Synthesis and Self-Assembly of β-Octa[(4-Diethoxyphosphoryl)phenyl]porphyrins

The β-substituted porphyrinoids commonly used to form functional assembled systems in Nature yet are still scarcely studied in material chemistry probably due to laborious synthesis of these compounds. In this work β-octa[(4-diethoxyphosphoryl)phenyl]porphyrin (2HOPPP) and their metal (Zn(II), Cd(II), Cu(II) and Ni(II)) complexes were prepared in good yields. These highly soluble polyfunctionalized chromophores were characterized in solution using spectroscopic (NMR, UV–vis, fluorescence), electrochemical and spectroelectrochemical methods. Attachment of the highly electron-withdrawing group (EWG) P(O)(OEt)2 to the porphyrin macrocycle leads to easier reductions and harder oxidations of the macrocycle for all complexes as compared to corresponding meso-tetra(diethoxyphosphorylphenyl)porphyrin derivatives reported previously. We demonstrated that the strong electron deficient character of the MOPPP porphyrins results principally from the increase in the number of EWG at the periphery of the tetrapyrrolic macrocycle. Electron deficient porphyrins are highly required in supramolecular and material chemistry in part due to their ability to form supramolecular assemblies via the coordination of axial ligands to the central metal atom. According single crystal X-ray data, ZnOPPP forms in the crystalline phase unusual mutually coordinated dimers in which two tetrapyrrolic macrocycles are connected through hydrogen bonding of two phosphoryl groups and water molecules axially coordinated to the zinc atoms of the partner molecule. The involvement of water molecules in porphyrin binding allows for an increase of distance between two porphyrin mean N4 planes, up to 4.478 Å. The off-set of phosphoryl groups attached to the macrocycle through a 1,4-phenylene spacer withdraws the whole porphyrin macrocycle of one molecule from spatial overlap with the macrocycle of a partner molecule and increases the Zn–Zn distance up to 10.372 Å. This still unknown type of porphyrin dimers allows to get deeper insight in the organization of naturally occurring tetrapyrrolic macrocycles