Metal complexes with tetrapyrrole ligands, LIV: Synthesis, spectra, structure, and redox properties of cerium(IV) Bisporphyrinates with identical and different porphyrin rings in the sandwich system

Abstract

Abstract Further symmetrical cerium(IV) bisporphyrinates are prepared from cerium(III) acetylacetonate and tetraphenylporphyrin, tetra‐ p ‐chlorophenylporphyrin, and hexadecahydrotetrabenzporphyrin. In the latter case, a biscerium(III) triple‐decker is also found which is the only product in the case of octamethylporphyrin. From a mixture of two different porphyrins, namely octaethylporphyrin [H 2 (OEP)] and either tetraphenylporphyrin [H 2 (TPP)] or tetra‐ p ‐chlorophenylporphyrin [H 2 (TClP)], besides the symmetrical species Ce(OEP) 2 and Ce(TPP) 2 , the unsymmetrical (“mixed”) double‐deckers Ce(OEP)(TPP) or Ce(OEP)(TClP) are obtained which have different porphyrin rings in the sandwich system and can be separated by chromatography. The crystal structure analysis of Ce(OEP)(TPP) shows Ce IV in a square‐antiprismatic geometry of the pyrrole N atoms of the porphyrin rings. While the IR and NMR spectra of the unsymmetrical double‐deckers are superpositions of the spectra of the individual rings, their UV/VIS spectra and cyclic voltammograms indicate that the two porphyrin rings behave as a common π‐electron system. The preparation of the π‐cation radical salts [Ce(OEP) 2 ]ClO 4 and [Ce(OEP)(TPP)]SbCl 6 is also described. In the latter, the defect electron seems to reside preferentially in the OEP ring.