An unprecedented family of novel electron-donor acceptor conjugates based on fullerenes have been synthesized and characterized in a variety of solvents.

A hexadodecyl‐substituted zinc phthalocyanine covalently linked through a flexible spacer to a fullerene—ZnPc−C60—has been investigated regarding electron transfer from the photoexcited, electron‐donating ZnPc to the electron‐accepting C60. While ground‐state interactions between electron donor and acceptor within ZnPc−C60 could not be detected via steady‐state absorption spectroscopy, clear proof for excited‐state interactions came from steady‐state fluorescence spectroscopy. To this end, the fluorescence in ZnPc−C60 is strongly quenched with quantum yields in THF as low as 0.05. Insight into excited‐state electron‐transfer deactivation within ZnPc−C60 came from time‐resolved femtosecond transient absorption spectroscopy. For example, upon exclusive excitation of the phthalocyanine within the ZnPc−C60 conjugate, a set of transients evolve featuring, on the one hand, the signature of the one‐electron oxidized ZnPc radical cation and, on the other hand, of the one‐electron reduced C60 radical anion. The analysis of the corresponding dynamics in chlorobenzene resulted in lifetimes for charge‐separation and charge‐recombination of 7.4 ps and 2.2 ns, respectively.

Self-assembly driven by crown ether complexation of zinc phthalocyanines equipped with one 18-crown-6 moiety and fullerenes bearing an ammonium head group afforded a novel donor-acceptor hybrid. In reference experiments, fullerenes containing a Boc-protected amine functionality have been probed. The circumvention of zinc phthalocyanine aggregation is important for the self-assembly, which required the addition of pyridine. From absorption and fluorescence titration assays, which provided sound and unambiguous evidence for mutual interactions between the electron donor and the electron acceptor within the hybrids, association constants in the order of 8.0×10 m have been derived. The aforementioned is based on 1:1 stoichiometries, which have been independently confirmed by Job's plot measurements. In the excited state, which has been examined by transient absorption experiments, intermolecular charge separation evolves from the photoexcited zinc phthalocyanine to the fullerene subunit and leads to short-lived charge-separated states. Interestingly, photoexcitation of zinc phthalocyanine dimers/aggregates can also be followed by an intermolecular charge separation between vicinal phthalocyanines. These multicomponent supramolecular ensembles have also been shown by in-depth electrospray ionization mass spectrometry (ESI-MS) studies, giving rise to the formation and detection of a variety of non-covalently linked species.

A zinc phthalocyanine endowed with four [18]-crown-6 moieties, ZnPcTeCr, has been prepared and self-assembled with either pyridyl-functionalized perylenebisimides (PDI-Py) or fullerenes (C60-Py) to afford a set of novel electron donor-acceptor hybrids. In the case of ZnPcTeCr, aggregation has been circumvented by the addition of potassium or rubidium ions to lead to the formation of monomers and cofacial dimers, respectively. From fluorescence titration experiments, which gave rise to mutual interactions between the electron donors and the acceptors in the excited state, the association constants of the respective ZnPcTeCr monomers and/or dimers with the corresponding electron acceptors were derived. Complementary transient-absorption experiments not only corroborated photoinduced electron transfer from ZnPcTeCr to either PDI-Py or C60-Py within the electron donor-acceptor hybrids, but also the unexpected photoinduced electron transfer within ZnPcTeCr dimers. In the electron donor-acceptor hybrids, the charge-separated-state lifetimes were elucidated to be close to 337 ps and 3.4 ns for the two PDI-Pys, whereas the longest lifetime for the photoactive system that contains C60-Py was calculated to be approximately 5.1 ns.