Azacalixphyrin (Fig.1, left) is the precursor of potentially highly versatile isostructural and isoelectronic "pyrrol-free" analogues to porphyrins (Fig.1, right) [1]. Like porphyrins, the molecular basis of azacalixphyrin is composed of a 16-membered ring containing 18 delocalized pi electrons, implying aromaticity according to the Hueckel's rule. Surprisingly, this new macrocyclic compound is stable to such an extend that it could be exposed to air for months as a solid or for days in solution without detectable changes. This high stability is preserved even in the presence of water under air. However, no rationalization of this specific property has been established yet.
Here, we present a theoretical study on the stability of azacalixphyrin. In addition, since we find that azacalixphyrin has the ability to capture easily two electrons, we also discuss the results obtained with its dianion. We show that the aromaticity of azacalixphyrin is very close to that of highly aromatic compounds such as benzene. We also find that all reactions with water are extremely endergonic, especially for the dianion.
[1] Chen, Z.; Giorgi, M.; Jacquemin, D.; Elhabiri, M.; Siri, O. Angew. Chem. Int. Ed. 2013, 52, 6250-6254
| Type : | : | affiche |
| Mots-Clés | : | Azacalixphyrin macrocycle ; porphyrin analogue ; stability ; dianion ; density functional theory |
| PDF version | : |  PDF version |
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