Syntheses, crystal structures, and characterizations of a series of divalent metal carboxylate-phosphonates

Abstract

The hydrothermal reactions of divalent metal salts with 4-HOOC–C6H4–CH2–NH2CH2PO3H2 (H3L) led to four Metal-organic phosphonates (MOPs), namely, Ni(HL)(H2O)2 (1), Cd(HL) (2), CdCl(H2L) (3), and Pb1.5Cl2(H2L) (4). All these compounds exhibited 2D layer substructures with various features based on metal centers and –PO3 groups of the ligands. Differently, the layers cross-linked each other in compounds 1 and 4via hydrogen bonds generating 3D supramolecular frameworks. While in compounds 2 and 3, they were connected by carboxylate group of the ligands to form 3D pillared-layer frameworks. Such differences were related to the coordination mode of the metal centers, and the pH of the reaction system also played a important role on the coordination ability of the ligands. The magnetic properties reveal the presence of ferromagnetic interactions in compound 1 through a Ni–O–P–O–Ni five-member chain. Luminescent measurements indicate that compounds 2–4 each displays strong blue fluorescent emissions.