A symmetry interaction approach to [M2L2]4+ metallocycles and their self-catenation.

Dinuclear [M2L2]n+ (M = Pd2+ or Pt2+) metallo-rectangles have a rich history, particularly in molecular recognition, including self-catenation events. These structures are mostly generated via a ligand-directed approach with cis-capped M2+ corners. We report here a symmetry interaction approach using 3 : 1 complementary denticity, giving a new route to [M2L2]4+ rectangles and their self-catenation.

Self-assembly and Cycling of a Three-state Pdx Ly Metallosupramolecular System.

The use of stimuli to induce reversible structural transformations in metallosupramolecular systems is of keen interest to chemists seeking to mimic the way that Nature effects conformational changes in biological machinery. While a wide array of stimuli have been deployed towards this end, stoichiometric changes have only been explored in a handful of examples. Furthermore, switching has generally been between only two distinct states. Here we use a simple 2-(1-(pyridine-4-methyl)-1H-1,2,3-triazol-4-yl)pyridine "click" ligand in combination with PdII in various stoichiometries and concentrations to quantitatively access and cycle between three distinct species: a [PdL2 ]2+ monomer, a [Pd2 L2 ]4+ dimer, and a [Pd9 L12 ]18+ cage.