“…For PcZn II , PcCo II , and PcFe II the vast majority of axial ligands (L) that have been reported are N-donors such as imidazole (Im), N -methyl imidazole (MeIm), pyridine (py), 4,4′-bipyridine (bpy), pyrazine (pyz), or piperidine (pip). 26–37 Based on a search of the Cambridge Structural Database (CSD), there are a few examples of carbon-donor axial ligands on PcFe II , but none exist for PcZn II or PcCo II . 38,39 All of these axial ligands were shown to improve the solubility of the unsubstituted PcM without inducing significant deformations to the Pc ring.…”