Photoactive Metal-to-Ligand Charge Transfer Excited States in 3d⁶ Complexes with Cr⁰, Mn^I, Fe^II, and Co^III

Journal of the American Chemical Society, Год журнала: 2023, Номер 145(9), С. 4903 - 4920

Опубликована: Фев. 21, 2023

Many coordination complexes and organometallic compounds with the 4d6 5d6 valence electron configurations have outstanding photophysical photochemical properties, which stem from metal-to-ligand charge transfer (MLCT) excited states. This substance class makes extensive use of most precious least abundant metal elements, consequently there has been a long-standing interest in first-row transition photoactive MLCT Semiprecious copper(I) its completely filled 3d subshell is relatively straightforward well explored case, but 3d6 partially d-orbitals lead to energetically low-lying metal-centered (MC) states that can cause undesirably fast state deactivation. Herein, we discuss recent advances made isoelectronic Cr0, MnI, FeII, CoIII compounds, for long-lived become accessible over past five years. Furthermore, possible future developments search new subshells next-generation applications photophysics photochemistry.

Язык: Английский

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A new era of LMCT: leveraging ligand-to-metal charge transfer excited states for photochemical reactions

Chemical Science, Год журнала: 2024, Номер 15(18), С. 6661 - 6678

Опубликована: Янв. 1, 2024

Ligand-to-metal charge transfer (LMCT) excited states showcase promise in enabling photochemical reactions. This article details design principles to enable low energy LMCT and notable examples that drive reactions from these states.

Язык: Английский

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Oxidative two-state photoreactivity of a manganese(IV) complex using near-infrared light

Nature Chemistry, Год журнала: 2024, Номер 16(5), С. 827 - 834

Опубликована: Фев. 8, 2024

Язык: Английский

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Efficient Triplet‐Triplet Annihilation Upconversion Sensitized by a Chromium(III) Complex via an Underexplored Energy Transfer Mechanism

Angewandte Chemie International Edition, Год журнала: 2022, Номер 61(27)

Опубликована: Март 28, 2022

Sensitized triplet-triplet annihilation upconversion (sTTA-UC) mainly relies on precious metal complexes thanks to their high intersystem crossing (ISC) efficiencies, excited state energies, and lifetimes, while of abundant first-row transition metals are only rarely utilized with often moderate UC quantum yields. [Cr(bpmp)

Язык: Английский

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Shedding Light on the Oxidizing Properties of Spin-Flip Excited States in a Cr^III Polypyridine Complex and Their Use in Photoredox Catalysis

Journal of the American Chemical Society, Год журнала: 2022, Номер 144(31), С. 14181 - 14194

Опубликована: Авг. 1, 2022

The photoredox activity of well-known RuII complexes stems from metal-to-ligand charge transfer (MLCT) excited states, in which a ligand-based electron can initiate chemical reductions and metal-centered hole trigger oxidations. CrIII polypyridines show similar properties, although they have fundamentally different electronic structures. Their photoactive state is spin-flip nature, differing the ground merely by change one spin, but with otherwise identical d-orbital occupancy. We find that driving-force dependence for photoinduced 10 donors to complex very polypyridine, thereby validate concept estimating redox potential d3 states analogous manner as MLCT d6 compounds. Building on this insight, we use our photocatalytic reactions not previously explored compound class, including aerobic bromination methoxyaryls, oxygenation 1,1,2,2-tetraphenylethylene, hydroxylation arylboronic acids, vinylation N-phenyl pyrrolidine. This work contributes understanding fundamental photochemical properties first-row transition-metal comparison well-explored precious-metal-based photocatalysts.

Язык: Английский

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Charge‐Transfer and Spin‐Flip States: Thriving as Complements

Angewandte Chemie International Edition, Год журнала: 2022, Номер 62(15)

Опубликована: Окт. 4, 2022

Abstract Transition metal complexes with photoactive charge‐transfer excited states are pervasive throughout the literature. In particular, [Ru(bpy) 3 ] 2+ (bpy=2,2′‐bipyridine), its metal‐to‐ligand emission, has been established as a key complex. Meanwhile, interest in so‐called spin‐flip metal‐centered risen dramatically after molecular ruby [Cr(ddpd) 2 3+ (ddpd= N , ′‐dimethyl‐ ′‐dipyridin‐2‐yl‐pyridine‐2,6‐diamine) led to design principles access strong, long‐lived emission from photostable chromium(III) complexes. This Review contrasts properties of emissive and by using prototypical examples. We discuss relevant states, tunability their energy lifetimes, response external stimuli. Finally, we identify strengths weaknesses applications such photocatalysis circularly polarized luminescence.

