title: The correlation of cathodic peak potentials of vitamin K(3) derivatives and their calculated electron affinities. The role of hydrogen bonding and conformational changes.
abstract: 2-methyl-1,4-naphtoquinone 1 (vitamin K(3), menadione) derivatives with different substituents at the 3-position were synthesized to tune their electrochemical properties. The thermodynamic midpoint potential (E(1/2)) of the naphthoquinone derivatives yielding a semi radical naphthoquinone anion were measured by cyclic voltammetry in the aprotic solvent dimethoxyethane (DME). Using quantum chemical methods, a clear correlation was found between the thermodynamic midpoint potentials and the calculated electron affinities (E(A)). Comparison of calculated and experimental values allowed delineation of additional factors such as the conformational dependence of quinone substituents and hydrogen bonding which can influence the electron affinities (E(A)) of the quinone. This information can be used as a model to gain insight into enzyme-cofactor interactions, particularly for enzyme quinone binding modes and the electrochemical adjustment of the quinone motif.
authors.affiliation: Institute of Organic Chemistry and Chemical Biology, Johann Wolfgang Goethe-University Frankfurt, Max-von-Laue-Str. 7, D-60438 Frankfurt am Main, Germany.
authors.forename: Hamid Reza
authors.initials: HR
authors.lastname: Nasiri
authors.forename: Robin
authors.initials: R
authors.lastname: Panisch
authors.forename: M Gregor
authors.initials: MG
authors.lastname: Madej
authors.forename: Jan W
authors.initials: JW
authors.lastname: Bats
authors.forename: C Roy D
authors.initials: CR
authors.lastname: Lancaster
authors.forename: Harald
authors.initials: H
authors.lastname: Schwalbe
mesh_terms: D018360:Crystallography, X-Ray; D004563:Electrochemistry; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D015394:Molecular Structure; D013816:Thermodynamics; D024483:Vitamin K 3 / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry
chemical_list: D024483:Vitamin K 3