Synthesis, Characterization, and Topoisomerase Studies with a Novel Cobalt(III) Complex Coordinated by an Aromatic Bidentate Ligand and N-(3,5-bis(trifluoromethyl)phenyl)pyridine-2-thiocarboxamide

The need for novel antibiotic drugs is urgent. Tuberculosis (TB) is one of the top ten leading causes of death worldwide, with 1.8 million deaths per year, and the number one killer of people who are HIV-positive. The emergence of multidrug-resistant TB (roughly 20% of new cases in 2015) and even extensively drug-resistant TB is a major cause for concern. As the war against bacterial pathogens continues, finding novel drugs and drug targets is essential. Topoisomerase IA is a novel and attractive drug target because it has never yet been targeted by antibiotics used clinically. Since the clinical success of cisplatin as an anticancer drug in the early 19th century, there has been substantial effort to discover novel metal-based therapeutics. In our contribution to the fight against bacterial infection, [[Co(phen)2(PCA-CF3)2)](PF6)2•1.25H2O 1 (where phen = 1,10-phenanthroline and PCA-(CF3)2 = N-(3,5-bis(trifluoromethyl)phenyl)pyridine-2-thiocarboxamide) was synthesized with PCA-(CF3)2 as a mixed ligand. Elemental analysis, FTIR spectroscopy, 1H, 13C, and 59Co NMR spectroscopy, and high resolution electrospray ionization mass spectroscopy were used to determine the structure of complex 1. Complex 1 was tested for inhibition of bacterial topoisomerase I as well as antibacterial activities. Complex 1 had an MtbTopI relaxation inhibition IC50 value of 55.5 µM when compared to an IC50 value of 0.8 µM for [Co(phen)2(MeATSC)](NO3)3·2.5H2O·C2H5OH 2 (where MeATSC = 9-anthraldehyde-N(4)-methylthiosemicarbazone). Complex 1 was able to prevent the growth of M. smegmatis, with an MIC value of 0.89 µM when compared to an MIC value of 6.25 µM for complex 2

CCDC 1956421: Experimental Crystal Structure Determination

Related Article: Michael J. Celestine, Mark A.W. Lawrence, Nicholas K. Evaristo, Benjamin W. Legere, James K. Knarr, Olivier Schott, Vincent Picard, Jimmie L. Bullock, Garry S. Hanan, Colin D. McMillen, Craig A. Bayse, Alvin A. Holder|2020|Inorg.Chim.Acta|510|119726|doi:10.1016/j.ica.2020.11972