Three coordination polymers of transition metals built using HPPC ligand: Crystal structures and novel topology

A new pyrazole-carboxylate type ligand, 3-(pyridin-3-yl)-1H-pyrazole-5-carboxylic acid (HPPC) was prepared from 3-acetylpyridine, diethyl oxalate and hydrazine hydrate. By employing this ligand, three new coordination complexes were prepared under solvothermal conditions: {[Ni(PPC)2]·3H2O}n (1), [Ag(PPC)]n (2) and [Cd(PPC)Cl]n (3). Single-crystal X-ray diffraction analyses reveal that 1–3 exhibit three different structural types. Complex 1 displays a 4-connected net with the Schläfli symbol (44·62) topology, several types of hydrogen bonds connect the 2-D layer to a 3-D structure. Complex 2 is built from [Ag(N2O)] clusters and PPC ligand as 3-connected linker with Schläfli symbol {36·46·53} without consideration of Ag⋯Ag interaction. The 2-D networks are also linked to form 3 D framework via Ag⋯Ag interaction. Complex 3 can be regarded as a (3, 3)-connected net with the Schläfli symbol {333·433}, which consists of [Cd(N2O2)] clusters and PPC ligand as 3-connected bridge. The layers are further linked by the cholride atoms to generate a 3-D network.

Graphical abstractIn this paper, we report three polymers which were obtained by 3-(pyridin-3-yl)-1H-pyrazole-5-carboxylic acid (HPPC) and M (NiII, AgI, CdII) under solvothermal conditions. The different coordination modes of HPPC result in one 2-D polymer and two 3-D polymers.Figure optionsDownload full-size imageDownload as PowerPoint slide