Facile Separation of Regioisomeric Compounds by a Heteronuclear Organometallic Capsule

Owing to the often-similar
physical and chemical properties of
structural isomers of organic molecules, large efforts have been made
to develop efficient strategies to isolate specific isomers. However,
facile separation of regio­isomeric compounds remains difficult.
Here we demonstrate a universal organometallic capsule in which two
silver centers are rigidly separated from each other by two tetranuclear
[Rh4] pyramidal frustums, which selectively encapsulate
a specific isomer from mixtures. Not only is the present heterometallic
capsule suitable as a host for the encapsulation of a series of aromatic
compounds, but also the receptor shows widely differing specificity
for the various isomers. Direct experimental evidence is provided
for the selective encapsulation of a series of para (p)-disubstituted benzene derivatives, such as p-xylene, p-dichloro­benzene, p-dibromo­benzene, and p-diiodo­benzene.
The size and shape matching, as well as the Ag−π interactions,
are the main forces governing the extent of molecular recognition.
The encapsulated guest p-xylene can be released by
using the solid–liquid solvent washing strategy, and the other
guest molecules are easily liberated by using light stimulus.