Self-assembly of organic acid–base compounds from 2-D layered network to 3-D supramolecular framework: synthesis, structure and photoluminescence

Abstract

The reactions of organophosphonic acids [1-aminoethylidenediphosphonic acid (AEDPH₄), 1-aminopropane-1,1,3-triphosphonic acid (APTPH₆)] and 2,2′-bipyridyl-like ligands [2,2′-bipyridyl (bipy), 1,10-phenanthroline (phen)] under low temperature hydrothermal conditions yielded four acid–base compounds, namely, (AEDPH₃)·(H₂bipy)_1/2·2H₂O (1), (AEDPH₃)·(Hphen)·2H₂O (2), (APTPH₅)·(Hbipy)·2H₂O (3) and (APTPH₄)·(Hphen)·(H₃O)·3H₂O (4). These four compounds were characterized by a single crystal X-ray diffraction method, elemental analysis (EA), infrared spectrometry (IR) and thermogravimetric analysis (TGA). They all crystallize in a triclinic system, with a P space group. In particular, the supramolecular structures of organophosphonic acids in these four compounds are different. In compounds 1 and 2, the dimer or dimer chains are formed by hydrogen bonds between adjacent phosphonate groups, while in compounds 3 and 4 two-dimensional (2-D) layered networks are constructed by the hydrogen bonds between the phosphonate groups. The diversity of supramolecular structures is due to the difference of AEDPH₄ and APTPH₆ ligands. Additionally, their luminescence in the solid state has also been studied at room temperature.