Visible‐to‐UV Photon Upconversion: Recent Progress in New Materials and Applications

Angewandte Chemie International Edition, Journal Year: 2023, Volume and Issue: 62(25)

Published: March 8, 2023

Ultraviolet (UV, λ<400 nm) light is essential for various photochemical reactions, but its intensity in the solar spectrum very low, and sources that artificially generate high-energy UV are inefficient environmentally unfriendly. A solution to this problem photon upconversion (UC) from visible (vis, λ>400 light. Among several mechanisms, UC based on triplet-triplet annihilation (TTA-UC) particular has made remarkable progress recent years. The development of new chromophores enabled highly efficient conversion low-intensity into In review, we summarize visible-to-UV TTA-UC, their production films application processes such as catalysis, bond activation polymerization. Finally, challenges opportunities future material applications will be discussed.

Language: Английский

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Cobalt(III) Carbene Complex with an Electronic Excited-State Structure Similar to Cyclometalated Iridium(III) Compounds

Journal of the American Chemical Society, Journal Year: 2022, Volume and Issue: 144(22), P. 9859 - 9873

Published: May 27, 2022

Many organometallic iridium(III) complexes have photoactive excited states with mixed metal-to-ligand and intraligand charge transfer (MLCT/ILCT) character, which form the basis for numerous applications in photophysics photochemistry. Cobalt(III) analogous MLCT excited-state properties seem to be unknown yet, despite fact that cobalt(III) can adopt identical low-spin d6 valence electron configurations due their close chemical relationship. Using a rigid tridentate chelate ligand (LCNC), central amido π-donor is flanked by two σ-donating N-heterocyclic carbene subunits, we obtained robust homoleptic complex [Co(LCNC)2](PF6), featuring state substantial character. Compared vast majority of isoelectronic iron(II) complexes, [Co(LCNC)2](PF6) long-lived because it does not deactivate as efficiently into lower-lying metal-centered states; furthermore, engages directly photoinduced reactions. The comparison [Fe(LCNC)2](PF6), well structural, electrochemical, UV–vis transient absorption studies, provides insight new design principles first-row transition-metal photophysical photochemical reminiscent those known from platinum group metals.

Language: 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, Journal Year: 2022, Volume and Issue: 144(31), P. 14181 - 14194

Published: Aug. 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.

Language: Английский

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Best practice in determining key photophysical parameters in triplet–triplet annihilation photon upconversion

Photochemical & Photobiological Sciences, Journal Year: 2022, Volume and Issue: 21(7), P. 1143 - 1158

Published: April 19, 2022

Triplet-triplet annihilation photon upconversion (TTA-UC) is a process in which low-energy light transformed into of higher energy. During the last two decades, it has gained increasing attention due to its potential in, e.g., biological applications and solar energy conversion. The highest efficiencies for TTA-UC systems have been achieved liquid solution, owing that several intermediate steps require close contact between interacting species, something more easily diffusion-controlled environments. There good understanding kinetics dictating performance systems, but so far, community lacks cohesiveness terms how important parameters are best determined experimentally. In this perspective, we discuss present "best practice" determination critical TTA-UC, namely triplet excited state energies, rate constants triplet-triplet ([Formula: see text]), excited-state lifetimes excitation threshold intensity text]). Finally, introduce newly developed method by [Formula: text], text] may be simultaneously using same set time-resolved emission measurements. experiment can performed with simple experimental setup, ran under mild conditions, entirely circumvents need challenging nanosecond transient absorption measurements, technique previously required extract text]. Our hope discussions methodologies presented herein will aid performing efficient manageable experiments while maintaining-and sometimes increasing-the accuracy validity extracted parameters.

Language: 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, Journal Year: 2022, Volume and Issue: 2(10), P. 2367 - 2380

Published: Oct. 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.

Language: Английский

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Water-Soluble Tris(cyclometalated) Iridium(III) Complexes for Aqueous Electron and Energy Transfer Photochemistry

Accounts of Chemical Research, Journal Year: 2022, Volume and Issue: 55(9), P. 1290 - 1300

Published: April 12, 2022

ConspectusCyclometalated iridium(III) complexes are frequently employed in organic light emitting diodes, and they popular photocatalysts for solar energy conversion synthetic chemistry. They luminesce from redox-active excited states that can have high triplet energies long lifetimes, making them well suited transfer photoredox catalysis. Homoleptic tris(cyclometalated) typically very hydrophobic do not dissolve polar solvents, somewhat limiting their application scope. We developed a family of water-soluble sulfonate-decorated variants with tailored redox potentials excited-state to address several key challenges aqueous photochemistry.First, we aimed at combining enzyme catalysis synthesize enantioenriched products cyclic reaction network. Since the biocatalyst operates best solution, photocatalyst was needed. A new complex provided enough reducing power photochemical reduction imines racemic mixtures amines furthermore compatible monoamine oxidase (MAO-N-9), which deracemized this mixture through kinetic resolution amine via oxidation corresponding imine. This process led accumulation unreactive enantiomer over time. In subsequent studies, discovered same photoionizes under intense irradiation give hydrated electrons as result consecutive two-photon excitation. With visible input, become available catalytic fashion, thereby allowing comparatively mild substrates would only be reactive harsher conditions. Finally, became interested upconversion it desirable obtain compounds energies. goal achieved improved ligand design ultimately enabled sensitized triplet–triplet annihilation unusually far into ultraviolet spectral range.Studies catalysis, rely on use solvents. Water could potentially an attractive alternative many cases, but development lags behind solution compared solvent. The purpose Account is provide overview breadth research perspectives emerged fac-[Ir(ppy)]3 (ppy = 2-phenylpyridine) sulfonated ligands. hope inspire some these or related coordination photochemistry stimulate further conceptual developments interfaces chemistry, photophysics, biocatalysis, sustainable

