Synthesis and characterization of halogeno- and pseudo-halogeno-thallium(III) porphyrin complexes. Variation of the co-ordination geometry as a function of the axial ligand

Several thallium(III) porphyrin complexes [Tl(por)X] with the axial ligand X = MeCO₂, CF₃CO₂, Cl, Br, I, CN, SCN or N₃, have been obtained via ligand-exchange reactions from the corresponding thallium(III) trifluoroacetates. All compounds were characterized by ¹H NMR, UV/VIS spectroscopy, and elemental analysis. Fourteen compounds were investigated in detail by X-ray crystallography to obtain information on the influence of the axial ligand on the macrocycle core conformation in main-group metalloporphyrins and to establish the molecular stereochemistry of thallium(III) porphyrins with cyano, acetato, thiocyanato, bromo, iodo and azido groups as axial ligands.