Aryl, bi-functionalised imidazo[4,5-f]-1,10-phenanthroline ligands and their luminescent rhenium(I) complexes

Five new imidazo[4,5-f]-1,10-phenanthroline based ligands (1-5) have been synthesised and characterised. The facile synthesis of 1-5 allows two regiochemical points of structural variety allowing highly conjugated and bulky aryl groups of varying functionalities, including azobenzene, trityl and terpyridine constituents, to be attached to the ligand core. 1-5 are fluorescent (lambda em = 410-415 nm), and react readily with [ReBr(CO)5] in toluene to give neutral coordination complexes of the form fac-[ReBr(CO)3(1-5)]. The series of complexes was characterised using a variety of spectroscopic and analytical techniques. Two examples of this series were characterised in the solid state using single crystal X-ray diffraction which confirmed the octahedral geometry and formulation. Photophysical studies showed that fac-[ReBr(CO)3(1-5)] are phosphorescent in solution under ambient conditions, revealing visible emission (558-585 nm) in aerated solution with corresponding lifetimes in the range 149-267 ns. These attributes are consistent with a triplet metal to ligand charge transfer (3MLCT) emitting state.

Automated summary

A series of new imidazo[4,5-f]-1,10-phenanthroline based ligands have been synthesized and characterized. These ligands, with conjugated aryl groups of varying functionalities, readily react with [ReBr(CO)5] to form neutral coordination complexes. The complexes exhibit fluorescent and phosphorescent properties, emitting visible light in solution.