Estudos estruturais por difração de raios X de complexos metálicos de Fe(II), Co(II), Ni(II), Cu(II) e Zn(II) com drogas utilizadas no tratamento da tuberculose

Abstract

This work deals with synthesis and characterization of eleven complexes formed between antituberculostatic isoniazid (INH) and pyrazinamide (PZA) with divalent metal ions Fe, Co, Ni, Cu and Zn, which were characterized by vibrational spectroscopic (IV as Raman). Five of these compounds were characterized by single crystal X-ray diffraction. This work is justified since the understanding of biological activity of drugs can be explained by the understanding of its structure. The PZA complexes series was only possible to obtain single crystals with Cu(II). The molecular formula of this complex is equal to [Cu(PZA)2](ClO4)2, and it is called PZACu(ClO4)2. This structure belongs to monoclinic crystal system, space group P21/c, where the metal ion adopts an octahedral geometry showing tetragonal distortion. The sites of the ligand PZA which are located in equatorial positions (O, N-alpha) have lower bond distances when compared to sites which are in axial position (N-delta). This interactions perform a twodimensional coordination polymer with (4.4) topology. The Spectroscopic and structural analysis, from the complex formed between Cu(II) and PZA can be rationalized and proposing, which sites of the ligand PZA has coordinated to the metal ions Co (II), Ni (II) and Zn (II), formed a series in which the counter ions were the perclorates. A synthetic route that was used heating and chlorid as counter-ions of metal salts to the ligand INH give rise to the ligand thermodecomposition, forming the ion isonicotinate that in situ coordinated to the bivalent ion Co, Ni and Zn, whose molecular formula of these complexes is [M(H2O)4(INA)2], and these structures named INAM. These structures belong to the triclinic system and space group P1. This ligand is coordinated to the metal center in trans position, which two isonicotinato ions through the nitrogen atoms of pyridine. The hydrogen interactions are present as well as π-stacking, which are responsible for the solid stability. We proposed a mechanism for the reaction path of¨ ligand thermodecomposition. In the sintesis of zinc(II) complexes with INH was used as counter-ion perchlorate in metallic salts of Zinc(II).This strategy was efficient to avoid the termodecomposition of ligand and to obtain single crystals subjected to X-ray diffraction, revealed that this structure belongs to monoclinic crystal system and space group P21. The molecular formula of this complex is [Zn(INH)2](ClO4)2.6H2O, which is named as INHZn. This structure is asymmetric, with Flack parameter equal to 0.013 (8). Four ligands of INH coordinate to metal center, two of them in equatorial position, by oxygen and nitrogen atoms, both from hydrazid grouping, while two other ligands, which occupy the axial positions, coordinate to the nitrogen pyridine atom. The ion Zn (II) adopts octahedral geometry, being located at the nodes of a two-dimensional polymer topology (4.4). A series with the ligand INH and divalent metal ion Fe, Co and Ni were obtained, with counter ions, sulfate, chloride and nitrate, respectively. The molecular proposal was based on spectroscopic data compared with the complex INHZn, as well as the results of thermogravimetric analysis. Biological tests were carried out with Artemia saline, with the complexes formed between the ligand and INH for bivalent ions, Co, Ni and Zn. The results indicate that the LC50 is equal to116, 61,5 e 269 µmol.L-1, respectively, this toxity is superior to free ligand.