Metal-cage interaction

The nearest La-C distance, 2.55(8) A (ionic radius of La(III) 1.15 A), is slightly larger than the nearest Sc-C distance, 2.53(8) A(ionic radius of Sc(III) 0.81 A), of Sc C82, which results in a weaker metal-cage interaction for La C82. In fact, the IR/Raman spectroscopic studies [31,32] on metallofullerenes by metal-cage vibrational mode measurements indicated that the La-cage vibration is much smaller in energy than those observed in other M C82 (M=Y, Sc, Tm)-type metallofullerenes. 

Fig. 36 A cage held together by both metal-ligand interactions and hydrogen bonds...

It is quite challenging to rmderstand in what way the zeolite influences the metal compared to other supports. The electronic changes that could be induced by the pore system are quite subtle and metal particle size effects may overrule these changes [200]. hi comparison to metal-support interactions on macroporous oxides, the interaction between metal particles and the supporting zeolite matrix seems more pronounced. This may be because the metal particles interact with the zeolite lattice over a substantial fraction of their surfece. It has also been suggested that in addition to the intrinsic electronic effects due to the small size of the metal particles in the zeolite cage, a modification of the electronic structure of the metal by the acidic zeolite framework has to be considered [201,202]. 

The possibility of using the ordering effect to induce unusual properties in the supported complexes was suggested by the authors, who included among the peculiar features the enhanced metal-substrate interactions, the reorientational of substrate molecules within the solvent cage and the possibility of directing the approach of molecules to catalytically active centers. 

Metal-ligand interactions are strong and highly directional and lead to the self-assembly of robust stable coordination cages. Kinetically labile metal-ligand (M-L) interactions... 

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