Synthesis, spectroscopy and magnetism of fluoridoborate transition metal complexes with aminoflavone ligand (3-af). X-ray crystal structure of [Cu(BF4)2(3-af)2] and [Zn(BF4)(3-af)2](BF4)·CH3C(O)OEt

The compounds of general formula M(BF4)2(3-af)2 3H2O where M = Ni(II), Co(II) and Cu(BF4)2(3-af)2, [Zn(BF4)(3-af)2](BF4)·CH3C(O)OEt with 3-aminoflavone (3-af) have been synthesized and characterized. The crystal structure of copper and zinc complexes has been determined by X-ray diffraction method. The complexes have been characterized by infrared, ligand field spectra and magnetic measurements. These mononuclear complexes are tetragonal, [4+2] coordinated (Cu, Ni and Co) and penta-coordinated (Zn). The ligand acts as N,O-chelate. The results of the magnetic studies of complexes in 1.8–300 K range indicate a very weak intermolecular interaction between magnetic centers. The magnetic behavior of cobalt and nickel complexes indicates an important orbital contribution via spin–orbit coupling. From X-ray powder-diffraction patterns, the complexes of Ni(II) (2) and Co(II) (3) were found not to be isomorphous.