Meso-Tetrapyrenylporphyrins: Synthesis, Structural, Spectra Electrochemical Properties And Forster Energy Transfer (Fret) Studies

Meso-tetrapyrenylporphyrin and its metal (Co-II, Cu-II, Ni-II and Zn-II) complexes were synthesized, characterized and studied for their spectral, electrochemical and energy transfer properties. DFT optimization was carried out to gain an insight into the interactions between the porphyrin pi-system and the pyrenyl substituents. The pyrenyl substituents and the porphyrin core remain essentially orthogonal to each other in both the free base and the metallated porphyrins. Redox potentials of the pyrenylporphyrins are marginally shifted as compared to their corresponding phenyl derivatives. Fiirster resonance energy transfer (FRET) studies were carried out in toluene for free-base pyrenylporphyrin and its Zn(II) complex. Since pyrene is a good donor, an efficient energy transfer from pyrene (D) to the porphyrin core (A) on the order of 80-85% was observed for these two compounds. It was observed that energy transfer occurs mainly via "through-bond" (TB) interaction rather than "through-space" (TS) interaction.