Old Clusters with New Tricks: Engineering S⋅⋅⋅S Interactions and Novel Physical Properties in Sulfite‐Based Dawson Clusters

Unprecedented 18‐molybdosulfite Dawson clusters encapsulate two pyramidal sulfite ions as templates, and exhibit a short S⋅⋅⋅S interaction between the two ions, which was characterized by DFT calculations. The [Mo18O54(SO3)2]4− ion is the first discrete thermochromic polyoxometalate cluster: its color varies from pale yellow at 77 K to deep red at 500 K (see picture).