Lanthanide oxalatophosphonates with two types of layered structures: syntheses, structures, luminescence and magnetic properties

Two types of lanthanide( iii ) oxalatophosphonates, namely, [Ln(H 2 L)(C 2 O 4 )]·H 2 O [Ln = La ( 1 ), Ce ( 2 ), Pr ( 3 )] and [Ln 2 (H 3 L)(C 2 O 4 ) 3 (H 2 O) 4 ]·2H 2 O [Ln = Eu ( 4 ) and Dy ( 5 )] have been hydrothermally obtained by using (4-carboxypiperidyl)- N -methylenephosphonic acid (H 3 L) as the phosphonate ligand and oxalate as the second ligand. These five compounds have the same precursor, but they exhibit two different 2D layered structures. Compounds 1-3 are isostructural and exhibit a 2D layered structure in which {Ln(1)O 9 }, {Ln(2)O 9 } and {CPO 3 } polyhedra via corner-sharing and edge-sharing are interconnected into a 1D chain. These chains are further cross-linked by oxalate anions into a 2D layered structure, and the uncoordinated carboxylate groups are oriented toward the interlayer space. Compounds 4 and 5 are isostructural and also show a 2D layered structure. Lanthanide ions are interconnected by oxalate anions forming a 2D layered structure, and the carboxyl groups of H 3 L are grafted on the two sides of the layer. The structure variations are attributed to the effect of lanthanide contraction. In addition, the luminescence properties of compounds 4 and 5 , and the magnetic properties of compound 5 have been studied. Five novel lanthanide( iii ) oxalatophosphonates with two types of 2D layered structures have been hydrothermally obtained and structurally characterized. The luminescence and magnetic properties of the title compounds have been studied.