NITRO COMPLEXOS DE FERRO(III) COM DERIVADOS DA BASE DE SCHIFF SALEN

Resumo

The iron(III) complexes with Schiff base salen present relevant applications such as chemotherapeutic agents and materials chemistry. Seeking to develop Schiff base coordination compounds with improved pharmacologics properties it was used nitrite ion as ligand due nitro complex usually act as pro-drug releasing nitric oxide in biological environment, an important cell protection agent and vasodilator. In this study were obtained new iron(III) nitro complexes of ligands derivatives from salen Schiff bases. The ligands 3-MeOsalen and 3- MeOsalophen and complexes [Fe(3MeOsalen)Cl], [Fe(3-MeOsalophen)Cl], [Fe(3- MeOsalen)NO2] and [Fe(3-MeOsalophen)NO2] were synthetized and characterized by vibrational spectroscopy in the infrared region and electronic spectroscopy in the ultraviolet and visible region. The infrared spectra allowed the characterization of the ligands 3-MeOsalen and 3-MeOsalophen, mostly by the presence of πC=N near 1620 cm-1. The synthesis of the precursor complexes as evidenced by changes in the vibrational frequencies of πC=N, πC-O and the presence of metal-oxygen and metal-nitrogen vibrational modes. The iron nitro complexes exhibited π(NO2)ass around 1300 cm-1 and π(NO2)sim at 1271 cm-1 and angular deformation around 830 cm-1, indicating so that the coordination is done via the nitrogen atom. Electronic spectra of the Schiff bases were marked by the presence of π-π* electronic transitions from aromatic ring and imino group and n-π* transitions related to free- electron pairs. For the complexes [Fe(3-MeOsalen)Cl] and [Fe(3-MeOsalophen)Cl] was evidenced shifts of intraligands transitions and the emergence of new bands such as LMCT (pπCl- π dπ*Fe3+). Such charge transfer were not observed in the spectra of [Fe(3- MeOsalen)NO2] and [Fe(3-MeOsalophen)NO2] indicating so the chloride ligand replacement by nitrite ion.