A Reversibly pH-Switchable Open/Closed Cage Constructed from Triangular Polyoxometalate Hybrid [(C₇H₇AsO₃)₆W₁₂O₃₆]^12– Cluster Anions Exhibiting Supramolecular Chirality

A new nanosized polyoxometalate modified by benzylarsonate ligands, [(C₇H₇AsO₃)₆W₁₂O₃₆]^12– (1a), was successfully isolated and structurally characterized as Na₂(C₂H₈N)₄H₆[(C₇H₇AsO₃)₆W₁₂O₃₆]·30H₂O (1). Controlled protonation of 1a led it to self-reorganize into isomer cage cluster [(C₇H₇AsO₃)₆W₁₂O₃₀(OH)₄(H₂O)₂]^4– (2a) with an organic ligand arranging in “half-open” mode. The reversibly switchable cage transform was monitored by ¹H NMR. Also, the origin of the solid supramolecular chirality in the crystal 1 and the aggregation process of 1a were preliminarily studied.