Leveraging Intramolecular π-Stacking to Access an Exceptionally Long-Lived ³MC Excited State in an Fe(II) Carbene Complex

Journal of the American Chemical Society, Год журнала: 2025, Номер 147(2), С. 1694 - 1708

Опубликована: Янв. 6, 2025

The ability to manipulate excited-state decay cascades using molecular structure is essential the application of abundant-metal photosensitizers and chromophores. Ligand design has yielded some spectacular results elongating charge-transfer excited state lifetimes Fe(II) coordination complexes, but triplet metal-centered (3MC) states─recently demonstrated be critical photoactivity isoelectronic Co(III) polypyridyls─have date remained elusive, with temporally isolable examples limited picosecond regime. With this report, we show how strong-field donors intramolecular π-stacking can conspire stabilize a long-lived 3MC for remarkable 4.1 ± 0.3 ns in fluid solution at ambient temperature. Analysis variable-temperature time-resolved absorption data theoretical models ranging from Arrhenius semiclassical Marcus theory, combined computational modeling X-ray crystallography, reveal Jahn-Teller stabilized high activation barrier ground-state recovery. net result chromophore lifetime that orders magnitude longer than anything yet observed an complex.

Язык: Английский

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Making Mo(0) a Competitive Alternative to Ir(III) in Phosphors and Photocatalysts

Journal of the American Chemical Society, Год журнала: 2025, Номер unknown

Опубликована: Янв. 23, 2025

Iridium is used in commercial light-emitting devices and photocatalysis but among the rarest stable chemical elements. Therefore, replacing iridium(III) photoactive molecular complexes with abundant metals of great interest. First-row transition generally tend to yield poorer luminescence behavior, it remains difficult obtain excited states redox properties that exceed those noble-metal-based photocatalysts. Here, we overcome these challenges a nonprecious second-row metal. Tailored coordination spheres for molybdenum(0) lead photoluminescence quantum yields rival photochemical reduction reactions not normally achievable become possible. These developments open new perspectives noble lighting applications Earth-abundant advancing metal-based beyond current limits.

Язык: Английский

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Factors that Impact Photochemical Cage Escape Yields

Chemical Reviews, Год журнала: 2024, Номер 124(11), С. 7379 - 7464

Опубликована: Май 14, 2024

The utilization of visible light to mediate chemical reactions in fluid solutions has applications that range from solar fuel production medicine and organic synthesis. These are typically initiated by electron transfer between a photoexcited dye molecule (a photosensitizer) redox-active quencher yield radical pairs intimately associated within solvent cage. Many these radicals undergo rapid thermodynamically favored "geminate" recombination do not diffuse out the cage surrounds them. Those escape useful reagents may subsequent important above-mentioned applications. process factors determine yields remain poorly understood despite decades research motivated their practical fundamental importance. Herein, state-of-the-art on light-induced appeared since seminal 1972 review J. P. Lorand entitled "The Cage Effect" is reviewed. This also provides some background for those new field discusses both homolytic bond photodissociation bimolecular induced reactions. concludes with key goals directions future promise elevate this very vibrant even greater heights.

Язык: Английский

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Controlling the Photophysical Properties of a Series of Isostructural d⁶ Complexes Based on Cr⁰, Mn^I, and Fe^II

Journal of the American Chemical Society, Год журнала: 2024, Номер 146(7), С. 4605 - 4619

Опубликована: Фев. 9, 2024

Development of first-row transition metal complexes with similar luminescence and photoredox properties as widely used RuII polypyridines is attractive because metals from the first series are comparatively abundant inexpensive. The weaker ligand field experienced by valence d-electrons challenges installation same types metal-to-ligand charge transfer (MLCT) excited states in precious complexes, due to rapid population energetically lower-lying metal-centered (MC) states. In a family isostructural tris(diisocyanide) 3d6 Cr0, MnI, FeII, increasing effective nuclear strength allow us control energetic order between 3MLCT 3MC states, whereas pyrene decoration isocyanide framework provides over intraligand (ILPyr) chromium(0) complex shows red phosphorescence all other higher energy. manganese(I) complex, microsecond-lived dark 3ILPyr state, reminiscent electronic encountered many polyaromatic hydrocarbon compounds, lowest becomes photoactive. iron(II) MLCT state has shifted so much energy that 1ILPyr fluorescence occurs, parallel excited-state deactivation pathways. Our combined synthetic-spectroscopic-theoretical study unprecedented insights into how charge, strength, π-conjugation affect ligand-based under what circumstances these individual become luminescent exploitable photochemistry. Such key further developments photoredox-active complexes.

Язык: Английский

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Aziridination via Nitrogen-Atom Transfer to Olefins from Photoexcited Azoxy-Triazenes

Journal of the American Chemical Society, Год журнала: 2024, Номер 146(14), С. 9499 - 9505

Опубликована: Март 24, 2024

Herein, we report that readily accessible azoxy-triazenes can serve as nitrogen atom sources under visible light excitation for the phthalimido-protected aziridination of alkenes. This approach eliminates need external oxidants, precious transition metals, and photocatalysts, marking a departure from conventional methods. The versatility this transformation extends to selective both activated unactivated multisubstituted alkenes varying electronic profiles. Notably, process avoids formation competing C–H insertion products. described protocol is operationally simple, scalable, adaptable photoflow conditions. Mechanistic studies support idea photofragmentation results in generation free singlet nitrene. Furthermore, mild photoredox-catalyzed N–N cleavage protecting group furnish aziridines reported. Our findings contribute advancement sustainable practical methodologies synthesis nitrogen-containing compounds, showcasing potential broader applications synthetic chemistry.

