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Vivian Wingwah Yam - One of the best experts on this subject based on the ideXlab platform.
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coordination compounds with photochromic ligands ready tunability and visible light sensitized photochromism
Accounts of Chemical Research, 2018Co-Authors: Vivian Wingwah YamAbstract:ConspectusPhotochromic compounds are well-known for their promising applications in many areas. In this context, many different photochromic families have been developed. As the early study of these photochromic compounds was mainly focused on the organic system, their photochromic reactivity was mainly derived from the singlet excited state. We hypothesized that the incorporation of the photochromic ligand to the transition metal complex and coordination complex systems would not only render the triplet state of the organic photochromic system more readily accessible due to the large spin–orbit coupling of the heavy metal center but also would lead to ready extension of the excitation wavelength to less destructive longer wavelength low-energy excitation. On the other hand, the long-lived triplet excited states of the metal complexes are also suitable for energy or electron transfer processes, which should lead to new photochromic behavior and photoswitchable functional properties.Through the incorporati...
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coordination compounds with photochromic ligands ready tunability and visible light sensitized photochromism
Accounts of Chemical Research, 2018Co-Authors: Vivian Wingwah YamAbstract:Photochromic compounds are well-known for their promising applications in many areas. In this context, many different photochromic families have been developed. As the early study of these photochromic compounds was mainly focused on the organic system, their photochromic reactivity was mainly derived from the singlet excited state. We hypothesized that the incorporation of the photochromic ligand to the transition metal complex and coordination complex systems would not only render the triplet state of the organic photochromic system more readily accessible due to the large spin-orbit coupling of the heavy metal center but also would lead to ready extension of the excitation wavelength to less destructive longer wavelength low-energy excitation. On the other hand, the long-lived triplet excited states of the metal complexes are also suitable for energy or electron transfer processes, which should lead to new photochromic behavior and photoswitchable functional properties. Through the incorporation of the stilbene-, azo-, spirooxazine-, and dithienylethene-containing ligands to transition metal complex systems with heavy metal centers and suitable excited states, triplet state photosensitized photochromism has been achieved. With the triplet state photosensitization, the photochromism of these compounds could be extended from the high energy UV region to the visible region. In the development of dithienylethene-containing ligands, we have adopted an alternative strategy, which involves the incorporation of nitrogen and sulfur heterocycles that directly form part of the dithienylethene framework as ligands to exert a much stronger perturbation and influence on the excited state properties of the photochromic unit by the metal center. On the basis of the new design, wide ranges of dithienylethene-containing ligands, including phenanthrolines, 2-pyridylimidazoles, N-pyridylimidazol-2-ylidenes, cyclometalating thienylpyridines, β-diketonates, and β-ketoiminates have been designed and incorporated into various coordination systems. Apart from the photosensitization, tuning of the closed form absorption and photochromic behavior based on the perturbation of the metal center, coordination-assisted planarization, modification of the ancillary ligands and introduction of various electronic excited states derived from the coordination system have been successfully demonstrated. This strategy can be used for developing NIR photochromic dithienylethenes. With the above effects observed upon the coordination to different transition metal centers and central atoms, this strategy offers a simple and effective way for the modification of the photochromic characteristics. Moreover, the emission and other functional properties of the coordination systems could also be photoswitched by the photochromic reactions.
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photochromic heterocycle fused thieno 3 2 b phosphole oxides as visible light switches without sacrificing photoswitching efficiency
Journal of the American Chemical Society, 2017Co-Authors: Wai Han Lam, Hoklai Wong, Vivian Wingwah YamAbstract:A series of novel photochromic thieno[3,2-b]phosphole oxides has been shown to demonstrate photochromism without the need for the use of high-energy ultraviolet (UV) light irradiation while maintaining promising photochromic properties such as excellent thermal irreversibility, robust fatigue resistance, and high photoswitching efficiency. Promising visible light-induced photochromic properties have been realized by the new molecular design, in which various π systems have been incorporated into the weakly aromatic phosphole backbone instead of the conventional modification of the peripheral diaryl units that usually leads to a drastic reduction of the photochromic quantum yields (ϕO→C and ϕC→O < 0.01) or even a loss of the photochromic behavior. Excellent fatigue resistance has been observed for a representative compound with no apparent loss of photochromic reactivity over ten photochromic cycles by alternate irradiation with violet (ca. 410 nm) and green (ca. 500 nm) light with high photochromic quantu...
