Four‐Shell Polyoxometalates Featuring High‐Nuclearity Ln₂₆ Clusters: Structural Transformations of Nanoclusters into Frameworks Triggered by Transition‐Metal Ions

Abstract

A series of polyoxometalates (POMs) that incorporate the highest-nuclearity Ln clusters that have been observed in such structures to date (Ln₂₆ , Ln=La and Ce) are described, which exhibit giant multishell configurations (Ln⊂W₆ ⊂Ln₂₆ ⊂W₁₀₀ ). Their structures are remarkably different from known giant POMs that feature multiple Ln ions. In particular, the incorporated Ln-O clusters with a nuclearity of 26 are significantly larger than known high-nuclearity (≤10) Ln-O clusters in POM chemistry. Furthermore, they also contain the largest number of La and Ce centers for any POM reported to date and represent a new kind of rare giant POMs with more than 100 W atoms. Interestingly, the La₂₆ -containing POM can undergo a single-crystal to single-crystal structural transformation in the presence of various transition-metal ions, such as Cu²⁺ , Co²⁺ , and Ni²⁺ , from an inorganic molecular nanocluster into an inorganic-organic hybrid extended framework that is built from POM building blocks with even higher-nuclearity La₂₈ clusters bridged by transition-metal complexes.