Luminescent rhenium(I) complexes of substituted imidazole[4,5-f]-1,10-phenanthroline derivatives

Seven new chromophoric ligands (L1–L7), based upon the fused imidazo[4,5-f]-1,10-phenanthroline core, were dually functionalised with a variety of aryl substituents of varying character, and can be synthesised utilising a one-pot methodology. The resultant ligands are fluorescent (λem = 408–425 nm) and amenable to further reactivity with pentacarbonylbromorhenium to give coordination complexes of the form fac-[ReBr(CO)3(NˆN)] (where NˆN = L1–L7). The complexes have been fully characterised using a variety of spectroscopic and analytical techniques, and structurally confirmed for three examples using X-ray diffraction studies. These new rhenium complexes are all luminescent, revealing classical 3MLCT emission in aerated solution; the complexes show that the 3MLCT excited state is moderately sensitive to the nature of functionalisation of the chelated imidazo[4,5-f]-1,10-phenanthroline ligand.