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Now showing items 1 - 16 of 19

  • A linear trinuclear ferrous single molecule magnet

    Liu, Shihao   Deng, Yi-Fei   Li, Chang'An   Chang, Xiaoyong   Zhang, Yuan-Zhu  

    A linear trinuclear ferrous complex [FeII3(pymp)(4)(MeOH)(2)][BPh4](2)2MeOH (1) (Hpymp =3D 2-[(pyridine-2-ylimine)-methyl]phenol) was isolated and characterized both structurally and magnetically. A magnetic study revealed the ferromagnetic coupling (J =3D +3.54 cm(-1)) within the [FeII3] units and uniaxial magnetic anisotropy (D =3D -1.21 cm(-1)) of the molecule. Slow relaxation of the magnetization at below 5 K and an effective energy barrier of 26.0(2) cm(-1) under a 1200 Oe applied dc field were evidenced. Moreover, clear magnetic hysteresis loops were observed at below 2.5 K, which further corroborated the single-molecule magnet behavior of 1.
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  • Active Disturbance Rejection Control for a Flywheel Energy Storage System

    Chang, Xiaoyong   Li, Yongli   Zhang, Weiya   Wang, Nan   Xue, Wei  

    This paper presents the application of the Active Disturbance Rejection Control Technique (ADRCT) to improve the performance of a Flywheel Energy Storage System (FESS). The FESS is designed for the DC MicroGrid (MG) application. It mainly consists of a flywheel with a coaxial BrushLess DC (BLDC) machine, a three-phase full-bridge circuit, and a bidirectional Buck-Boost converter. A model-independent controller based on the ADRCT, which can estimate and compensate model uncertainties and unknown disturbances in real time, is designed for the bidirectional Buck-Boost converter control in the FESS. Simulations and experiments are conducted in both charge and discharge mode to verify the performance of the proposed controller by comparison with a traditional double loop PI controller. Results show that the new controller is more robust and more adaptive. It has a better anti-disturbance capability and a higher dynamic performance than the PI controller. Moreover, to adapt to different applications and operating conditions, the charging process of the FESS is further improved. Strategies on maximum torque control and power limiting control are developed and realized on the experimental platform.
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  • Multi-stimuli responsive cyanostilbene derivatives:pH,amine vapor sensing and mechanoluminescence

    Huang, Guangxi   Chang, Xiaoyong   Jiang, Yuqing   Lin, Bei   Li, Bing Shi   Tang, Ben Zhong  

    Two multi-stimuli responsive compounds 1 and 2, obtained by the introduction of a carboxyl group to a cyanostilbene skeleton, revealed a fluorescence response to a change in the pH, amine vapors and mechanical stimulus. After scrutinizing their single crystal structures and comparing them with those of reference compounds 3 and 4, the molecules were found to demonstrate face-to-face stacking through multiple pi-pi interactions to restrain the non-radiative relaxation of the excited state, which led to mechanoluminescence (ML) during the fracturing process of the crystal. The discovery of these novel ML luminogens provides guidance for the design of pure organic ML materials.
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  • A Benzo[1,2-b:4,5-c ']Dithiophene-4,8-Dione-Based Polymer Donor Achieving an Efficiency Over 16%

    Chao, Pengjie   Chen, Hui   Zhu, Yulin   Lai, Hanjian   Mo, Daize   Zheng, Nan   Chang, Xiaoyong   Meng, Hong   He, Feng  

