Anthraquinone Derivative Chiral Schiff Base Copper(II) Complexes for Enzyme Type Bio-Fuel Cell Mediators

Abstract

Electrochemically, laccase, a family of multi-copper oxidase, has specificity for performing not only one-electron oxidation of phenolic-related compounds but also four-electron reduction of oxygen, which is expected to be a cathode of biofuel cells. We have prepared three amino-acid derivatives (for enhancing affinity to laccase) and one control (just for determining redox behavior of ligands and Cu(II/I)) copper(II) complexes 0-3 having phenolic-related ligands involving anthraquinone moiety. Enhancing current density of electron transfer between the cathode (composed of electron conducting materials such as Nafion and carbon nanotube) and laccase could be observed for all 1-3 acting as good mediators according to (spectro)electrochemical results.

Electron Transfer via Helical Oligopeptide to Laccase Including Chiral Schiff Base Copper Mediators

“…Docking simulation suggested thermodynamically stable docking conformation of the complexes onto the surface of laccase, especially around the hydrophobic pocket near the Type-1 copper site [33][34][35]. The lowest energy docking poses for both complexes are very close to the laccase, with interatomic distance of the two Cu atoms of 8.107 (docking score = 41.4037) for 1 and 6.330 The results of cyclic voltammetry (CV) of 1 and 2 are shown in Figure 4.…”

Chiral Recognition of Azo-Schiff Base Ligands, Their Cu(II) Complexes, and Their Docking to Laccase as Mediators

“…In this case, a redox substance called a mediator is generally used for electron transfer between the electrode and laccase [2]. In order to facilitate electron transfer between the electrode and the oxygen reductase in the biofuel cell cathode, our laboratory studied the use of Schiff base metal complexes as mediators [8][9][10][11]. Mediators are required to be able to fit to the hydrophobic pocket sites on the laccase surface to supply electrons to the electron accepting T1 site inside the laccase molecule.…”

“…Mediators are required to be able to fit to the hydrophobic pocket sites on the laccase surface to supply electrons to the electron accepting T1 site inside the laccase molecule. We have searched for methods to introduce not only central metal ions (Cu, Mn), but also redox groups of anthraquinone [8,9] and polarization orientation of azobenzene [10,11], to organic ligands. However, whether photoisomerization and photo-induced orientation of the azobenzene moiety is effective for increasing current, and what the appropriate way to fit a complex to laccase is, are still unknown.…”

“…It was found that chiral molecular recognition resulting from spontaneous resolution could be observed for the racemic organic ligand. oxygen reductase in the biofuel cell cathode, our laboratory studied the use of Schiff base metal complexes as mediators [8][9][10][11]. Mediators are required to be able to fit to the hydrophobic pocket sites on the laccase surface to supply electrons to the electron accepting T1 site inside the laccase molecule.…”

Computational Design of Azo-anthraquinone Schiff Base Mn Complexes as Mediators for Biofuel Cell Cathode

“…To improve this electron transfer, we have investigated several types of metal complexes as mediators between the electrode and laccase [5][6][7][8][9][10][11]. Molecular docking of suitable compound (both ligands and complexes) to the hydrophobic pocket of laccase may be useful in predicting the redox activity and their utility in biofuel cells [8,9]. Presence of noncoordinating, non-innocent substituent to the ligand backbone in the metal ligand or complex may be induced by the polarized UV-light to control the rate of redox processes.…”