Chiral nanostructuring of multivalent macrocycles in solution and on surfaces

Abstract

We describe the design and synthesis of a novel functionality-rich, homochiral macrocycle, possessing the overall molecular D₂ symmetry, in which multivalency is introduced into the covalent framework by means of four suitably positioned pyridine moieties. The macrocycle synthesis is carried out with functionalized, enantiopure 1,1′-binaphthyl synthons as the source of chirality by means of a room temperature esterification reaction as the cyclization procedure. Upon addition of Pd²⁺, coordination of the pyridine moieties occurs both intra and intermolecularly, to afford chiral ordered mono and dimeric macrocycles or multimeric aggregates depending on the solvents and conditions used. The metal binding event takes place in combination with a significant macrocyclic conformational rearrangement detected by circular dichroism spectroscopy. When in combination with a third component (C₆₀), the macrocycle-Pd²⁺ hybrid undergoes surface-confined nanostructuring into chiral nanofibres.