    It is of great significance to develop efficient donor polymers during the rapid development of acceptor materials for nonfullerene bulk-heterojunction (BHJ) polymer solar cells. Herein, a new donor polymer, named PBTT-F, based on a strongly electron-deficient core (5,7-dibromo-2,3-bis(2-ethylhexyl)benzo[1,2-b:4,5-c ']dithiophene-4,8-dione, TTDO), is developed through the design of cyclohexane-1,4-dione embedded into a thieno[3,4-b]thiophene (TT) unit. When blended with the acceptor Y6, the PBTT-F-based photovoltaic device exhibits an outstanding power conversion efficiency (PCE) of 16.1% with a very high fill factor (FF) of 77.1%. This polymer also shows high efficiency for a thick-film device, with a PCE of approximate to 14.2% being realized for an active layer thickness of 190 nm. In addition, the PBTT-F-based polymer solar cells also show good stability after storage for approximate to 700 h in a glove box, with a high PCE of approximate to 14.8%, which obviously shows that this kind of polymer is very promising for future commercial applications. This work provides a unique strategy for the molecular synthesis of donor polymers, and these results demonstrate that PBTT-F is a very promising donor polymer for use in polymer solar cells, providing an alternative choice for a variety of fullerene-free acceptor materials for the research community.
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  • Improved power allocation strategy of hybrid energy storage system in islanding DC micro-grid

    Chang, Xiaoyong   Chen, Fufeng   Li, Yuping   Wang, Yuting   Xu, Chengji  

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  • Tunable Multicolor Phosphorescence of Crystalline Polymeric Complex Salts with Metallophilic Backbones

    Liu, Qi   Xie, Mo   Chang, Xiaoyong   Cao, Shuang   Zou, Chao   Fu, Wen-Fu   Che, Chi-Ming   Chen, Yong   Lu, Wei  

    A total of 35 [Au(NHC)(2)][MX2] (NHC=3DN-heterocyclic carbene; M=3DAu or Cu; X=3Dhalide, cyanide or arylacetylide) complex salts were synthesized by co-precipitation of [Au(NHC)(2)](+) cations and [MX2](-) anions. These salts contain crystallographically determined polymeric Au...Au or Au...Cu interactions and are highly phosphorescent with quantum yields up to unity and emission color tunable in the entire visible regions. The nature of the emissive excited states is generally assigned to ligand (anion)-to-ligand (cation) charge-transfer transitions assisted by d(10)d(10) metallophilicity. The emission properties can be further tuned by controlled triple-component co-crystallization or by epitaxial growth. Correct recipes for white light-emitting phosphors with quantum yields higher than 70% have been achieved by screening the combinatorial pool.
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  • Dinuclear Zn-II Complexes Exhibiting Thermally Activated Delayed Fluorescence and Luminescence Polymorphism

    Xiong, Jinfan   Li, Kai   Teng, Teng   Chang, Xiaoyong   Wei, Yaxiong   Wu, Chao   Yang, Chuluo  

    Zn-II complexes exhibiting strong emission in the solid state remain scarce, and most of them exhibit only prompt fluorescence. Herein the synthesis, structures, and photoluminescence properties of two Zn-II complexes containing new donor-acceptor ligands is reported. The new Zn-II complexes have dinuclear structures in which each metal ion adopts a distorted square-pyramidal geometry. The Zn-II complexes show strong emission in the solid state with quantum yields up to 50 %. Variable-temperature transient photoluminescence studies revealed an emission mechanism involving prompt and thermally activated delayed fluorescence (TADF). DFT calculations showed well-separated HOMO and LUMO in the ground state and small excited singlet-triplet energy splitting, accounting for the TADF. The complexes also exhibit different emission colors in the as-synthesized powder state and in single crystals, that is, they exhibit luminescence polymorphism. The single-crystal emission is responsive to mechanical grinding and was characterized by powder XRD.
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  • Four-Electron Oxidation of Phenols to p-Benzoquinone Imines by a (Salen)ruthenium(VI) Nitrido Complex

    Xie, Jianhui   Man, Wai-Lun   Wong, Chun-Yuen   Chang, Xiaoyong   Che, Chi-Ming   Lau, Tai-Chu  

