Our original synthetic method using bis(azafulvene) (Org. Biomol. Chem., 2006, 4, 2247; J. Am. Chem. Soc., 2000, 122, 12405) allows preparation of giant porphyrinoids.  The largest porphyrinoid with 44 pyrroles (name: cyclotetratetracontapyrrole) was isolated.

Octaphyrins with eight pyrrole units are of great interest because of their helical figure eight loop structure.  Complexation with optically active carboxylic acids causes unidirectional helicity induction to the pi-conjutation systems of octaphyrins.  Thus, very small amounts of chiral compounds can induce CD signal in the visible region.

Artificial receptors showing homotropic positive allosteric effect are drawing considerable attention, but there are a limited number of successful examples. Cryptand-like hosts can provide not only an inside space but also three crevices towards ligands.  Of great importance in the present receptor is that the pi-conjugated pyrroles and pyridine are involved in the hydrogen bondings with ligands at different crevices, which leads to strong homotropic positive allostericity in binding guest molecules such as alcohols and carboxylic acids.

Hybrid Octaphyrins with four pyrrole units and four pyridine units generate dinuclear metal complexes with a figure eight loop structure.  They can pick up amino acid in water as their axial ligands, which causes unidirectional helicity induction to the macrocycle. Threonine, phenylalanine, tryptophan, tyrosine are excellent helicity regulators with almost 100% stereoselection as evidenced by NMR analysis and their CD signal in the visible region.