[2]Catenanes and inclusion complexes derived from self-assembled rectangular PdII and PtII metallocycles

Abstract

New inclusion complexes and [2]catenanes were self-assembled from a fluorescent diazapyrenium based ligand, a Pd^II or Pt^II complex, and cyclic or acyclic electron rich aromatic guests in aqueous and organic media. The molecular rectangles display a π-deficient cavity suitable to incorporate π-donor aromatic systems. The inclusion complexes between the metallocycles and phenylenic (2a,b) and naphthalenic (3a,b–5a,b) derivatives were studied by NMR, UV-vis and fluorescence spectroscopy. The crystal structure of (3b) ⊂ 1a·6PF₆ confirmed the insertion of the guest into the cavity of the metallocycle. Following the same self-assembly strategy, the use of polyethers 6,7 as π-donors resulted in the self-assembly of the [2]catenanes 1a(6,7)·6PF₆. Single-crystal X-ray analysis of 1a(7)·6PF₆ revealed the [2]catenane structure being stabilized by π-stacking and [C–H⋯O] interactions.