TY - JOUR
T1 - Electrochemical Reduction of CO2 Catalyzed by Re(pyridine-oxazoline)(CO)3Cl Complexes
AU - Nganga, John K.
AU - Samanamu, Christian R.
AU - Tanski, Joseph M.
AU - Pacheco, Carlos
AU - Saucedo, Cesar
AU - Batista, Victor S.
AU - Grice, Kyle A.
AU - Ertem, Mehmed Z.
AU - Angeles-Boza, Alfredo M.
N1 - Funding Information:
A.M.A.-B. is grateful for support from the University of Connecticut. The authors gratefully acknowledge support for the X-ray diffraction facilities at Vassar College from the National Science Foundation under Grant No. 0521237. V.S.B. acknowledges high-performance computing time from the NERSC and support from the Argonne-Northwestern Solar Energy Research (ANSER) Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001059. Computational work at Brookhaven National Laboratory (M.Z.E.) was supported by the U.S. Department of Energy, Office of Science, Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences, under contract DE-SC00112704. C.S. acknowledges the Illinois Louis Stokes Alliance for Minority Participation (ILSAMP) program for support (National Science Foundation Grant 1411219) as well as the McNair Scholars Program.
Publisher Copyright:
© 2017 American Chemical Society.
PY - 2017/3/20
Y1 - 2017/3/20
N2 - A series of rhenium tricarbonyl complexes coordinated by asymmetric diimine ligands containing a pyridine moiety bound to an oxazoline ring were synthesized, structurally and electrochemically characterized, and screened for CO2 reduction ability. The reported complexes are of the type Re(N-N)(CO)3Cl, with N-N = 2-(pyridin-2-yl)-4,5-dihydrooxazole (1), 5-methyl-2-(pyridin-2-yl)-4,5-dihydrooxazole (2), and 5-phenyl-2-(pyridin-2-yl)-4,5-dihydrooxazole (3). The electrocatalytic reduction of CO2 by these complexes was observed in a variety of solvents and proceeds more quickly in acetonitrile than in dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). The analysis of the catalytic cycle for electrochemical CO2 reduction by 1 in acetonitrile using density functional theory (DFT) supports the C-O bond cleavage step being the rate-determining step (RDS) (ΔG⧧ = 27.2 kcal mol-1). The dependency of the turnover frequencies (TOFs) on the donor number (DN) of the solvent also supports that C-O bond cleavage is the rate-determining step. Moreover, the calculations using explicit solvent molecules indicate that the solvent dependence likely arises from a protonation-first mechanism. Unlike other complexes derived from fac-Re(bpy)(CO)3Cl (I; bpy = 2,2′-bipyridine), in which one of the pyridyl moieties in the bpy ligand is replaced by another imine, no catalytic enhancement occurs during the first reduction potential. Remarkably, catalysts 1 and 2 display relative turnover frequencies, (icat/ip)2, up to 7 times larger than that of I.
AB - A series of rhenium tricarbonyl complexes coordinated by asymmetric diimine ligands containing a pyridine moiety bound to an oxazoline ring were synthesized, structurally and electrochemically characterized, and screened for CO2 reduction ability. The reported complexes are of the type Re(N-N)(CO)3Cl, with N-N = 2-(pyridin-2-yl)-4,5-dihydrooxazole (1), 5-methyl-2-(pyridin-2-yl)-4,5-dihydrooxazole (2), and 5-phenyl-2-(pyridin-2-yl)-4,5-dihydrooxazole (3). The electrocatalytic reduction of CO2 by these complexes was observed in a variety of solvents and proceeds more quickly in acetonitrile than in dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). The analysis of the catalytic cycle for electrochemical CO2 reduction by 1 in acetonitrile using density functional theory (DFT) supports the C-O bond cleavage step being the rate-determining step (RDS) (ΔG⧧ = 27.2 kcal mol-1). The dependency of the turnover frequencies (TOFs) on the donor number (DN) of the solvent also supports that C-O bond cleavage is the rate-determining step. Moreover, the calculations using explicit solvent molecules indicate that the solvent dependence likely arises from a protonation-first mechanism. Unlike other complexes derived from fac-Re(bpy)(CO)3Cl (I; bpy = 2,2′-bipyridine), in which one of the pyridyl moieties in the bpy ligand is replaced by another imine, no catalytic enhancement occurs during the first reduction potential. Remarkably, catalysts 1 and 2 display relative turnover frequencies, (icat/ip)2, up to 7 times larger than that of I.
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U2 - 10.1021/acs.inorgchem.6b02384
DO - 10.1021/acs.inorgchem.6b02384
M3 - Article
C2 - 28277679
AN - SCOPUS:85015724319
SN - 0020-1669
VL - 56
SP - 3214
EP - 3226
JO - Inorganic chemistry
JF - Inorganic chemistry
IS - 6
ER -