Metalloporphyrins. The nature of ligand bonding and the mechanism of replacements

Other - Other

• Author: Smiljko Ašperger
• Author: Biserka Cetina-Čižmek
• Author's institution: University of Zagreb; Faculty of Pharmacy and Biochemistry; (Department of physical chemistry)
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Chemistry; Physical Chemistry

Abstract (english)

The imidazole ring is an essential component of many biological systems (hemoglobin and myoglobin, nucleic acids, vitamin B^, cytochromes, metalloenzymes, etc.). The nature of the bond between imidazole-nitrogen and the metal is therefore of biological interest. Imidazole is an electron-donating ligand in both a and n sense, much more electron donating than the majority of nitrogen heterocycles. As ligands, most imidazoles are good a donors and moderate n donors. They can also function as n acceptors if the imidazole ring has one or more electron-withdrawing substituents. Our recent study of bonding modes of pyridine and imidazole type ligands in the transition state of a Conl(protoporphyrin IX) model complex enabled us to conclude that stabilization of the reaction transition state is more sensitive to the change in the strength of n bonding than in that of a bonding. This observation is important for some metallo-enzymatic reactions. Mechanisms of replacements in porphyrin and in corrin rings are discussed.

• Language: english
• Publication type: Other - Other
• Publication status: Published
• Peer review: Peer review
• Publication version: Published version
• Journal title: Croatica Chemica Acta
• Numbering: vol. 69, no. 4, pp. 1305-1328
• p-ISSN: 0011-1643
• e-ISSN: 1334-417X
• URN:NBN: urn:nbn:hr:163:315859
• Publication: 1996
• Document URL: https://hrcak.srce.hr/135971
• Type of resource: Text
• Access conditions: Open access
• Created on: 2020-04-29 14:35:08