Influence of the size of the counter-ion on the conformational stability of the alkali metal complexes of 2,2'-dithienyl ketyl

The ratio between the trans-trans and cis-trans isomers has been measured in the 2,2'-dithienyl ketyl and in its Li, Na, K and Cs complexes. The stability of the trans-trans conformation was found to increase with increasing size of the alkali counter-ion. This trend has been interpreted in terms of steric interaction between the cation and the atoms adjacent to the binding site. © 1974.