A biradical chelate Zn(II) complex with phenoxazin-1-one ligands

A stable biradical bis-chelate complex 3, bis-[2,4,6,8-tetra-(tert-butyl)phenoxazinonato] Zn(II), based on redox-active ligands has been prepared and structurally characterized by X-ray crystallography. Lengths of the coordination Zn–O bonds are equal to 1.938 and 2.008 Å and those of the intraligand C–N and C–O bonds (1.356 and 1.308 Å, respectively) point to radical-anion form of the phenoxazinone ligand. Effective magnetic moment of a microcrystalline sample of 3 measured at 70 K is equal 2.53 μB, and steadily decreases to 2.39 μB upon elevation of temperature. EPR, UV–Vis measurements and DFT B3LYP∗/6-311++G(d,p) calculations show that 3 has the ground triplet electronic state characterized with weak ferromagnetic coupling of the unpaired electrons localized on the ligands.