Efficient Photoinduced Energy and Electron Transfer in ZnII–Porphyrin/Fullerene Dyads with Interchromophoric Distances up to 2.6 nm and No Wire‐like Connectivity

Abstract The dyads 1 – 3 made of an alkynylated Zn II –porphyrin and a bis‐methanofullerene derivative connected through a copper‐catalyzed azide–alkyne cycloaddition have been synthesized. The porphyrin and fullerene chromophores are separated through a bridge made of a bismethanofullerene tether linked to different spacers conjugated to the porphyrin moiety [i.e., m ‐phenylene ( 1 ), p ‐phenylene ( 2 ), di‐ p ‐phenylene‐ethynylene ( 3 )]. Compounds 1 – 3 exhibit relatively rigid structures with an interchromophoric separation of 1.7, 2.0, and 2.6 nm, respectively, and no face‐to‐face or direct through‐bond conjugation. The photophysical properties of compounds 1 – 3 have been investigated in toluene and benzonitrile with steady‐state and time‐resolved techniques as well as model calculations on the Förster energy transfer. Excited‐state interchromophoric electronic interactions are observed with a distinct solvent and distance dependence. The latter effect is evidenced in benzonitrile, where compounds 1 and 2 exhibit a photoinduced electron transfer in the Marcus‐inverted region, with charge‐separated (CS) states living for 0.44 and 0.59 μs, respectively, whereas compound 3 only undergoes energy transfer, as in apolar toluene. The quantum yield of the charge separation (φ CS ) of compounds 1 and 2 in benzonitrile is ≥0.75. It is therefore demonstrated that photoinduced energy and electron transfers in porphyrin–fullerene systems with long interchromophoric distances may efficiently occur also when the bridge does not provide a wire‐like conjugation and proceed through the triplet states of the chromophoric moieties.