Four M(II)-coordination polymers (M = Zn(II) and Cd(II)) based on a flexible 1,2-bis(pyridin-3-yloxy)ethane ligand: Syntheses, structures and photoluminescent properties

Four coordination polymers, namely {[Zn(L)2](ClO4)2}n (1), [Zn(L)(ipa)]n (2), [Cd(L)(chdc)⋅2H2O]n (3) and [Cd(L)0.5(pydc)⋅0.5H2O]n (4) (H2ipa = isophthalic acid, H2chdc = cyclohexane-1,4-dicarboxylic acid, H2pydc = pyridine-2,6-dicarboxylic acid), have been synthesized based on a flexible ligand 1,2-bis(pyridin-3-yloxy)ethane (L) under hydrothermal conditions. Their structures are determined by X-ray single-crystal analyses, IR spectra and X-ray powder diffractions (XRPD). In 1, the infinite 2D square sheets arrange regularly to form 1D channels containing ClO 4 - anions. 2 exhibits wave-like network, which is further extended into a 3D framework via interlayer C−H⋯X (X = π, O) interactions. With different co-ligands, 3 shows a 2D structure, while 4 exhibits a intriguing 3D supramolecular framework. In 1–4, L adopts different conformations in the solid state. The various conformations of L, with the different co-ligands, play an important role in structural diversity. The thermogravimetric analyses and photoluminescent properties of them were also investigated.