π‐Dimerization ability of conjugated oligomer dication diradicaloids composed of dithienylpyrrole and benzodithiophene units

Abstract

AbstractStable conjugated oligomer dications 12+ and 22+ composed of 2,5‐di(2‐thienyl)‐N‐methylpyrrole (DTP) units at the both ends of the π‐systems with methoxy substituents at the 3‐position of thienyl units and methylthio end‐capping group and benzo[2,1‐b:3,4‐b′]dithiophene (BDT) unit(s) at the central part with sterically demanding phenyl substituents were synthesized. From DFT calculations and ESR experiments, it was concluded that the diradical character in 12+ and 22+ was reduced in comparison with the radical character of their reference compound 3·+ composed of one DTP and one BDT units. In addition, the shorter 12+ was considered to have a further lower diradical character than that of 22+. Nevertheless, judging from the results of VT‐UV‐vis‐NIR measurements, both 12+ and 22+ showed a comparable π‐dimerization ability at the DTP moiety in dichloromethane solution with 3·+.