Attraction between Long Polyconjugated Chain Molecules

Abstract

The attraction forces between large molecules having highly mobile electrons distributed over many atoms are not well understood. The Coulombic interaction between electrons within a molecule causes the motion of each mobile electron to be correlated with those of many other electrons of the molecule. These correlation effects modify the attraction forces. A proper assessment of these effects at present is extremely difficult, and usually impossible to do. In this paper we calculate the ``mobile electron'' attraction force between long, equal bond polyenes (one of the most simple examples of large molecules having mobile, distributed electrons), and use the Tomonaga method to assess the correlation effects. We compare our results with those of earlier investigators who used an ``independent electron'' model which ignored correlation effects. We find that correlation effects are very important—their neglect leads to significant overestimation of the attraction. We give a simple physical interpretation of our results. Many of our conclusions should be applicable to other large molecules, such as the polyacenes.