Metallosupramolecular zippers generated by self-organization of self-complementary molecular clefts

The binding of Co(2+) and Pb(2+) ions to the terpyridine and pyridine subunits of the ligand 1 leads to the self-complementary molecular clefts 2-6, which result from the crossover combination of orthogonal-terpyridine and linear-pyridine metal-coordination subprograms and are stabilized by strong pi-pi stacking interactions. Four different cleft-type entities, [Co(2+) (2)(1)(2)] (3), [Pb(2+) (2)(1)(2)] (4), [Co(2+) (4)(1)(2)] (5), [Pb(2+) (4)(1)(2)] (6), are generated in both solution and the solid state, and may be interconverted as a function of metal/ligand stoichiometry. One- and two-dimensional metallosupramolecular zipper architectures result from self-assembly in the solid state driven by a combination of different pi-pi stacking subprograms. The U-shaped geometry of the ligand influences the possibility of zipping and thus, in turn, the generation of different zipper architectures. The structures of 2-5 have been confirmed by X-ray crystallography; that of 6 is based on NMR spectral data.