Chemically Driven Contraction and Elongation: Interconversion between Molecular Figure of Eight

A 90-membered macrocycle having two functional moiety, diphenyl-phenanthroline (dpp) and two tri-dentate pyridine-diamide (pda) as templating center has been synthesized from precursor molecules via amide bond formation in 10 steps. dpp and pda are arranged alternatively around the macrocycle in a sequence of dpp-pda-dpp-pda and demeostrated orthogonal behaviour, when treated with transition metal such as Cu(I) and Co(III): It forms figure of eight complexes selectively between dpp units and pda units respectively due to the geomtric preferance. This makes the macrocycle operates in bimodal manner. Interconversion between figure of eight complexes has been witnessed by metal-exchange via demetalation and subsequent re-metalation between orthogonal templating centres. Removal of Cu(I) template is performed using a common and less toxic reagent NH₂CH₂CH₂NH₂ and Co(III) by Zn/CH₃COOH at RT.