Complex-as-Ligand Strategy as a Tool for the Design of a Binuclear Nonsymmetrical Chromium(III) Assembly: Near-Infrared Double Emission and Intramolecular Energy Transfer

Doistau, Benjamin; Jiménez, Juan‐Ramón; Daku, Latévi Max Lawson; Piguet, Claude

doi:10.1021/acs.inorgchem.2c01940

Cited by 4 publications

(1 citation statement)

References 81 publications

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“…The ILCT states of our Zn II complexes complement the different types of photoactive excited states reported recently for first-row and other Earth-abundant transition-metal complexes, which includes the classical MLCT states for d 6 complexes (Cr 0 , Mn I , Fe II , Co III ), ,,,− square-planar d 8 compounds (Ni II ) , and four-coordinate d 10 complexes (Cu I ), , ligand-to-metal charge-transfer (LMCT) states for Ti IV , Zr IV , , Mn IV , Fe III and Co III , − − metal-centered (MC) states for V III , Cr III and Co III , − as well as ligand-to-ligand charge-transfer (LLCT) excited states for two-coordinate Cu I complexes. − Given these findings, it seems reasonable to conclude that Zn II complexes with charge-transfer and triplet excited states would perhaps deserve greater attention in future studies aiming to discover new photophysics and photochemistry in first-row transition-metal complexes.…”

Section: Discussionsupporting

confidence: 75%

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

Kübler

Pfund

Wenger

2022

JACS Au

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

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Section: Discussionsupporting

confidence: 75%

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

Kübler

Pfund

Wenger

2022

JACS Au

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

Trippmacher,

Demeshko,

Prescimone

et al. 2024

Chemistry A European J

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

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Maximizing Nanoscale Downshifting Energy Transfer in a Metallosupramolecular Cr(III)–Er(III) Assembly

Poncet,

Besnard,

Jiménez

et al. 2024

Inorg. Chem.

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Pseudo-octahedral Cr III N 6 chromophores hold a unique appeal for low-energy sensitization of NIR lanthanide luminescence due to their exceptionally long-lived spin-flip excited states. This allure persists despite the obstacles and complexities involved in integrating both elements into a metallosupramolecular assembly. In this work, we have designed a structurally optimized heteroleptic Cr III building block capable of binding rare earths. Following a complex-as-ligand synthetic strategy, two heterometallic supramolecular assemblies, in which three peripherical Cr III sensitizers coordinated through a molecular wire to a central Er III or Y III , have been prepared. Upon excitation of the Cr III spin-flip states, the downshifted Er( 4 I 13/2 → 4 I 15/2 ) emission at 1550 nm was induced through intramolecular energy transfer. Time-resolved experiments at room temperature reveal a Cr III → Er III energy transfer of 62−73% efficiencies with rate constants of about 8.5 × 10 5 s −1 despite the long donor−acceptor distance (circa 14 Å). This efficient directional intermetallic energy transfer can be rationalized using the Dexter formalism, which is promoted by a rigid linear electronrich alkyne bridge that acts as a molecular wire connecting the Cr III and Er III ions.

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Complex-as-Ligand Strategy as a Tool for the Design of a Binuclear Nonsymmetrical Chromium(III) Assembly: Near-Infrared Double Emission and Intramolecular Energy Transfer

Cited by 4 publications

References 81 publications

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

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

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

Maximizing Nanoscale Downshifting Energy Transfer in a Metallosupramolecular Cr(III)–Er(III) Assembly

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