Effect of Anion Ligation on Electron Transfer of Double-Linked Zinc Porphyrin−Fullerene Dyad

Charge transfer excitations in cofacial fullerene-porphyrin complexes

Porphyrin and fullerene donor-acceptor complexes have been extensively studied for their photo-induced charge transfer characteristics. We present the electronic structure of ground states and a few charge transfer excited states of four cofacial porphyrin-fullerene molecular constructs studied using density functional theory at the all-electron level using large polarized basis sets. The donors are base and Zn-tetraphenyl porphyrins and the acceptor molecules are C(60) and C(70). The complexes reported here are non-bonded with a face-to-face distance between the porphyrin and the fullerene of 2.7 to 3.0 Å. The energies of the low lying excited states including charge transfer states calculated using our recent excited state method are in good agreement with available experimental values. We find that replacing C(60) by C(70) in a given dyad may increase the lowest charge transfer excitation energy by about 0.27 eV. Variation of donor in these complexes has marginal effect on the lowest charge transfer excitation energy. The interfacial dipole moments and lowest charge transfer states are studied as a function of face-to-face distance.

Free-base tetraarylporphyrin covalently linked to [60]fullerene through ethynylfluorene spacer

The synthesis, structural and electronic characterization of novel electroactive systems based on porphyrin-fullerene in which the chromophores are linked by an ethynylfluorene spacer unit is reported. Sonogashira couplings have been used in short and efficient sequences to give access to these new molecules on a practical scale. The absorption studies, voltamperometric measurements and theoretical calculations at DFT level reveal the push-pull behavior for these systems.