Allosteric regulation of the ligand-binding ability of Zn–porphyrin by metal complexation

Zn–porphyrin with bipyridyl units at the ends of a conjugated chain, in addition to two alkyl side chains, was prepared as an artificial allosteric system. The axial ligand-binding ability of the compound was considerably reduced by the formation of a Fe(bpy)3-type complex. The degree of the allosteric suppression strongly depended on both alkyl chain length and the steric demand of the pyridyl ligand.