Not only hydrogen bonds but also Li+, Nai, K+ and Be2+ bonds may show catio
n 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 reversible
arrow O- ... Li+ON bonds shift to the acceptor. The same is true for Na+ b
onds. 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 flu
ctuation of one H+, one Li+ and one Na+ in multi-minima potentials are disc
ussed with crown ether systems. (C) 1999 Elsevier Science B.V. All rights r
eserved.