Conformation-Selective Self-Assembly of Pd 6 Trifacial Molecular Barrels Using a Tetrapyridyl Ligand.

A conformationally flexible tetrapyridyl ligand L was assembled separately with three cis-blocked 90° Pd II acceptors ( M1 , M2 , and M3 ) containing different blocking diamines. Surprisingly, different conformations of the donor L were arrested by the acceptors depending on the nature of the blocking amine, leading to the formation of isomeric Pd 6 barrels ( B1 , B2 , and B3 ). B2 and B3 with larger windows have been used to encapsulate polyaromatic hydrocarbons.