Sínteses e caracterizações estruturais de complexos de FeIII, CoII , CuII, ZnII e CdII com ligantes bases de schiff acilhidrazonas e estudo de interação com o dna

Abstract

In this work, three acylhydrazone Schiff base ligands were synthesized: salicylaldehydeisonicotinoyl hydrazone (H2La), salicylaldehyde-4-chlorobenzoyl hydrazone (H2Lb) and o-vanillin-4-chlorobenzoyl hydrazone (H2Lc). The characterization of the ligands involved techniques such as melting point (m.p.), nuclear magnetic resonance (NMR) spectroscopy, vibrational spectroscopy in the mid-infrared region (IR) and electronic absorption in the ultraviolet-visible (UV-Vis). Once the structure was elucidated, these ligands were used in complexation reactions with different metal ions, resulting in seven unprecedented crystalline complexes, numbered from 1 to 7, which were divided into three specific groups: I) (1) Zn(H2L a)2(Cl)2]·2/3(CH3OH)·2/3(H2O); (2) [Cd(H2La)2(NO3)2(CH3OH)2]; II) (3) [Fe(HLb)Cl)2(CH3CH2OH)]·(CH3CH2OH); (4) [Co2(HLb)2(CH3OH)4](NO3)2·2(CH3OH); (5) [Cu2(HLb )2(ClO4)2]·2(H2O); III) (6) [Cu(HLc)(CH3OH)(H2O)](NO3) and (7) [Cd2(HLc)2(NO3)2(CH3OH)2]·4(CH3OH). Structural analysis of single-crystalline complexes by X-ray diffraction (XRD) revealed detailed information, including the metal coordination sphere, the presence of counter ions and solvent molecules, intramolecular and intermolecular interactions. Using IR spectroscopy, information about molecular vibrations corroborated the crystallographic data, highlighting the points of coordination of the ligand with the metals, such as the C=O and C=N stretching bands that were displaced by approximately 1650 cm-1and 1620 cm-1, respectively, in the ligand spectra for lower wavenumbers in those complexes where coordination occurred in a tridentate manner. Furthermore, using this technique it was possible to observe the stretching vibrations, characteristic of the nitrate ions in complexes 2, 4, 6 and 7 and of the perchlorate ion in complex 5. Spectroscopy in the UV-Vis region revealed characteristic bands of the intra- π→π* ligand around 300 nm, coming from the aromatic rings of the ligand structure and n→π* transitions around 330 nm. In addition to charge transfers occurring between ligand and metal in the 400 nm region in the spectra of the complexes. Biological study of the complexes was carried out using calf thymus DNA (CT-DNA). The study by spectroscopic titration and viscosity revealed the presence of intercalative DNA-complex interactions, highlighting them as moderate with Kb values ranging from 104-105 L mol-1, in addition to showing significantly greater hypochromism compared to free ligands, indicating that complexation resulted in stronger interaction with DNA. The partition coefficients, with positive log P values, obtained in water and n-octanol, suggest potential for easy permeation of these complexes through biological membranes, indicating a notable preference for the organic phase, similar to lipids. This characteristic is advantageous in drug development and design, especially when compounds require efficient access to intracellular targets.