Chiroptical features and luminescence behaviour of macrocyclic tetra(4-quinolyl)-complexes: surprising absence of exciton coupling

The C4-symmetric (S)-tetra(4-quinolyl) tetraamide derivative of dota has been prepared. The sodium complex has been characterised by X-ray crystallography and although the quinolyl groups are appropriately oriented for exciton coupling in the solid-state, in solution no evidence for coupling was found for the free ligand nor its protonated, Na, Ca or Eu complexes. Instead, excimer formation was observed in emission consistent with a coplanar arrangement of the quinolyl groups.