Dicyanamide mediated construction of 1D polymeric networks of quinoxaline with d10 metal ions: Synthesis, thermogravimetric analysis, photoluminescence and a theoretical investigation on the π⋯π interactions

Three new dicyanamide (dca) mediated isostructural polymeric complexes of quinoxaline (quin) of d10 metal ions having the formula [M(quin)2(dca)2]n [where M = Zn(II), Cd(II) and Hg(II)] have been synthesized and two of them have been characterized by X-ray single crystal structure analysis. The structure analyses reveal that the complexes are 1D coordination polymers. The π⋯π interaction between the trans-axially coordinated quinoxaline ligand helps in augmenting the dimensionality of the complexes, aligning the coordination polymers into a 2D supramolecular sheet. Hirshfeld surface analysis estimates the relative contribution of various weak forces, accountable for the generation of the supramolecular assembly of the coordination polymers. DFT calculations reveal that the interaction energy amongst the quinoxaline moieties is 0.1357 kcal/mol. All the species exhibit interesting luminescence properties in solution, as well as in the solid state. The π–π interactions occurring between the organic rings and the heavy atom perturbation effect are supposed to be the key factors in controlling the fluorescence efficiency of the complexes. A thermal study indicates the formation of metallic oxide as a thermally stable end product in each case.

Graphical abstractThe interaction of quinoxaline with M(OAc)2 [where M = Zn(II), Cd(II) and Hg(II)] in the presence of the spacer dicyanamide generates one-dimensional coordination polymers. Although the metal ions have no influence in making the structural motifs, they play a crucial role in controlling the luminescence properties of the complexes.Figure optionsDownload full-size imageDownload as PowerPoint slide