Multiple folding structures mediated by metal coordination of acyclic multidentate ligand.

Four kinds of folded structures are formed upon the metal complexation of a bis(N(2)O(2)) ligand in which two oxime-type N(2)O(2) chelate ligands are connected by a flexible diethyleneoxy linker. The N(2)O(2) coordination sites are intended for d-block transition-metal ions, and the diethyleneoxy linker can interact with hard metal cations. Meso double helical, folded Omega-shaped, S-shaped helical, and single helical structures were formed depending on the metal combination. The difference in the affinity to metal cations resulted in variation of the folding modes and enabled the structural conversion between the folded structures.