Abstract
The formation of certain classes of organic molecular complexes has been discussed from the viewpoint of an electron transfer between a donor molecule (D) and an acceptor molecule (A), i.e. D + A ⇄ D+A, leading to what might be termed a charge transfer salt. In certain situations, the ions can lead a more or less independent existence; this is realized sometimes in solvents of high dielectric constants (D+A + solvent ⇄ DS + + AS ). In the majority of cases, the electron appears to remain coupled to the positive hole of the donor, these compounds then show the physical properties of the bound electron—hole pair.