    Proton-coupled electron-transfer reactions of phenols have received considerable attention because of their fundamental interest and their relevance to many biological processes. Here we describe a remarkable four electron oxidation of phenols by a (salen)ruthenium(VI) complex in the presence of pyridine in CH3OH to afford (salen)ruthenium(I) p-benzoquinone imine complexes. Mechanistic studies indicate that this reaction occurs in two phases. The first phase is proposed to be a two electron transfer process that involves electrophilic attack by Ru N at the phenol aromatic ring, followed by proton shift to generate a Ru(W) p-hydroxyanilido intermediate. In the second phase the intermediate undergoes infra molecular two-electron transfer, followed by rapid deprotonation to give the Ru(II) p-benzoquinone imine product.
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  • Chirality-Economy Catalysis:Asymmetric Transfer Hydrogenation of Ketones by Ru-Catalysts of Minimal Stereogenicity

    Chen, Fumin   He, Dongxu   Chen, Li   Chang, Xiaoyong   Wang, David Zhigang   Xu, Chen   Xing, Xiangyou  

    This manuscript describes the design and synthesis of Ru catalysts that feature only a single stereogenic element, yet this minimal chirality resource is demonstrated to be competent for effecting high levels of stereoinduction in the asymmetric transfer hydrogenation over a broad range of ketone substrates, including those that are not accommodated by known catalyst systems. The single stereogenic center of the (1-pyridine-2-yl)methanamine) is the only point-chirality in the catalysts, which simplifies this catalyst system relative to existing literature protocols.
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  • Isomer-free:Precise Positioning of Chlorine-Induced Interpenetrating Charge Transfer for Elevated Solar Conversion

    Lai, Hanjian   Chen, Hui   Zhou, Jiadong   Qu, Jianfei   Chao, Pengjie   Liu, Tao   Chang, Xiaoyong   Zheng, Nan   Xie, Zengqi   He, Feng  

    The influence caused by the position of the chlorine atom on end groups of two non-fullerene acceptors (ITIC-2Cl-delta and ITIC-2Cl-gamma) was intensely investigated. The single-crystal structures show that ITIC-2Cl-gamma has a better molecular planarity and closer pi-pi interaction distance. More importantly, a 3D rectangle-like interpenetrating network is formed in ITIC-2Cl-gamma and is beneficial to rapid charge transfer along multiple directions, whereas only a linear stacked structure could be observed in ITIC-2Cl-delta. The two acceptor-based solar cells show power conversion efficiencies (PCEs) over 11%, higher than that of the ITIC-2Cl-m-based device (10.85%). An excellent PCE of 13.03% is obtained by the ITIC-2Cl-gamma-based device. In addition, the ITIC-2Cl-gamma-based device also shows the best device stability. This study indicates that chlorine positioning has a great impact on the acceptors; more importantly, the 3D network structure may be a promising strategy for non-fullerene acceptors to improve the PCE and stability of organic solar cells.
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  • Efficient Color-Tunable Copper(I) Complexes and Their Applications in Solution-Processed Organic Light-Emitting Diodes

    So, Gary Kwok-Ming   Cheng, Gang   Wang, Jian   Chang, Xiaoyong   Kwok, Chi-Chung   Zhang, Hongxing   Che, Chi-Ming  

    A series of dppnc-and neocuproine-based CuI complexes (dppnc =3D 7,8-bis(diphenylphosphino)-7,8-dicarbanido- undecaborate) are synthesized and the emission color of these CuI complexes can be tuned from green to deep red via rational modification of the neocuproine ligand structure. The molecular structures of the emissive CuI complexes, Cu(dppnc)-G (green emitting), Cu(dppnc)-Y (yellow emitting), and Cu(dppnc)-R (red emitting), are characterized and their electronic structures and related transition properties are elucidated by photo-physical and computational (density functional theory) studies. The calculation results suggest that thermally activated delayed fluorescence (TADF) is the emission mechanism for these CuI complexes. Efficient solution-processed green-, yellow-, and red-emitting OLEDs are fabricated based on the emissive complexes as the dopants. High external quantum efficiency (EQE) of 15.20% and current efficiency of 48.15 cdA(-1) at 1000 cdm(-2) are achieved in the green-emitting device with Cu(dppnc)-G. A maximum EQE of 10.17 %, CIE coordinates of (0.61, 0.38) and a maximum electroluminescent peak of 631 nm are achieved in the red device based on Cu(dppnc)-R.
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  • Organocatalytic enantioselective direct vinylogous Michael addition of gamma-substituted deconjugate butenolides to azadienes

