Synthesis and antiproliferative study of phosphorescent multimetallic Re(I)/Au(I) complexes containing fused imidazo[4,5‐f]‐1,10‐phenanthroline core

Five heterobimetallic Re I /Au I and a tri‐metallic Re I /Au I /Re I species following the formulas fac‐ [ReCl (CO) 3 (N^N^CAuR)] 0/+ and [( fac‐ [ReCl (CO) 3 (N^N^C)]) 2 Au] + , where R is an iodide ( 1 ), phenylacetylene ( 2 ), dodecanethiol ( 3 ), 2,3,4,6‐tetra‐ O ‐acetyl‐1‐thio‐β‐D‐glucopyranose ( 4 ) and JohnPhos ( 5 ) and N^N^C is the fused imidazo[4,5‐f]‐1,10‐phenanthroline heterotopic ligand, were synthesised and fully characterised by a variety of spectroscopic and analytical techniques. The resultant complexes are luminescent in the orange region, revealing classical metal‐to‐ligand charge transfer ( 3 MLCT) ((Re (dπ) → (N^N^C)(π*)) emission in aerated DMSO solution. The red shifted emission observed on going from 3 to 4 suggests that the electronic properties of the gold ancillary ligand are implicated in the emissive properties. Antiproliferative activity in tumour cell lines, lung (A549) and cervix (HeLa) cells revealed that only complex 4 containing a 2,3,4,6‐tetra‐ O ‐acetyl‐1‐thio‐β‐D‐glucopyranose as gold ancillary ligand possesses certain cytotoxicity in both cell lines.