Rhodium(I) Complexes Containing the N^N^N-Chelating Ligand: Synthesis, Structure, and Biological Activity

Abstract

Rhodium complexes have garnered extensive attention owing to their inherent potential for biological activity. The catalytic properties of Rh−N^N^N complexes have been investigated extensively, whereas there is a paucity of studies regarding their antitumor activity. In this study, we present four rhodium(I) complexes, each distinguished by a different anion. These complexes incorporate 2,6-bis(1,5-diphenyl-1H-pyrazol-3yl)pyridine as the tridentate N^N^N-chelating ligand and one carbonyl ligand. These complexes underwent rigorous evaluation for cytotoxicity against a spectrum of human tumor cell lines, including MCF-7, HeLa, and HepG2, alongside a nontumor cell line, HUVEC, employing MTT assays and flow cytometry. Our results unveiled that complex 1 Rh(N^N^N)(CO)Cl exhibited remarkable cytotoxicity and demonstrated a favorable selectivity index against tumor cells, with a particularly notable impact on breast adenocarcinoma (selectivity index = 5.2). To further ascertain its potential utility, we probed the interactions between complex 1 and ctDNA/BSA. Both UV and fluorescence scan data indicated that complex 1 was able to intercalate into ctDNA and bind with BSA. Meanwhile, comprehensive assessments, encompassing the mobility shift assay and the micronucleus test, consistently showed that complex 1 could not induce DNA fragmentation in vitro and the formation of micronucleus in mouse erythrocytes. All of these findings suggest that complex 1 could be a promising antitumor compound.

N^N^C-Cyclometalated rhodium(iii) complexes with isomeric pyrimidine-based ligands: unveiling the impact of isomerism on structural motifs, luminescence and cytotoxicity

“…Our particular interest to rhodium complexes stems partly from our experience in rhodium chemistry 82–84 and partly from appealing properties this metal shows in the C–H bond activation and catalysis, 85–91 photochemistry 92–107 and bioinorganic chemistry. 108–128 Along with the synthesis of HL 2,5 and HL 2,6 and their rhodium( iii ) complexes [RhL 2,5 (Solv)Cl 2 ]· n EtOH and [RhL 2,6 (Solv)Cl 2 ]· n EtOH , here we report the impact of isomerism on molecular and supramolecular structures of these compounds, on the photophysical properties of the rhodium( iii ) complexes and on the cytotoxic activity of the ligands and complexes. These experimental studies are supplemented by the theoretical investigation of photophysical properties of the complexes and by theoretical modelling of the sp 2 C–H bond activation which occurs upon the coordination of HL 2,5 and HL 2,6 to RhCl 3 .…”