Synthesis, Characterization and Protonation Behavior of Quinoxaline-Fused Porphycenes.

Daiki Kuzuhara,Wataru Furukawa,Mika Sakaguchi,Naoki Aratani,Takuya Okabe,Hiroko Yamada

doi:10.3390/molecules22060908

Daiki Kuzuhara, Wataru Furukawa + Show 4 more

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https://doi.org/10.3390/molecules22060908

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Abstract

9,10-Quinoxaline-fused porphycenes 1a-H2 and 1b-H2 were synthesized by intramolecular McMurry coupling. As a result of the annulation of the quinoxaline moiety on the porphycene skeleton, 1a-H2 and 1b-H2 display absorption and fluorescence in the near infra-red (NIR) region. Additionally, the quinoxaline moieties of 1a-H2 and 1b-H2 act as electron-withdrawing groups, introducing lower reduction potentials than for pristine porphycene. The protonation occurred at the nitrogen atoms in the cavity of freebase porphycenes and at the quinoxaline moieties for their nickel complexes to give diprotonic species.

Highlights

Porphycene (Pc < Figure 1) is the first reported constitutional isomer of porphyrin [1]
There have been only a few reports on porphycenes having near infra-red (NIR) absorption, NIR absorbing materials can be utilized in organic solar cells, biomarkers and photodynamic reagents
We have previously reported on tetrabenzo-porphycene (β-TBPc, Figure 1) [13] and tetranaphthoporphycene (β-TNPc) [14], which demonstrated red-shifted absorption from pristine Pc with an increasing number of benzene rings

Summary

Introduction

Porphycene (Pc < Figure 1) is the first reported constitutional isomer of porphyrin [1] It has a rectangular-shaped structure with two bipyrrole units connected by two ethylene bridges. This structural change leads to a lower LUMO level and narrower HOMO-LUMO energy difference compared with those of porphyrin [2]. As a result of these electronic and optical properties, porphycene derivatives are applied as photosensitizers for photodynamic therapy [5,6]. There have been only a few reports on porphycenes having near infra-red (NIR) absorption, NIR absorbing materials can be utilized in organic solar cells, biomarkers and photodynamic reagents. We have previously reported on tetrabenzo-porphycene (β-TBPc, Figure 1) [13] and tetranaphthoporphycene (β-TNPc) [14], which demonstrated red-shifted absorption from pristine Pc with an increasing number of benzene rings

Methods

Discussion

Conclusion