Synthesis and Characterization of Palladium(II) Complexes of meso-Substituted [14]Tribenzotriphyrin(2.1.1)

Metalation of 6,13,20,21-tetrakis-aryl-22H-[14]­tribenzotriphyrin­(2.1.1) (TriPs) with PdCl2 provides PdII–TriP complexes in 45–56% yields. The complexes were characterized by mass spectrometry, and UV–visible absorption, magnetic circular dichroism, and 1H NMR spectroscopy. A single crystal X-ray analysis reveals that the PdII–TriPs adopts a deeply saddled conformation. The palladium­(II) ion is coordinated by two pyrrole nitrogen atoms and two chloride ions to form the square-planar coordination environment. The redox properties of the PdII–TriPs were studied by cyclic voltammetry. Each compound undergoes one irreversible and two reversible one-electron reductions. There is a marked red-shift of the main spectral bands, relative to those of the free-base TriP ligand, due to a marked relative stabilization of the LUMO upon coordination by PdCl2.