An Air‐ and Moisture‐stable Zinc(II) Carbene Dithiolate Dimer Showing Fast Thermally Activated Delayed Fluorescence and Dexter Energy Transfer Catalysis**

Mrózek, Ondřej; Mitra, Mousree; Hupp, Bejamin; Belyaev, Andrey; Lüdtke, Nora; Wagner, Dorothee; Wang, Cui; Wenger, Oliver S.; Marian, Christel M.; Steffen, Andreas

doi:10.1002/chem.202203980

Cited by 12 publications

(24 citation statements)

References 66 publications

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“…The development of photoactive metal complexes with earth-abundant metals holds great promise to enable sustainable photocatalysis, (solar) energy conversion, and light-emitting diodes (LEDs). − Hence, considerable efforts have been undertaken to explore this compound class in the recent years , with creative designs utilizing excited states of different characters like metal-to-ligand charge transfer (MLCT), ligand-to-metal charge transfer (LMCT), ligand-to-ligand charge transfer (LL’CT), and metal-centered (MC) states, , covering zirconium, − vanadium, − chromium, − iron, − manganese, − cobalt, , copper, − molybdenum, − and zinc as metal centers , among others.…”

Section: Introductionmentioning

confidence: 99%

Stable Molybdenum(0) Carbonyl Complex for Upconversion and Photoredox Catalysis

Kitzmann

Bertrams

Boden³

et al. 2023

J. Am. Chem. Soc.

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Photoactive complexes with earth-abundant metals have attracted increasing interest in the recent years fueled by the promise of sustainable photochemistry. However, sophisticated ligands with complicated syntheses are oftentimes required to enable photoactivity with nonprecious metals. Here, we combine a cheap metal with simple ligands to easily access a photoactive complex. Specifically, we synthesize the molybdenum(0) carbonyl complex Mo(CO)3(tpe) featuring the tripodal ligand 1,1,1-tris(pyrid-2-yl)ethane (tpe) in two steps with a high overall yield. The complex shows intense deep-red phosphorescence with excited state lifetimes of several hundred nanoseconds. Time-resolved infrared spectroscopy and laser flash photolysis reveal a triplet metal-to-ligand charge-transfer (3MLCT) state as the lowest excited state. Temperature-dependent luminescence complemented by density functional theory (DFT) calculations suggest thermal deactivation of the 3MLCT state via higher lying metal-centered states in analogy to the well-known photophysics of [Ru(bpy)3]2+. Importantly, we found that the title compound is very photostable due to the lack of labilized Mo–CO bonds (as caused by trans-coordinated CO) in the facial configuration of the ligands. Finally, we show the versatility of the molybdenum(0) complex in two applications: (1) green-to-blue photon upconversion via a triplet–triplet annihilation mechanism and (2) photoredox catalysis for a green-light-driven dehalogenation reaction. Overall, our results establish tripodal carbonyl complexes as a promising design strategy to access stable photoactive complexes of nonprecious metals avoiding tedious multistep syntheses.

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Section: Introductionmentioning

confidence: 99%

Stable Molybdenum(0) Carbonyl Complex for Upconversion and Photoredox Catalysis

Kitzmann

Bertrams

Boden³

et al. 2023

J. Am. Chem. Soc.

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“…Photocatalysis driven by charge-transfer (CT) excited states in transition-metal complexes is a central area of investigation in organic synthesis − and in the conversion of solar energy into electricity − (dye-sensitized solar cellsDSSCs) or fuels. − These catalysts are dominated by rare and expensive second- and third-row transition metals such as Ru and Ir . Thus, there has been significant effort over the past decade to replace these metals with earth-abundant metals. − Significant progress has been made using complexes of Cr, − Mo, , W, , Mn, Fe, − Co, , Ni, Cu, − and Zn. , One feature that complicates the use of many metals with d 1 through d 9 configurations is the presence of low-lying metal-centered (MC) or d–d excited states. , Such states are typically highly distorted and have very short lifetimes. Thus, thermal access of such states provides a rapid, nonradiative decay pathway, rendering the overall excited-state lifetime too short to undergo the type of collisional energy or electron transfer necessary for photocatalysis.…”

Section: Introductionmentioning

confidence: 99%

Design Strategies for Luminescent Titanocenes: Improving the Photoluminescence and Photostability of Arylethynyltitanocenes

Barker,

Whittemore,

London

et al. 2023

Inorg. Chem.

