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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Rationalizing Photophysics of Co(III) Complexes with Pendant Pyrene Moieties

Inorganic Chemistry, Год журнала: 2025, Номер unknown

Опубликована: Янв. 9, 2025

Pendant organic chromophores have been used to improve the photocatalytic performance of many metal-based photosensitizers, particularly in first-row metals, by increasing π conjugation ligands and lowering energy photoactive absorption band. Using a combination spectroscopic studies computational modeling, we rationalize excited state dynamics Co(III) complex containing pendant pyrene moieties, CoL1, where L1 = 1,1′-(4-(pyren-1-yl)pyridine-2,6-diyl)bis(3-methyl-1H-imidazol-3-ium). CoL1 displays higher visible absorptivity, blue luminescence from singlet states compared with CoL0 [L0 1,1′-(pyridine-2,6-diyl)bis(3-methyl-1H-imidazol-3-ium)] which moiety is absent. Emissive properties are highly influenced metal center, reducing fluorescence lifetime 5.9 3.5 ns, shift 43 nm. The lower d orbitals Fe(II) drastically affects character state, resulting mixture intraligand charge-transfer (1ILCT) ligand-to-metal (1LMCT) character. Transient experiments revealed that although dark triplet (3ILPyrene) present, it not efficiently populated possesses short nanosecond-scale lifetime. Instead, metal-centered (3MC) dominate decay path 2.4 ps lifetime, no photoactivity toward oxygen formation or triplet–triplet transfer (TTET). This work shows how various factors can influence excited-state dynamics.

Язык: Английский

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Beyond the First Coordination Sphere─Manipulating the Excited-State Landscape in Iron(II) Chromophores with Protons

Journal of the American Chemical Society, Год журнала: 2024, Номер 146(29), С. 19710 - 19719

Опубликована: Июль 11, 2024

Molecular transition metal chromophores play a central role in light harvesting and energy conversion. Recently, earth-abundant transition-metal-based have begun to challenge the dominance of platinum group complexes this area. However, development new with optimized photophysical properties is still limited by lack synthetic methods, especially respect heteroleptic functional ligands. Here, we demonstrate facile efficient method for combination strong-field carbenes 2,2'-bibenzimidazole ligand iron(II) chromophore complex. Our approach yields two isomers that differ predominantly their excited-state lifetimes based on symmetry field. Deprotonation both leads significant red-shift metal-to-ligand charge transfer (MLCT) absorption shortening lifetimes. Femtosecond transient spectroscopy quantum chemical simulations resonance Raman reveals complex relationship between protonation properties. Protonation found tip balance MLCT metal-centered (MC) excited states favor former. This study showcases first example fine-tuning landscape an through second-sphere manipulations provides perspective optimizations 3d chromophores.

Язык: Английский

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High-Efficiency, Long-Lived, Multicolor Tunable Pure Organic Materials for Dual Fluorescent-Phosphorescent Emission at Room Temperature

ACS Applied Optical Materials, Год журнала: 2025, Номер unknown

Опубликована: Янв. 10, 2025

Currently, numerous afterglow materials often suffer from low phosphorescence quantum yields (ΦPh) and are confined to a singular luminescent color. In this study, we devised an approach by incorporating four distinct carbazole derivative guest molecules, featuring varying degrees of halogen substitution naphthalene group sites, into β-estradiol host molecules through high-temperature melt doping create exceptional organic composites. Remarkably, all exhibit characteristics, including prolonged lifetimes ultrahigh yields, with the pinnacle lifetime soaring 904.76 ms peak yield achieving remarkable 40.0%. Notably, even without heavy atom incorporation, phosphors managed attain ΦPh 18.0%, underscoring their unique properties. Furthermore, our experiments unveiled intriguing phenomenon: rather than single fluorescence or emission, these dual-emission encompassing both phosphorescence. The versatility in luminescence color manipulation was further demonstrated adjusting temperature excitation wavelength, offering unparalleled flexibility. Moreover, hues could be finely tuned number atoms, adding another layer tunability. Theoretical calculations provided valuable insights, showing that changes bromine substitutions positions significantly affect molecule's spin–orbit coupling constants nature its excited states. This understanding not only highlights molecular mechanisms behind observed properties but also provides roadmap for future design optimization such advanced materials.

