Construction of four coordination polymers with helical character based on a flexible bis(triazole) derivative and dicarboxylate coligands

Based on the flexible bis(triazole) derivative 1,4-bis(1,2,4-triazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene (btmx) and dicarboxylate coligands, four new coordination polymers, namely, [Zn(phsa)(btmx)]n (1), [Zn(o-phda)(btmx)]n (2), {[Cd(p-phda)(btmx)(H2O)]·H2O}n (3), and [Cd(4,4′-sdba)(btmx)]n (4) have been synthesized under hydrothermal conditions. Structural analyses reveal that complexes 1–4 display diverse helical characters under the influence of dicarboxylates with different spacers. Complex 1 exhibits a 3D framework structure with left- and right-handed triple-stranded helices. Complex 2 features an irregular 2D grid constructed from double helices with (44·62) topology. The point symbol of complex 3 is (68·82)(63). Remarkably, it possesses a binodal (3,5)-connected 3D framework with the appearance of left- and right-handed triple-helical chains along the c axis. Moreover, left- and right-handed single-helical chains come into being through alternative arrangement of these triple-helical chains. To the best of our knowledge, coordination polymers containing triple- and single-helical chains along the same crystallographic axis are rare. The structure of complex 4 is a 2D grid comprising double helix components with (44·62) topology. These results indicate that the spacers of dicarboxylate coligands have significant effects on the helical character and ultimate frameworks. In addition, the investigation of photoluminescence properties reveals that complexes 1–4 show different photoluminescent behaviors.