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 (λ_ex = 320 nm) and 517 nm (λ_ex = 312 nm), respectively, which originate from the ligand-to-metal charge transfer (LMCT) transition.