1
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Lim H, Yang X, Larsen CB, Ledbetter K, Zoric MR, Raj SL, Kumar G, Powers-Riggs N, Hoffmann MC, Chollet M, Gee LB, van Driel TB, Alonso-Mori R, Kabanova V, Kahraman A, Johnson PJM, Cirelli C, Bacellar C, Gaffney KJ, Li X, Cordones AA. Excited State Covalency, Dynamics, and Photochemistry of Square Planar Ni-Thiolate Complexes Revealed by Ultrafast X-ray Absorption. J Am Chem Soc 2025; 147:7496-7506. [PMID: 39993950 DOI: 10.1021/jacs.4c16212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/26/2025]
Abstract
Highly covalent Ni bis(dithiolene) and related complexes provide an ideal platform for investigating the effects of metal-ligand orbital hybridization on excited state character and dynamics. In particular, we focus on the ligand field excited states that dominate the photophysics of first-row transition metal complexes. We investigate if they can be significantly delocalized off the metal center, possibly yielding photochemical reactivity more similar to charge transfer excited states than metal-centered ligand field excited states. Here, [Ni(mpo)2] (mpo = 2-mercaptopyridine-N-oxide) provides a representative example for the larger chemical class and is an active electro- and photocatalyst for proton reduction. A detailed characterization of the excited state electronic structure, dynamics, and photochemistry of [Ni(mpo)2] is presented based on ultrafast transient X-ray absorption spectroscopy at the Ni and S 1s core absorption K-edges. By comparing the ultrafast Ni K-edge absorption to ab initio calculations, we identify an excited state relaxation mechanism where an initial ligand-to-metal charge transfer excitation results in both excited state electron transfer (generating a catalytically relevant reduced photoproduct [Ni(mpo)2]-) and relaxation to a pseudotetrahedral triplet ligand field excited state. From the ultrafast S K-edge absorption, the ligand field excited state is found to be highly delocalized onto the thiolate ligands, and a tetrahedral structural distortion is shown to substantially influence the degree of delocalization. The results identify a significant structural coordinate to target when aiming to control the excited state covalency in square planar complexes.
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Affiliation(s)
- Hyeongtaek Lim
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Xinzheng Yang
- University of Washington, Seattle, Washington 98195, United States
| | - Christopher B Larsen
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Kathryn Ledbetter
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Marija R Zoric
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Sumana L Raj
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Gaurav Kumar
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Natalia Powers-Riggs
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Matthias C Hoffmann
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Matthieu Chollet
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Leland B Gee
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Tim B van Driel
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Roberto Alonso-Mori
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | | | | | | | | | | | - Kelly J Gaffney
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Xiaosong Li
- University of Washington, Seattle, Washington 98195, United States
| | - Amy A Cordones
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
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2
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Gao M, To W, Tong GSM, Du L, Low K, Tang Z, Lu W, Che C. Dinuclear Cyclometalated Pincer Nickel(II) Complexes with Metal-Metal-to-Ligand Charge Transfer Excited States and Near-Infrared Emission. Angew Chem Int Ed Engl 2025; 64:e202414411. [PMID: 39320051 PMCID: PMC11720376 DOI: 10.1002/anie.202414411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2024] [Revised: 09/04/2024] [Accepted: 09/25/2024] [Indexed: 09/26/2024]
Abstract
Facile non-radiative decay of low-lying metal-centered (MC) dd excited states has been well documented to pose a significant obstacle to the development of phosphorescent NiII complexes due to substantial structural distortions between the dd excited state and the ground state. Herein, we prepared a series of dinuclear Ni2 II,II complexes by using strong σ-donating carbene-phenyl-carbene (CNHC Cphenyl CNHC) pincer ligands, and prepared their dinuclear Pt2 II,II and Pd2 II,II analogues. Dinuclear Ni2 II,II complexes bridged by formamidinate/α-carbolinato ligand exhibit short Ni-Ni distances of 2.947-3.054 Å and singlet metal-metal-to-ligand charge transfer (1MMLCT) transitions at 500-550 nm. Their 1MMLCT absorption energies are red-shifted relative to the Pt2 II,II and Pd2 II,II analogues at ~450 nm and ≤420 nm respectively. One-electron oxidation of these Ni2 II,II complexes produces valence-trapped dinuclear Ni2 II,III species, which are characterized by EPR spectroscopy. Upon photoexcitation, these Ni2 II,II complexes display phosphorescence (τ=2.6-8.6 μs) in the NIR (800-1400 nm) spectral region in 2-MeTHF and in the solid state at 77 K, which is insensitive to π-conjugation of the coordinated [CNHC Cphenyl CNHC] ligand. Combined with DFT calculations, the NIR emission is assigned to originate from the 3dd excited state. Studies have found that the dinuclear Ni2 II,II complex can sensitize the formation of singlet oxygen and catalyze the oxidation of cyclo-dienes under light irradiation.
