Various coordination behavior of coumarin appended Schiff bases towards Ruthenium(II) ion: Synthesis, spectral characterization and biological evaluation

Abstract

Four new organometallic bivalent ruthenium(II) complexes were synthesized by the direct reaction of 3-acetyl-6-chloro-2H-chromen-2-one-semicarbazone HL1, 3-acetyl-6-chloro-2H-chromen-2-one-thiosemicarbazone HL2, 3-acetyl-7-hydroxy-2H-chromen-2-one-semicarbazone HL3, 3-acetyl-7-hydroxy-2H-chromen-2-one- thiosemicarbazone HL4 with [RuHCl(CO)(PPh3)3]. The newly synthesized complexes were characterized by elemental analysis, FT-IR, UV–Vis, 1H NMR, 13C NMR, thermal analysis, mass and X-ray diffraction techniques. From the spectral data we revealed that the ligands coordinated to the metal in a tridentate dibasic manner through pyrone carbon, azomethine nitrogen and thiolate sulphur (CNS-) in complexes Ru 2 and Ru 4, tridentate monobasic manner through lactone oxygen, azomethine nitrogen and enolate oxygen (ONO–) in complex Ru 1 and neutral tridentate manner through lactone oxygen, azomethine nitrogen and enone oxygen (ONO) in complex Ru 3. The XRD patterns of the ligands (HL1-4) and complex Ru 4 showed polycrystalline nature and the metal complexes Ru 1 and Ru 2 showed the amorphous nature, whereas complex Ru 3 showed mixture of crystalline with amorphous nature. The antimicrobial activity of the ligands and their metal complexes were examined with two bacterial species such as Staphylococcus aureus and Pseudomonas aeruginosa and two fungi namely Candida albicans and Candida tropicalis and the results revealed that the compounds showed significant antimicrobial activity compared with the standard drugs Gentamycin and ketoconazole. The anticancer potential of the ligands and newly synthesized Ru(II) complexes were examined with MCF-7 (human breast cancer cells), A549 (human lung carcinoma cells) and human normal keratinoyte cells (HaCaT) by using MTT assay. The activity of the complexes exceeded that of their parent ligands and the standard drug cisplatin, and the order of activity observed was Ru 4 > Ru 3 > Ru 2 > Ru 1 > cisplatin > ligands. The IC50 values of the complexes were >100 μM for non-cancerous cells (HaCaT) indicating the specificity of the complexes towards cancer cells.