Acridine‐containing RuII, OsII, RhIII and IrIII Half‐Sandwich Complexes: Synthesis, Structure and Antiproliferative Activity

Research aimed at enhancing the efficacy of organometallic complexes against
cancer, has shown that attaching bio‐active molecules to (metallo)drugs often
enhances their biological properties. New salicylaldimine and 2‐pyridylimine
ligands (L2 and L3), containing a bio‐active acridine scaffold, were synthesized
and complexed to Rh(III), Ir(III), Ru(II) and Os(II) metal ion centers. The resulting
acridine‐containing half‐sandwich complexes have been characterized fully by
elemental analysis, FT‐IR and NMR spectroscopy, HR‐ESI mass spectrometry as
well as single crystal X‐ray diffraction, for the Rh(III) N^N bidentate complex
[RhCp*Cl(L3)][BPh4]. The antiproliferative activity of the ligands (L2 and L3)
and complexes (C1 to C9) were evaluated in vitro against human promyelocytic leukemia
cells (HL60) and normal skin fibroblast cells (FG0). The compounds exhibit
good activities against HL60 cells and are consistently selective towards cancerous
cells over non‐tumorous cells. This study demonstrates the potential of such hybrid
compounds to target cancer cells specifically. The most active complex,
[RhCp*Cl(L2)], exhibited binding to DNA model guanosine‐5’‐monophosphate
(5’‐GMP) which suggests a mode of action involving interaction of the complex
with 5’‐GMP found on DNA backbone