Hydrothermal reactions of manganese(II) salts with o-sulfophenylarsonic acid (o-HO3S-C6H4-AsO3H2, H3L) afforded Mn-3(L)(2)(H2O)(3)center dot H2O (1) with a layered structure. When 1,10-phenanthroline (phen), 2,2'-bipyridine (bipy), and 2,2':6',2 ''-terpyridine (terpy) were used as auxiliary chelating ligands, a series of mixed-ligand manganese(II) sulfonate-arsonates with lower dimensional structures, namely, [Mn(HL)(phen)(2)](2)center dot 8.5H(2)O (2), Mn(HL)(phen)(2)(H2O)center dot 2H(2)O (3), [Mn(HL)(bipy)(2)][Mn(H2L)(bipy)(2)](CIO4)center dot 3H(2)O (4), [Mn(HL)(phen)][Mn(HL)-(phen)(H2O)] (5), [Mn-2(HL)(phen)(4)(H2O)](CIO4)(2)center dot 4H(2)O (6), [Mn-2(HL)(phen)(4)(H2O)(CIO4)(2)center dot H2O (7), Mn-2(HL)(2)-(bipy)(3)(H2O)center dot H2O] (8), [Mn(HL)(terpy)](2) (9), Mn-7(OH)(2)(L)(4)(phen)(8)center dot 10H(2)O center dot phen (10), and Mn(HL)(bipy)-(H2O)center dot 2H(2)O (11) have been obtained. 2-4 are mononuclear (4 contains two different mononuclear cluster units) whereas 5-9 feature three types of isolated dinuclear cluster units in which the two Mn2+ ions are bridged by one or two sulfonate-arsonate ligands. 10 exhibits an interesting heptanuclear cluster in which the Mn2+ centers are bridged by arsonate, sulfonate groups and hydroxyl anions. 11 features a one-dimensional (1D) chain in which two neighboring Mn2+ centers are bridged by an arsonate group of a sulfonate-arsonate ligand. Magnetic measurements indicate that 1 exhibits an unprecedented spin topology and behaves as a homospin ferrimagnet whereas 2-4 are essentially paramagnetic. 5-9 and 11 are weakly ant ferromagnetic.