Coordination Chemistry‐Assembled Multicomponent Systems Built from a Gable‐Like Bis‐Porphyrin: Synthesis and Photophysical Properties

Abstract

Multiporphyrinic assemblies were quantitatively formed, in one step, from a gable-like zinc(II) bis-porphyrin ZnP 2 and free-base porphyrins bearing pyridyl groups. The different fragments are held together by axial 4′-N(pyridyl)-Zn interactions. Formation of a macrocycle ZnP 2 •(4′-cisDPyP) and a bis-macrocycle (ZnP 2 ) 2 •(TPyP) is discussed. The macrocycle and the bis-macrocycle were crystallized and studied by Xray diffraction, which confirmed the excellent complementarity between the various components. Spectrophotometric and spectrofluorimetric titrations and studies reveal high association constants for both multiporphyrinic assemblies due to the almost perfect geometrical match between the interacting units. As expected, energy transfer from the zinc porphyrin component to the free-base porphyrin quenches the fluorescence of the zinc porphyrin components in both compounds. But while in ZnP 2 •(4′-cis DPyP) sensitization of the emission of the free-base porphyrin was observed, in (ZnP 2 ) 2 •(TPyP) excitation of the peripheral Zn porphyrin units does not lead to quantitative sensitization of the luminescence of the freebase porphyrin acceptor. An unusual HOMO-HOMO electron transfer reaction from ZnP 2 to the excited TPyP unit was detected and studied.

Multiporphyrinic Cages: Architectures and Functions

“…They have attracted the attention of a broad range of researchers because their stable aromatic core can be functionalized on meso or pyrrolic β positions and the inserted metal can modulate their chemical, electronic, and photophysical properties. Chemists have incorporated them in lots of different molecular architectures for various fields of applications, like artificial photosynthesis, molecular electronics, , molecular machines, catalysis, therapy, and surface engineering . The design of molecular cages including porphyrins in the host structure opens several attractive opportunities: porphyrin, as a large structural element will delineate the molecular cavity; as an active component, its large π-delocalized core can stabilize π-conjugated guest molecules inside the cavity, whereas its metalated form can coordinate various ligands within the cage; as a redox and photoactive component, it can participate directly to the reactivity performed inside the structure.…”