Synthesis, characterization and biological activity of Cu(II), Ni(II) and Zn(II) complexes of biopolymeric Schiff bases of salicylaldehydes and chitosan

Abstract

Schiff bases have been prepared from biopolymer chitosan and salicylaldehyde, 5-methoxysalicylaldehyde, and 5-nitrosalicylaldehyde. Ligands were synthesized in a 1:1.5mol ratio, and their Cu(II), Ni(II) and Zn(II) complexes in a 1:1mol ratio (ligand:metal). Ligands were characterized by H NMR and FTIR, resulting in degrees of substitution from 43.7 to 78.7%. Complexes were characterized using FTIR, electronic spectra, XPRD. The compounds were confirmed by the presence of an imine bond stretching in the 1630-1640cm and νMetal-N and νMetal-O at <600cm. Electronic spectra revealed that both Cu(II) and Ni(II) complexes present a square plane geometry. The crystallinity values were investigated by X-ray powder diffraction. Thermal behavior of all compounds was evaluated by TGA/DTG and DTA curves with mass losses related to dehydration and decomposition, with characteristic events for ligand and complexes. Schiff base complexes presented lower thermal stability and crystallinity than the starting chitosan. Residues were the metallic oxides as confirmed by XPRD, whose amounts were used in the calculation of the percentage of complexed metal ions. Surface morphologies were analyzed with SEM-EDAX. Preliminary cytotoxicity tests were performed using MTT assay with HeLa cells. Despite the differences in solubility, the free bases presented relatively low toxicity.

In Vitro Degradation of Pure Magnesium―The Effects of Glucose and/or Amino Acid

“…The absorption bands at 3698 cm −1 and 550 cm −1 corresponding to Mg-OH stretching vibrations revealed the existence of an Mg(OH) 2 film. A band at approximately 1648 cm −1 could be ascribed to the bending vibration of an azomethine group (-C=N-) [ 37 ] resulting from the reaction between L-cysteine and glucose. The bands at 1450 cm −1 were typical vibration modes of C-H, which are included in L-cysteine and glucose molecules.…”

Preparation and spectroscopic studies of Fe(II), Ru(II), Pd(II) and Zn(II) complexes of Schiff base containing terephthalaldehyde and their transfer hydrogenation and Suzuki-Miyaura coupling reaction

“…Schiff bases belong to a prominent class of compounds and they draw significant attention in many different fields because of their characteristic features [1]. The main advantages of Schiff bases are their ease of formation under mild conditions and the linking of additional functional groups for developing new structures and chemo-physical properties.…”

Analysis of different factors affecting a liquid chromatographic chiral separation of some imino-hesperetin compounds

“…Schiff bases represent an important class of ligands in coordination chemistry, by producing very stable complexes; Thus, they have been extensively investigated regarding their electronic properties, catalytic activity in [43]. Schiff bases became a favored way for synthesis of new chemical compounds and have been used widely for pharmacological effects in different uses: antimicrobial, anticancer, antifungal, antiviral, antimalarial, anti-inflammatory, analgesic, antioxidant, antihypertensive and lipid-lowering activities [44].…”