Di‐2,7‐pyrenidecaphyrin(1.1.0.0.0.1.1.0.0.0) and Its Bis‐Organopalladium Complexes: Synthesis and Chiroptical Properties

A non‐aromatic expanded carbaporphyrinoid, incorporating two built‐in 2,7‐pyrenylene moieties was synthesized. The intrinsically labile structure was demonstrated by proton‐triggered conformational changes between the figure‐of‐eight and quasi‐Möbius conformers. Upon treatment with Pd(OAc)2, the reaction produces two bis‐PdII complexes with distinct coordination modes. Metal coordination serves to fix the macrocyclic frameworks with the net result that both bis‐PdII complexes could be resolved by high performance liquid chromatography (HPLC) on a chiral stationary phase. The isolated enantiomers showed persistent chiroptical properties as evidenced by the intense response in the circular dichroism (CD) spectra and the record high absorption dissymmetry factors (gabs of up to 0.038) seen in the near‐infrared spectral region. Moreover, the mutual interconversion of these two PdII complexes was found to be stereospecific and to favor the more stable isomers under weakly acidic conditions. Expanded porphyrins containing 2,7‐pyrenylene as key structural elements have been prepared. The resulting macrocycle showed unexpected coordination modes toward PdII. The two bis‐Pd complexes characterized in this study exhibited noteworthy chiroptical properties, including dissymmetry factors (gabs) as high as 0.038 at 763 nm, and low energy absorption bands extending into the NIR‐II region.