Stereoretentive Ligand Exchange Reactions of N-Fused Porphyrin Ruthenium(II) Complexes

Creation from Confusion and Fusion in the Porphyrin World─The Last Three Decades of N-Confused Porphyrinoid Chemistry

Confusion is a novel concept of isomerism in porphyrin chemistry, delivering a steady stream of new chemistry since the discovery of N-confused porphyrin, a porphyrin mutant, in 1994. These days, the number of confused porphyrinoids is increasing, and confusion and associated fusion are found in various fields such as supramolecular chemistry, materials chemistry, biological chemistry, and catalysts. In this review, the birth and growth of confused porphyrinoids in the last three decades are described.

Porphyrinoids with Vinylene Bridges

Porphyrinoids containing vinylene bridges, such as triphyrin(2.1.1), porphycene, porphyrin(2.1.2.1), and hexaphyrin(2.1.2.1.2.1), are a relatively new family of porphyrinoids. Vinylene bridges give porphyrinoids a lower symmetry and a flexibility of the framework and they permit cis/trans-isomerization reactions; these factors confer unique properties to these substances, such as coordination to metal ions and aromaticity switching. In this account, the synthesis, crystal structures, and properties of new porphyrinoids containing vinylene bridges are summarized.

1 Introduction

2 Triphyrin(2.1.1)

3 Porphycene

4 Porphyrin(2.1.2.1)

5 Hexaphyrin(2.1.2.1.2.1)

6 Conclusion

Tungsten(VI) Complex of N-Fused Porphyrin Absorbing Near-Infrared Light beyond 1000 nm

Incorporating tungsten into the N3 core of a N-fused porphyrin (NFP; 1) affords high-valent tungsten(VI)-NFP complexes, WClO₂ -1 and 21-chlorinated WClO₂ -3. The X-ray structure of WClO₂ -1 reveals a distorted octahedral geometry with sitting atop metal coordination. The absorption spectrum of WClO₂ -1 displays bathochromically shifted Q-like bands beyond 1000 nm, indicating an inherently narrow HOMO-LUMO energy gap. DFT calculations show that the degeneracy of the LUMO and LUMO+1 pair of 1 is significantly resolved by the tungsten(VI) coordination. Conclusively, magnetic circular dichroism (MCD) spectroscopy and cyclic voltammetry provide a rationale for the narrow HOMO-LUMO energy gap in the "16-electron" d⁰ tungsten(VI)-NFP complexes.