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photochromic benzo b phosphole oxide with excellent thermal irreversibility and fatigue resistance in the thin film solid state via direct attachment of dithienyl units to the weakly aromatic heterocycle
Chemical Science, 2017Co-Authors: Hoklai Wong, Vivian Wingwah YamAbstract:A novel photochromic benzo[b]phosphole oxide has been demonstrated to display photochromic properties with excellent fatigue resistance and thermal irreversibility in polymethylmethacrylate (PMMA) thin film under ambient conditions. The remarkable photochromic behaviour can be achieved by rational molecular design, in which the weakly aromatic phosphole oxide is directly incorporated into the photo-responsive dithienylethene units. Photopatterning via photoinduced colouration and decolouration has been performed to demonstrate the repeatable and distinct transformation between the bistable states, making it a promising candidate with photoswitching properties for optoelectronic applications.
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Photochromic Heterocycle-Fused Thieno[3,2‑b]phosphole Oxides as Visible Light Switches without Sacrificing Photoswitching Efficiency
2017Co-Authors: Wai Han Lam, Hoklai Wong, Vivian Wingwah YamAbstract:A series of novel photochromic thieno[3,2-b]phosphole oxides has been shown to demonstrate photochromism without the need for the use of high-energy ultraviolet (UV) light irradiation while maintaining promising photochromic properties such as excellent thermal irreversibility, robust fatigue resistance, and high photoswitching efficiency. Promising visible light-induced photochromic properties have been realized by the new molecular design, in which various π systems have been incorporated into the weakly aromatic phosphole backbone instead of the conventional modification of the peripheral diaryl units that usually leads to a drastic reduction of the photochromic quantum yields (ϕO→C and ϕC→O < 0.01) or even a loss of the photochromic behavior. Excellent fatigue resistance has been observed for a representative compound with no apparent loss of photochromic reactivity over ten photochromic cycles by alternate irradiation with violet (ca. 410 nm) and green (ca. 500 nm) light with high photochromic quantum yields (ϕO→C = 0.87 and ϕC→O = 0.44), rendering it a new promising candidate as visible light photoswitches for various potential applications
Natia L Frank - One of the best experts on this subject based on the ideXlab platform.
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incorporating optical bistability into a magnetically bistable system a photochromic redox isomeric complex
Chemical Communications, 2009Co-Authors: Michelle M Paquette, Roni A Kopelman, Natia L Frank, Elvira BeitlerAbstract:A photochromic cobalt–bis(dioxolene)spirooxazine metal complex has been synthesized which exhibits both photochromic and redox-active behavior, providing a potentially powerful approach to the development of optically induced changes in redox, magnetic, or optical properties of a metal center.
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tunable photochromism of spirooxazines via metal coordination
Journal of the American Chemical Society, 2003Co-Authors: Roni A Kopelman, Sean M Snyder, Natia L FrankAbstract:Through the incorporation of a phenanthroline ligand into the oxazine moiety of photochromic spirooxazines, a series of photochromic spirooxazine-phenanthroline metal complexes have been synthesized, resulting in tunable and significantly increased photoresponsivities. Such systems are of interest for the investigation of multifunctional photochromic materials. These novel metal complexes retain their photochromic activity in the complexed state, leading to ligand binding in both the spirooxazine and the photomerocyanine forms during the photoconversion. A significant stabilization of the photomerocyanine form results from metal complexation, as indicated by the shift in thermal equilibrium values (KT = 0.06) upon metal complexation (KT = 0.6−1.2). Photoconversion occurs with first-order kinetics, suggesting the absence of an intermediate state. A third photostationary state is observed in these systems induced by visible irradiation of the thermal equilibrium state, leading to a three-state system. This ...
Ben Zhong Tang - One of the best experts on this subject based on the ideXlab platform.
