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Preparation of Polyoxometalate-based Photo-responsive Membranes for the Photo-activation of Manganese Oxide Catalysts
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Harnessing the Metal-Centered State of a Quadruply-Bonded Dimolybdenum Complex for Photon Upconversion and Photoredox
1School of Chemistry and Chemical Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan250353, China.
Abstract:
In contrast to widely studied mononuclear metal complexes, the photochemical potential of metal-metal bonded complexes remains underexplored. Herein, we report a heteroleptic quadruply bonded dimolybdenum (Mo2) complex exhibiting a metal-to-ligand charge transfer (MLCT) absorption that extends into the red visible region. Photophysical investigations reveal dual phosphorescence from the MLCT and metal-centered (MC) triplet excited states (3MLCT and 3MC). The higher-energy 3MLCT state exhibits a low photoluminescence quantum yield (ΦPL = 0.07%) due to rapid internal conversion to the lower-lying 3MC state. Despite its low energy (1.50 eV), this 3MC state displays a long lifetime (τ ≈ 20 μs), serving as a persistent triplet reservoir. Leveraging this long-lived MC state, we report the application of this Mo2 complex as a photosensitizer for triplet-triplet annihilation photon upconversion, achieving red-to-green upconversion with 9,10-bis(phenylethynyl)anthracene (BPEA) as the annihilator (ΦUC = 0.54%). Additionally, the Mo2 complex exhibits strong reducing power (E*red = -1.46 V vs SCE), enabling reductive debromination of α-bromoacetophenone and photocontrolled polymerization under red light excitation corresponding to a direct singlet to triplet transition. These findings establish metal-metal bonded complexes as a versatile platform for photochemical energy conversion and red-light-driven photoredox catalysis, opening new opportunities for the rational design of bimetallic excited-state systems.
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