No pyrrol: Azacalixphyrin (see picture), a novel isostructural and isoelectronic “pyrrol-free” analogue of porphyrins is easily prepared in two straightforward steps. The azacalixphyrin is aromatic, absorbs in the entire visible region, and is highly stable (even in the presence of water under air) owing to its unusual bis-zwitterionic character.
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Chen et al. (2013) studied this question.
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