Cu(ii) templated formation of [n]pseudorotaxanes (n = 2, 3, 4) using a tris-amino ether macrocyclic wheel and multidentate axles.

Abstract

A tris-amine and oxy-ether functionalised macrocyclic wheel (NaphMC) and various phenanthroline based multidentate axles (L1, L2 and L3) are utilised for the formation of [n]pseudorotaxanes (n = 2, 3, 4) in high yields via Cu(ii) temptation and π-π stacking interactions. The systematic development of threaded supramolecular architectures i.e. [2]pseudorotaxane {[2]CuPR(ClO4)2}, [3]pseudorotaxane {[3]CuPR(ClO4)4} and [4]pseudorotaxane {[4]CuPR(ClO4)6} from bidentate L1, linear tetradentate L2 and tripodal hexadentate L3 respectively is described. All the [n]pseudorotaxanes are well characterized by several spectroscopy and other experimental techniques such as electrospray ionization mass spectrometry (ESI-MS), isothermal titration calorimetric (ITC) study, UV/Vis, EPR, IR and elemental analysis. Moreover, the single crystal X-ray analysis of [2]pseudorotaxane confirmed the threading of L1 in the cavity of NaphMC, resulting in the formation of a penta-coordinated Cu(ii) ternary complex. ITC studies revealed the order of binding constant values for the formation of [n]pseudorotaxanes from the NaphMC-Cu(ii) complex and multidentate axles as L3 > L2 > L1. Finally, we have also shown the ability of Ni(ii) to act as a metal template in the formation of [n]pseudorotaxanes.