Date of Award
Summer 1998
Document Type
Dissertation - Restricted
Degree Name
Doctor of Philosophy (PhD)
Department
Chemistry
First Advisor
Ryan, Michael D.
Second Advisor
Haworth, Daniel T.
Third Advisor
Feinberg, Benjamin A.
Abstract
Of all elements, nitrogen is the one that most often limits the growth of plants and the yields of crops. Plants require nitrogen as an ingredient of proteins, nucleic acids, and other important organic molecules. Most of the nitrogen atoms which enter the biosphere of plants or animals have arrived via assimilatory nitrite reduction. This six-electron reduction of nitrite to ammonia is catalyzed by assimilatory nitrite reductases. The enzyme has a heme-type group as its active site, but its structure is an isobacteriochlorin rather than a porphyrin. Considerable progress has been made over the past twenty years in the synthesis of sophisticated complexes that can model the active site by influencing the steric, electronic and environmental factors controlling the reactivity. For these models, there are two questions that must be addressed in order to understand the nitrite reductase. (1) What is the mechanism for the reduction of nitrite? (2) What is the effect of porphine structure on the reduction mechanism? It is the aim of this work to answer these questions by the use of electrochemical and spectroscopic methods. This dissertation is presented in five chapters. The first chapter gives a review of literature about nitrite reductase model complexes. Chapter 2 describes chemicals and experimental methods. Chapter 3 discusses the electrochemical reduction mechanism of nitrite by iron porphyrins. Chapter 4 is devoted to the study of the reaction of hydroxylamine with a series of metal porphyrins. Chapter 5 deals with the infrared spectroelectrochemistry of the reduction of iron porphinone and iron nitrosyl complexes.