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

Abstract

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.

Authors:
 [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)
Publication Date:
Research Org.:
Brookhaven National Lab. (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1337642
Report Number(s):
BNL-113279-2016-JA
Journal ID: ISSN 1359-6640; FDISE6; R&D Project: CO026; KC0304030
Grant/Contract Number:  
SC00112704
Resource Type:
Accepted Manuscript
Journal Name:
Faraday Discussions
Additional Journal Information:
Journal Name: Faraday Discussions; Journal ID: ISSN 1359-6640
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Manbeck, Gerald F., Garg, Komal, Shimoda, Tomoe, Szalda, David J., Ertem, Mehmed Z., Muckerman, James T., and Fujita, Etsuko. Hydricity, electrochemistry, and excited-state chemistry of Ir complexes for CO2 reduction. United States: N. p., 2016. Web. doi:10.1039/C6FD00223D.
Manbeck, Gerald F., Garg, Komal, Shimoda, Tomoe, Szalda, David J., Ertem, Mehmed Z., Muckerman, James T., & Fujita, Etsuko. Hydricity, electrochemistry, and excited-state chemistry of Ir complexes for CO2 reduction. United States. doi:10.1039/C6FD00223D.
Manbeck, Gerald F., Garg, Komal, Shimoda, Tomoe, Szalda, David J., Ertem, Mehmed Z., Muckerman, James T., and Fujita, Etsuko. Thu . "Hydricity, electrochemistry, and excited-state chemistry of Ir complexes for CO2 reduction". United States. doi:10.1039/C6FD00223D. https://www.osti.gov/servlets/purl/1337642.
@article{osti_1337642,
title = {Hydricity, electrochemistry, and excited-state chemistry of Ir complexes for CO2 reduction},
author = {Manbeck, Gerald F. and Garg, Komal and Shimoda, Tomoe and Szalda, David J. and Ertem, Mehmed Z. and Muckerman, James T. and Fujita, Etsuko},
abstractNote = {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.},
doi = {10.1039/C6FD00223D},
journal = {Faraday Discussions},
number = ,
volume = ,
place = {United States},
year = {2016},
month = {12}
}

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Figures / Tables:

Figure 1. Figure 1.: Ligands and Ir complex nomenclature used in this paper. The cyclometalated phenyl ligand loses a proton upon coordination. The crystal structure of [Ir(L3)(ppy)Cl]•CH3CN with 50% probability ellipsoids omitting CH3CN of crystallization is also shown.

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Works referenced in this record:

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Universal Solvation Model Based on Solute Electron Density and on a Continuum Model of the Solvent Defined by the Bulk Dielectric Constant and Atomic Surface Tensions
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Hydricities of d 6 Metal Hydride Complexes in Water
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    Works referencing / citing this record:

    Visible-Light-Induced Selective CO 2 Reduction Utilizing a Ruthenium Complex Electrocatalyst Linked to a p-Type Nitrogen-Doped Ta 2 O 5 Semiconductor
    journal, June 2010

    • Sato, Shunsuke; Morikawa, Takeshi; Saeki, Shu
    • Angewandte Chemie International Edition, Vol. 49, Issue 30
    • DOI: 10.1002/anie.201000613

    A Highly Efficient Mononuclear Iridium Complex Photocatalyst for CO 2 Reduction under Visible Light
    journal, November 2012

    • Sato, Shunsuke; Morikawa, Takeshi; Kajino, Tsutomu
    • Angewandte Chemie International Edition, Vol. 52, Issue 3
    • DOI: 10.1002/anie.201206137

    Striking Differences in Properties of Geometric Isomers of [Ir(tpy)(ppy)H] + : Experimental and Computational Studies of their Hydricities, Interaction with CO 2 , and Photochemistry
    journal, October 2015

    • Garg, Komal; Matsubara, Yasuo; Ertem, Mehmed Z.
    • Angewandte Chemie International Edition, Vol. 54, Issue 47
    • DOI: 10.1002/anie.201506961

    Synthesis of some imidazole- and pyrazole- derived chelating agents
    journal, June 1981

    • Addison, Anthony W.; Burke, Philip J.
    • Journal of Heterocyclic Chemistry, Vol. 18, Issue 4
    • DOI: 10.1002/jhet.5570180436

    CO 2 Hydrogenation to Formate and Methanol as an Alternative to Photo- and Electrochemical CO 2 Reduction
    journal, August 2015


    Thermodynamic Hydricity of Transition Metal Hydrides
    journal, June 2016


    Molecular Approaches to the Photocatalytic Reduction of Carbon Dioxide for Solar Fuels
    journal, December 2009

    • Morris, Amanda J.; Meyer, Gerald J.; Fujita, Etsuko
    • Accounts of Chemical Research, Vol. 42, Issue 12
    • DOI: 10.1021/ar9001679

    Chemical Redox Agents for Organometallic Chemistry
    journal, January 1996

    • Connelly, Neil G.; Geiger, William E.
    • Chemical Reviews, Vol. 96, Issue 2
    • DOI: 10.1021/cr940053x

    Molecular Tricorns:  Self-Assembly of Trinuclear Palladium(II) Complexes
    journal, April 2001

    • Carina, Riccardo F.; Williams, Alan F.; Bernardinelli, Gérald
    • Inorganic Chemistry, Vol. 40, Issue 8
    • DOI: 10.1021/ic0009526

    Syntheses and Properties of Emissive Iridium(III) Complexes with Tridentate Benzimidazole Derivatives
    journal, June 2005

    • Yutaka, Tomona; Obara, Shinya; Ogawa, Satoshi
    • Inorganic Chemistry, Vol. 44, Issue 13
    • DOI: 10.1021/ic048622z

