Synthesis of (trans-A2)BC-Type Porphyrins with Acceptor Diethoxyphosphoryl and Various Donor Groups and their Assembling in the Solid State and at Interfaces

A versatile synthetic approach to accessing unsymmetrically substituted (trans-A(2))BC-type porphyrins bearing two heteroatoms at the macrocycle periphery is developed. For this purpose, experimental conditions for the substitution of the bromine atom in zinc 5-bromo-15-(diethoxyphosphoryl)-10,20-diphenylporphyin (2) by S-, O-, and N-nucleophiles were explored. SNAr reactions afford AlkO-, ArO-, and AlkS-substituted porphyrins in good to high yields. In contrast, SNAr reactions of 2 with N-nucleophiles lead to meso-amino-substituted porphyrins in preparative yields only with cyclic secondary amines. Primary amines, anilines and azacrowns may also react with bromide 2 but the palladium catalyst is needed to obtain the products in acceptable yields. The interest of the compounds under investigation for biomimetic assembly of tetrapyrroles was demonstrated by the studies of self-assembly of ditopic morpholinyl-substituted porphyrin 5a in the solid state. Moreover, we have prepared emissive porphyrin monolayers at the air/water interface and revealed that these porphyrin films were suitable for detection of zinc(II) ions in aqueous solutions.