Anion-Dependent Synthesis of Cu(II) Complexes with 2-(1 H -Tetrazol-5-yl)-1 H -indole: Synthesis, X-Ray Structures, and Radical Scavenging Activity.

Two mononuclear Cu(II) complexes, [Cu(phen) 2 (HL)]ClO 4 ·H 2 O·2DMF ( 1 ) and [Cu(phen) 2 (HL) 2 ]·EtOH ( 2 ), comprising 1,10-phentantroline (phen) and 2-(1 H -tetrazol-5-yl)-1 H -indole ligand (H 2 L) ligands are reported. Analysis and characterization of the samples were performed using standard physicochemical techniques, elemental analysis, nuclear magnetic resonance, Fourier transform infrared spectroscopy, and UV-vis spectroscopy. Single-crystal X-ray crystallography revealed the formation of a pentacoordinate complex in 1 and a hexacoordinate complex in 2 , in which the anionic ligand HL - has undergone monodentate coordination through the tetrazole unit. Furthermore, the crystal structure of H 2 L·MeOH is also discussed. The potential application of compounds 1 and 2 in bioinorganic chemistry was addressed by investigating their radical scavenging activity with the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and the results were supported also by theoretical calculations.