Homo‐ and Heteroduplex Complexes Containing Terpyridine‐Type Ligands and Zn²⁺

Abstract

Abstract We describe a study of the equilibrium binding of Zn 2+ 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 X‐ray 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 Zn 2+ metal ions. The heteroduplex Zn 2+ 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. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)