Structural Diversity and Fluorescence Regulation of Three ZnII Coordination Polymers Assembled from Mixed Ligands Tectons

Abstract

By adopting a mixed-ligand strategy, three ZnII coordination polymers were prepared by hydrothermal reactions of zinc(ii) acetate with flexible 1,2-phenylenediacetic acid (H2phda) combining with three nitrogen-rich tectons namely, [Zn2(phda)2(bpo)2]n·2H2O (1), [Zn(phda)(pytz)]n (2), and [Zn(phda)(bib)]n·H2O (3) (where bpo = 2,5-bis(4-pyridyl)-1,3,4-oxadiazole, pytz = 3,5-di(4-pyridyl)-1,2,4-triazole, and bib = 1,4-bis(imidazol-1-yl)benzene). The single-crystal X-ray diffraction patterns reveal that the three compounds contain metal(ii)-carboxylate chains further extended by such nitrogen-rich co-ligands to afford a vast diversity of structures from two-dimensional (2D) stepwise grids (1), 2D double layers (2), to three-dimensional (3D)→3D 4-fold interpenetrating diamondoid networks. Furthermore, the structural differences in these complexes are primarily affected by the introduction of N-donor ancillary co-ligands so that their solid-state photoluminescence properties exhibit various emission spectra. Especially, compound 3 shows a guest-sensitive luminescence behaviour, which may be useful in applications as guest sensors.