Novel metal complexes with pyrano[3,2-c]quinoline-3-carboxaldehyde: Synthesis, spectroscopic, molecular modeling, QSAR, antimicrobial, and antitumor studies

Reaction of 6-ethyl-4-hydroxy-2,5-dioxo-5,6-dihydro-2H-pyrano[3,2-c]quinoline-3-carboxaldehyde (HL) with some metal ions, namely, manganese (II), cobalt (II), nickel (II), zinc (II), cadmium (II), chromium (III), iron (III), cerium (III), oxovanadium (IV), and dioxouranium (VI), yielded a new series of metal complexes; with the general formula, [MH(n)LA(m)(H2O)(x)]X-y center dot zH(2)O, n = 0-1, A = NO3- or OAc-, m = 0-2, X = NO3- or SO42-, y = 0-1, and z = 0-3. The metal complexes were characterized by elemental analysis, molar conductance, magnetic moment, thermal analysis, and spectroscopic studies. The HL ligand coordinated with metal ions as monobasic or neutral bidentate via OO donor sites of aldehyde -O and phenolic -OH producing metal complexes with tetrahedral, octahedral, and pentagonal bipyramidal geometries. On the bases of PM3 level, molecular orbital calculations were performed for metal complexes using HyperChem 7.52 program, and the results were correlated with the experimental data. The biological activity of chelating agent and its metal complexes was screened towards Staphylococcus aureus and Bacillus subtilis as Gram-positive bacteria; Salmonella typhimurium and Escherichia coli as Gram-negative bacteria, as well as Candida albicans (yeast) and Aspergillus fumigatus (fungus). The antitumor activity of the HL ligand and its metal complexes was tested against Ehrlich Ascites Carcinoma cell line (EAC), which revealed promising IC50 values, comparable with that of cisplatin. Additional QSAR models were developed to predict the biodistribution of a smaller set of metal complexes and the calculated data correlated with antitumor results.