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reversible photochromic system based on rhodamine b salicylaldehyde hydrazone metal complex
Journal of the American Chemical Society, 2014Co-Authors: Yu Xiang, Xiaoyan Wang, Aijun Tong, Ben Zhong TangAbstract:Photochromic molecules are widely applied in chemistry, physics, biology, and materials science. Although a few photochromic systems have been developed before, their applications are still limited by complicated synthesis, low fatigue resistance, or incomplete light conversion. Rhodamine is a class of dyes with excellent optical properties including long-wavelength absorption, large absorption coefficient, and high photostability in its ring-open form. It is an ideal chromophore for the development of new photochromic systems. However, known photochromic rhodamine derivatives, such as amides, exhibit only millisecond lifetimes in their colored ring-open forms, making their application very limited and difficult. In this work, rhodamine B salicylaldehyde hydrazone metal complex was found to undergo intramolecular ring-open reactions upon UV irradiation, which led to a distinct color and fluorescence change both in solution and in solid matrix. The complex showed good fatigue resistance for the reversible photochromism and long lifetime for the ring-open state. Interestingly, the thermal bleaching rate was tunable by using different metal ions, temperatures, solvents, and chemical substitutions. It was proposed that UV light promoted isomerization of the rhodamine B derivative from enol-form to keto-form, which induced ring-opening of the rhodamine spirolactam in the complex to generate color. The photochromic system was successfully applied for photoprinting and UV strength measurement in the solid state. As compared to other reported photochromic molecules, the system in this study has its advantages of facile synthesis and tunable thermal bleaching rate, and also provides new insights into the development of photochromic materials based on metal complex and spirolactam-containing dyes.
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reversible photochromic system based on rhodamine b salicylaldehyde hydrazone metal complex
Journal of the American Chemical Society, 2014Co-Authors: Kai Li, Yu Xiang, Xiaoyan Wang, Aijun Tong, Ji Li, Rongrong Hu, Ben Zhong TangAbstract:Photochromic molecules are widely applied in chemistry, physics, biology, and materials science. Although a few photochromic systems have been developed before, their applications are still limited by complicated synthesis, low fatigue resistance, or incomplete light conversion. Rhodamine is a class of dyes with excellent optical properties including long-wavelength absorption, large absorption coefficient, and high photostability in its ring-open form. It is an ideal chromophore for the development of new photochromic systems. However, known photochromic rhodamine derivatives, such as amides, exhibit only millisecond lifetimes in their colored ring-open forms, making their application very limited and difficult. In this work, rhodamine B salicylaldehyde hydrazone metal complex was found to undergo intramolecular ring-open reactions upon UV irradiation, which led to a distinct color and fluorescence change both in solution and in solid matrix. The complex showed good fatigue resistance for the reversible ...
Wai Han Lam - One of the best experts on this subject based on the ideXlab platform.
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photochromic heterocycle fused thieno 3 2 b phosphole oxides as visible light switches without sacrificing photoswitching efficiency
Journal of the American Chemical Society, 2017Co-Authors: Wai Han Lam, Hoklai Wong, Vivian Wingwah YamAbstract:A series of novel photochromic thieno[3,2-b]phosphole oxides has been shown to demonstrate photochromism without the need for the use of high-energy ultraviolet (UV) light irradiation while maintaining promising photochromic properties such as excellent thermal irreversibility, robust fatigue resistance, and high photoswitching efficiency. Promising visible light-induced photochromic properties have been realized by the new molecular design, in which various π systems have been incorporated into the weakly aromatic phosphole backbone instead of the conventional modification of the peripheral diaryl units that usually leads to a drastic reduction of the photochromic quantum yields (ϕO→C and ϕC→O < 0.01) or even a loss of the photochromic behavior. Excellent fatigue resistance has been observed for a representative compound with no apparent loss of photochromic reactivity over ten photochromic cycles by alternate irradiation with violet (ca. 410 nm) and green (ca. 500 nm) light with high photochromic quantu...
