Synthetic, structural and spectroscopic studies of complexes derived from the copper(II) perchlorate/fumaric acid/ N, N′-chelates tertiary reaction systems

Abstract

The synthetic investigation of the Cu(ClO 4) 2·6H 2O/fumaric acid (H 2fum)/ N, N’-chelates (1,10-phen, 2,2′-bpy) tertiary reaction systems has yielded mononuclear, dinuclear and tetranuclear complexes, and three coordination polymers. The chemical and structural identity of the products depends on the solvent, the absence or presence of external hydroxides in the reaction mixtures and the N, N’-donor. Three fumarato(−2) complexes, i.e. compounds [Cu 2(fum)(phen) 4](ClO 4) 2·2H 2O ( 1·2H 2O), [Cu(fum)(phen)(H 2O)] n ( 3) and [Cu 2(fum)(bpy) 2(H 2O) 2] n (ClO 4) 2 n ( 6), were isolated and structurally characterized, and four non-fumarato complexes, i.e. compounds [Cu 4(μ 3-ΟΗ) 2(μ 2-ΟΗ) 2(phen) 4(H 2O) 2](ClO 4) 4·2H 2O ( 2·2H 2O), [Cu(ClO 4)(phen) (MeCN) 2(H 2O)](ClO 4) ( 4), [Cu(ClO 4)(phen)(MeCN) 2] n (ClO 4) n ( 5) and [Cu(ClO 4) 2(bpy)(MeCN) 2] ( 7), were simultaneously obtained from the reaction systems investigated. The coordination versatility of the fumarato(−2) ligand is reflected to the three different coordination modes observed in 1·2H 2O, 3 and 6; the monodentate bridging μ 2-κ O:κ O′ mode in 3, the asymmetric chelating bridging μ 2-κ O:κ O′:κ O′′:κ O′′′ mode in 1·2H 2O and 3, and the syn, syn bridging μ 4-κ O:κ O′:κ O′′:κ O′′′ mode in 6. The crystal structures of the complexes are stabilized by intra- and inter-molecular hydrogen bonding and π–π stacking interactions leading to interesting supramolecular architectures. Characteristic IR bands of the complexes are discussed in terms of the known structures, and the coordination modes of the fum 2− ligands.