Synthesis and electronic properties of (oligo)phenothiazine-ethynyl-hydro-C60 dyads

Ethynyl bridged (oligo)phenothiazine–C60 dyads 2 can be readily synthesized by addition of the corresponding (oligo)phenothiazinyl lithium acetylides 1 to C60 followed by protonation with acetic acid. Cyclovoltammetric data of 1 and 2 reveal that the (oligo)phenothiazinyl moieties (donor) and the fullerene fragment (acceptor) are electronically decoupled in ground state, yet, each additional phenothiazine lowers the HOMO–LUMO gap by 100 mV. Upon UV excitation the phenothiazinyl fluorescence is considerably quenched, presumably as a consequence of a charge separation by an intramolecular photo-induced electron transfer from phenothiazine to fullerene.