Binary and ternary copper(II) complexes with 6-ethyl-4-hydroxy-2,5-dioxo-5,6-dihydro-2H-pyrano[3,2-c]quinoline-3-carboxaldehyde: Synthesis, spectral, thermal, molecular modeling, antimicrobial and antitumor studies

Abstract

6-Ethyl-4-hydroxy-2,5-dioxo-5,6-dihydro-2H-pyrano[3,2-c]quinoline-3-carboxaldehyde (HL) was synthesized as a ligand and subject to chelate with Cu(II) ion of different anions (AcO–, NO3–, SO42–ClO4–, Cl– and Br–) in presence and absence of auxiliary ligands (L′); N,O-donor; or N,N-donor such as 8-hydroxyquinoline, 1,10-phenanthroline and 2,2′-bipyridyl. The obtained results revealed that the ligand behaves as a neutral/monoanionic bidentate, forming chelates with molar ratio 1:1, (M:L). The metal complexes were fully characterized by analytical and spectral techniques in addition to thermal, magnetic susceptibility and conductivity measurements. The metal complexes displayed square planar and octahedral geometrical arrangements depending on the nature of the anion. The ligand and its complexes were screened for their antimicrobial activity against Gram–positive bacteria which are Staphylococcus aureus and Bacillus subtilis, Gram–negative bacteria which are E. coli and S. typhimurium, yeast (Candida albicans) and fungus (Aspergillus fumigatus). The antitumor activity of the HL ligand and its Cu(II) complexes were examined against Ehrlich Ascites Carcinoma cell line (EAC) from ascetic fluid of the female Swiss albino mice. To explore the most probable structure and the nature of bonding of HL ligand to metal ions; semi-emperical (PM3) calculations were achieved in gas phase. All theoretically possible structural data of the free ligand (HL) and its complexes have been correlated with the experimental data to explore the most probable structure.