Anisole as an ambidentate ligand: Ab initio molecular orbital study of alkali metal cations binding to anisole
The authors present optimized geometries and binding energies for alkali metal cation complexes with anisole (methoxybenzene). Results are obtained for Li{sup +} through Cs{sup +} at the RHF/6-311G* and MP2/6-311+G* levels of theory, with K{sup +}, Rb{sup +}, and Cs{sup +} represented by relativistic ECPs and associated valence basis sets. RHF/6-311G{sup {minus}} frequencies are used to verify that the optimized geometries are minima and to calculate binding enthalpies. The effects of basis set superposition error (BSSE) are estimated at both the RHF and MP2 levels. The alkali metals bind to anisole in two ways, either predominantly through interactions with the aromatic ring or with the ether oxygen. For binding to the ring, BSSE-corrected MP2/6-311+G* binding enthalpies (in kcal/mol) of {minus}38.1 (Li{sup +}), {minus}23.6 (Na{sup +}), {minus}18.3 (K{sup +}), {minus}15.4 (Rb{sup +}), and {minus}13.6 (Cs{sup +}) were obtained. The average distances (in {angstrom}) between the ring carbons and the cations are 2.33 (Li{sup +}), 2.79 (Na{sup +}), 3.20 (K{sup +}), 3.44 (Rb{sup +}), and 3.70 (Cs{sup +}). For binding to the ether oxygen, the BSSE-corrected MP2/6-311+G* binding enthalpies (in kcal/mol) are {minus}37.6 (Li{sup +}), {minus}25.2 (Na{sup +}), {minus}19.4 (K{sup +}), {minus}16.4 (Rb{sup +}), and {minus}14.3 (Cs{sup +}). The distances (in {angstrom}) between the ether oxygen and the cations are 1.82 (Li{sup +}), 2.24 (Na{sup +}), 2.62 (K{sup +}), 2.87 (Rb{sup +}), and 3.10 (Cs{sup +}). Although the differences in binding energy between the two sites are small, the cations generally prefer to bind to the oxygen.
- Research Organization:
- Pacific Northwest National Lab., Richland, WA (US)
- OSTI ID:
- 20013060
- Journal Information:
- Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Vol. 103, Issue 48; Other Information: PBD: 2 Dec 1999; ISSN 1089-5639
- Country of Publication:
- United States
- Language:
- English
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