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 <b>1</b>–<b>5</b> with a flexible disulfide derivative of the nicotinate 6,6′-dithiodinicotinic acid (H₂cpds) and two rodlike <i>N</i>,<i>N</i>′-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}_<i>n</i> (<b>1</b>), {[Zn(cpds)(bpa)_0.5]}_<i>n</i> (<b>2</b>), {[Zn(cpds)(bpp)]}_<i>n</i> (<b>3</b>), {[Cd(cpds)(bpa)_1.5]·H₂O}_<i>n</i> (<b>4</b>), and {[Cd₂(cpds)₂(bpp)·(H₂O)₃]·4H₂O}_<i>n</i> (<b>5</b>). Complexes <b>1</b>–<b>5</b> 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 <b>2</b>–<b>4</b> all exhibit 2D layer structures, in which <b>2</b> displays a 2-fold 2D → 2D parallel interpenetration framework containing a rotaxane-like motif and <b>3</b> is a 2D 4⁴ gridlike layer. Compound <b>4</b> 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 <b>1</b>, and a 3-fold interpenetrating network with (4⁶·6⁴) topology by considering the cadmium dimer unit as a five-connected node for <b>5</b>, 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.