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Affiliation(s)
- Mengyue Gao
- Department of ChemistryState Key Laboratory of Synthetic ChemistryCAS-HKU Joint Laboratory on New MaterialsThe University of Hong KongPokfulam RoadHong KongP. R. China
| | - Wai‐Pong To
- Department of ChemistryState Key Laboratory of Synthetic ChemistryCAS-HKU Joint Laboratory on New MaterialsThe University of Hong KongPokfulam RoadHong KongP. R. China
| | - Glenna So Ming Tong
- Department of ChemistryState Key Laboratory of Synthetic ChemistryCAS-HKU Joint Laboratory on New MaterialsThe University of Hong KongPokfulam RoadHong KongP. R. China
| | - Lili Du
- Department of ChemistryState Key Laboratory of Synthetic ChemistryCAS-HKU Joint Laboratory on New MaterialsThe University of Hong KongPokfulam RoadHong KongP. R. China
| | - Kam‐Hung Low
- Department of ChemistryState Key Laboratory of Synthetic ChemistryCAS-HKU Joint Laboratory on New MaterialsThe University of Hong KongPokfulam RoadHong KongP. R. China
| | - Zhou Tang
- Department of ChemistryState Key Laboratory of Synthetic ChemistryCAS-HKU Joint Laboratory on New MaterialsThe University of Hong KongPokfulam RoadHong KongP. R. China
- Laboratory for Synthetic Chemistry and Chemical Biology LimitedUnits 1503-1511, 15/F, Building 17W, Hong Kong Science Park, New TerritoriesHong KongP. R. China
| | - Wei Lu
- Department of ChemistrySouthern University of Science and TechnologyShenzhenGuangdong518055P. R. China
| | - Chi‐Ming Che
- Department of ChemistryState Key Laboratory of Synthetic ChemistryCAS-HKU Joint Laboratory on New MaterialsThe University of Hong KongPokfulam RoadHong KongP. R. China
- HKU Shenzhen Institute of Research and InnovationShenzhenGuangdong518057P. R. China
- Department of ChemistrySouthern University of Science and TechnologyShenzhenGuangdong518055P. R. China
- Laboratory for Synthetic Chemistry and Chemical Biology LimitedUnits 1503-1511, 15/F, Building 17W, Hong Kong Science Park, New TerritoriesHong KongP. R. China
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3
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Wallick R, Chakrabarti S, Burke JH, Gnewkow R, Chae JB, Rossi TC, Mantouvalou I, Kanngießer B, Fondell M, Eckert S, Dykstra C, Smith LE, Vura-Weis J, Mirica LM, van der Veen RM. Excited-State Identification of a Nickel-Bipyridine Photocatalyst by Time-Resolved X-ray Absorption Spectroscopy. J Phys Chem Lett 2024; 15:4976-4982. [PMID: 38691639 PMCID: PMC11089568 DOI: 10.1021/acs.jpclett.4c00226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Revised: 03/18/2024] [Accepted: 04/16/2024] [Indexed: 05/03/2024]
Abstract
Photoassisted catalysis using Ni complexes is an emerging field for cross-coupling reactions in organic synthesis. However, the mechanism by which light enables and enhances the reactivity of these complexes often remains elusive. Although optical techniques have been widely used to study the ground and excited states of photocatalysts, they lack the specificity to interrogate the electronic and structural changes at specific atoms. Herein, we report metal-specific studies using transient Ni L- and K-edge X-ray absorption spectroscopy of a prototypical Ni photocatalyst, (dtbbpy)Ni(o-tol)Cl (dtb = 4,4'-di-tert-butyl, bpy = bipyridine, o-tol = ortho-tolyl), in solution. We unambiguously confirm via direct experimental evidence that the long-lived (∼5 ns) excited state is a tetrahedral metal-centered triplet state. These results demonstrate the power of ultrafast X-ray spectroscopies to unambiguously elucidate the nature of excited states in important transition-metal-based photocatalytic systems.
