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

A new multifunctionalized phosphoric acid , (2-(diphosphonomethylamino)nicotinic acid, Py(COOH)(NHCH(PO 3 H 2 ) 2 ), H 5 L 1 ), 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, [Co 2 (H L 1 )(H 2 O) 5 ][H 2 O] 3 ( 1 ), Zn(H 3 L 1 ) ( 2 ) and [Cd(H 3 L 1 )(H 2 O) 2 ][H 2 O] ( 3 ) were successfully obtained. The single-crystal structure measurements indicated that the coordination mode of ligand H 5 L 1 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.