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Photochromic Heterocycle-Fused Thieno[3,2‑b]phosphole Oxides as Visible Light Switches without Sacrificing Photoswitching Efficiency
2017Co-Authors: Wai Han Lam, Hoklai Wong, Vivian Wingwah YamAbstract:A series of novel photochromic thieno[3,2-b]phosphole oxides has been shown to demonstrate photochromism without the need for the use of high-energy ultraviolet (UV) light irradiation while maintaining promising photochromic properties such as excellent thermal irreversibility, robust fatigue resistance, and high photoswitching efficiency. Promising visible light-induced photochromic properties have been realized by the new molecular design, in which various π systems have been incorporated into the weakly aromatic phosphole backbone instead of the conventional modification of the peripheral diaryl units that usually leads to a drastic reduction of the photochromic quantum yields (ϕO→C and ϕC→O < 0.01) or even a loss of the photochromic behavior. Excellent fatigue resistance has been observed for a representative compound with no apparent loss of photochromic reactivity over ten photochromic cycles by alternate irradiation with violet (ca. 410 nm) and green (ca. 500 nm) light with high photochromic quantum yields (ϕO→C = 0.87 and ϕC→O = 0.44), rendering it a new promising candidate as visible light photoswitches for various potential applications
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gated photochromism in triarylborane containing dithienylethenes a new approach to a lock unlock system
Journal of the American Chemical Society, 2011Co-Authors: Chunting Poon, Wai Han Lam, Vivian Wingwah YamAbstract:Photochromic inactive dithienylethene derivatives appended with 3- or 5-dimesitylboryl-2,2′-bithiophene have been synthesized. Upon fluoride ion-binding, the photochromic reactivity is “unlocked”, displaying a novel gated photochromic property.
Guocong Guo - One of the best experts on this subject based on the ideXlab platform.
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Two New Coordination Compounds with a Photoactive Pyridinium-Based Inner Salt: Influence of Coordination on Photochromism
2016Co-Authors: Mingsheng Wang, Guocong GuoAbstract:The past years have evidenced the rapid development of photochromic coordination compounds; however, the impact of coordination on the photochromic behavior of organic dyes has never been explored in the pyridinium derivative photochromic system. In this work, two new coordination compounds with a photoactive pyridinium-based inner salt, [Zn(H2O)6](PTA)·(CEbpy)2·2H2O (1, PTA = terephthalate, CEbpy = 1-carboxyethyl-4,4′-bipyridine) and [Zn(H2O)2(CEbpy)2]nBr2n·[Zn(H2O)4(PTA)]n (2), were selected as model compounds for this purpose. Compound 1 features an isolated structure, where uncoordinated photoactive CEbpy ligands connect to hexahydrated zinc ions through hydrogen bonds. Compound 2 features a 1-D chain structure with CEbpy ligands coordinating to zinc ions. Compound 1 shows faster coloration speed upon irradiation than 2, demonstrating that coordination of the electron donor in CEbpy is not in favor of photochromic behavior. Both compounds show significant photoluminescence quenching after coloration, and the intensity contrast before and after coloration for 1 is larger than that for 2. This finding will help to design and synthesize new photochromic compounds with high performance
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design and syntheses of electron transfer photochromic metal organic complexes using nonphotochromic ligands a model compound and the roles of its ligands
Inorganic Chemistry, 2014Co-Authors: Cuijuan Zhang, Ziwei Chen, Rongguang Lin, Mingjian Zhang, Mingsheng Wang, Guocong GuoAbstract:The model compound [Zn(HCOO)2(4,4'-bipy)] (1; 4,4'-bipy = 4,4'-bipyridine) is selected in this work to demonstrate the effectiveness of our previously proposed design strategy for electron-transfer photochromic metal-organic complexes. The electron-transfer photochromic behavior of 1 has been discovered for the first time. Experimental and theoretical data illustrate that the photochromism of 1 can be attributed to the electron transfer from formato to 4,4'-bipy and the formation of a radical photoproduct. The electron transfer prefers to occur between formato and 4,4'-bipy, which are combined directly by the Zn(II) atoms. A high-contrast (up to 8.3 times) photoluminescence switch occurs during the photochromic process. The similarity of photochromic behaviors among 1 and its analogues as well as viologen compounds has also been found. Photochromic studies of this model compound indicate that new electron-transfer photochromic metal-organic complexes can be largely designed and synthesized by the rational assembly of nonphotochromic electron-donating and electron-accepting ligands.
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inorganic organic hybrid photochromic materials
Chemical Communications, 2010Co-Authors: Mingsheng Wang, Zhangjing Zhang, Guocong GuoAbstract:The distinct synergetic characteristics between each component in inorganic–organic hybrids offer various possibilities to obtain new “smart”, high performing materials. Growing interest in this field has largely expanded the content of photochromic materials for the purpose of improving existing photochromic materials, fabricating photoresponsive devices, and exploring new families of photochromic materials. In this feature article, we give a brief review of photochromic hybrids of metal halides, metal cyanides, polyoxometalates, and metal chalcogenides as well as photochromic metal–organic complexes.