Effect of halide binding on intramolecular exciplex of double-linked zinc porphyrin-fullerene dyad

The effect of chloride or bromide ion coordination to a doubly-linked zinc porphyrin-fullerene dyad was studied by quantitative analysis of the absorption band in the red and near infrared spectral range. The absorption band in question corresponds to the direct excitation to the intramolecular exciplex and it can be analyzed using the semi-quantum charge transfer theory. Compared to the nonligated compounds the energy of the exciplex decreased by ∼0.3 eV and the oscillator strength of the transition increased by ∼15–20%. This is explained by the effect of the electric field created by the negative charge of the halide.