Symmetry breaking of α-[H₂W₁₂O ₄₀]^6- depends on the transformation of isopolyoxotungstates

Two enantiotopic 1D chain compounds, [Cu₃(L1)₃(H ₂O)₂(H₂W₁₂O₄₀)] ·4H₂O (1a,b; L1 = 2-(4,6-bis(pyridin-2-yl)pyridin-2-yl) pyridine), crystallizing in the chiral space group P2₁2 ₁2₁ 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-C ₄H₉)₄N]₄[W₁₀O ₃₂], 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 [W₇O ₂₄]^6- aqueous solution or Na₁₀[H ₂W₁₂O₄₂], but from [H₂W ₁₂O₄₀]^6- aqueous solution only compound [Cu₂(L2)₂Cl₂]₂[W₁₀O ₃₂] (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 [H ₂W₁₂O₄₀]^6- cluster can be obtained from several isopolyoxotungstate sources except for [H₂W ₁₂O₄₀]^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(H ₄W₁₁O₃₈)] (5), has been presented and characterized by density functional theory (DFT) calculations.