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 [Cd6L32] gave rise to the exclusive self-assembly of the star hexagon [(Cd18L6L33)-L-1] 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: [(Cd12L3L34)-L-1] and [(Cd12L3L35)-L-1]. In the self-assembly of [(Cd12L3L34)-L-1], the conformational movements of hexatopic ligand L-4 could be regulated by L-1 to promote the subsequent coordination event, which was the key step to the successful multicomponent self-assembly. In contrast, the formation of [(Cd12L3L35)-L-1] was hampered by the geometrically mismatched intermediates.