Mechanisms of Photoredox Catalysis Featuring Nickel–Bipyridine Complexes

ACS Catalysis, Journal Year: 2024, Volume and Issue: 14(11), P. 9055 - 9076

Published: May 29, 2024

Metallaphotoredox catalysis can unlock useful pathways for transforming organic reactants into desirable products, largely due to the conversion of photon energy chemical potential drive redox and bond transformation processes. Despite importance these processes cross-coupling reactions other transformations, their mechanistic details are only superficially understood. In this review, we have provided a detailed summary various photoredox mechanisms that been proposed date Ni-bipyridine (bpy) complexes, focusing separately on photosensitized direct excitation reaction By highlighting multiple key findings, depict how mechanisms, which ultimately define substrate scope, themselves defined by ground- excited-state geometric electronic structures Ni-based intermediates. We further identify knowledge gaps motivate future studies development synergistic research approaches spanning physical, organic, inorganic chemistry communities.

Language: Английский

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Ultrafast Photophysics of Ni(I)–Bipyridine Halide Complexes: Spanning the Marcus Normal and Inverted Regimes

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(22), P. 15506 - 15514

Published: May 22, 2024

Owing to their light-harvesting properties, nickel–bipyridine (bpy) complexes have found wide use in metallaphotoredox cross-coupling reactions. Key these transformations are Ni(I)–bpy halide intermediates that absorb a significant fraction of light at relevant reaction irradiation wavelengths. Herein, we report ultrafast transient absorption (TA) spectroscopy on library eight complexes, the first such characterization any Ni(I) species. The TA data reveal formation and decay Ni(I)-to-bpy metal-to-ligand charge transfer (MLCT) excited states (10–30 ps) whose relaxation dynamics well described by vibronic Marcus theory, spanning normal inverted regions as result simple changes bpy substituents. While lifetimes relatively long for MLCT first-row transition metal duration precludes excited-state bimolecular reactivity photoredox We also present one-step method generate an isolable, solid-state species, which decouples light-initiated from dark, thermal cycles catalysis.

Language: Английский

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Excited State Covalency, Dynamics, and Photochemistry of Square Planar Ni-Thiolate Complexes Revealed by Ultrafast X-ray Absorption

Journal of the American Chemical Society, Journal Year: 2025, Volume and Issue: 147(9), P. 7496 - 7506

Published: Feb. 24, 2025

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 dynamics. In particular, we focus ligand field states that dominate photophysics first-row transition metal complexes. We investigate if they can be significantly delocalized off center, possibly yielding photochemical reactivity more similar to charge transfer than metal-centered states. Here, [Ni(mpo)2] (mpo = 2-mercaptopyridine-N-oxide) provides a representative example larger chemical class is active electro- photocatalyst proton reduction. A detailed characterization electronic structure, dynamics, photochemistry presented based ultrafast transient X-ray absorption spectroscopy at S 1s core K-edges. By comparing K-edge ab initio calculations, identify relaxation mechanism where initial ligand-to-metal excitation results in both electron (generating catalytically relevant reduced photoproduct [Ni(mpo)2]-) pseudotetrahedral triplet state. From absorption, found highly onto thiolate ligands, tetrahedral structural distortion shown substantially influence degree delocalization. The significant coordinate target when aiming control covalency square planar

Language: Английский

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Cyclometallated Co(III) Complexes with Lowest-Energy Charge Transfer Excited States Accessible with Visible Light

Journal of the American Chemical Society, Journal Year: 2025, Volume and Issue: unknown

Published: April 10, 2025

The Co(III) complexes, cis-[Co(ppy)2(L)]PF6, where ppy = 2-phenylpyridine and L bpy (2,2'-bipyridine; 1), phen (1,10-phenanthroline; 2), DAP (1,12-diazaperylene; 3), are reported their photophysical properties were investigated to evaluate potential as sensitizers for applications that include solar energy conversion schemes photoredox catalysis. Calculations show cyclometallation in the cis-[Co(ppy)2(L)]PF6 series affords strong Co(dπ)/ppy(π) orbital interactions result a Co/ppy(π*) highest occupied molecular (HOMO) lowest unoccupied (LUMO) localized on diimine ligand, L(π*). Complexes 1-3 exhibit relatively invariant oxidation potentials, whereas reduction event is dependent identity of L, consistent with theoretical predictions. For 3 broad → L(π*) metal/ligand-to-ligand charge transfer (ML-LCT) absorption band observed CH3CN maxima at 507 nm, extending beyond 600 nm. Upon excitation 1ML-LCT transition, transient features population 3ML-LCT excited state lifetimes, τ, 3.0 ps, 4.6 42 ps 1, 2 respectively observed. irradiation 505 able reduce methyl viologen (MV2+), an electron acceptor commonly photocatalytic schemes. To our knowledge, represents first heteroleptic complex combines ligand lowest-lying metal-to-ligand states undergo photoinduced low-energy green light. As such, structural design important step toward d6 photosensitizers based earth abundant metals.

Language: Английский

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Ancillary Ligand-Promoted Charge Transfer in Bis-indole Pyridine Ligand-Based Nickel Complexes

Inorganic Chemistry, Journal Year: 2024, Volume and Issue: unknown

Published: Oct. 16, 2024

There is growing demand for the utilization of first-row transition metal complexes in light-driven processes instead their conventional noble counterparts due to greater sustainability complexes. However, major drawback ultrafast lifetime electronic excited states these complexes, particularly those d

Language: Английский

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Catalytic reduction of trifluoromethylated alkyl bromides and synthesis of alkylated heterocycles under visible light irradiation: synergetic action of a halogen bond and Ni catalysis

Organic Chemistry Frontiers, Journal Year: 2024, Volume and Issue: 11(17), P. 4722 - 4729

Published: Jan. 1, 2024

The concurrent reduction of α-trifluoromethyl alkyl bromides and the cross-coupling THF with heterocycles in one pot have been realized through synergetic action a halogen bond Ni catalysis.

Language: Английский

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A Comprehensive Multireference Study of Excited-State Ni–Br Bond Homolysis in (dtbbpy)Ni^II(aryl)(Br)

Inorganic Chemistry, Journal Year: 2024, Volume and Issue: 63(43), P. 20361 - 20371

Published: Oct. 17, 2024

The mechanism of visible light-driven Ni-C(aryl) bond homolysis in (2,2'-bipyridine)Ni

Language: Английский

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