The construction of versatile azido-bridged Schiff base Copper(II) complexes with xanthine oxidase inhibitory activity

Three new versatile azido-bridged Schiff base Copper(II) complexes, [Cu2(L1)2(μ1,1-N3)2]·2CH3OH (1), [Cu(L2)(μ1,3-N3)]n (2), and [Cu2(L3)(μ1,1-N3)2(N3)]2 (3), where L1, L2, and L3 are the deprotonated form of the Schiff bases 5-diethylamino-2-[(2-isopropylaminoethylimino)methyl]phenol (HL1), 5-methoxy-2-[(2-morpholin-4-ylethylimino)methyl]phenol (HL2), and 5-methoxy-2-[(2-piperidin-1-ylethylimino)methyl]phenol (HL3), respectively, have been prepared and structurally characterized by elemental analysis, IR spectra, and single-crystal X-ray crystallography. Complex 1 is a crystallographic centro-symmetric end-on azido-bridged dinuclear Copper(II) compound, with the Cu···Cu distance of 3.512(1) Å. Complex 2 is an end-to-end azido-bridged polymeric Copper(II) compound, with the Cu···Cu distance of 5.716(2) Å. Complex 3 is a phenolato-O and end-on azido-bridged tetranuclear Copper(II) compound, with the Cu···Cu distances of 3.122(1) and 3.108(1) Å. The Cu atoms in 1 and 2, and the inner two Cu atoms in 3 are in square-pyramidal coordination. The outer two Cu atoms in 3 are in square planar coordination. The azide ligands are dramatic bridging groups for the construction of versatile polynuclear Copper complexes with Schiff bases. The xanthine oxidase inhibitory activity of the complexes was evaluated.