Homo- and heteroduplex complexes containing terpyridine-type ligands and Zn2+

We describe a study of the equilibrium binding of Zn2+ to binary mixtures of tridentate terpy-type ligands 1-3, which leads to the formation of a dynamic mixture of homo (4-6) and hetero (7-9) coordination compounds. We report the crystal structures of five such complexes (4, 5, 7-9) which assemble into complementary duplex compounds that further self-organize into double helical- or lamellar-type architectures in the solid state. The ligand exchange between homoduplex complexes in solution leads to the preferential formation of the heteroduplex complexes. As might be expected, these processes display a statistical distribution of homoduplex:heteroduplex:homoduplex complexes of 1:2:1 for the mixtures resulting from 4:6 and 5:6 ligands. However, complex 8 is preferred in a 4:5 mixture which presents a composition of 1:4:1 (amplification factor of about 33%). The Xray structural determinations of selected single crystals resulting from the stoichiometric mixtures of homoduplex complexes show unique heteroduplex superstructures 7-9 in the solid state. The present results present the solid-state structures of homo- and heterocomplexes resulting from terpyridine-type ligands 1-3 and Zn2+ metal ions. The heteroduplex Zn2+ complexes 7-9 are quantitatively crystallized in the solid state by statistical (7, 9) and structural (8) driven selection in solution from a binary mixture of the terpyridine -type complexes and then trapped by crystallization in the solid state.