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Electrocatalytic Carbon Dioxide Reduction by Using Cationic Pentamethylcyclopentadienyl–Iridium Complexes with Unsymmetrically Substituted Bipyridine Ligands
Author(s) -
Sypaseuth Fanni D.,
Matlachowski Corinna,
Weber Manuela,
Schwalbe Matthias,
Tzschucke C. Christoph
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201404367
Subject(s) - chemistry , iridium , cyclic voltammetry , formic acid , redox , acetonitrile , electrocatalyst , catalysis , inorganic chemistry , electrochemical reduction of carbon dioxide , carbon monoxide , formaldehyde , bipyridine , cationic polymerization , electrochemistry , electrolysis , bulk electrolysis , perchlorate , 2,2' bipyridine , polymer chemistry , organic chemistry , electrolyte , electrode , crystal structure , ion
Eight [Ir(bpy)Cp*Cl] + ‐type complexes (bpy= bipyridine, Cp*=1,2,3,4,5‐pentamethylcyclopentadienyl) containing differently substituted bipyridine ligands were synthesized and characterized. Cyclic voltammetry (CV) of the complexes in Ar‐saturated acetonitrile solutions showed that the redox behavior of the complexes could be fine tuned by the electronic properties of the substituted bipyridine ligands. Further CV in CO 2 ‐saturated MeCN/H 2 O (9:1, v/v ) solutions showed catalytic currents for CO 2 reduction. In controlled potential electrolysis experiments (MeCN/MeOH (1:1, v/v ), E app =−1.80 V vs Ag/AgCl), all of the complexes showed moderate activity in the electrocatalytic reduction of CO 2 with good stability over at least 15 hours. This electrocatalytic process was selective toward formic acid, with only traces of dihydrogen or carbon monoxide and occasionally formaldehyde as byproducts. However, the turnover frequencies and current efficiencies were quite low. No direct correlation between the redox potentials of the complexes and their catalytic activity was observed.