Language: Английский

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Au⋅⋅⋅H−C Interactions Support a Robust Thermally Activated Delayed Fluorescence (TADF) Gold(I) Complex for OLEDs with Little Efficiency Roll‐Off and Good Stability

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(40)

Published: Aug. 6, 2022

Abstract The practical use of luminescent mononuclear gold(I) complexes as optoelectronic materials has been limited by their inferior stability. Herein we demonstrate a strategy to improve the stability which display thermally activated delayed fluorescence (TADF). A highly rigid and groove‐like σ‐donating aryl ligand used form dual Au⋅⋅⋅H−C hydrogen bonds. secondary metal‐ligand interactions have authenticated single‐crystal structure, NMR spectroscopy theoretical simulations. TADF Au I complex exhibits appealing emission properties (photoluminescence quantum yield=76 %; lifetime=1.2 μs) much improved thermal photo‐stability. Vacuum‐deposited organic light‐emitting diodes (OLEDs) show promising electroluminescence with maximum external efficiency (EQE) over 23 % negligible roll‐off even at 10 000 cd m −2 . An estimated LT 50 longer than 77 h initial luminance 100 reveals good operational This work suggests way for design stable complexes.

Language: 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, Journal Year: 2022, Volume and Issue: 144(48), P. 21948 - 21960

Published: Nov. 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.

Language: Английский

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Blue‐to‐UVB Upconversion, Solvent Sensitization and Challenging Bond Activation Enabled by a Benzene‐Based Annihilator

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 62(8)

Published: Nov. 18, 2022

Several energy-demanding photoreactions require harsh UV light from inefficient sources. The conversion of low-energy visible to high-energy singlet states via triplet-triplet annihilation upconversion (TTA-UC) could offer a solution for driving such reactions under mild conditions. We present the first annihilator with an emission maximum in UVB region that, combined organic sensitizer, is suitable blue-to-UVB upconversion. was successfully employed as energy donor subsequent FRET activations aliphatic carbonyls. This hitherto unreported UC-FRET reaction sequence directly monitored using laser spectroscopy and applied mechanistic irradiation experiments demonstrating feasibility Norrish chemistry. Our results provide clear evidence novel blue light-driven substrate or solvent activation strategy, which important context developing more sustainable light-to-chemical systems.

Language: Английский

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Green Light-Triggered Photocatalytic Anticancer Activity of Terpyridine-Based Ru(II) Photocatalysts

Inorganic Chemistry, Journal Year: 2024, Volume and Issue: 63(16), P. 7493 - 7503

Published: April 5, 2024

The relentless increase in drug resistance of platinum-based chemotherapeutics has opened the scope for other new cancer therapies with novel mechanisms action (MoA). Recently, photocatalytic therapy, an intrusive catalytic treatment, is receiving significant interest due to its multitargeting cell death mechanism high selectivity. Here, we report synthesis and characterization three photoresponsive Ru(II) complexes, viz., [Ru(ph-tpy)(bpy)Cl]PF6 (Ru1), [Ru(ph-tpy)(phen)Cl]PF6 (Ru2), [Ru(ph-tpy)(aip)Cl]PF6 (Ru3), where, ph-tpy = 4′-phenyl-2,2′:6′,2″-terpyridine, bpy 2,2′-bipyridine, phen 1,10-phenanthroline, aip 2-(anthracen-9-yl)-1H-imidazo[4,5-f][1,10] phenanthroline, showing anticancer activity. X-ray crystal structures Ru1 Ru2 revealed a distorted octahedral geometry RuN5Cl core. complexes showed intense absorption band 440–600 nm range corresponding metal-to-ligand charge transfer (MLCT) that was further used achieve green light-induced effect. mitochondria-targeting photostable complex Ru3 induced phototoxicity IC50 PI values ca. 0.7 μM 88, respectively, under white light irradiation 1.9 35 against HeLa cells. (Ru1–Ru3) negligible dark cytotoxicity toward normal splenocytes (IC50s > 50 μM). mechanistic study ROS-mediated apoptosis cells via mitochondrial depolarization or exposure. Interestingly, also acted as highly potent catalyst NADH photo-oxidation light. This process contributed photocytotoxicity complexes. Overall, presented synergistic type I II photochemotherapeutic effects.

Language: Английский

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