Atropisomers of meso-conjugated uracyl porphyrin derivatives and their assembling structures.

We have synthesized a 5,15 meso-substituted methyluracyl porphyrin derivative bearing 6-methyluracyl units directly at the meso positions. The atropisomerization was regulated by steric replusion between the methyl substituents. When the atropisomers were mixed with alkylated melamine as a complementary hydrogen-bonding unit, the hydrogen-bonded assemblies were analyzed by diffusion-ordered spectroscopy (DOSY) in solution, which clarified that the αα isomer formed a face-to-face dimer, whereas the αβ isomer took a zigzag structure.