Conformational Regulation of Multivalent Terpyridine Ligands for Self-Assembly of Heteroleptic Metallo-Supramolecules.

A two-ligand system composed of the predesigned multivalent and complementary terpyridine-based ligands was exploited to construct heteroleptic metallo-supramolecules and to investigate the self-assembly mechanism. Molecular stellation of the trimeric hexagon [Cd6L23] gave rise to the exclusive self-assembly of the star hexagon [Cd18L16L33] through complementary ligand pairing between the ditopic and octatopic tectons. To understand how the intermolecular heteroleptic complexation influenced the self-assembly pathway, the star hexagon was truncated into two triangular fragments: [Cd12L13L43] and [Cd12L13L53]. In the self-assembly of [Cd12L13L43], the conformational movements of hexatopic ligand L4 could be regulated by L1 to promote the subsequent coordination event, which was the key step to the successful multicomponent self-assembly. In contrast, the formation of [Cd12L13L53] was hampered by the geometrically mismatched intermediates.