Installation of an exocyclic triphenylamine group at the phosphorus center provides access to dithienophosphole materials with lateral charge-transfer (CT) ability. The degree of CT can be significantly manipulated not only via oxidation of the P-center but also surprisingly by alkylation of the 2,6-position of the scaffold.

A series of dithienophospholes featuring polyaromatic hydrocarbon (PAH) substituents, with increasing number of fused rings ranging from 2 to 4 at the phosphorus center, have been synthesized and characterized. The installation of a large π-system in the vicinity of the dithienophosphole scaffold was found to induce unusual photophysics for this system that are based on the creation of two neighboring chromophores within the same molecular scaffold. Extensive photophysical studies revealed that significant energy transfer (ET) occurs from the PAH unit, which acts as a donor, to the dithienophosphole acceptor, showing ET efficiencies of almost 90%. TD-DFT calculations confirm the possibility for the two subunits to communicate with each other. Furthermore, due to the presence of the out-of-plane dithienophosphole unit, the PAH species do not show any significant tendency to form aggregates, such as excimers/exciplexes, even in colloidal suspensions.

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 signifi-