Investigation on three new metal carboxydiphosphonates: Syntheses, structures, magnetic and luminescent properties

A new multifunctionalized phosphoric acid, (2-(diphosphonomethylamino)nicotinic acid, Py(COOH)(NHCH(PO3H2)2), H5L1), has been employed as ligand for the construction of new metal phosphonates. By reacting it with different metal chlorides under hydrothermal condition, three new transition metal phosphonates, namely, [Co2(HL1)(H2O)5][H2O]3 (1), Zn(H3L1) (2) and [Cd(H3L1)(H2O)2][H2O] (3) were successfully obtained. The single-crystal structure measurements indicated that the coordination mode of ligand H5L1 is metal-dependant and results in different structures. For compound 1, it features 2D layered structure. Whereas compounds 2 and 3 have 1D chain structures. Under the excitation of 250 nm light, both compounds 2 and 3 show intraligand and ligand to metal charge transfer (LMCT) emission bands at about 415 and 420 nm, respectively. Magnetic study shows that compound 1 displays antiferromagnetic behavior.