Isolation of Non-covalently Bonded Aggregates

In absence of a suitable guest molecule, in general the cavities are filled with solvent molecules. Usually, several of these small compounds are enclosed in the inner space and are relatively loosely bonded and disordered. Using as a host the coordination cage 

Structures held together by metal-metal d-d interaction can also be prepared using encapsulation. Infinite stacking of metal complexes is quite common in the soUd or in the liquid crystalline state and these structures possess interesting electroconductive and 

NMR signal upon inclusion, and by UV spectra of the powdered orange crystals showing a new absorption band at 500 nm. The interactions are weaker in aqueous solution and the color disappears. Similar stacked dimers can be obtained with Pd(acac)2 (2b) and Cu(acac)2 (2c). As a monomer, Cu(acac)2 is a radical with one unpaired electron (S = Vi). ESR spectroscopy reveals the presence of a triplet species (S = 1) and spin-spin interaction between the copper atoms in the complex (26c)2 27. Using a similar approach, higher definite stacked towers can be synthesized consisting of seven or nine large aromatic molecnles.  

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