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A - 12
116
Infrared Spectroscopy of CO2 Containing Cluster Anions
Holger Schneider 1 , A. Daniel Boese 2 1, *
, J. Mathias Weber
1 Institut für Physikalische Chemie, Universität Karlsruhe, Kaiserstr. 12, 76229 Karlsruhe, Germany
* email: jmathias.weber@chemie.uni-karlsruhe.de
2 Institut für Nanotechnologie, Forschungszentrum Karlsruhe, Pstfach 3640, 76021 Karlsruhe, Germany
Molecular clusters are relevant model systems for the study of intermolecular interaction
potentials governing the structures of molecular complexes. Structural information on clusters
can be gained from infrared photodissociation spectroscopy in molecular beams [1, 2], and we
have applied this technique to several species, probing the interaction of various anions with
CO2. The experimental results are interpreted in the framework of density functional theory with
anharmonic calculations of vibrational spectra.
Halide-CO2 complexes afford the study of the interaction of CO2 with closed shell anions of low
reactivity [3]. The results are compared with those for Au - ·CO2 [4], which is relevant for the
study of catalytic oxidation of CO by gold clusters on surfaces [5, 6]. This complex shows
strong interaction between CO2 and the Au - anion, with a strongly deformed CO2 unit.
Complexes of O2 - with CO2 show very interesting motifs of ion solvation [7]. The π* orbital of
O2 - offers a template with four a priori equivalent binding sites for the structure of the
microsolvation environment. However, only one CO2 ligand is strongly bound, with additional
molecules weakly attached to the resulting CO4 - anion.
The general motif of anions binding to CO2 is binding to CO2 via the carbon atom, in contrast to
cations, which generally dock to one of the oxygen atoms. The geometry of the CO2 molecule is
changed upon complexation with the anion by electrostatic and charge transfer effects. Both
contributions deform the molecule away from the linear configuration of neutral CO2 towards
the bent anionic shape.
References
[1] W.H. Robertson and M.A. Johnson, Annu. Rev. Phys. Chem. 54 (2003) 173.
[2] M.A. Duncan, Int. Rev. Phys. Chem. 22 (2003) 407.
[3] J.M. Weber and H. Schneider, J. Chem. Phys. 120 (2004) 10056.
[4] A.D. Boese, H. Schneider, A.N. Gloess, and J.M. Weber, in preparation (2004).
[5] A. Sanchez, et al., J. Phys. Chem. A 103 (1999) 9573.
[6] L.D. Socaciu, et al., J. Am. Chem. Soc. 125 (2003) 10437.
[7] H. Schneider, A.D. Boese, and J.M. Weber, in preparation (2004).