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Molecular Catalysts for Multielectron Redox Reactions of Small Molecules: The “Cofacial Metallodiporphyrin” Approach
Author(s) -
Collman James P.,
Wagenknecht Paul S.,
Hutchison James E.
Publication year - 1994
Publication title -
angewandte chemie international edition in english
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 0570-0833
DOI - 10.1002/anie.199415371
Subject(s) - redox , chemistry , catalysis , substrate (aquarium) , combinatorial chemistry , reactivity (psychology) , bimetallic strip , non innocent ligand , electron transfer , metal , molecule , enzyme catalysis , photochemistry , organic chemistry , medicine , oceanography , alternative medicine , pathology , geology
The role of metalloenzymes in important biological transformations has attracted increasing attention over the past several decades. Of the many chemical transformations mediated by enzymes, few are as challenging as multielectron redox reactions. Recent studies have revealed a partial structural and mechanistic description of these redox‐active metalloenzymes, but there is much still to be learned regarding the mechanisms of substrate transformation. Due to the complexity of the metalloenzyme systems, simplified model systems are employed to mimic structural or functional features of the enzyme. In multielectron redox enzymes, several metals are probably in‐volved in both substrate binding and the subsequent redox reactions. Thus, functional mimics of multielectron redox enzymes might also need two or more metal centers to be efficacious. The roles of multiple metal centers are to (1) increase the substrate's affinity for the catalyst, (2) increase the rate of electron transfer to the bound substrate, (3) increase the reactivity of the bound substrate, and (4) inhibit deleterious side reactions. Deter‐mining the importance of each factor may help in the development of these catalysts. Cofacial metallodiporphyrins, because of the control they provide over the geometric and electronic properties of the synthetic reaction center, are ideal bimetallic model complexes. The knowledge gained from model studies will help in understanding the mechanisms of metalloenzymes and can be used to design new homogeneous catalysts to effect multielectron transformations.