Naphthalene containing amino-ether macrocycle based Cu(ii) templated [2]pseudorotaxanes and OFF/ON fluorescence switching via axle substitution

Abstract

A new naphthalene containing macrocycle, NaphMC, and a new fluorophoric bidentate linear axle derivative of 5,5′-dimethyl-2,2′-bipyridine (L3) along with two other ligands 1,10-phenanthroline (L1) and 5,5′-dimethyl-2,2′-bipyridine (L2) are explored towards the synthesis of Cu(II) templated [2]pseudorotaxanes. All ternary complexes are well characterized by ESI-MS, UV/Vis, EPR spectroscopy, elemental analysis and emission spectroscopic studies. Single crystal X-ray diffraction studies confirm the geometry around the Cu(II) center as a distorted trigonal bipyramid via the contribution of [3 + 2] orthogonal motifs of the wheel (NaphMC) and the bidentate chelating ligands L1 and L2 in the cases of pseudorotaxanes, CuPR1 and CuPR2, respectively. Furthermore, the fluorescence “OFF” state of the fluorophoric axle L3 is achieved via threading it to the Cu(II) complex of NaphMC, whereas fluorescence switching “ON” is demonstrated by the substitution of L3 of CuPR3 with a stronger chelating ligand L1.