Язык: Английский

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A Blessing and a Curse: Remote Ligand Functionalization Modulates ³MLCT Relaxation in Group 6 Tricarbonyl Complexes

Inorganic Chemistry, Год журнала: 2025, Номер unknown

Опубликована: Фев. 25, 2025

We recently reported a molecular design for carbonylpyridine molybdenum(0) complexes that unlocks long-lived luminescent and photoactive charge-transfer states. Here, we translate this strategy to chromium(0), tungsten(0) report three fully characterized tricarbonyl metal(0) featuring tripodal ligand with remote n-butyl substituent in the backbone. All show phosphorescence red near-infrared spectral region from metal-to-ligand excited Surprisingly, alkyl chain significantly affects state relaxation: lifetimes are shortened solution but extended solid by one order of magnitude compared complex methyl substituent. Temperature-dependent luminescence NMR spectroscopy combination quantum chemical calculations reveal reasons these disparate effects. The distorts metal coordination geometry. resulting structural flexibility flattens potential energy surfaces solution, which lowers barrier population distorted metal-centered states facilitates nonradiative relaxation. In state, rigidified separates neighboring molecules, reduces self-quenching. Our study sheds light on relationship between structure relaxation inform development based earth-abundant metals.

Язык: Английский

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Molecular Design Principles for Photoactive Transition Metal Complexes: A Guide for “Photo-Motivated” Chemists

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

Опубликована: Март 27, 2025

Luminescence and photochemistry involve electronically excited states that are inherently unstable therefore spontaneously decay to electronic ground states, in most cases by nonradiative energy release generates heat. This dissipation can occur on a time scale of 100 fs (∼10–13 s) usually needs be slowed down at least the nanosecond (∼10–9 for luminescence intermolecular occur. is challenging task with many different factors consider. An alternative emerging strategy target dissociative lead metal–ligand bond homolysis subnanosecond access synthetically useful radicals. Based thorough review recent advances field, this article aims provide concise guide obtaining luminescent photochemically coordination compounds d-block elements. We hope encourage "photo-motivated" chemists who have been reluctant apply their synthetic other knowledge photophysics photochemistry, we intend stimulate new approaches control state behavior.

Язык: 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, Год журнала: 2025, Номер unknown

Опубликована: Апрель 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.

Язык: Английский

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Sterically Encumbered Aryl Isocyanides Extend Excited-State Lifetimes and Improve the Photocatalytic Performance of Three-Coordinate Copper(I) β-Diketiminate Charge-Transfer Chromophores

Journal of the American Chemical Society, Год журнала: 2024, Номер 146(24), С. 16848 - 16855

Опубликована: Июнь 10, 2024

Copper(I) complexes are prominent candidates to replace noble metal-based photosensitizers. We recently introduced a three-coordinate design for copper(I) charge-transfer chromophores that pair β-diketiminate ligands with aryl isocyanides. The excited-state lifetime in these compounds can be extended using bichromophoric "triplet reservoir" strategy, which comes at the expense of decrease energy and reducing power. In this work, we introduce complementary, sterically driven strategy increasing lifetimes photosensitizers, gives higher-energy, more strongly triplet state than does bichromophore approach. presented (Cu1–Cu4) have general formula Cu(CyNacNacMe)(CN-Ar), where CyNacNacMe is cyclohexyl-substituted CN-Ar an isocyanide variable steric profile. Their structural features electrochemical photophysical properties described. encumbered 2,6-diisopropylphenyl or m-terphenyl (Cu2–Cu4) exhibit prolonged relative those parent 2,6-dimethylphenyl compound Cu1. Specifically, one compounds, Cu3, displays 276 ns, approximately 30 times longer Cu1 (9.3 ns). photoluminescence quantum yield Cu3 (0.09) also increases by two orders magnitude compared (0.0008). strong power (*Eox = −2.4 V vs Fc+/0) long lead higher yields photoredox photocatalytic isomerization reactions, include dehalogenation and/or hydrodgenation benzophenone substrates, C–O bond activation lignin model substrate, E/Z stilbene.

Язык: Английский

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Ferromagnetically Coupled Chromium(III) Dimer Shows Luminescence and Sensitizes Photon Upconversion

Chemistry - A European Journal, Год журнала: 2024, Номер 30(31)

Опубликована: Март 25, 2024

Abstract There has been much progress on mononuclear chromium(III) complexes featuring luminescence and photoredox activity, but dinuclear have remained underexplored in these contexts until now. We identified a tridentate chelate ligand able to accommodate both meridional facial coordination of chromium(III), either access mono‐ or complex depending reaction conditions. This causes tetragonally distorted primary spheres around complexes, entailing comparatively short excited‐state lifetimes the range 400 800 ns solution at room temperature making photoluminescence essentially oxygen insensitive. The two ions dimer experience ferromagnetic exchange interactions that result high spin ( S =3) ground state with coupling constant +9.3 cm −1 . Photoinduced energy transfer from luminescent ferromagnetically coupled an anthracene derivative results sensitized triplet‐triplet annihilation upconversion. Based proof‐of‐principle studies, seem attractive for development fundamentally new types photophysics photochemistry enabled by magnetic interactions.

Язык: Английский

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Isostructural Series of a Cyclometalated Iron Complex in Three Oxidation States

Inorganic Chemistry, Год журнала: 2024, Номер 63(37), С. 16964 - 16980

Опубликована: Сен. 2, 2024

An isostructural series of Fe

Язык: Английский

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