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Li Wang

Bio: Li Wang is an academic researcher from University of North Carolina at Chapel Hill. The author has contributed to research in topics: Chromophore & Electron transfer. The author has an hindex of 15, co-authored 18 publications receiving 421 citations. Previous affiliations of Li Wang include Memorial University of Newfoundland & St. John's University.

Papers
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TL;DR: In this paper, the results of a detailed meta-analysis of available experimental data to delineate the factors that govern how the excited state electron density evolves over the time from excitation until final excited state equilibration are presented.

60 citations

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TL;DR: Analysis of the transient spectra of the assembly reveal that photoexcitation initiates electron injection, which is then followed by the transfer of the oxidative equivalent from the chromophore to the catalyst with a rate of kET = 5.9 × 10(9) s(-1) (τ = 170 ps).
Abstract: Femtosecond transient absorption spectroscopy is used to characterize the first photoactivation step in a chromophore/water oxidation catalyst assembly formed through a “layer-by-layer” approach. Assemblies incorporating both chromophores and catalysts are central to the function of dye-sensitized photoelectrosynthesis cells (DSPECs) for generating solar fuels. The chromophore, [RuaII]2+ = [Ru(pbpy)2(bpy)]2+, and water oxidation catalyst, [RubII-OH2]2+ = [Ru(4,4′-(CH2PO3H2)2bpy)(Mebimpy)(H2O)]2+, where bpy = 2,2′-bipyridine, pbpy = 4,4′-(PO3H2)2bpy, and Mebimpy = 2,6-bis(1-methylbenzimidazol-2-yl)pyridine), are arranged on nanocrystalline TiO2 via phosphonate-Zr(IV) coordination linkages. Analysis of the transient spectra of the assembly (denoted TiO2-[RuaII-Zr-RubII-OH2]4+) reveal that photoexcitation initiates electron injection, which is then followed by the transfer of the oxidative equivalent from the chromophore to the catalyst with a rate of kET = 5.9 × 109 s–1 (τ = 170 ps). While the assembly, TiO...

47 citations

Journal ArticleDOI
TL;DR: In this paper, the authors examined the ultrafast dynamics of the initial photoactivation step in a molecular assembly consisting of a chromophore (denoted [RuaII]2+) and a water-splitting catalyst anchored to TiO2.
Abstract: This paper examines the ultrafast dynamics of the initial photoactivation step in a molecular assembly consisting of a chromophore (denoted [RuaII]2+) and a water-splitting catalyst (denoted [RubII]2+) anchored to TiO2. Photoexcitation of the chromophore is followed by rapid electron injection from the Ru(II) metal-to-ligand charge-transfer (MLCT) excited state. The injection process was followed via the decay of the bpy radical anion absorption at 375 nm. Injection is ∼95% efficient and exhibits multiple kinetic components with decay times ranging from <250 fs to 250 ps. Electron injection is followed by the transfer of the oxidative equivalent from the chromophore to the catalyst (ΔG = −0.28 eV) with a transfer time of 145 ps. In the absence of subsequent photoexcitation events, the charge-separated state undergoes electron-transfer recombination on the microsecond time scale.

42 citations

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TL;DR: The synthesis of a class of highly pi-extended tetrathiafulvalene derivatives (1a and 1b) was explored using Sonogashira macrocyclization as a key step, showing a substantially bent, S-shaped molecular backbone and an ordered packing geometry in a pi-alkyl-alky-pi stacking fashion.

41 citations

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TL;DR: A combination of time-resolved absorption and emission spectroscopies with observation times that span 9 orders of magnitude are used to follow the excited-state evolution within polymer-based molecular assemblies, complementing experimental observations with molecular dynamics simulations to develop a microscopic view of these dynamics.
Abstract: ConspectusThe use of sunlight to make chemical fuels (i.e., solar fuels) is an attractive approach in the quest to develop sustainable energy sources. Using nature as a guide, assemblies for artificial photosynthesis will need to perform multiple functions. They will need to be able to harvest light across a broad region of the solar spectrum, transport excited-state energy to charge-separation sites, and then transport and store redox equivalents for use in the catalytic reactions that produce chemical fuels. This multifunctional behavior will require the assimilation of multiple components into a single macromolecular system.A wide variety of different architectures including porphyrin arrays, peptides, dendrimers, and polymers have been explored, with each design posing unique challenges. Polymer assemblies are attractive due to their relative ease of production and facile synthetic modification. However, their disordered nature gives rise to stochastic dynamics not present in more ordered assemblies. ...

