Novel amine templated three-dimensional zinc-organophosphonates with variable pore-openings

Abstract

Five new amine-templated zinc-organophosphonate compounds have been synthesized hydrothermally in the presence of zinc, 1-hydroxyethane-1,1-diphosphonic acid (H₄hedp) as the diphosphonate ligand and different aliphatic amines. All the five compounds have three-dimensional open-framework structures, which are formed by the connectivity between zinc ions and diphosphonate ligands, and the biprotonated amines are present inside the open-channels. Five different amines, namely ethylenediamine (EDA), diethylenetriamine (DETA), 1,2-diaminopropane (1,2-DAP), 1,3-diaminopropane (1,3-DAP) and diazobicyclooctane (DABCO), have been used to obtain three different classes of framework structures, and such types of amine-templated frameworks are observed for the first time in the family of organophosphonates. Compound I, [C₂N₂H₁₀][Zn₃(hedp)₂]·H₂O, and compound II, [C₄N₃H₁₅][Zn₃(hedp)₂], have similar framework structures, though these compounds have been synthesized in the presence of EDA and DETA, respectively. Compound III, [C₃N₂H₁₂][Zn₃(hedp)₂], and compound IV, [C₃N₂H₁₂][Zn₃(hedp)₂], have the same molecular formula and framework structures; however, their amines are different, i.e. 1,2-DAP and 1,3-DAP, respectively. Compound V, [C₆N₂H₁₄][Zn₃(hedp)₂], forms a different three-dimensional framework from the above structures in the presence of DABCO. By varying the amine molecules from EDA to 1,2-DAP or DABCO, the ring size can be tuned from 4-, 5-, 6-, and 8-membered to only 6-, and 8-membered. All the compounds have also been characterized by powder XRD, IR spectroscopy, and TGA. The luminescence properties of compounds I–V have also been studied.