Indaphyrins and Indachlorins: Optical and Chiroptical Properties of a Family of Helimeric Porphyrinoids

摘要

Indaphyrins and indachlorins possess large chiral porphyrinoid -systems with particularly long-wavelength absorption properties. All indaphyrin derivatives, including the indaphyrin M-II complexes (M = Ni-II, Cu-II, Zn-II, and Pt-II), adopt strongly ruffled conformations incorporating a helimeric twist, thus forming two stereochemically stable helimeric enantiomers. Their degree of ruffling is modulated by the coordination to metal ions or pyrrole ring modifications. Resolution of the racemic mixtures of the helimers of all derivatives was achieved by HPLC on a chiral phase and their absolute stereostructures were assigned. The much altered UV/Vis spectra of the indaphyrin derivatives, when compared to those of porphyrins, were rationalized using excited state calculations. The conformational stability of the conformers toward thermally induced racemization was also shown. The report forms the basis for future applications that exploit the chiral properties of the chromophores.