Luminescent Ru(II) complexes based on functionalised 1,10-phenanthroline derivatised ligands towards bioconjugated probes

A series of photoluminescent, heteroleptic [Ru(bipy)2(Ln)](PF6)2 (2,2 '-bipyridine = bipy; Ln = 1,10-phenanthroline derivative) analogues have been prepared. Within the series of complexes the structural variation is provided by the ancillary ligand, Ln, which is based upon a 5-substituted 1,10-phenanthroline species. The synthesis of the ligands was achieved in two steps from 5,6-epoxy-5,6-dihydro-1,10-phenanthroline allowing a range of different morpholine, piperazine and piperidine derivatives to be attached to the 1,10-phenanthroline core at the 5-position. Furthermore, the synthetic utility of the piperazine derivative (L1) was demonstrated by bioconjugating a cholesteryl moiety to the ligand (yielding L8). Following complexation, the isolated Ru(II) complexes show classical 3MLCT characteristics with phosphorescent emission at 605-610 nm.