P-terthienyl-functionalized dithieno[3,2-b:2′,3′-d]phospholes

Abstract

A series of dithienophospholes with different P-thienyl substituents have been synthesized and characterized. Alkyl groups at the 2,6-positions of the scaffold were introduced for solubility, but were found to also prevent π stacking with this scaffold. Whereas a simple thienyl does not affect the overall photophysics of the dithienophosphole, the installation of terthienyl units creates a considerable subchromophore that can communicate through the phosphole-typical σ-π* orbital interaction with the main scaffold. The overall architecture of the terthienyl was also found to have a significant impact on the photophysics of the system. Although a heavily twisted, branched terthienyl does not allow for any intermolecular π-stacking interaction, the exposed nature of a linear terthiophene does, and gives rise to the formation of excimers in solution, as evident in shifted emission properties as a function of the concentration. Time-dependent DFT calculations have revealed that in this case, the terthienyl group becomes the main chromophore and the dithienophosphole only plays a supportive role. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.