34 citations


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TL;DR: The structural origin of chirality in different supramolecular structures through combinations of structural analysis methods has been investigated in this article, where the most ideal building blocks would need to display shape persistence in solution and in the solid state, since only this feature provides access to the use of complementary methods of structural analyses.
Abstract: Dendron-mediated self-assembly, disassembly, and self-organization of complex systems have been investigated. The most ideal building blocks would need to display shape persistence in solution and in the solid state, since only this feature provides access to the use of complementary methods of structural analysis. Most supramolecular dendrimers are chiral even when they are constructed from nonchiral building blocks and are equipped with mechanisms that amplify chirality. This poses additional challenges associated with the understanding of the structural origin of chirality in different supramolecular structures through combinations of structural analysis methods. While many supramolecular structures assembled from dendrimers and dendrons resemble some of the related morphologies generated from block-copolymers, they are much more complex and are not determined by the volume ratio between the dissimilar parts of the molecule.

1,061 citations

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TL;DR: Site Heterogeneous Catalysts: Strategies, Methods, Structures, and Activities
Abstract: Site Heterogeneous Catalysts: Strategies, Methods, Structures, and Activities Christophe Copeŕet,*,† Aleix Comas-Vives,† Matthew P. Conley,† Deven P. Estes,† Alexey Fedorov,† Victor Mougel,† Haruki Nagae,†,‡ Francisco Nuñ́ez-Zarur,† and Pavel A. Zhizhko†,§ †Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir Prelog Weg 1−5, CH-8093 Zürich, Switzerland ‡Department of Chemistry, Graduate School of Engineering Science, Osaka University, CREST, Toyonaka, Osaka 560-8531, Japan A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov str. 28, 119991 Moscow, Russia

561 citations

Journal ArticleDOI
TL;DR: In molecular-catalysis-based AP, much has been attained, but more challenges remain with regard to long-term stability and heterogenization techniques, and an analysis of the advantages, challenges, and stability of molecular catalysts is provided.
Abstract: Molecular catalysis plays an essential role in both natural and artificial photosynthesis (AP). However, the field of molecular catalysis for AP has gradually declined in recent years because of doubt about the long-term stability of molecular-catalyst-based devices. This review summarizes the development history of molecular-catalyst-based AP, including the fundamentals of AP, molecular catalysts for water oxidation, proton reduction and CO2 reduction, and molecular-catalyst-based AP devices, and it provides an analysis of the advantages, challenges, and stability of molecular catalysts. With this review, we aim to highlight the following points: (i) an investigation on molecular catalysis is one of the most promising ways to obtain atom-efficient catalysts with outstanding intrinsic activities; (ii) effective heterogenization of molecular catalysts is currently the primary challenge for the application of molecular catalysis in AP devices; (iii) development of molecular catalysts is a promising way to solve the problems of catalysis involved in practical solar fuel production. In molecular-catalysis-based AP, much has been attained, but more challenges remain with regard to long-term stability and heterogenization techniques.

512 citations

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TL;DR: This Review focuses on nanosized π-conjugated macrocycles (<1 nm diameter) and giant macrocycles (>2 nm diameter), and summarizes their syntheses and properties.
Abstract: One of the most important objectives in materials, chemical, and physical sciences is the creation of large conjugated macrocycles with well-defined shapes, since such molecules are not only theoretically and experimentally interesting but also have potential applications in nanotechnology. Fully unsaturated macrocycles are regarded as models for infinitely conjugated π systems with inner cavities, and exhibit unusual optical and magnetic behavior. Macrocycles have interior and exterior sites, and site-specific substitution at both or either site can afford attractive structures, such as 1D, 2D, and 3D supramolecular nanostructures. These nanostructures could be controlled through the use of π-extended large macrocycles by a bottom-up strategy. Numerous shape-persistent π-conjugated macrocycles have been synthesized, but only a few are on the nanoscale. This Review focuses on nanosized π-conjugated macrocycles (>1 nm diameter) and giant macrocycles (>2 nm diameter), and summarizes their syntheses and properties.

409 citations

Journal ArticleDOI
TL;DR: Applications Dennis L. Ashford,† Melissa K. Gish,† Aaron K. Vannucci,‡ M. Kyle Brennaman,† Joseph L. Templeton,† John M. Papanikolas,† and Thomas J. Meyer are submitted.
Abstract: Applications Dennis L. Ashford,† Melissa K. Gish,† Aaron K. Vannucci,‡ M. Kyle Brennaman,† Joseph L. Templeton,† John M. Papanikolas,† and Thomas J. Meyer*,† †Department of Chemistry, University of North Carolina at Chapel Hill, CB 3290, Chapel Hill, North Carolina 27599, United States ‡Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States

394 citations