title: Flavin Derivatives with Tailored Redox Properties: Synthesis, Characterization, and Electrochemical Behavior.
abstract: This study establishes structure-property relationships for four synthetic flavin molecules as bioinspired redox mediators in electro- and photocatalysis applications. The studied flavin compounds were disubstituted with polar substituents at the N1 and N3 positions (alloxazine) or at the N3 and N10 positions (isoalloxazines). The electrochemical behavior of one such synthetic flavin analogue was examined in detail in aqueous solutions of varying pH in the range from 1 to 10. Cyclic voltammetry, used in conjunction with hydrodynamic (rotating disk electrode) voltammetry, showed quasi-reversible behavior consistent with freely diffusing molecules and an overall global 2e(-) , 2H(+) proton-coupled electron transfer scheme. UV/Vis spectroelectrochemical data was also employed to study the pH-dependent electrochemical behavior of this derivative. Substituent effects on the redox behavior were compared and contrasted for all the four compounds, and visualized within a scatter plot framework to afford comparison with prior knowledge on mostly natural flavins in aqueous media. Finally, a preliminary assessment of one of the synthetic flavins was performed of its electrocatalytic activity toward dioxygen reduction as a prelude to further (quantitative) studies of both freely diffusing and tethered molecules on various electrode surfaces.
authors.affiliation: Department of Chemistry and Biochemistry, University of Texas at Arlington, Texas, 76019, USA.|Department of Physical Chemistry and Materials Science, University of Szeged, Szeged, 6720, Hungary.|MTA-SZTE "Lendület" Photoelectrochemistry Research Group, Rerrich Square 1, Szeged, 6720, Hungary.
authors.forename: Attila
authors.initials: A
authors.lastname: Kormányos
authors.affiliation: Department of Chemistry and Biochemistry, University of Texas at Arlington, Texas, 76019, USA.
authors.forename: Mohammad S
authors.initials: MS
authors.lastname: Hossain
authors.affiliation: Department of Chemistry and Biochemistry, University of Texas at Arlington, Texas, 76019, USA.
authors.forename: Ghazaleh
authors.initials: G
authors.lastname: Ghadimkhani
authors.affiliation: Department of Chemistry and Biochemistry, University of Texas at Arlington, Texas, 76019, USA.
authors.forename: Joe J
authors.initials: JJ
authors.lastname: Johnson
authors.affiliation: Department of Physical Chemistry and Materials Science, University of Szeged, Szeged, 6720, Hungary.|MTA-SZTE "Lendület" Photoelectrochemistry Research Group, Rerrich Square 1, Szeged, 6720, Hungary.
authors.forename: Csaba
authors.initials: C
authors.lastname: Janáky
authors.affiliation: Department of Chemistry and Biochemistry, University of Texas at Arlington, Texas, 76019, USA.
authors.forename: Norma R
authors.initials: NR
authors.lastname: de Tacconi
authors.affiliation: Department of Chemistry and Biochemistry, University of Texas at Arlington, Texas, 76019, USA.
authors.forename: Frank W
authors.initials: FW
authors.lastname: Foss
authors.affiliation: Department of Chemical Engineering, Technion, Haifa, 32000, Israel.
authors.forename: Yaron
authors.initials: Y
authors.lastname: Paz
authors.affiliation: Department of Chemistry and Biochemistry, University of Texas at Arlington, Texas, 76019, USA. rajeshwar@uta.edu.
authors.forename: Krishnan
authors.initials: K
authors.lastname: Rajeshwar
mesh_terms: D002384:Catalysis; D055664:Electrochemical Techniques; D004566:Electrodes; D004579:Electron Transport; D005415:Flavins / Q000138:chemical synthesis / Q000737:chemistry*; D057446:Hydrodynamics; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D013329:Structure-Activity Relationship
chemical_list: D005415:Flavins; C008173:isoalloxazine; D010100:Oxygen
keywords: cyclic voltammetry; hydrodynamic voltammetry; proton-coupled electron transfer; riboflavin mimics