Язык: Английский

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Zinc(II) Complexes with Triplet Charge-Transfer Excited States Enabling Energy-Transfer Catalysis, Photoinduced Electron Transfer, and Upconversion

JACS Au, Год журнала: 2022, Номер 2(10), С. 2367 - 2380

Опубликована: Окт. 11, 2022

Many CuI complexes have luminescent triplet charge-transfer excited states with diverse applications in photophysics and photochemistry, but for isoelectronic ZnII compounds, this behavior is much less common, they typically only show ligand-based fluorescence from singlet π–π* states. We report two closely related tetrahedral which intersystem crossing occurs appreciable quantum yields leads to the population of intraligand (ILCT) character. In addition showing their initially 1ILCT states, these new compounds therefore undergo triplet–triplet energy transfer (TTET) 3ILCT consequently can act as sensitizers photo-isomerization reactions annihilation upconversion blue ultraviolet spectral range. The photoactive state furthermore facilitates photoinduced electron transfer. Collectively, our findings demonstrate that mononuclear photophysical photochemical properties reminiscent well-known are accessible suitable ligands potentially amenable many different applications. Our insights seem relevant greater context obtaining based on abundant transition metals, complementing precious-metal-based luminophores photosensitizers.

Язык: Английский

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Molecular Design Principles to Elongate the Metal-to-Ligand Charge Transfer Excited-State Lifetimes of Square-Planar Nickel(II) Complexes

Journal of the American Chemical Society, Год журнала: 2022, Номер 144(48), С. 21948 - 21960

Опубликована: Ноя. 23, 2022

Square-planar NiII complexes and their electronically excited states play key roles in cross-coupling catalysis could offer new opportunities to complement well-known isoelectronic PtII luminophores. Metal-to-ligand charge transfer (MLCT) deactivation pathways are particularly relevant these contexts. We sought extend the lifetimes of 3MLCT square-planar by creating coordination environments that seemed well adapted 3d8 valence electron configuration. Using a rigid tridentate chelate ligand, which central cyclometalated phenyl unit is flanked two coordinating N-heterocyclic carbenes, along with monodentate isocyanide very strong ligand field created. Bulky substituents at backbone furthermore protect center from nucleophilic attack axial directions. UV-Vis transient absorption spectroscopies reveal upon excitation into 1MLCT bands ultrafast intersystem crossing state, latter relaxes onward metal-centered triplet state (3MC). A torsional motion NiII-carbon bond elongation facilitate relaxation 3MC state. The lifetime gets longer increasing strength improved steric protection, thereby revealing clear design guidelines for enhanced photophysical properties. longest reached solution room temperature 48 ps, factor 5-10 compared previously investigated complexes. Our study contributes making first-row transition metal partially filled d-orbitals more amenable applications photophysics photochemistry.

Язык: Английский

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NIR‐Circularly Polarized Luminescence from Chiral Complexes of Lanthanides and d‐Metals

Angewandte Chemie International Edition, Год журнала: 2023, Номер 62(25)

Опубликована: Март 22, 2023

Abstract In recent years, circularly polarized luminescence (CPL) has witnessed a renaissance, due to the increased popularity of CPL as spectroscopic technique and greater accessibility instrumentation. New efficient emitters have been designed many applications, ranging from electronic devices microscopy proposed. Most examples are within visible range, while few cases near infrared (NIR) active complexes available. NIR‐CPL compounds may applications in telecommunication industry, bioassays. following, we shall give an overview developments allowing for measurements NIR‐CPL, describe chiroptical properties metal which achieve this feat.

Язык: Английский

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The Nephelauxetic Effect Becomes an Important Design Factor for Photoactive First‐Row Transition Metal Complexes

Angewandte Chemie International Edition, Год журнала: 2023, Номер 62(30)

Опубликована: Апрель 14, 2023

Abstract The expansion of d‐orbitals as a result metal‐ligand bond covalence, the so‐called nephelauxetic effect, is well‐established concept coordination chemistry, yet its importance for design new photoactive complexes based on first‐row transition metals only beginning to be recognized. Until recently, much focus has been optimizing ligand field strength, geometries, and molecular rigidity, but now it becomes evident that effect can game changer regarding photophysical properties 3d metal in solution at room temperature. In Cr III Mn IV with d 3 valence electron configuration, was exploited shift well‐known ruby‐like red luminescence near‐infrared spectral region. Fe II Co low‐spin 6 charge‐transfer excited states were stabilized respect detrimental metal‐centered states, improve their enhance application potential. isoelectronic (3d ) isocyanide 0 I , likely play well, enabling other favorable photoreactivity. This minireview illustrates broad applicability tailoring photochemical compounds made from abundant metals.

Язык: Английский

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