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Issue 7, 2003
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The synthesis and studies towards the self-replication of bis(capped porphyrins)

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Abstract

Connecting two facially-protected porphyrins was expected to lead to an equal mixture of laterally-bridged doubly-protected bis-porphyrins; one in which the two porphyrin units were protected on the same face (syn) and one with the two porphyrin units protected on opposite faces (anti). Addition of a co-factor (bidentate ligand) was expected to lead predominantly to the syn-bis-porphyrin by a templated self-replication process. This concept was explored using Baldwin's capped porphyrin. Bis(capped porphyrins) were synthesised in several steps starting from zinc(II) capped porphyrin 2. Nitration of 2 followed by reduction and photo-oxidation yields a mixture of zinc(II) porphyrin-diones 7 and 8 that can be separated by HPLC. The condensation of 2 molar eq. of zinc(II) porphyrin-7,8-dione 8 with 1,2,4,5-benzenetetramine leads to the formation of a 1 : 1 mixture of syn- and anti-dizinc(II) bis(7,8-capped porphyrins), 11 and 12, respectively, that have almost identical spectroscopic properties. These two geometric isomers were distinguished by significant differences in their molecular recognition properties. Likewise the syn- and anti-dizinc(II) bis(2,3-capped porphyrins), 9 and 10, respectively, are synthesised from the related zinc(II) capped porphyrin-2,3-dione 7, and were also identified using molecular recognition studies. The molecular recognition properties of these bis(capped porphyrins) were utilised in studies of self-replicating porphyrin systems. The results show that tetraazaanthraceno-bis-porphyrins 9–12 can catalyse their own formation but self-replication was not observed. These results highlight the potential that these interesting hosts could have as templates in supramolecular chemistry, synthesis and catalysis.

Graphical abstract: The synthesis and studies towards the self-replication of bis(capped porphyrins)

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Publication details

The article was received on 11 Nov 2002, accepted on 20 Feb 2003 and first published on 06 Mar 2003


Article type: Paper
DOI: 10.1039/B211015F
Citation: Org. Biomol. Chem., 2003,1, 1216-1225
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    The synthesis and studies towards the self-replication of bis(capped porphyrins)

    P. Thordarson, A. Marquis and M. J. Crossley, Org. Biomol. Chem., 2003, 1, 1216
    DOI: 10.1039/B211015F

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