Case Study for Artificial Photosynthesis: Noncovalent Interactions between C₆₀-Dipyridyl and Zinc Porphyrin Dimer

In this study, a new modified C₆₀ derivative with an oPE/oPPV conjugated bridge bearing two pyridyl groups has been used in combination with a flexible porphyrin dimer (<b>ZnP</b>_<b>2</b>) to construct an electron donor/acceptor hybrid (<b>C</b>_<b>60</b><b>-dipyr·ZnP</b>_<b>2</b>). This hybrid is based on metal to ligand coordination between the zinc centers of the porphyrin dimer and the two pyridyl groups that oPE/oPPV linker bears. In order to investigate the interactions between the electron donor and acceptor entities, both in the ground state and in the excited states, comprehensive photophysical assays have been carried out. In particular, both absorption and fluorescence titrations provided evidence for strong interactions between the electron donor and the electron acceptor within the hybrid. A binding constant (<i>K</i>_ass) in the order of 5.0 × 10⁵ M^–1 has been derived. Furthermore, transient absorption measurements revealed intramolecular electron-transfer from the photoexcited porphyrin dimer (<b>ZnP</b>_<b>2</b>) to the fullerene derivative (<b>C</b>_<b>60</b><b>-dipyr</b>), leading to a long-lived charge-separated state with a lifetime of up to 1525 ps

Design and Synthesis of Porphyrin–Nitrilotriacetic Acid Dyads with Potential Applications in Peptide Labeling through Metallochelate Coupling

The need to detect and monitor biomolecules, especially within cells, has led to the emerging growth of fluorescent probes. One of the most commonly used labeling techniques for this purpose is reversible metallochelate coupling via a nitrilotriacetic acid (NTA) moiety. In this study, we focus on the synthesis and characterization of three new porphyrin–NTA dyads, TPP-Lys-NTA, TPP-CC-Lys-NTA, and Py3P-Lys-NTA composed of a porphyrin derivative covalently connected with a modified nitrilotriacetic acid chelate ligand (NTA), for possible metallochelate coupling with Ni2+ ions and histidine sequences. Emission spectroscopy studies revealed that all of the probes are able to coordinate with Ni2+ ions and consequently can be applied as fluorophores in protein/peptide labeling applications. Using two different histidine-containing peptides as His6-tag mimic, we demonstrated that the porphyrin–NTA hybrids are able to coordinate efficiently with the peptides through the metallochelate coupling process. Moving one step forward, we examined the ability of these porphyrin–peptide complexes to penetrate and accumulate in cancer cells, exploring the potential utilization of our system as anticancer agents