Ligand Isomer Effect on the Formations of Supramolecular Lead(II), Mercury(II), and Copper(II)/Mercury(II) Complexes of Bis-O₂S₂-Macrocycle

Abstract

In addition to ortho-isomer (o-bis-L) and meta-isomer (m-bis-L) of bis-O2S2-macrocycle obtained previously, its para-isomer (p-bis-L) was newly isolated, and the complete isomer series were structurally characterized by single crystal X-ray analysis. In complexations, borderline (Pb2+) and soft (Hg2+ and Cu+) metal salts were employed to investigate the isomer effect on the coordination modes and topologies of the supramolecular complexes. Lead(II) perchlorate afforded an infinite one-dimensional (1-D) coordination polymer {[Pb2(o-bis-L)(μ-ClO4)2(ClO4)2]}n (1) and a discrete complex [Pb2(m-bis-L)(CH3CN)2(H2O)2(ClO4)2](ClO4)2 (2), both of which are based on the endocyclic binuclear complexes mainly due to the oxophilicity of the lead(II) ion. Meanwhile, mercury(II) halides showed an endocyclic dinuclear complex [Hg2(o-bis-L)I2][Hg3I8] (3) and an exocyclic 1-D coordination polymer [Hg3(m-bis-L)Br6]n (4) because the differences of sulfur-to-sulfur separation in the free ligand isomers might induce the different coordination modes. When a mixture of mercury(II) iodide and copper(I) iodide was used in the reaction with m-bis-L, a heterometallic 1-D coordination polymer [Cu2Hg2(m-bis-L)(μ-Cu2I2)(CH3CN)2I6]n (5) was obtained. In 5, exocyclic dicopper(I) complex units are linked by −Hg-Cu2I4-Hg– segments to form an infinite zigzag chain. Consequently, unlike the borderline metal, the soft metal ions show the sulfur-to-sulfur separation dependent coordination modes. These results demonstrate how small differences in the ligand isomers impact their self-assembled coordination products in terms of coordination mode and topological structure including dimensionality.