An aromatic expanded triphyrin, [22]triphyrin(6.6.0) 2, containing a pyrrole unit, a bipyrrole moiety, and annulene links, was obtained from a tellurium-containing precursor meso-tetraaryl-26,28-ditellurasapphyrin 1. The reaction path proceeds through an acid-promoted tellurium extrusion from 1 yielding directly 2, characterized in a dicationic form by X-ray crystallography. In solution the neutral macrocycle 2 reveals flexibility typical for annulenes and it exists as a mixture of conformers that differ by the configuration of the annulene fragments, as proven by 1 H NMR studies and analyzed by DFT methods. The conformation is controlled by protonation state, the nature of an interacting anion, solvent identity, and by interaction with water.
Keywords: anions; annulenes; host-guest systems; tellurium; triphyrin.
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