文摘
While the antiaromatic tetraoxa[24]porphyrinogen(2.2.2.2) 1 (trans,cis,trans,cis) and the corresponding aromatic dication 12+ have been published recently, the synthesis of the title compounds is described for the first time. Beside the cis,trans,cis,trans-tetraoxa[24]porphyrinogen(4.0.4.0) 2b the isomeric porphyrinogens 2a (trans, cis,cis,trans) and 2c (all-trans in the cisoid conformation) could be isolated. The tetraoxa[22] porphyrin(4.0.4.0) dication is an aromatic 22π-system, it exists only in the cis,trans,cis,trans-configuration. The dication 2b2+ can be reduced with tetrakis-N,N-dimethylaminoethene to give pure porphyrinogen 2b. The electrochemistry of the system 2/2b2+ and AM1 calculations are described.