Язык: Английский

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Reversible Photoinduced Ligand Substitution in a Luminescent Chromium(0) Complex

Journal of the American Chemical Society, Год журнала: 2024, Номер 146(15), С. 10418 - 10431

Опубликована: Апрель 8, 2024

Light-triggered dissociation of ligands forms the basis for many compounds interest photoactivated chemotherapy (PACT), in which medicinally active substances are released or "uncaged" from metal complexes upon illumination. Photoinduced ligand is usually irreversible, and recent studies performed context PACT focused on ruthenium(II) polypyridines related heavy complexes. Herein, we report a first-row transition complex, photoinduced spontaneous recoordination unit occurs. Two scorpionate-type tridentate chelates provide an overall six-coordinate arylisocyanide environment chromium(0). Photoexcitation causes decoordination one these six ligating units coordination solvent molecule, at least tetrahydrofuran 1,4-dioxane solvents, but far less toluene, below detection limit cyclohexane. Transient UV-vis absorption spectroscopy quantum chemical simulations point to directly excited metal-to-ligand charge-transfer state. Owing chelate design substitution lability metal, photodissociated can occur spontaneously millisecond time scale. This work provides insight into possible self-healing mechanisms counteracting unwanted photodegradation processes seems furthermore relevant contexts photoswitching (photo)chemical information storage.

Язык: Английский

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Iron(III) Carbene Complexes with Tunable Excited State Energies for Photoredox and Upconversion

Journal of the American Chemical Society, Год журнала: 2024, Номер unknown

Опубликована: Апрель 10, 2024

Substituting precious elements in luminophores and photocatalysts by abundant first-row transition metals remains a significant challenge, iron continues to be particularly attractive owing its high natural abundance low cost. Most complexes known date face severe limitations due undesirably efficient deactivation of luminescent photoredox-active excited states. Two new iron(III) with structurally simple chelate ligands enable straightforward tuning ground state properties, contrasting recent examples, which chemical modification had minor impact. Crude samples feature two luminescence bands strongly reminiscent complex, this observation was attributed dual luminescence, but our case, there is clear-cut evidence that the higher-energy stems from an impurity only red photoluminescence doublet ligand-to-metal charge transfer (2LMCT) genuine. Photoinduced oxidative reductive electron reactions methyl viologen 10-methylphenothiazine occur nearly diffusion-limited kinetics. Photocatalytic not previously reported for compound class, particular C–H arylation diazonium salts aerobic hydroxylation boronic acids, were achieved low-energy light excitation. Doublet–triplet energy (DTET) 2LMCT anthracene annihilator permits proof principle triplet–triplet annihilation upconversion based on molecular photosensitizer. These findings are relevant development featuring photophysical photochemical properties competitive noble-metal-based compounds.

Язык: Английский

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Low-energy photoredox catalysis

Nature Reviews Chemistry, Год журнала: 2024, Номер unknown

Опубликована: Ноя. 11, 2024

Язык: Английский

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Efficient Energy and Electron Transfer Photocatalysis with a Coulombic Dyad

Journal of the American Chemical Society, Год журнала: 2024, Номер 146(37), С. 25799 - 25812

Опубликована: Сен. 3, 2024

Photocatalysis holds great promise for changing the way value-added molecules are currently prepared. However, many photocatalytic reactions suffer from quantum yields well below 10%, hampering transition lab-scale to large-scale or even industrial applications. Molecular dyads can be designed such that beneficial properties of inorganic and organic chromophores combined, resulting in milder reaction conditions improved reactions. We have developed a novel approach obtaining advantages molecular without time- resource-consuming synthesis these tailored photocatalysts. Simply by mixing cationic ruthenium complex with an anionic pyrene derivative water salt bichromophore is produced owing electrostatic interactions. The long-lived triplet state obtained static quantitative energy transfer preorganized complex. exploited this so-called Coulombic dyad catalysis similar reactivity higher photostability compared reference photosensitizers several photooxygenations. In addition, it was shown system also used maximize yield photoredox This due intrinsically cage escape after photoinduced electron purely compounds heavy atom-containing molecules. combination laboratory-scale as mechanistic irradiation experiments detailed spectroscopic investigations provided deep insights into easy-to-use photocatalyst class.

Язык: Английский

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Low Temperature Emissive Cyclometalated Cobalt(III) Complexes

Inorganic Chemistry, Год журнала: 2025, Номер unknown

Опубликована: Янв. 14, 2025

A series of CoIII complexes [Co(RImP)2][PF6], with HMeImP = 1,1'-(1,3-phenylene)bis(3-methyl-1-imidazole-2-ylidene)) and R Me, Et, iPr, nBu, is presented in this work. The influence the strong donor ligand on ground excited-state photophysical properties was investigated context different alkyl substituents at imidazole nitrogen. X-ray diffraction revealed no significant alterations structures all differences emerge from electronic structures. These were probed via cyclic voltammetry UV-vis spectroscopy, detailing ground-state properties. All are emissive 77 K a 3MC state, which exhibits lifetimes range 1-5 ns room temperature, depending substituent. Therefore, it clearly shown that even small structure have large impact details excited state landscape. observed behavior rationalized by detailed DFT analysis, shows minimum-energy crossing point to located only slightly above MC energy: Consequently, nonradiative decay temperature enabled, while path prohibited, leading low-temperature emission.

Язык: Английский

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