Topological modulation of metal–thiadiazole dicarboxylate coordination polymers through auxiliary ligand alteration

Abstract

Five new Co^II/Zn^II coordination polymers (CPs), namely [Co(tdzdc)(4,4′-bipy)(H₂O)]_n (1), {[Co(tdzdc)(bpp)(H₂O)]·3H₂O}_n (2), {[Zn₂(tdzdc)₂(4,4′-bipy)(H₂O)₂]·3H₂O}_n (3), [Zn₂(tdzdc)₂(obpy)(H₂O)₂]_n (4) and [Zn(tdzdc)(tmb)]_n (5), have been synthesized based on the primary ligand 1,2,5-thiadiazole-3,4-dicarboxylic acid (H₂tdzdc) together with four selected N/O-donor auxiliary ligands, i.e., 4,4′-bipy: 4,4′-bipyridine, bpp: 1,3-bi(pyridin-4-yl)propane, obpy: [4,4′-bipyridine]-N,N′-dioxide, and tmb: 1,4-bis((1H-1,2,4-triazol-1-yl)methyl)benzene. Single-crystal structural analyses unveil different topologies and interpenetration degrees of 1–5, associated with four different kinds of coordination modes of H₂tdzdc that depend on the auxiliary ligands used. CPs 1–4 are all constructed by extending the one-dimensional metal–ligand chain through the respective auxiliary ligands. Among them, the linear rigid auxiliary ligands (i.e., bipy and obpy) generate two-dimensional planes of 1, 3 and 4, which exhibit different interpenetration degrees of 0, 2 and 3, respectively, while the flexible bpp auxiliary ligand forms a three-dimensional net of 2. In contrast, CP 5 has a basic structural unit comprising dinuclear metal clusters that facilitate the formation of a 3-fold interpenetrated two-dimensional net extended through the tmb auxiliary ligand. Furthermore, magnetic investigations of the two Co^II-based CPs reveal that despite being mediated by syn–anti bridging of the carboxylate, both 1 and 2 display antiferromagnetic and canted antiferromagnetic behaviors, respectively.