Supramolecular complexes obtained from the interaction of violuric acid with manganese ion and nitrogenous ligands

This work describes the synthesis, spectroscopic characterization (Raman and infrared) and structural arrangement of three new supramolecular complexes named [Mn(H2Vi)2(H2O)4)](bpy)2 (1), [Mn(bpa)2(H2O)4](H2Vi)2 (2) and [Mn(bpp)2(H2Vi)2]·(bpp)2(H2O)2 (3); these compounds have been obtained making use of different building blocks such as 4,4′-bipyridyne (bpy), 1,2-bis(4-pyridyl)ethane (bpa) and 4,4′-trimethylene-dipyridine (bpp) acting as spacers with violuric acid and manganese ion, presenting behavior related to processes of molecular self-assembling and self-organization, very common in studies of supramolecular systems. In all these compounds the violurate anion appears in the crystalline arrangement as monodentate, anionic and chelate forms for 1, 2 and 3, respectively. The important to note is that monodentate coordination in 1 and chelate in 3 through O2 and O3 oxygen atoms from the oxime group can be considered the first example in literature involving violuric acid, both in coordination or interaction with manganese ion. Moreover, it can be seen a good agreement between the structural results and the spectroscopic data; for instance the presence of an intense band in the Raman spectrum around 1603 and 1012 cm−1 in all obtained compounds, assigned to the ν(CC)/ν(CN) and ν(ring)modes of the pyridyl ligand, respectively. Other important band can be observed in 1031 cm−1 only for compound 3, assigned to the ν(NO) mode of the violurate ligand; the band at 1284 cm−1 referring to the ν(NO) mode, very characteristic of violurate species is not seen in the spectrum, thus confirming the coordination of this building block by the oxime moiety.