Symmetry Breaking of α‑[H₂W₁₂O₄₀]^6– Depends on the Transformation of Isopolyoxotungstates

Two enantiotopic 1D chain compounds, [Cu3(L1)3(H2O)2(H2W12O40)]·4H2O (1a,b; L1 = 2-(4,6-bis­(pyridin-2-yl)­pyridin-2-yl)­pyridine), crystallizing in the chiral space group P212121 were prepared and spontaneously resolved in the absence of any chiral source. Interestingly, compounds 1a,b can be prepared from a [W7O24]6– aqueous solution, [(n-C4H9)4N]4[W10O32], or Na10[H2W12O42], but when [H2W12O40]6– aqueous solution was the starting material, the achiral compound [CuL1]2[H4W12O40]·5H2O (2) was obtained. When a terpyridine ligand (L2) having a coordination mode similar to that of L1 was used, the mesomeric dimer [Cu3(L2)3(H2O)­(H2W12O40)]2·4H2O (3) was obtained from [W7O24]6– aqueous solution or Na10[H2W12O42], but from [H2W12O40]6– aqueous solution only compound [Cu2(L2)2Cl2]2[W10O32] (4) was isolated. It is notable that in compounds 1a,b and 3 the symmetry of the α-[H2W12O40]6– cluster is broken by asymmetric coordination with metal–organic units in a similar mode. As the asymmetric subunit based on a tridecorated [H2W12O40]6– cluster can be obtained from several isopolyoxotungstate sources except for [H2W12O40]6–, we speculate that the symmetry breaking of α-[H2W12O40]6– depends on the transformation of isopolyoxotungstates. Furthermore, during the transformation a possible reaction intermediate as the precursor for 1a,b, compound [Cu3(L1)3(H2O)3(H4W11O38)] (5), has been presented and characterized by density functional theory (DFT) calculations.