Patwari G Naresh, Lisy James M
Department of Chemistry, University of Illinois at Urbana Champaign, Urbana, Illinois 61801, USA.
J Phys Chem A. 2007 Aug 9;111(31):7585-8. doi: 10.1021/jp070803+. Epub 2007 Jun 13.
The M+[cyclohexane][Ar] (M = Li, Na, and K) cluster ions were investigated using infrared photodissociation spectroscopy in the C-H stretching region. The alkali metal cation binds to the cyclohexane ring above the ring on the S6 axis via eta3 coordination. The C-H stretching modes are perturbed due to binding of the metal cation and display a significant spread in frequency. The shifts are greatest for the Li+ and decrease for Na+ and K+ with increasing ionic radius. It has been observed that cyclohexane displays greater selectivity for Li+ over Na+ than the cyclic ether, 12-crown-4. The charge transfer interaction between Li+ and cyclohexane is believed to be responsible for the selectivity of Li+ over other alkali metal ions.
