion at room temperature. Single crystal of complex 1 was obtained. The structural characterization and electronic structure analysis were carried out through X-ray single crystal diffraction, elemental analysis, and quantum chemical calculations. Single crystal X-ray diffraction analysis reveals that complex 1 is triclinic, space group of P1 with a=0.825 3(2) nm, b=0.892 0(3) nm, c=0.898 7(3) nm, α=106.497(4)°, β=90.281(4)°, γ=113.861(4)°, V=0.574 7(3) nm³. The central ion Co(Ⅲ) has an elongated octahedral configuration. Each complex is composed of Co³⁺ cation, three azide anions and one diethylenetriamine ligand. A disordered azide anion has a site occupancy of 50%, and 1D chain-like supermolecular was formed by N—H…N hydrogen bond and π…π packing interations. In addition, based on crystal structure of complex 1 determined by X-ray crystallographic analysis, the full geometry optimized and frequency calculations have been performed by density functional theory. The single-point energy, atomic charges and frontier molecular orbital were analyzed. The theoretical calculation results indicate that the complex configuration is stable and consistent with the experimental results.

Key words: Co(III) supramolecular complex, crystal structure, quantum chemical calculation, density functional theory, atomic charge, frontier molecular orbital