Please do not adjust margins
ChemComm
Page 4 of 5
COMMUNICATION
Journal Name
4D). Under Ar atmosphere, complex 1mFe displays the FeIII/II cou-
ple at -0 44 V vs. Fc/Fc+ (ΔEp = 87 mV). The reductions also ap-
pear at -2.15 (ΔEp = 165 mV) and -2.40 V (ΔEp = 139 mV). The
former is assignable to the reduction at the metal ion (i.e., FeII/I).
The latter is assigned to the ligand-based reduction, derived
from the LN4H2/LN4H2•- couple, due to the similarity in the re-
duction potential observed for complex 4Zn (E1/2 = -2.36 V) (Fig.
S45). All these three reductions are assignable as a one-electron
process due to the similarity in their peak heights.
Notes and references
DOI: 10.1039/C9CC04191E
1. a) A. J. Morris, G. J. Meyer and E. Fujita, Acc. Chem. Res., 2009,
42, 1983-1994; b) J. Barber, Chem. Soc. Rev., 2009, 38, 185–
196.
2. a) H. Takeda, C. Cometto, O. Ishitani and M. Robert, ACS Catal.,
2017, 7, 70-88; b) N. Elgrishi, M. B. Chambers, X. Wang and M.
Fontecave, Chem. Soc. Rev., 2017, 46, 761-796
3. J.-X. Zhang, C.-Y. Hu, W. Wang, H. Wang and Z.-Y. Bian, Appl.
Catal. A, 2016, 522, 145-151.
On the other hand, under CO2 atmosphere, a significant cat-
alytic current (icat/ip = 5.6) is observed. The onset potential for
the catalytic current, sharply rising at –2.10 V, is slightly more
positive than the FeII/I couple. This behaviour is likely to reveal
that the CO2 binding is triggered by the formation of the FeI spe-
4. H. Rao, J. Bonin and M. Robert, ChemSusChem, 2017, 10
,
4447-4450.
5. Z. Guo, S. Cheng, C. Cometto, E. Anxolabéhère-Mallart, S. M.
Ng, C. C. Ko, G. Liu, L. Chen, M. Robert and T. C. Lau, J. Am.
Chem. Soc., 2016, 138, 9413-9416.
cies FeI(LN4H2)Cl Moreover, the values of E1/2 Cu-PS•-) =
(Cu-PS/
6. C. Cometto, R. Kuriki, L. Chen, K. Maeda, T. C. Lau, O. Ishitani
and M. Robert, J. Am. Chem. Soc., 2018, 140, 7437-7440.
7. Y. Zhang, M. Schulz, M. Wächtler, M. Karnahl and B. Dietzek,
Coord. Chem. Rev., 2018, 356, 127-146.
-2.01 V vs. Fc/Fc+ (Fig. S48) and E1/2 (FeII/FeI)= -2.15 V vs. Fc/Fc+
reveal that the reduction of the FeII species by Cu-PS•- to yield
the FeI species during the photolysis is only slightly uphill (ΔG =
0.14 eV, i.e., 3.2 kcal/mol) and is thereby judged to be a feasible
process leading to trigger the CO2 reduction.
8. H. Takeda, K. Ohashi, A. Sekine and O. Ishitani, J. Am. Chem.
Soc., 2016, 138, 4354-4357.
The combined results described above allow us to propose
the photocatalytic cycle of CO2 reduction by 1mFe. The CO2 bind-
ing to the FeI(LN4H2)Cl species may afford the FeIII species for-
9. A. Rosas-Hernández, C. Steinlechner, H. Junge and M. Beller,
Green Chem., 2017, 19, 2356-2360
10. a) H. Takeda, H. Kamiyama, K. Okamoto, M. Irimajiri, T.
Mizutani, K. Koike, A. Sekine and O. Ishitani, J. Am. Chem. Soc.,
2018, 140, 17241–17254; b) C. Steinlechner, A. F. Roesel, E.
