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

Abstract

Five new CoII/ZnII 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 CoII-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.