# Cyclometalated Rhodium(III) Polypyridyl Complexes with Anti-Cancer Stem Cell Activity

## TL;DR

This study introduces new rhodium complexes that effectively target cancer stem cells, outperforming existing drugs like cisplatin and salinomycin.

## Contribution

The paper presents a novel rhodium(III) scaffold with anti-cancer stem cell activity, offering a new direction for metallodrug development.

## Key findings

- Complex 4 shows sub-micromolar to low micromolar anti-CSC activity against breast and osteosarcoma stem cells.
- The rhodium complex outperforms cisplatin and salinomycin in anti-CSC activity.
- The cyclometalated scaffold is proposed as a useful synthon for future anti-CSC rhodium complexes.

## Abstract

Investigations into
the anticancer stem cell (CSC) properties of
rhodium complexes are extremely rare. Here we report the synthesis,
characterization, photophysical properties, and in vitro anti-CSC activity of a series of cyclometalated rhodium­(III)-polypyridyl
complexes 1-4. The 4,7-diphenyl-1,10-phenanthroline-bearing
complex 4 exhibits activity against monolayer- and three-dimensionally
cultured breast CSCs and osteosarcoma stem cells in the sub-micromolar
to low micromolar range, outperforming the metallodrug cisplatin and
the established anti-CSC agent salinomycin. Our results suggest that
the reported rhodium­(III) scaffold, containing cyclometalated 2,2′-(phenylmethylene)­dipyridine,
could be a useful synthon for the future development of anti-CSC rhodium
complexes.