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Affiliation(s)
- Rachel
F. Wallick
- Department
of Chemistry, University of Illinois at
Urbana—Champaign, Urbana, Illinois 61801, United States
| | - Sagnik Chakrabarti
- Department
of Chemistry, University of Illinois at
Urbana—Champaign, Urbana, Illinois 61801, United States
| | - John H. Burke
- Department
of Chemistry, University of Illinois at
Urbana—Champaign, Urbana, Illinois 61801, United States
| | - Richard Gnewkow
- Department
of Atomic-Scale Dynamics in Light-Energy Conversion, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin 14109, Germany
- Institute
of Optics and Atomic Physics, Technische
Universität Berlin, Berlin 10623, Germany
| | - Ju Byeong Chae
- Department
of Chemistry, University of Illinois at
Urbana—Champaign, Urbana, Illinois 61801, United States
| | - Thomas C. Rossi
- Department
of Atomic-Scale Dynamics in Light-Energy Conversion, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin 14109, Germany
| | - Ioanna Mantouvalou
- Department
of Atomic-Scale Dynamics in Light-Energy Conversion, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin 14109, Germany
- Institute
of Optics and Atomic Physics, Technische
Universität Berlin, Berlin 10623, Germany
| | - Birgit Kanngießer
- Department
of Atomic-Scale Dynamics in Light-Energy Conversion, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin 14109, Germany
- Institute
of Optics and Atomic Physics, Technische
Universität Berlin, Berlin 10623, Germany
| | - Mattis Fondell
- Department
of Atomic-Scale Dynamics in Light-Energy Conversion, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin 14109, Germany
| | - Sebastian Eckert
- Department
of Atomic-Scale Dynamics in Light-Energy Conversion, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin 14109, Germany
| | - Conner Dykstra
- Department
of Chemistry, University of Illinois at
Urbana—Champaign, Urbana, Illinois 61801, United States
| | - Laura E. Smith
- Department
of Chemistry, University of Illinois at
Urbana—Champaign, Urbana, Illinois 61801, United States
| | - Josh Vura-Weis
- Department
of Chemistry, University of Illinois at
Urbana—Champaign, Urbana, Illinois 61801, United States
| | - Liviu M. Mirica
- Department
of Chemistry, University of Illinois at
Urbana—Champaign, Urbana, Illinois 61801, United States
| | - Renske M. van der Veen
- Department
of Chemistry, University of Illinois at
Urbana—Champaign, Urbana, Illinois 61801, United States
- Department
of Atomic-Scale Dynamics in Light-Energy Conversion, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin 14109, Germany
- Institute
of Optics and Atomic Physics, Technische
Universität Berlin, Berlin 10623, Germany
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4
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Hung TC, Godinez-Loyola Y, Steinbrecher M, Kiraly B, Khajetoorians AA, Doltsinis NL, Strassert CA, Wegner D. Activating the Fluorescence of a Ni(II) Complex by Energy Transfer. J Am Chem Soc 2024; 146:8858-8864. [PMID: 38513215 PMCID: PMC10996004 DOI: 10.1021/jacs.3c07716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 03/07/2024] [Accepted: 03/07/2024] [Indexed: 03/23/2024]
Abstract
Luminescence of open-shell 3d metal complexes is often quenched due to ultrafast intersystem crossing (ISC) and cooling into a dark metal-centered excited state. We demonstrate successful activation of fluorescence from individual nickel phthalocyanine (NiPc) molecules in the junction of a scanning tunneling microscope (STM) by resonant energy transfer from other metal phthalocyanines at low temperature. By combining STM, scanning tunneling spectroscopy, STM-induced luminescence, and photoluminescence experiments as well as time-dependent density functional theory, we provide evidence that there is an activation barrier for the ISC, which, in most experimental conditions, is overcome. We show that this is also the case in an electroluminescent tunnel junction where individual NiPc molecules adsorbed on an ultrathin NaCl decoupling film on a Ag(111) substrate are probed. However, when an MPc (M = Zn, Pd, Pt) molecule is placed close to NiPc by means of STM atomic manipulation, resonant energy transfer can excite NiPc without overcoming the ISC activation barrier, leading to Q-band fluorescence. This work demonstrates that the thermally activated population of dark metal-centered states can be avoided by a designed local environment at low temperatures paired with directed molecular excitation into vibrationally cold electronic states. Thus, we can envisage the use of luminophores based on more abundant transition metal complexes that do not rely on Pt or Ir by restricting vibration-induced ISC.
