Free-base C60-(meso-tri-thienyl)porphyrin dyads and their Zn-complexes: new additions to the library of donor-acceptor assemblies

The article introduces covalently functionalized free-base porphyrin fullerene (C60) dyads and their corresponding zinc complexes. The donor unit is a meso-tri substituted thienyl porphyrin. The mode of attachment of the porphyrin to the fullerene unit differs in the lengths of the spacers linking the donor and acceptor units. The characterization of the four dyads through 1HNMR, MALDI-TOF, UV-Vis, and emission spectra confirm the formation of the dyads. Additionally, the study of fluorescence lifetime reveals the impact of the length of the flexible linkers on the free-base and zinc complexes of the dyads. Each dyad showed the presence of two types of fluorescent transients corresponding to fluorescence quenching through either charge transfer or intermolecular π-π interactions. The recorded fluorescent lifetime values for the dyads are: T3OHA1C60 (𝜏1 = 1.275 and 𝜏3 = 4.725 ns), T3OHA1C60Z (𝜏1 = 0.758 and 𝜏3 = 2.660 ns), T3OHA2C60 (𝜏1 = 0.819 and 𝜏2 = 2.456 ns), and T3OHA2C60Z (𝜏1 = 0.993 and 𝜏2 = 3.675 ns), the fluorescent quantum yields are 0.038, 0.041, 0.031, and 0.019, respectively.