Oberem, A. Päpcke, N. Rockstroh, F. Gloaguen, S. Lochbrunner,
R. Ludwig, A. Spannenberg, H. Junge, R. Francke and M. Beller,
mulated as FeIII(LN4H2)(CO2 )Cl followed by the second one-
2-
electron reduction and protonation using TEOA as a proton
source, leading to form FeII(LN4H2)(CO2H-)(Cl). Our preliminary
DFT results show that the CO2 binding to the FeI(LN4H2)Cl into
FeIII(LN4H2)(CO2 )Cl is slightly uphill but energetically feasible
(∆
G = + 6.12 kcal·mol-1) (Fig. S49). The next step may be the dis-
sociation of OH- from FeII(LN4H2)(CO2H-)(Cl) to give
[FeII(LN4H2)(CO)(Cl)]+, as recently described for the CO2-to-CO
conversion by the cobalt porphyrin CO2 reduction catalysts.22
The OH- elimination may also be coupled with the protonation
of OH- to afford H2O. The final step is the exchange of CO with
either Cl- or DMF to regenerate FeII(LN4H2)Cl2.
2-
ACS Catal., 2019, 9, 2091-2100.
11. S. P. Luo, E. Mejia, A. Friedrich, A. Pazidis, H. Junge, A. E.
Surkus, R. Jackstell, S. Denurra, S. Gladiali, S. Lochbrunner and
M. Beller, Angew. Chem. Int. Ed., 2013, 52, 419-423.
12. F. Bottino, M. Di Grazia, P. Finocchiaro, F. R. Fronczek, A.
Mamo and S. Pappalardo, J. Org. Chem., 1988, 53, 3521-3529.
13. D. M. Kurtz, Chem. Rev., 1990, 90, 585-606.
14.a) J. R. Khusnutdinova, J. Luo, N. P. Rath and L. M. Mirica, Inorg.
Chem., 2013, 52, 3920-3932; b) W.-T. Lee, S. B. Muñoz III, D.
In conclusion, we have developed a new efficient photocata-
lytic system for CO2 reduction based on earth-abundant ele-
ments, consisting of a well-defined iron catalyst and a copper
photosensitizer. Under optimized conditions, CO2 is preferen-
tially reduced to CO with a TONCO up to 565 (TOFCOmax = 114 h-1)
after 8 h of light irradiation, and a high selectively for CO2 re-
duction vs. H2 formation (SelCO2 = 84%). Mechanistic studies
prove that Cu-PS* is reductively quenched by BIH generating the
reduced Cu-PS•- species, which enables the formation of the FeI
species capable of binding CO2 to promote the catalytic cycle.
This work was supported by JSPS KAKENHI Grant Number
JP18H01996 (Grant-in-Aid for Scientific Research (B)), and
JP18K05150 (Grant-in-Aid for Scientific Research (C)). This work
was also supported by JSPS KAKENHI Grant Number
JP18H05171 in a Grant-in-Aid for Scientific Research on Innova-
tive Areas “Innovations for Light-Energy Conversion (I4LEC)”.
This work was also supported by the International Institute for
Carbon Neutral Energy Research (WPI-I2CNER), sponsored by
the World Premier International Research Center Initiative
(WPI), MEXT, Japan. MC thanks le Fonds du Québec pour la
recherché sur la nature et les technologies (FRQNT) for a PD
scholarship.
A. Dickie and J. M. Smith, Angew. Chem. Int. Ed., 2014, 53
,
9856-9859.
15. Q. X. Wang, K. Jiao, W. Sun, F. F. Jian and X. Hu, Eur. J. Inorg.
Chem., 2006, 2006, 1838-1845.
16. A. J. J. Lennox, S. Fischer, M. Jurrat, S.-P. Luo, N. Rockstroh, H.
Junge, R. Ludwig and M. Beller, Chem. Eur. J., 2016, 22, 1233-
1238.
17. N. Armaroli, Chem. Soc. Rev., 2001, 30, 113-124.
18. Z. A. Siddique, Y. Yamamoto, T. Ohno and K. Nozaki, Inorg.
Chem. , 2003, 42, 6366-6378.
19. T. Morimoto, T. Nakajima, S. Sawa, R. Nakanishi, D. Imori and
O. Ishitani, J. Am. Chem. Soc., 2013, 135, 16825-16828.
20. E. Mejía, S. P. Luo, M. Karnahl, A. Friedrich, S. Tschierlei, A. E.
Surkus, H. Junge, S. Gladiali, S. Lochbrunner and M. Beller,
Chem. Eur. J., 2013, 19, 15972-15978.
21. Y. Pellegrin and F. Odobel, C. R. Chimie, 2017, 20, 283-295.
22. A. Call, M. Cibian, K. Yamamoto, T. Nakazono, K. Yamauchi and
K. Sakai, ACS Catal., 2019, 9, 4867-4874.
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins