Interchain interactions and the staging structure in charge-transfer complexes with neutral-ionic transitions

A superstructure named staging structure has been proposed in some mixed-stack charge-transfer complexes showing neutral-ionic transitions. It consists of an alternate sequence of the ionic and neutral layers. We investigate its stability by calculations of electrostatic energies. We show the stability is determined by the difference of the intramolecular charge distribution between the ionic and neutral states. The staging structure is slightly stable than the uniform ionic or neutral state in TMB-TCNQ ((3,3',5,5')-tetramethylbenzidine(7,7,8,8)tetracyanoquinodimethane) in which the structure has been suggested accompanying the transition.