Structural Diversity of Lanthanum–Organic Frameworks Based on 1,4-Phenylenebis(methylene)diphosphonic Acid

Abstract

The preparation of five different compounds, [La2(H2pmd)3(H2O)12] (1: 1D), [La2(H2pmd)(pmd)(H2O)2] (2: 3D), [La(H3pmd)(H2pmd)(H2O)] (3: 3D), [La2(H2pmd)3(H2O)2] (4: 3D), and [La2(H2pmd)(pmd)(H2O)4] (5: 3D), as crystalline materials from the reaction of 1,4-phenylenebis(methylene)diphosphonic acid (H4pmd) with lanthanum chloride is reported. Two different, fast, and economically viable synthetic approaches were employed with their various parameters being probed and, when possible, optimized to increase yields and purity: microwave-assisted synthesis (MWAS, in ca. 1 min) and a bench procedure using standard ambient conditions (one-pot, ca. 10 min). Compounds 1 and 2 were isolated as phase-pure crystalline materials. Compounds 3 and 4 were characterized by single-crystal X-ray diffraction from mixtures, and compound 5 was identified by powder X-ray diffraction studies (also from a physical mixture with 2). Structural details for all compounds were investigated by using in tandem X-ray diffraction (single-cr...