Oxazolidine copper complexes: Synthesis, characterization and superoxide dismutase activity of copper(II) complexes with oxazolidine ligands derived from hydroxyquinoline carboxaldehyde

Abstract

ProcThis work describes the synthesis of copper(II) complexes, their identification using spectroscopic and electrochemical methods, structural characterization with X-ray diffraction and density functional theory calculations (DFT), as well as their catalytic activity mimicking that of superoxide dismutase. Structural analysis revealed the formation of complexes with cyclization of ligands L1 and L2 with the formation of a heterocycle, 1,3-oxazolidine. The DFT calculations confirmed this trend by stabilizing with lower energy. In addition, evaluations of mimetic enzymatic activity of complexes C1, C2, C3 and C4 revealed promising IC 50 values compared to other results seen in the literature (IC 50 = 0.22, 0.328, 0.55 and 0.92). Also, calf thymus DNA interactive experiments using UV-visible spectroscopy were conducted in the presence of the copper(II) complexes.

Copper(II) Binding to PBT2 Differs from That of Other 8-Hydroxyquinoline Chelators: Implications for the Treatment of Neurodegenerative Protein Misfolding Diseases

“…This crystal structure, FEXYAL, shows Cu(II)-bis-8HQ coordination in an octahedral-type coordination environment, 55 with both 8HQs acting as tridentate ligands. Few crystal structures suggest the formation of Cu(II)-mono-8HQ complexes and those that do often portray tetradentate coordination with two ligands from the 2-position substituent (e.g., CSDS IMUFAY, 56 FEXXOY, 55 and FEXXUE 55 ), which is not possible for PBT2. Similarly, one crystal structure shows tetradentate coordination of one 8HQ, including the coordination of two ligands from the 2position substituent and bidentate coordination of the second 8HQ in a bis complex (i.e., CSDS FEXXIS 55 ).…”

“…Other than the crystal structure of Cu­(II)- bis -PBT2 (i.e., CSDS entry WAXPIX), there is only one crystallographic example of tridentate coordination of Cu­(II) by 8HQs with a 2-position amine group of formula 2-CH x NR x in the Cambridge Structural Database (i.e., CSDS entry FEXYAL), and no bidentate examples could be found. This crystal structure, FEXYAL, shows Cu­(II)- bis -8HQ coordination in an octahedral-type coordination environment, with both 8HQs acting as tridentate ligands.…”

“…Few crystal structures suggest the formation of Cu­(II)- mono -8HQ complexes and those that do often portray tetradentate coordination with two ligands from the 2-position substituent (e.g., CSDS IMUFAY, FEXXOY, and FEXXUE), which is not possible for PBT2. Similarly, one crystal structure shows tetradentate coordination of one 8HQ, including the coordination of two ligands from the 2-position substituent and bidentate coordination of the second 8HQ in a bis complex (i.e., CSDS FEXXIS). Additionally, one crystal structure shows a dimeric species in which two Cu­(II) moieties are each coordinated by a tridentate 8HQ with a fourth ligand from the phenolate oxygen of another tridentate 8HQ Cu­(II) complex (i.e., CSDS ACUZUT).…”

“…This study used the results of X-ray crystallography, EPR, NMR, and UV−visible absorption spectroscopy to propose four structures for Cu(II)-PBT2, including a five-coordinate Cu(II)-bis-PBT2 crystal structure with coordination from the tertiary amine in the 2-position (i.e., CSDS entry WAXPIX), and three calculated Cu(II)mono-PBT2 structures with H 2 O and Cl − ligands. 29 Other than the crystal structure of Cu(II)-bis-PBT2 (i.e., CSDS entry WAXPIX), there is only one crystallographic example of tridentate coordination of Cu(II) by 8HQs with a 2-position amine group of formula 2-CH x NR x in the Cambridge Structural Database (i.e., CSDS entry FEXYAL 55 ), and no bidentate examples could be found. This crystal structure, FEXYAL, shows Cu(II)-bis-8HQ coordination in an octahedral-type coordination environment, 55 with both 8HQs acting as tridentate ligands.…”

“…29 Other than the crystal structure of Cu(II)-bis-PBT2 (i.e., CSDS entry WAXPIX), there is only one crystallographic example of tridentate coordination of Cu(II) by 8HQs with a 2-position amine group of formula 2-CH x NR x in the Cambridge Structural Database (i.e., CSDS entry FEXYAL 55 ), and no bidentate examples could be found. This crystal structure, FEXYAL, shows Cu(II)-bis-8HQ coordination in an octahedral-type coordination environment, 55 with both 8HQs acting as tridentate ligands. Few crystal structures suggest the formation of Cu(II)-mono-8HQ complexes and those that do often portray tetradentate coordination with two ligands from the 2-position substituent (e.g., CSDS IMUFAY, 56 FEXXOY, 55 and FEXXUE 55 ), which is not possible for PBT2.…”