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Affiliation(s)
- Tzu-Chao Hung
- Institute
for Molecules and Materials, Radboud University, 6500 GL Nijmegen, The Netherlands
- Institute
for Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany
| | - Yokari Godinez-Loyola
- Institut
für Anorganische und Analytische Chemie, University of Münster, 48149 Münster, Germany
- Center
for Nanotechnology (CeNTech), University
of Münster, 48149 Münster, Germany
| | - Manuel Steinbrecher
- Institute
for Molecules and Materials, Radboud University, 6500 GL Nijmegen, The Netherlands
| | - Brian Kiraly
- Institute
for Molecules and Materials, Radboud University, 6500 GL Nijmegen, The Netherlands
| | | | - Nikos L. Doltsinis
- Institut
für Festkörpertheorie and Center for Multiscale Theory
and Computation, University of Münster, 48149 Münster, Germany
| | - Cristian A. Strassert
- Institut
für Anorganische und Analytische Chemie, University of Münster, 48149 Münster, Germany
- Center
for Nanotechnology (CeNTech), University
of Münster, 48149 Münster, Germany
- Cells in
Motion Interfaculty Centre (CiMIC) and Center for Soft Nanoscience
(SoN), University of Münster, 48149 Münster, Germany
| | - Daniel Wegner
- Institute
for Molecules and Materials, Radboud University, 6500 GL Nijmegen, The Netherlands
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5
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Kinigstein ED, Otolski C, Jennings G, Doumy G, Walko DA, Zuo X, Guo J, March AM, Zhang X. Asynchronous x-ray multiprobe data acquisition for x-ray transient absorption spectroscopy. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2023; 94:014714. [PMID: 36725554 DOI: 10.1063/5.0100596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 01/05/2023] [Indexed: 06/18/2023]
Abstract
Laser pump X-ray Transient Absorption (XTA) spectroscopy offers unique insights into photochemical and photophysical phenomena. X-ray Multiprobe data acquisition (XMP DAQ) is a technique that acquires XTA spectra at thousands of pump-probe time delays in a single measurement, producing highly self-consistent XTA spectral dynamics. In this work, we report two new XTA data acquisition techniques that leverage the high performance of XMP DAQ in combination with High Repetition Rate (HRR) laser excitation: HRR-XMP and Asynchronous X-ray Multiprobe (AXMP). HRR-XMP uses a laser repetition rate up to 200 times higher than previous implementations of XMP DAQ and proportionally increases the data collection efficiency at each time delay. This allows HRR-XMP to acquire more high-quality XTA data in less time. AXMP uses a frequency mismatch between the laser and x-ray pulses to acquire XTA data at a flexibly defined set of pump-probe time delays with a spacing down to a few picoseconds. AXMP introduces a novel pump-probe synchronization concept that acquires data in clusters of time delays. The temporally inhomogeneous distribution of acquired data improves the attainable signal statistics at early times, making the AXMP synchronization concept useful for measuring sub-nanosecond dynamics with photon-starved techniques like XTA. In this paper, we demonstrate HRR-XMP and AXMP by measuring the laser-induced spectral dynamics of dilute aqueous solutions of Fe(CN)6 4- and [FeII(bpy)3]2+ (bpy: 2,2'-bipyridine), respectively.
