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Title: Hydricity, electrochemistry, and excited-state chemistry of Ir complexes for CO2 reduction

Journal Article · · Faraday Discussions
DOI:https://doi.org/10.1039/C6FD00223D· OSTI ID:1337642
 [1];  [1];  [1];  [2];  [1];  [1];  [1]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States)
  2. Baruch College, CUNY, New York, NY (United States)
+ Show Author Affiliations

Here, we prepared electron-rich derivatives of [Ir(tpy)(ppy)Cl]+ with modification of the bidentate (ppy) or tridentate (tpy) ligands in attempt to increase the reactivity for CO2 reduction and the ability to transfer hydrides (hydricity). Density functional theory (DFT) calculations reveal that complexes with dimethyl-substituted ppy have similar hydricities to the non-substituted parent complex, and photocatalytic CO2 reduction studies show selective CO formation. Substitution of tpy for bis(benzimidazole)-phenyl or -pyridine (L3 and L4, respectively) induces changes in the physical properties much more pronounced than addition of methyl groups to ppy. Theoretical data predict [Ir(L3)(ppy)(H)] is the strongest hydride donor among complexes studied in this work, but [Ir(L3)(ppy)(NCCH3)]+ cannot be reduced photochemically because the excited state reduction potential is only 0.52 V due to the negative ground state potential of –1.91 V. The excited state [Ir(L4)(ppy)(NCCH3)]2+ is the strongest oxidant among complexes studied in this work and the singly reduced species is formed readily upon photolysis in the presence of tertiary amines. Both [Ir(L3)(ppy)(NCCH3)]+ and [Ir(L4)(ppy)(NCCH3)]2+ exhibit electrocatalytic current for CO2 reduction. While a significantly greater overpotential is needed for the L3 complex, a small amount of formate (5-10 %) generation in addition to CO was observed as predicted by the DFT calculations.

Research Organization:
Brookhaven National Lab. (BNL), Upton, NY (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
Grant/Contract Number:
SC00112704
OSTI ID:
1337642
Report Number(s):
BNL-113279-2016-JA; FDISE6; R&D Project: CO026; KC0304030
Journal Information:
Faraday Discussions, Journal Name: Faraday Discussions; ISSN 1359-6640
Publisher:
Royal Society of ChemistryCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 10 works
Citation information provided by
Web of Science

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Cited By (2)

Solvent and Ligand Substitution Effects on the Electrocatalytic Reduction of CO 2 with [Mo(CO) 4 ( x,x ′-dimethyl-2,2′-bipyridine)] ( x =4-6) Enhanced at a Gold Cathodic Surface journal August 2018
Surprisingly big linker-dependence of activity and selectivity in CO 2 reduction by an iridium( i ) pincer complex journal January 2020

Linked Research (1)

Figures / Tables (9)

Figure 1.(p. 5)figure Figure 1.
Figure 2.(p. 7)figure Figure 2.
Figure 3.(p. 8)figure Figure 3.
Table 1.(p. 9)table Table 1.
Table 2.(p. 10)table Table 2.
Figure 4.(p. 11)figure Figure 4.
Figure 5.(p. 11)figure Figure 5.
Table 3.(p. 12)table Table 3.
Table 4.(p. 13)table Table 4.

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