The first examples of lanthanide(III) organoarsonates, Ln(L1)(H2O)3 (Ln = La (1), H3L1 = 4-hydroxy-3-nitrophenylarsonic acid), Ln(L1)(H2O)2 (Ln = Nd (2), Gd (3)), and mixed-ligand lanthanide(III) organoarsonates, Ln2(HL1)2(C2O4)(H2O)2 (Ln = Nd (4), Sm (5), Eu (6)), were hydrothermally synthesized and structurally characterized. Compounds 1–3 feature a corrugated lanthanide arsonate layer, in which 1D lanthanide arsonate inorganic chains are further interconnected via bridging L13− ligands. Compounds 4–6 exhibit a complicated 3D network. The interconnection of the lanthanide(III) ions by the bridging arsonate ligand leads to the formation of a novel 3D framework with long narrow 1D tunnels along the a-axis, with the oxalate anions are located at the above tunnels and bridging with lanthanide(III) ions. Compounds 2 and 4 exhibit the characteristic emission bands of the Nd(III) ion, whereas compound 6 displays the characteristic emission bands of the Eu(III) ion. The magnetic properties of compounds 3–6 were also investigated.
