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Synthesis of Re(I) Rings Comprising Different Re(I) Units and Their Light-Harvesting Abilities
摘要： Trimethylamine N-oxide (Me3NO) could selectively remove only one CO ligand from fac-[Re(N^N)(CO)3(PR2R′)]+ (N^N = diimine ligand), whereby only the CO ligand in the trans position to the phosphorus ligand was selectively removed to give cis,trans-[ReI(N^N)(CO)2(PR2R′)(L)]n+ in good yields. This decarbonylation reaction using Me3NO was found to be especially useful for synthesizing biscarbonyl Re(I) complexes with electron-withdrawing groups in the diimine ligand, which could not be synthesized or were obtained only in low yields by the photochemical method. Me3NO also selectively removed the carbonyl ligands in the trans position to the phosphorus ligands from the edge Re(I) complex units, which have the fac-[Re(N^N)(CO)3(PR2R′)]+ structure, in linear-shaped Re(I) multinuclear complexes. This reaction was successfully applied to synthesize a novel precursor with ring-shaped multinuclear Re complexes (Re-rings) comprising different kinds of Re(I) units. The newly synthesized Re-rings, which consist of one Re unit with a 4,4′-bis(trifluoromethyl)-2,2′-bipyridine (CF3bpy) ligand and one or two Re unit(s) with a 2,2′-bipyridine (bpy) ligand, showed almost quantitative excitation-energy harvesting ability from the Re unit(s) with bpy to that with CF3bpy.
关键词： multinuclear complexes,decarbonylation reaction,excitation-energy transfer,light-harvesting abilities,Re(I) rings
更新于2025-09-09 09:28:46
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Low-Energy Chlorophylls in Fucoxanthin Chlorophyll <i>a/c</i> -Binding Protein Conduct Excitation Energy Transfer to Photosystem I in Diatoms
摘要： Photosynthetic organisms handle solar energy precisely to achieve efficient photochemical reactions. Since there are a wide variety of light-harvesting antennas in oxyphototrophs, the excitation-energy-transfer mechanisms are thought to differ significantly. In this study, we compared excitation-energy dynamics between photosystem I (PSI) cores and a complex between PSI and fucoxanthin chlorophyll a/c-binding protein (PSI-FCPI) isolated from a diatom, Chaetoceros gracilis, by means of picosecond time-resolved fluorescence analyses. Time-resolved spectra measured at 77 K clearly show that low-energy Chls in the FCPI transfers not only most of the excitation energy to the reaction-center Chls in the PSI cores but also the remaining energy to carotenoids for quenching. Under room-temperature conditions, the energy in the low-energy Chls is rapidly equilibrated on Chls in the PSI cores by uphill energy transfer within a few tens of ps. These findings provide solid evidence that the low-energy Chls in the FCPI contribute to the photochemical reactions in PSI.
关键词： light-harvesting antennas,low-energy Chls,Photosynthetic organisms,PSI-FCPI,excitation-energy-transfer mechanisms,photochemical reactions
更新于2025-09-09 09:28:46
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Metal–Organic Frameworks for Photocatalysis and Photothermal Catalysis
摘要： To meet the ever-increasing global demand for energy, conversion of solar energy to chemical/thermal energy is very promising. Light-mediated catalysis, including photocatalysis (organic transformations, water splitting, CO2 reduction, etc.) and photothermal catalysis play key roles in solar to chemical/thermal energy conversion via the light?matter interaction. The major challenges in traditional semiconductor photocatalysts include insufficient sunlight utilization, charge carrier recombination, limited exposure of active sites, and particularly the difficulty of understanding the structure?activity relationship. Metal?organic frameworks (MOFs), featuring semiconductor-like behavior, have recently captured broad interest toward photocatalysis and photothermal catalysis because of their well-defined and tailorable porous structures, high surface areas, etc. These advantages are beneficial for rational structural modulation for improved light harvesting and charge separation as well as other effects, greatly helping to address the aforementioned challenges and especially facilitating the establishment of the structure?activity relationship. Therefore, it is increasingly important to summarize this research field and provide in-depth insight into MOF-based photocatalysis and photothermal catalysis to accelerate the future development.
关键词： Charge separation,Photocatalysis,Light harvesting,Solar energy conversion,Photothermal catalysis,Metal?organic frameworks
更新于2025-09-04 15:30:14
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Simulating Fluorescence Detected Two-Dimensional Electronic Spectroscopy of Multi-Chromophoric Systems
摘要： We present a theory for modeling fluorescence detected two-dimensional electronic spectroscopy of multichromophoric systems. The theory is tested by comparison of the predicted spectra of the light-harvesting complex LH2 with experimental data. A qualitative explanation of the strong cross-peaks as compared to conventional two-dimensional electronic spectra is given. The strong cross-peaks are attributed to the clean ground state signal that is revealed when the annihilation of exciton pairs created on the same LH2 complex cancels oppositely-signed signals from the doubly-excited state. This annihilation process occurs much faster than the non-radiative relaxation. Furthermore, the lineshape difference is attributed to slow dynamics, exciton delocalization within the bands and intraband exciton-exciton annihilation. This is in line with existing theories presented for model systems. We further propose the use of time-resolved fluorescence detected two-dimensional spectroscopy to study state resolved exciton-exciton annihilation.
关键词： fluorescence detected two-dimensional electronic spectroscopy,multichromophoric systems,light-harvesting complex LH2,exciton-exciton annihilation,time-resolved fluorescence detected two-dimensional spectroscopy
更新于2025-09-04 15:30:14