Insertion of early lanthanide(III) ions into the coordination cavity of porphyrins is a slow and complicated process in aqueous solution, originating from the stability of their aqua complexes and their possible oligomerization. The presence of potential axial ligands can accelerate the coordination of the first porphyrin, but it can hinder the connection of a further porphyrin. Lanthanide ions may coordinate not only to the pyrrolic nitrogens of porphyrins but, under kinetic control, also to the peripheral substituents possessing O-donor atoms. In the case of such anionic porphyrins, the coordination position of metal ions can be influenced by the change of temperature
