Bis-Metal Coordination Chemistry of Doubly N-Confused Hexaphyrins

Expanded porphyrins have been received great interest due to the extended p-conjugation, multi-metal coordination, and multiple oxidation states, which consequently make them to be useful for optoelectronic applications, especially in the near-infrared (NIR) region. In contrast to the standard porphyrin with rigid planarity, expanded porphyrins are generally rather flexible and show the uncommon electronic and/or electromagnetic behaviors. However, the large flexibility of the molecules allows them to take various structures with many conformers and tautomers, which sometimes makes the metal coordination difficult and unpredictable. Thus, it has been awaited to synthesize the rigid-shaped expanded porphyrins possessing a large cavity that can accept bis-metals in the core without difficulty. Considering how enormous the achievement of porphyrin chemistry with a single metal is, the development of NIR dye chemistry with bis-metal expanded porphyrin ligands should be promising.   

   We have been working on N-confused porphyrinoids and exploring the unique features in view of their structures and electronic states.¹ Replacing the regular pyrrole with N-confused pyrrole ring in the pyrrolic macrocycle, which we call “confusion approach”, is now recognized an effective strategy for controlling the electronic state and molecular shape (Figure 1).² Recently, we have succeeded in synthesizing the singly, doubly, and triply N-confused [26]hexaphyrins and revealed the effects of confusion on the structures, optical properties, and metal coordination.^3-7In this presentation, recent progress of the coordination chemistry of doubly N-confused hexaphyrins is overviewed.

References

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