Record High-Nuclearity Polyoxoniobates: Discrete Nanoclusters {Nb114}, {Nb81}, and {Nb52}, and Extended Frameworks Based on {Cu3Nb78} and {Cu4Nb78}

A series containing the highest nuclearity polyoxoniobate (PONb) nanoclusters, ranging from dimers to tetramers, has been obtained. They include one 114-nuclear {Li-8 subset of Nb114O316}, one 81-nuclear {Li3K subset of Nb81O225}, and one 52-nuclear {H4Nb52O150}. The Nb nuclearity of these PONbs is remarkably larger than those of all known high-nuclearity PONbs (<= 32). Furthermore, the introduction of 3d Cu2+ ions can lead to the generation of extended inorganic-organic hybrid frameworks built from novel, high-nuclearity, nanoscale heterometallic PONb building blocks {H3Cu3Nb78O222} or {H3Cu4(en)Nb78O222}. These building blocks also contain the largest number of Nb centers of any heterometallic PONbs reported to date. The synthesis of new-type PONbs has long been a challenging subject in PONb chemistry.