Syntheses and Crystal Structures of a Series of Zn(II)/Cd(II) Coordination Polymers Constructed from a Flexible 6,6′-Dithiodinicotinic Acid

Abstract

Five novel Zn(II)/Cd(II)-based coordination polymers 1–5 with a flexible disulfide derivative of the nicotinate 6,6′-dithiodinicotinic acid (H2cpds) and two rodlike N,N′-donor ligands (bpa =1,2-bi(4-pyridyl)ethane; bpp = 1,3-bis(4-pyridyl)propane) have been successfully synthesized under the liquid diffusion condition and characterized by elemental analysis, IR spectra, and X-ray diffraction, namely {[Zn(cpds)]·H2O}n (1), {[Zn(cpds)(bpa)0.5]}n (2), {[Zn(cpds)(bpp)]}n (3), {[Cd(cpds)(bpa)1.5]·H2O}n (4), and {[Cd2(cpds)2(bpp)·(H2O)3]·4H2O}n (5). Complexes 1–5 display various coordination motifs due to different conformations, and coordination modes of the H2cpds ligand, at the same time the effect of the auxiliary ligands plays important roles in the construction of extended supramolecular networks. Complexes 2–4 all exhibit 2D layer structures, in which 2 displays a 2-fold 2D → 2D parallel interpenetration framework containing a rotaxane-like motif and 3 is a 2D 44 gridlike layer. Compound 4 contains two kinds of 2D chiral layers composed of three types of single-helical chains and two types of double-stranded helices. Two high-dimensional complexes (3D) with a microporous network containing a 1D metal–organic nanotube filled with plenty of free water molecules for 1, and a 3-fold interpenetrating network with (46·64) topology by considering the cadmium dimer unit as a five-connected node for 5, are observed. Solid-state properties of thermal stability, X-ray powder diffractions, and the photoluminescence properties at room temperature for these crystalline materials have been investigated.