Electronic structure of the π-bonded
Al-C2H4 complex: Characterization of the
ground and low-lying excited states
A. M. C. Cristian and A. I. Krylov
J. Chem. Phys. 118, 10912 – 10918
(2003)
The equilibrium properties of the π-bonded Al-ethylene complex in
its ground state are calculated at the CCSD(T)/aug-cc-pVTZ
level of theory. Significant changes in the geometry of the ethylene
molecule upon complexation (elongation of the CC bond, pyramidalization
of CH2 groups) are consistent with the formation of a chemical
bond between fragments. The overall interaction is rather weak because
bonding is derived from the overlap between: (i) a singly occupied
p-orbital of Al and the antibonding π*-orbital of
ethylene; and (ii) a vacant Al sp hybrid and π of
C2H4. Electronically excited states are studied at
the EOM-CCSD/6-311(2+,2+)G(3df,3pd) level. The covalent
nature of the interaction between fragments is reflected in excited
states' delocalization over both fragments (as opposed to the
corresponding van der Waals complex). In the examined energy range
(0 – 5.18 eV) both valence and Rydberg excited states are
found. Bonding in the valence states is explained in terms of a simple
molecular orbital picture. Two very intense transitions at 3.50 eV
and at 3.79 eV can be used as a probe in experimental studies.
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