Cation-induced assembly of Zn(II), Cd(II) and Hg(II) coordination complexes and DFT calculations to evaluate weak interactions between the helical chains

Abstract

Two new coordination polymers [ZnLI2]∞ (1) and [CdLI2]∞ (2) (L: 3,6-di-(1,2,4-triazole-1-yl)-N-hexylcarbazole) were synthesized and their crystal structures were determined by single-crystal X-ray diffraction techniques. Complexes are both constructed with the helical chains along the 2 1 screw axis. The coordination bond, C-H…I weak interactions and π-π interactions play significant roles in constructing their 3D or 2D frameworks. Two different DFT calculations are performed for the weak interactions between the helical chains of the three different coordination polymers ([ZnLI2]∞, [CdLI2]∞ and the reported [HgLI2]∞). The results reveal that weak interactions play important roles in these supramolecular systems of helical configuration, namely, the trend is the shorter H…I distance and π-π stacking distance, the stronger the intermolecular interactions. The photoluminescence of the complexes measured in the solid state at room temperature indicates that the emission intensity varies extensively, which can be rationalized by the heavy atom effect.