    Dinuclear Iridium(III) Complexes Consisting of Back-to-Back tpy−(ph) n tpy Bridging Ligands ( n = 0, 1, or 2) and Terminal Cyclometallating Tridentate N−C−N Ligands
    journal, December 2006

    • Auffrant, Audrey; Barbieri, Andrea; Barigelletti, Francesco
    • Inorganic Chemistry, Vol. 45, Issue 26
    • DOI: 10.1021/ic061009q

    Excited-State Absorption Properties of Platinum(II) Terpyridyl Acetylides
    journal, April 2007

    • Shikhova, Elena; Danilov, Evgeny O.; Kinayyigit, Solen
    • Inorganic Chemistry, Vol. 46, Issue 8
    • DOI: 10.1021/ic0618652

    Tracking of Tuning Effects in Bis-Cyclometalated Iridium Complexes: A Combined Time Resolved Infrared Spectroscopy, Electrochemical, and Computational Study
    journal, July 2013

    • Chirdon, Danielle N.; McCusker, Catherine E.; Castellano, Felix N.
    • Inorganic Chemistry, Vol. 52, Issue 15
    • DOI: 10.1021/ic401009q

    [Ir(N^N^N)(C^N)L] + : A New Family of Luminophores Combining Tunability and Enhanced Photostability
    journal, January 2014

    • Chirdon, Danielle N.; Transue, Wesley J.; Kagalwala, Husain N.
    • Inorganic Chemistry, Vol. 53, Issue 3
    • DOI: 10.1021/ic402411g

    Excited-state absorption spectroscopy of ortho-metalated iridium(III) complexes
    journal, November 1987

    • Ichimura, K.; Kobayashi, T.; King, K. A.
    • The Journal of Physical Chemistry, Vol. 91, Issue 24
    • DOI: 10.1021/j100308a012

    Hydride Donor Abilities and Bond Dissociation Free Energies of Transition Metal Formyl Complexes
    journal, March 2002

    • Ellis, William W.; Miedaner, Alex; Curtis, Calvin J.
    • Journal of the American Chemical Society, Vol. 124, Issue 9
    • DOI: 10.1021/ja0116831

    Rapid Transfer of Hydride Ion from a Ruthenium Complex to C 1 Species in Water
    journal, August 2007

    • Creutz, Carol; Chou, Mei H.
    • Journal of the American Chemical Society, Vol. 129, Issue 33
    • DOI: 10.1021/ja074158w

    Rh-Catalyzed Ortho -Selective C–H Borylation of N -Functionalized Arenes with Silica-Supported Bridgehead Monophosphine Ligands
    journal, December 2011

    • Kawamorita, Soichiro; Miyazaki, Tatsuya; Ohmiya, Hirohisa
    • Journal of the American Chemical Society, Vol. 133, Issue 48
    • DOI: 10.1021/ja208364a

    Three-Component Coupling Sequence for the Regiospecific Synthesis of Substituted Pyridines
    journal, December 2011

    • Chen, Ming Z.; Micalizio, Glenn C.
    • Journal of the American Chemical Society, Vol. 134, Issue 2
    • DOI: 10.1021/ja2105703

    Thermodynamic and Kinetic Hydricity of Ruthenium(II) Hydride Complexes
    journal, September 2012

    • Matsubara, Yasuo; Fujita, Etsuko; Doherty, Mark D.
    • Journal of the American Chemical Society, Vol. 134, Issue 38
    • DOI: 10.1021/ja302937q

    Turnover Numbers, Turnover Frequencies, and Overpotential in Molecular Catalysis of Electrochemical Reactions. Cyclic Voltammetry and Preparative-Scale Electrolysis
    journal, June 2012

    • Costentin, Cyrille; Drouet, Samuel; Robert, Marc
    • Journal of the American Chemical Society, Vol. 134, Issue 27, p. 11235-11242
    • DOI: 10.1021/ja303560c

    Hydricities of d 6 Metal Hydride Complexes in Water
    journal, March 2009

    • Creutz, Carol; Chou, Mei H.
    • Journal of the American Chemical Society, Vol. 131, Issue 8
    • DOI: 10.1021/ja809724s

    Solvation Effects on Transition Metal Hydricity
    journal, November 2015

    • Tsay, Charlene; Livesay, Brooke N.; Ruelas, Samantha
    • Journal of the American Chemical Society, Vol. 137, Issue 44
    • DOI: 10.1021/jacs.5b07777

    Highly Fluorinated Ir(III)–2,2′:6′,2″-Terpyridine–Phenylpyridine–X Complexes via Selective C–F Activation: Robust Photocatalysts for Solar Fuel Generation and Photoredox Catalysis
    journal, July 2016

    • Porras, Jonathan A.; Mills, Isaac N.; Transue, Wesley J.
    • Journal of the American Chemical Society, Vol. 138, Issue 30
    • DOI: 10.1021/jacs.6b03246

    Universal Solvation Model Based on Solute Electron Density and on a Continuum Model of the Solvent Defined by the Bulk Dielectric Constant and Atomic Surface Tensions
    journal, May 2009

    • Marenich, Aleksandr V.; Cramer, Christopher J.; Truhlar, Donald G.
    • The Journal of Physical Chemistry B, Vol. 113, Issue 18, p. 6378-6396
    • DOI: 10.1021/jp810292n

    Calculation of thermodynamic hydricities and the design of hydride donors for CO2 reduction
    journal, July 2012

    • Muckerman, J. T.; Achord, P.; Creutz, C.
    • Proceedings of the National Academy of Sciences, Vol. 109, Issue 39
    • DOI: 10.1073/pnas.1201026109