New thorium(iv)–arsonates with a [Th8O13]6+ octanuclear core†
Abstract
Three new octanuclear Th(IV) arsonates, namely [Th8(O)(L)6(HL)6(H2O)12]·19.5H2O (1) (H3L = o-HO3S–C6H4–AsO3H2), [Th8(O)(L)6(HL)6(H2O)10]·17H2O (2) and [Th8(O)(L)6(HL)6(H2O)5]·0.5H2O (3), with o-sulfophenylarsonic acid as the bridging ligand, have been prepared under hydrothermal conditions. Each complex contains [Th8O13]6+ octanuclear cluster cores composed of two [Th4O6]4+ units bridged by a μ2-oxo anion. The structure of compound 1 features a 0D highly symmetric polynuclear cluster encapsulating the octanuclear core of [Th8O13]6+ which is further decorated by six L3− and six HL2− ligands. Compound 2 features one-dimensional chains along the b-axis in which the neighboring clusters similar to 1 are bridged by a pair of sulfophenylarsonate ligands via M–O–S–O–M bridges. Compound 3 with chiral P212121 features two-dimensional cluster layers, in which each cluster connects with four neighbors via four M–O–S–O–M linkages. Compounds 2 and 3 display unusual broad green light emission bands at 523 nm (λex = 320 nm) and 517 nm (λex = 312 nm), respectively, which originate from the ligand-to-metal charge transfer (LMCT) transition.