Positional isomerism of unsymmetrical semirigid ligands toward the construction of discrete and infinite coordination architectures of zinc(ii) and cadmium(ii) complexes

Abstract

Three unsymmetrical semirigid ligands, HInMe-n-py (n = 2, 3, 4), showing positional isomerism have assembled with ZnCl 2 and CdCl 2 to yield supramolecular coordination assemblies. Compoundhas a two-dimensional rhombus gridlike (4,4) layer structure constructed from the dinuclear paddlewheel [Zn 2 (O 2 C) 4 N 2 ] units with two pendant side-arms. Compound [Zn 2 Cl 2 (InMe-3-py) 2 (HInMe-3-py) 2 ] (2) forms a discrete armed M 2 L 2 macrocycle, which connects with others by intermolecular O-H⋯O and C-H⋯Cl hydrogen bonds to give rise to a decorated three-dimensional supramolecular pcu net. Compound [Zn(InMe-4-py) 2 ]•1/2H 2 O (3) adopts a two-dimensional chiral wavy (4,4) square grid. Opposite-handedness chiral wavy grids are stacked in an ABAB type of sequence that has small voids accommodating lattice water molecules. Compound [CdCl(InMe-3-py)] (4) displays a two-dimensional achiral meso layer in which the opposite-handedness Cd-L helical chains are interconnected by the Cd-O bridging bonds and stitched by zigzag Cd-Cl chains. Compound [Cd(InMe-4-py) 2 (H 2 O) 2 ] (5) features a two-dimensional rhombus gridlike (4,4)-net.Through the connections of net-to-net O-H⋯O hydrogen bonds, the grids are offset-stacked to be a hydrogen-bonded three-dimensional oblique pcu net. The structural diversity and complexity in these supramolecular coordination architectures are most likely attributed to the various coordination modes adopted by these N-and O-donor ligands of different substituent position and the coordination preference exhibited by the metal ions. Thermogravimetric (TG) analyses showed that all the frameworks of compounds 1-5 exhibit a thermal stability higher than 300 °C. In addition, the solid-state photoluminescent properties of compounds 1-5 were investigated.

Concomitant Crystallization of Genuine Supramolecular Isomeric Rhombus Grid and Ribbon

“…Their molecular structures were determined by single-crystal X-ray structure analyses and further characterized by elemental analyses, infrared (IR) spectra, and thermogravimetric (TG) analyses, and the bulk phase purity of the compounds were confirmed by X-ray powder diffraction (XRPD) patterns (Figures S1 and S2, Supporting Information). In the solid IR spectra of 1 and 2 (Figure S3), the characteristic absorptions of the trimellitic imide carbonyl groups were observed at 1772 and 1714 cm –1 for 1 and at 1775 and 1712 cm –1 for 2 , which are slightly blue-shifted relative to those of the free HInMe-4-py ligand (1770 and 1703 cm –1 ) . Further, the broad bands centered at 3406 cm –1 for 1 and 3471 and 3384 cm –1 for 2 indicate the presence of hydroxyl groups from the coordinated water molecules.…”

“…In the solid IR spectra of 1 and 2 (Figure S3), the characteristic absorptions of the trimellitic imide carbonyl groups were observed at 1772 and 1714 cm −1 for 1 and at 1775 and 1712 cm −1 for 2, which are slightly blue-shifted relative to those of the free HInMe-4-py ligand (1770 and 1703 cm −1 ). 18 Further, the broad bands centered at 3406 cm −1 for 1 and 3471 and 3384 cm −1 for 2 indicate the presence of hydroxyl groups from the coordinated water molecules.…”

“…Chemical reagents were purchased commercially and were used as received without further purification. 4-(2-Pyridylmethyl)-1,3-dioxoisoindoline-5-carboxylic acid (HInMe-4-py) ligand was prepared according to a literature method . Thermogravimetric (TG) analyses were performed under nitrogen with a Thermo Cahn VersaTherm HS TG analyzer.…”

“…4-(2-Pyridylmethyl)-1,3-dioxoisoindoline-5-carboxylic acid (HInMe-4py) ligand was prepared according to a literature method. 18 Thermogravimetric (TG) analyses were performed under nitrogen with a Thermo Cahn VersaTherm HS TG analyzer. X-ray powder diffraction (XRPD) measurements were recorded on a Siemens D-5000 diffractometer with a graphite monochromatized Cu Kα radiation (λ = 1.5406 Å) at 40 kV and 30 mA, with a step size of 0.02°in θ and a scan speed of 1 s per step size.…”

“…As part of our ongoing efforts directed toward the design and synthesis of functional crystalline materials, − we report herein on two infinite coordination architectures of different polymorphs and network topologies (a rhombus grid and a ribbon) obtained from the assembly of Co(NO 3 ) 2 ·6H 2 O and 4-(2-pyridylmethyl)-1,3-dioxoisoindoline-5-carboxylic acid (HInMe-4-py). These two cobalt(II) compounds having exactly the same chemical components are important genuine supramolecular isomers because they are crystallized in the same reaction bath under hydro(solvo)thermal conditions.…”