Nitroaromatic-detecting zinc and cadmium coordination polymers with methyl-substituted aliphatic dicarboxylate and 4,4′-dipyridylamine ligands and diverse topologies

Abstract

Hydrothermal reaction of a metal nitrate, a methyl-substituted aliphatic dicarboxylic acid, and the hydrogen-bonding capable 4,4′-dipyridylamine (dpa) ligand afforded four crystalline coordination polymers whose dimensionality, topology, and interpenetration scheme depends on the aliphatic tether length, methyl group position, and coordination geometry at the metal. The four new phases were structurally characterized via single-crystal X-ray diffraction. [Zn(22dmg)(dpa)]n (1, 22dmg = 2,2-dimethylglutarate) displays a system of mutually inclined interpenetrated (4,4) grid coordination polymer layers. [Zn(33dmg)(dpa)]n (2, 33dmg = 3,3-dimethylglutarate), in contrast to 1, displays a stacked arrangement of pairs of (4,4) grid coordination polymer layers, without any interpenetration. [Zn(3mad)(dpa)]n (3, 3mad = 3-methyladipate) possesses a system of four-fold interpenetrated 66dia topology coordination polymer networks. [Cd(33dmg)(dpa)]n (4) displays a 2-fold interpenetrated 41263pcu 3D topology, based on pillaring of dimer-based [Cd2(33dmg)2]n layers by pairs of dpa ligands. Luminescent behavior in 1–4 is attributed to intra-ligand molecular orbital transitions within the dpa aromatic pyridyl rings. The new phases were also surveyed for the ability to detect nitroaromatics in ethanol suspension, with 4 providing optimum response for nitrobenzene detection. Thermal decomposition behavior is also discussed herein.