Hydrothermal reactions of lanthanide(III) salts with m-sulfophenylphosphonic acid (H3L1) and 1,10-phenanthroline (phen) or N, N'-piperazinebis(methylenephosphonic acid) (H4L2) afforded six novel lanthanide(III) sulfonate-phosphonates based on tetranuclear clusters, namely, [La-2(L-1)(2)(phen)(4)(H2O)], 4.5H(2)O (1), [Ln(2)(L-1)(2)(phen)(2)(H2O)(5)] center dot 3H(2)O (Ln = Nd, 2; Eu, 3; Er, 4), and [Ln(2)(HL1)(H2L2)(2)(H2O)(4)]center dot 8H(2)O (Ln = La, 5; Nd, 6). Compounds 2 - 4 contain discrete tetranuclear lanthanide( III) cluster units in which four lanthanide(III) ions are bridged by two tridentate and two tetradentate phosphonate groups. In compound 1, the tetranuclear clusters are further interconnected into a 1D chain through the coordination of the sulfonate groups. The structures of compounds 5 and 6 can be viewed as a 3D architecture based on a different types of tetranuclear cluster units that are interconnected by bridging H2L2 anions. In the tetranuclear clusters of compounds 5 and 6, the four lanthanide(III) centers are interconnected by only two HL1 ligands. Compound 2 is a luminescent material in the near-IR region, whereas compound 3 displays a strong luminescent emission band in the red-light region. Magnetic property measurements of compounds 2 - 4 and 6 indicate that there are strong antiferromagetic interactions between magnetic centers within the cluster units.