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Affiliation(s)
- Eli Diego Kinigstein
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave., Lemont, Illinois 60439, USA
| | - Christopher Otolski
- Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S. Cass Ave., Lemont, Illinois 60439, USA
| | - Guy Jennings
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave., Lemont, Illinois 60439, USA
| | - Gilles Doumy
- Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S. Cass Ave., Lemont, Illinois 60439, USA
| | - Donald A Walko
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave., Lemont, Illinois 60439, USA
| | - Xiaobing Zuo
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave., Lemont, Illinois 60439, USA
| | - Jinghua Guo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94702, USA
| | - Anne Marie March
- Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S. Cass Ave., Lemont, Illinois 60439, USA
| | - Xiaoyi Zhang
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave., Lemont, Illinois 60439, USA
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6
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Su MF, Tong J, Wang XY, Yu SY. Ancillary ligand-assisted self-assembly of a pyrenylpyridine with Zn(II), Cu(II), Ni(II), and Co(II): Syntheses, structural characterization, and photoluminescence properties. J Mol Struct 2022. [DOI: 10.1016/j.molstruc.2022.133671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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7
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Hu W, Wang D, Ma Q, Reinhart BJ, Zhang X, Huang J. The Impact of Axial Ligation on the Excited State Dynamics of Cobalt(II) Phthalocyanine. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY 2022. [DOI: 10.1016/j.jpap.2022.100132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022] Open
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8
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Samira S, Hong J, Camayang JCA, Sun K, Hoffman AS, Bare SR, Nikolla E. Dynamic Surface Reconstruction Unifies the Electrocatalytic Oxygen Evolution Performance of Nonstoichiometric Mixed Metal Oxides. JACS AU 2021; 1:2224-2241. [PMID: 34977894 PMCID: PMC8715492 DOI: 10.1021/jacsau.1c00359] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Indexed: 05/26/2023]
Abstract
Compositionally versatile, nonstoichiometric, mixed ionic-electronic conducting metal oxides of the form A n+1B n O3n+1 (n = 1 → ∞; A = rare-earth-/alkaline-earth-metal cation; B = transition-metal (TM) cation) remain a highly attractive class of electrocatalysts for catalyzing the energy-intensive oxygen evolution reaction (OER). The current design strategies for describing their OER activities are largely derived assuming a static, unchanged view of their surfaces, despite reports of dynamic structural changes to 3d TM-based perovskites during OER. Herein, through variations in the A- and B-site compositions of A n+1B n O3n+1 oxides (n = 1 (A2BO4) or n = ∞ (ABO3); A = La, Sr, Ca; B = Mn, Fe, Co, Ni), we show that, in the absence of electrolyte impurities, surface restructuring is universally the source of high OER activity in these oxides and is dependent on the initial oxide composition. Oxide surface restructuring is induced by irreversible A-site cation dissolution, resulting in in situ formation of a TM oxyhydroxide shell on top of the parent oxide core that serves as the active surface for OER. The rate of surface restructuring is found to depend on (i) composition of A-site cations, with alkaline-earth-metal cations dominating lanthanide cation dissolution, (ii) oxide crystal phase, with n = 1 A2BO4 oxides exhibiting higher rates of A-site dissolution in comparison to n = ∞ ABO3 perovskites, (iii) lattice strain in the oxide induced by mixed rare-earth- and alkaline-earth-metal cations in the A-site, and (iv) oxide reducibility. Among the in situ generated 3d TM oxyhydroxide structures from A n+1B n O3n+1 oxides, Co-based structures are characterized by superior OER activity and stability, even in comparison to as-synthesized Co-oxyhydroxide, pointing to the generation of high active surface area structures through oxide restructuring. These insights are critical toward the development of revised design criteria to include surface dynamics for effectively describing the OER activity of nonstoichiometric mixed-metal oxides.
