CYCLOPHANE PORPHYRINS AND THEIR METAL COMPLEXES. BIOMIMETIC STUDY ON RECEPTOR SITE OF HEMOPROTEIN OXYGEN BINDING

Article abstract of DOI:10.1016/0040-4020(84)85063-2

A new symmetric porphyrin, 7,8,17,18-tetraethyl-3,13-dimethylporphyrin-2,12-dipropionic acid and its derivatives were synthesized by the a,c-biladiene route.Condensation of the dipropionic acid with diamine, , afforded the corresponding cyclophane porphyrins.The bridged groups were characterized by the (1)H-NMR spectra of their zinc complexes.The spin state of the Fe(III) complexes of the cyclophane porphyrins was investigated by changing the size of the bridged chain or size of axial ligand.The cyclophane-porphyrinato(III) perchlorate complexes in a mixture of MeOH and CHCl3 with 4-benzylpyridine provide a model for methemoproteins.Steric constraint between an axial ligand and the bridge group, <-CH2CH2CONH(CH2)nNHCOCH2CH2> at the bridged face determines the ratio of the penta- and hexa-coordinated ferric complexes.The ratio of O-binding to the Co(II) cyclophane porphyrins is markedly dependent on the size of the bridge chain.The present result indicates that removal of a solvent molecule or sixth axial ligand from the near proximity of the Co(II) complex increases the rate of O-binding.