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.