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Affiliation(s)
- Samji Samira
- Department
of Chemical Engineering and Materials Science, Wayne State University, Detroit, Michigan 48202, United States
| | - Jiyun Hong
- Stanford
Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - John Carl A. Camayang
- Department
of Chemical Engineering and Materials Science, Wayne State University, Detroit, Michigan 48202, United States
| | - Kai Sun
- Department
of Materials Science and Engineering, University
of Michigan, Ann Arbor, Michigan 48109, United States
| | - Adam S. Hoffman
- Stanford
Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Simon R. Bare
- Stanford
Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Eranda Nikolla
- Department
of Chemical Engineering and Materials Science, Wayne State University, Detroit, Michigan 48202, United States
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9
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Phelan BT, Mara MW, Chen LX. Excited-state structural dynamics of nickel complexes probed by optical and X-ray transient absorption spectroscopies: insights and implications. Chem Commun (Camb) 2021; 57:11904-11921. [PMID: 34695174 DOI: 10.1039/d1cc03875c] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Excited states of nickel complexes undergo a variety of photochemical processes, such as charge transfer, ligation/deligation, and redox reactions, relevant to solar energy conversion and photocatalysis. The efficiencies of the aforementioned processes are closely coupled to the molecular structures in the ground and excited states. The conventional optical transient absorption spectroscopy has revealed important excited-state pathways and kinetics, but information regarding the metal center, in particular transient structural and electronic properties, remains limited. These deficiencies are addressed by X-ray transient absorption (XTA) spectroscopy, a detailed probe of 3d orbital occupancy, oxidation state and coordination geometry. The examples of excited-state structural dynamics of nickel porphyrin and nickel phthalocyanine have been described from our previous studies with highlights on the unique structural information obtained by XTA spectroscopy. We close by surveying prospective applications of XTA spectroscopy to active areas of Ni-based photocatalysis based on the knowledge gained from our previous studies.
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Affiliation(s)
- Brian T Phelan
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, USA.
| | - Michael W Mara
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, USA. .,Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
| | - Lin X Chen
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, USA. .,Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
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10
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Ting SI, Garakyaraghi S, Taliaferro CM, Shields BJ, Scholes GD, Castellano FN, Doyle AG. 3d-d Excited States of Ni(II) Complexes Relevant to Photoredox Catalysis: Spectroscopic Identification and Mechanistic Implications. J Am Chem Soc 2020; 142:5800-5810. [PMID: 32150401 DOI: 10.1021/jacs.0c00781] [Citation(s) in RCA: 162] [Impact Index Per Article: 32.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Synthetic organic chemistry has seen major advances due to the merger of nickel and photoredox catalysis. A growing number of Ni-photoredox reactions are proposed to involve generation of excited nickel species, sometimes even in the absence of a photoredox catalyst. To gain insights about these excited states, two of our groups previously studied the photophysics of Ni(t-Bubpy)(o-Tol)Cl, which is representative of proposed intermediates in many Ni-photoredox reactions. This complex was found to have a long-lived excited state (τ = 4 ns), which was computationally assigned as a metal-to-ligand charge transfer (MLCT) state with an energy of 1.6 eV (38 kcal/mol). This work evaluates the computational assignment experimentally using a series of related complexes. Ultrafast UV-Vis and mid-IR transient absorption data suggest that a MLCT state is generated initially upon excitation but decays to a long-lived state that is 3d-d rather than 3MLCT in character. Dynamic cis,trans-isomerization of the square planar complexes was observed in the dark using 1H NMR techniques, supporting that this 3d-d state is tetrahedral and accessible at ambient temperature. Through a combination of transient absorption and NMR studies, the 3d-d state was determined to lie ∼0.5 eV (12 kcal/mol) above the ground state. Because the 3d-d state features a weak Ni-aryl bond, the excited Ni(II) complexes can undergo Ni homolysis to generate aryl radicals and Ni(I), both of which are supported experimentally. Thus, photoinduced Ni-aryl homolysis offers a novel mechanism of initiating catalysis by Ni(I).
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Affiliation(s)
- Stephen I Ting
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Sofia Garakyaraghi
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Chelsea M Taliaferro
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Benjamin J Shields
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Gregory D Scholes
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Felix N Castellano
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Abigail G Doyle
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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Ryland ES, Zhang K, Vura-Weis J. Sub-100 fs Intersystem Crossing to a Metal-Centered Triplet in Ni(II)OEP Observed with M-Edge XANES. J Phys Chem A 2019; 123:5214-5222. [DOI: 10.1021/acs.jpca.9b03376] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Elizabeth S. Ryland
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Kaili Zhang
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Josh Vura-Weis
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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Hong J, Fauvell TJ, Helweh W, Zhang X, Chen LX. Investigation of the photoinduced axial ligation process in the excited state of nickel(II) phthalocyanine. J Photochem Photobiol A Chem 2019. [DOI: 10.1016/j.jphotochem.2018.12.026] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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