DFT Reactivity Descriptors and Catalysis - Vrije Universiteit Brussel
DFT Reactivity Descriptors and Catalysis - Vrije Universiteit Brussel
DFT Reactivity Descriptors and Catalysis - Vrije Universiteit Brussel
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4. Towards the Inclusion of Confinement Effects<br />
• Relevance cfr. PCCP Thematic Issue “Molecules in Confined Space”<br />
“ … intricate chemistry of molecules taking place in the confined space of<br />
e.g. zeolites …”<br />
• Zeolites with their 3D network involving cages are archetypal structures<br />
• Early work (C.M. Zicovich- Wilson, A. Corma, P. Viruela, J.Phys.Chem., 98, 10863 (1993)<br />
• New concept: “electronic confinement”: density of the guest molecule orbitals suddenly<br />
drops to nearly zero when reaching the walls of the zeolite as a consequence of the shortrange<br />
repulsion with the delocalized electronic cloud of the lattice change is orbital<br />
energy levels<br />
•Hückel Theory ethylene HOMO-LUMO gap, <strong>and</strong> so the hardness, decreases if the<br />
molecule is spatially confined.<br />
c=c<br />
η<br />
LUMO<br />
HOMO<br />
η<br />
LUMO<br />
HOMO<br />
Pag.<br />
30-9-2008 35
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