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Complexes that undergo ligand-to-metal charge transfer (LMCT) to d0 metals are of interest as possible photocatalysts. Cp2Ti(C2Ph)2 (where C2Ph = phenylethynyl) was reported to be weakly emissive in room-temperature (RT) fluid solution from its phenylethynyl-to-Ti 3LMCT state but readily photodecomposes. Coordination of CuX between the alkyne ligands to give Cp2Ti(C2Ph)2CuX (X = Cl, Br) has been shown to significantly increase the photostability, but such complexes are not emissive in RT solution. Herein, we investigate whether inhibition of alkyne-Ti-alkyne bond compression might be responsible for the increased photostability of the CuX complexes by investigating the decomposition of a structurally constrained analogue, Cp2Ti(OBET) (OBET = o-bis(ethynyl)tolane). To investigate the mechanism of nonradiative decay from the 3LMCT states in Cp2Ti(C2Ph)2CuX, the photophysical properties were investigated both upon deuteration and upon rigidifying in a poly(methyl methacrylate) film. These investigations suggested that inhibition of structural rearrangement may play a dominant role in increasing emission lifetimes and quantum yields. The bulkier Cp*2Ti(C2Ph)2CuBr was prepared and is emissive at 693 nm in RT THF solution with a photoluminescent quantum yield of 1.3 × 10–3 (τ = 0.18 μs). Time-dependent density functional theory (TDDFT) calculations suggest that emission occurs from a 3LMCT state dominated by Cp*-to-Ti charge transfer.

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“…This finding is in stark contrast to carbene-zinc-thiolate emitters based on cyclic(alkyl)(amino)carbenes (cAAC), showing fast TADF. 5 For 8, the π* orbital located on carbene lies higher in energy than in the cAAC complexes, destabilizing the 1/3LLCT (bdt → ITr) states. As a result, ITr-Zn II -thiolate 8 preferably populates the 3 LC(bdt) electronically excited state, yielding long-lived phosphorescence potentially useful for photocatalytic or photochemical transformations, which we are currently investigating.…”

Section: ■ Conclusionmentioning

confidence: 98%

“…The Zn−X bond distances of 1− 3 are in the range of those reported for tetra-coordinated zinc(II) halide complexes and trigonal-planar compounds of Zn II . 12,13,1714 For instance, the Zn−Cl bonds of 2.2170 (5) 13 In addition, the Zn−C carbene interatomic distances for 1− 3 (∼2.03 Å; Table 1) show almost no variations because Zn II does not undergo π-back-donation, and thus, the bonding interaction is purely of σ-type. Indeed, shorter Zn−C carbene were reported only for stronger σ-donating carbenes, such as in [ZnCl 2 (CDP′)] (1.994(2) Å).…”

Section: ■ Introductionmentioning

confidence: 99%

Synthesis, Structural Characterization, and Phosphorescence Properties of Trigonal Zn(II) Carbene Complexes

Koop,

Mrózek,

Janiak

et al. 2023

Inorg. Chem.

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The sterically demanding N-heterocyclic carbene ITr (N,N′-bis(triphenylmethyl)imidazolylidene) was employed for the preparation of novel trigonal zinc(II) complexes of the type [ZnX 2 (ITr)] [X = Cl (1), Br (2), and I (3)], for which the low coordination mode was confirmed in both solution and solid state. Because of the atypical coordination geometry, the reactivity of 1− 3 was studied in detail using partial or exhaustive halide exchange and halide abstraction reactions to access [ZnLCl(ITr)] [L = carbazolate (4), 3,6-di-tert-butyl-carbazolate (5), phenoxazine (6), and phenothiazine ( 7 (9), Br (10), and I (11)], all of which were isolated and structurally characterized. Importantly, for all complexes 4−11, the trigonal coordination environment of the Zn II ion is maintained, demonstrating a highly stabilizing effect due to the steric demand of the ITr ligand, which protects the metal center from further ligand association. In addition, complexes 1−3 and 8−11 show longlived luminescence from triplet excited states in the solid state at room temperature, according to our photophysical studies. Our quantum chemical density functional theory/multireference configuration interaction (DFT/MRCI) calculations reveal that the phosphorescence of 8 originates from a locally excited triplet state on the bdt ligand. They further suggest that the phenyl substituents of ITr are photochemically not innocent but can coordinate to the electron-deficient metal center of this trigonal complex in the excited state.

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An Air‐ and Moisture‐stable Zinc(II) Carbene Dithiolate Dimer Showing Fast Thermally Activated Delayed Fluorescence and Dexter Energy Transfer Catalysis**

Abstract: Supporting information for this article is given via a link at the end of the document.

Cited by 12 publications

References 66 publications

Stable Molybdenum(0) Carbonyl Complex for Upconversion and Photoredox Catalysis

Stable Molybdenum(0) Carbonyl Complex for Upconversion and Photoredox Catalysis

Design Strategies for Luminescent Titanocenes: Improving the Photoluminescence and Photostability of Arylethynyltitanocenes

Synthesis, Structural Characterization, and Phosphorescence Properties of Trigonal Zn(II) Carbene Complexes

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