Encaged molecular sieves zeolite

IRON-PHTHALLOCYANINES ENCAGED IN ZEOLITE Y AND VPI-5 MOLECULAR SIEVE AS CATALYSTS FOR THE OXYFUNCTIONALIZATION OF n-ALKANES... 

Fig. 8A shows that the selectivity for ketone and alcohol formation is quite similar for both molecular sieves. Fig. 8B indicates that regioselectivity exists for both molecular sieves, possibly due to the encaged nature of the complex. However, lower values of the C2/C3 and C2/C4 ratios are obtained in VPI-5 compared to zeolite Y, pointing to the existence of shape selectivity. The molecular graphics analysis, which enabled quantification of the free pore apertures, shows that the difference in selectivity can hardly be caused by differences in the zeolitic environment. The enhanced constraint observed for FePcY should then be related to the saddle-type deformation of the complex. 

Various metal complexes such as metal phthalocyanines, metal salenes or Ru pyridyl complexes have been incorporated in molecular sieves such as cavity-structured zeolites (faujasites, supercages with 1.3-nm diameter), channel-structured aluminium phosphates (AIPO4-5, channel diameter 0.73 nm) and channel-structured silicates MCM-41 (channel diameter 3.2 nm) [51-53]. Different strategies were applied for the inclusion of the phthalocyanines. For example, whereas the zeolite-encaged phthalocyanines (1 R = -FI M = Co(II), Ru(II), etc.) are synthesized by the reaction of a transition metal ion-exchanged zeolite with phthalonitrile in a closed-bomb vessel [54], in the cases of AIPO4-5 and MCM-41 substituted derivatives of phthalocyanines were added to the mixture during the hydrothermal synthesis of the molecular sieve [55,56]. 

In the pages that follow, we summarize methods for the synthesis of clusters in cages, their structural characterization, reactivity, and catalytic and other properties. The literature of encaged clusters is limited to clusters in zeolites, and thus little is included here about other molecular sieves or potential cluster hosts. The literature dtations are not comprehensive rather, examples are dted to illustrate prindples and to emphasize the unique properties of encaged clusters and the... 

Elemental semiconductor clusters encaged in zeolites provide a valuable opportunity for gaining a fundamental understanding of semiconductor clusters because stoichiometry is not a concern in the synthesis. Selenium is of interest because it has an intermediate electrical conductivity and a negative coefficient of resistivity in the dark hence it is markedly photoconductive. It has uses in, for example, photoelectric devices and xerography. When Se is sorbed into a molecular sieve, it gives markedly different optical absorption spectra from those of the bulk material. 

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