Li+, Na+, K+ and Be2+ bonds—IR continua and cation polarizabilities of these bonds

Abstract

Not only hydrogen bonds but also Li+, Na+, K+ and Be2+ bonds may show cation polarizabilities because of fluctuation and shifts of the cations. These polarizabilities are indicated by continua in the far infrared region. The electron density at the acceptor groups can be changed by the substituents. With increasing electron density the Li+ ions in the −OLi+⋯ON⇌−O⋯Li+ON bonds shift to the acceptor. The same is true for Na+ bonds. The fluctuation amplitude of K+ in potassium bonds is very small. The wavenumber regions are compared in which the continua in H+, Li+, Na+ and K+ bonds occur. There are also cation polarizabilities observed because of collective cation fluctuation in two or four cation bonds. Finally, the fluctuation of one H+, one Li+ and one Na+ in multi-minima potentials are discussed with crown ether systems.