Reactivity Studies of Supramolecules in Solution

Carbonyl-substituted catechols (Fig. 5.21) react with Ti(IV) salts under slightly basic conditions to yield tris-catecholates in a first assembly step. In the presence of Li+ ions (Na and K+ don t do the trick because their ion sizes are larger ), two of these tris-catecholate complexes form dimers bridged by three Li ions [52]. The crystal structures of three representative examples only differing with respect to the 

Tltis example for mass-spectrometrically followed solution-phase reactivity clearly shows, how much information can be derived from some simple measurements. Qualitatively, it can be deduced which mechanisms contribute, which don t. Quantitatively, at least a ranking of the relative rates for the different processes is obtained. Finally, this example makes clear how large the infiuence of the solvent may be. Tlte change of the mixture from pure THF to THF methanol mixtures is not too drastical, but still, significant changes in reaction mechanism and rates are found. 

Reactivity in the Cas Phase Isolated Species instead of Dynamic Interconverting Complexes 

In this Section, two examples will be discussed which rely on IRMPD and CID experiments. It is important to keep in mind that ions in the gas phase are isolated particles, which do not undergo exchange processes among each other. Also, the neutral fragment formed upon dissociation does not come back there is no equilibrium situation. This is the most important difference as compared to condensed-phase studies. The experiments described here thus provide a completely new view on these supramolecules and add new mechanistic insight into their reactivity which cannot be gained in solution where the equilibria present are complex. 

1 Metallosupramolecular Squares A Supramolecular Equivalent to Neighbor Croup Assistance 

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