Porphyrins. 36. <i>cis </i>, <i>trans </i>-Isomerism and atropisomerism in molecules of ethylenebisporphyrins

Abstract

The synthesis of octaalkyl esters of 1,2-(meso-coproporphyrin-I-yl)ethane has been carried out from the corresponding copper complexes of meso-hydroxymethyl- and the nickel complexes of meso-dimethylaminomethylporphyrins. Their conversion into the corresponding trans- and cis-ethylenebisporphyrins has been investigated. On boiling in AcOH or xylene, ethylenebisporphyrins form an equilibrium mixture of cis and trans isomers. The cis and trans isomers of 1,2-di(octaethylporphyrin-I-yl)ethylene and the octaethyl ester of 1,2-di(coproporphyrin-I-yl)ethylene have been isolated and their interconversions investigated. It was demonstrated by PMR that the cis isomers of ethylenebisporphyrins have a rigid structure in which there is no free rotation of the porphyrin rings. The presence of two atropisomers is also a characteristic of the cis isomer of the coproporphyrin-I derivative. The formation of metal complexes in combination with the preparation of complexes with additional ligands enables control of the conformation of ethanebisporphyrins in solution. A mechanism has been proposed for the oxidation of ethanebisporphyrins to trans-ethylenebisporphyrins in acetic and other lower aliphatic acids.

How to Cite
Ponomarev, G .V.; Yashunskii, D. V.; Borovkov, V. V.; Sakata, E.; Arnold, D. Chem. Heterocycl. Compd. 1997, 33, 1405. [Khim. Geterotsikl. Soedin. 1997, 1627.]

For this article in the English edition, see DOI https://doi.org/10.1007/BF02291641