ISSN:
1573-935X
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
Notizen:
Abstract A comparative study of the geometric and electronic structure of the chromate anion CrO 4 2− and a chromate group on the surface of finely divided silica (≡Si-O)2-CrO2, which was simulated by a CrO9Si6H12 cluster, has been carried out by the SCF-MO-LCAO method in the all-valence-electron CNDO/2 approximation. The data obtained on the equilibrium geometry of the chromate group attest to the formation of a double bond between the Cr atom and each O atom (which is not bonded to Si). It has been shown that the support has a significant stabilizing influence on the energy of the MO's of the chromate group. The chromate group on an SiO2 surface is characterized by partial delocalization of the frontier MO's among the skeletal bonds; however, the dominant contribution to the HOMO is made by the 2p AO of the oxygen atoms in the coordination shell of the Cr atom (∼70%), and the dominant contribution to the LUMO is made by the 3d AO of the chromium atom (∼50%). The positions and composition of the lowest unoccupied molecular orbitals point out the possibility of the display of electron-acceptor properties by a chromate group on an SiO2 surface.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00534425
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