Insights into the crystal packing of phosphorylporphyrins based on the topology of their intermolecular interaction energies

Four metal complexes of 5,15-bis(diethoxyphosphoryl)-10,20-diphenylporphyrin 1M (M = Cd(II), Ni(II), Pd(II), and Pt(II)) were synthesized and crystallographically characterized. The crystal organization patterns were analyzed using DFT (B97-D3/def2-SVP) calculations of the intermolecular interaction energies between complexes in the crystals. For the systematic analysis of crystal packing, the calculations were extended to previously reported compounds 1M (M = H2, Cu(II), and Zn(II)). Quantitative analysis of the interaction energies shows the essential role of weak intermolecular interactions, such as C-H⋯O, C-H⋯π and M⋯π, in the formation of basic structural motifs and their organization within the crystals. Interplay between the axial coordination and weak intermolecular interactions provides the basis for rationalizing the observed polymorphism and crystals' isomorphism in this series of porphyrin complexes.