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The crystal structures of trifluoroacetato-[meso-tetra(p-chlorophenyl)porphyrinato]thallium(III), Tl[(p-Cl)4tpp](O2CCF3) (1), and pentafluoropropionato-[meso-tetra(p-chlorophenyl)porphyrinato]thallium(III) Tl[(p-Cl)4tpp](O2CCF2CF3) (2), were determined. The coordination sphere around the Tl3+ ion is described as five-coordinate regular square-based pyramid (RSBP) in which the apical site is occupied by an unidentate CF3CO2− ligand for 1 whereas the unidentate CF3CF2CO2− ligand occupies the axial site for 2. The plane of the four pyrrole nitrogen atoms [i.e., N(1)–N(4)] strongly bonded to Tl3+ is adopted as a reference plane 4N. The Tl3+ is moderately out of the 4N plane; its displacement of 0.58 A˚ (or 0.59 A˚) for 1 (or 2) is in the same direction as that of the trifluoroacetate oxygen for 1 (or pentafluoropropionate oxygen for 2). The free energy of activation at the coalescence temperature Tc for the intermolecular trifluoroacetate exchange for 1 in CD2Cl2 is found to be ΔG≠178=36.6 kJ/mol whereas the intermolecular pentafluoropropionate exchange for 2 in CD2Cl2 is determined to be ΔG≠213=41.5 kJ/mol through 19F and 13C NMR temperature-dependent measurements. [Copyright &y& Elsevier]