Synthesis and X-ray crystallographic characterization of copper and iron complexes with tetradentate-N4 ligands: Reactivity towards catechol oxidation

The reaction of copper chloride dihydrate and ferric chloride hexahydrate with a tripodal N4 ligand (ntb) under mild conditions affords two novel complexes [Cu(ntb)Cl]2[CuCl4] · 2H2O (1) and [Fe(ntb)Cl2]Cl · 3H2O (2). The reaction of ferric chloride with another N4 ligand, bispicpn, forms an octahedral mononuclear complex, [Fe(bispicpn)Cl2]Cl (3). Single-crystal X-ray structural studies of 1, 2 and 3 reveal the formation of hydrogen-bond sustained 3D, 2D and 1D networks, respectively, involving (N–H⋯O) and (N–H⋯Cl) interactions. The packing arrangement in 2 further reveals the existence of hexagonal channels with helical propagation along the diagonal of the crystallographic b- and c-axes. The reactions of these complexes with 3,5-di-tert-butylcatechol have been studied in dimethylformamide. NMR techniques have been used to identify the reaction products.

The synthesis and structural characterization of new copper and iron complexes [Cu(ntb)Cl]2[CuCl4] · 2H2O (1), [Fe(ntb)Cl2]Cl · 3H2O (2) and [Fe(bispicpn)Cl2]Cl (3) with tetradentate N-ligands, ntb (ntb = tris(2-benzimidazolylmethyl)amine) and bispicpn (bispicpn = N,N′-bis(2-pyridylmethyl)-1,2-propanediamine) are reported. Detailed structural analysis revealed 3D, 2D and 1D networks. The packing diagram of 2 shows interesting hexagonal pores. Oxidation reactions of 3,5-di-tert-butylcatechol by oxygen were performed with these complexes; the copper complex exhibits catechol oxidase like activity while the two iron complexes show catechol dioxygenase like activity.Figure optionsDownload as PowerPoint slide