Control of Conformation and Chirality of Nonplanar π-Conjugated Diporphyrins Using Substituents and Axial Ligands

Nonplanar conformations of pyrazine-fused Zn-II diporphyrins could be controlled by the choice of the meso-aryl substituents and an axial ligand on the central metals. Zn-II diporphyrins bearing sterically demanding meso-aryl groups with ortho-substituents led to a twisted chiral D-2 conformation, while an achiral C-2h form was preferred in the case of aryl groups without ortho-substituents. Helical chirality induction on Zn-II diporphyrins in the twisted conformation was achieved by controlling their handedness of the molecular twist through coordination of optically active 1-phenethylamine.