Microwave assisted synthesis of rhodium(I) N-heterocyclic carbene complexes and their cytotoxicity against tumor cell lines

Organometallic rhodium(I) complexes of the general type [(COD)(NHC)RhCl] (where COD = 1,5-cyclooctadiene, NHC = N-heterocyclic carbene) were prepared according to a two-step transmetalation method via a silver carbene intermediate. The procedure was supported by microwave irradiation allowing reduced reaction periods. The complexes were evaluated for cytotoxic effects in selected cancer cell lines, namely HT-29 colon adenocarcinoma, MDA-MB-231 breast carcinoma and MCF-7 breast adenocarcinoma, and generally triggered strong cytotoxic effects with IC50 values in the low micromolar range. Evaluation of structure-activity relationships clearly indicated a preference for branched isopropyl side chains at the nitrogen atoms of the NHC ligands versus non-branched ethyl side chains. Further studies on selected examples in HT-29 cells indicated that this could be the result of a higher cellular uptake. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

Organometallic rhodium(I) complexes were synthesized and evaluated for their cytotoxic effects against cancer cells. The complexes exhibited strong cytotoxic effects on various cancer cell lines, with a preference for branched isopropyl side chains on the N-heterocyclic carbene ligands. Further studies suggested that the increased cytotoxicity might be attributed to higher cellular uptake.