Optically pure heterobimetallic helicates from self-assembly and click strategies

Abstract

Single diastereomer, diamagnetic, octahedral Fe(II) tris chelate complexes are synthesised that contain three pendant pyridine proligands pre-organised for coordination to a second metal. They bind Cu(I) and Ag(I) with coordination geometry depending on the identity of the metal and the detail of the ligand structure, but for example homohelical (Δ_Fe,Δ_Cu) configured systems with unusual trigonal planar Cu cations are formed exclusively in solution as shown by VT-NMR and supported by DFT calculations. Similar heterobimetallic tris(triazole) complexes are synthesised via clean CuAAC reactions at a tris(alkynyl) complex, although here the configurations of the two metals differ (Δ_Fe,Λ_Cu), leading to the first optically pure heterohelicates. A second series of Fe complexes perform less well in either strategy as a result of lack of preorganisation.