    Lin, Wei   Lin, Xiao   Cheng, Yuyu   Chang, Xiaoyong   Zhou, San   Li, Pengfei   Li, Wenjun  

    The diastereoselective and enantioselective direct vinylogous Michael addition of gamma-substituted beta,gamma-unsaturated gamma-lactones to 2-arylidene-N-tosylbenzofuran-3(2H)-imines has been achieved with the aid of a quinine-derived squaramide. The protocol features a low catalyst loading, mild reaction conditions, and enables the formation of butenolides bearing both benzofurans and adjacent quaternary and tertiary stereocenters in high to excellent yields with generally high enantioselectivities and perfect diastereoselectivities.
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  • Controlled Synthesis of Pd-II and Pt-II Supramolecular Copolymer with Sequential Multiblock and Amplified Phosphorescence

    Wan, Qingyun   To, Wai-Pong   Chang, Xiaoyong   Che, Chi-Ming  

    Supramolecular copolymers constitute a fundamental new class of functional materials attracting burgeoning interest, but examples that display phosphorescence and long-lived excited states are rare. Herein, we describe the synthesis of sequential phosphorescent multi-block supramolecular copolymers in one and multiple dimensions using pincer Pt-II and Pd-II complexes as building blocks by manipulating out-of-equilibrium self-assemblies via the living supramolecular polymerization approach. Doping a small amount of Pt-II complexes (2 mol %) into the Pd-II assemblies significantly boosted the emission efficiency and radiative decay rate constant (Phi(em) =3D 3.7%, k(r) =3D 1.8 x 10(4) s(-1) in Pd-II assemblies; (Phi(em) =3D 76.2%, k(r) =3D 58.6 x 10(4) s(-1) in Pt-II-Pd-II co-assemblies), which is ascribed to an external heavy-atom spin-orbital coupling effect arising from the doped Pt-II complex with a delocalized (3)[d sigma* -> pi*] excited state. The findings on Pt-II and Pd-II supramolecular copolymers with controlled sequences and greatly enhanced phosphorescence efficiencies open the door to new photofunctional and responsive luminescent metal-organic supramolecular materials.
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  • cis-Dioxorhenium(V/VI) Complexes Supported by Neutral Tetradentate N4 Ligands. Synthesis, Characterization, and Spectroscopy.

    Ng, Vicky Yin-Ming   Tse, Chun-Wai   Guan, Xiangguo   Chang, Xiaoyong   Yang, Chen   Low, Kam-Hung   Lee, Hung Kay   Huang, Jie-Sheng   Che, Chi-Ming  

    A series of cis-dioxorhenium(V) complexes containing chiral tetradentate N4 ligands, including cis-[ReV(O)2(pyxn)]+ (1; pyxn =3D N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)cyclohexane-1,2-diamine), cis-[ReV(O)2(6-Me2pyxn)]+ (cis-2), cis-[ReV(O)2(R,R-pdp)]+ (3; R,R-pdp =3D 1,1'-bis((R,R)-2-pyridinylmethyl)-2,2'-bipyrrolidine), cis-[ReV(O)2(R,R-6-Me2pdp)]+ (4), and cis-[ReV(O)2(bqcn)]+ (5; bqcn =3D N,N'-dimethyl-N,N'-di(quinolin-8-yl)cyclohexane-1,2-diamine), were synthesized. Their structures were established by X-ray crystallography, showing Re-O distances in the range of 1.740(3)-1.769(8) A and O-Re-O angles of 121.4(2)-124.8(4)=C2=B0. Their cyclic voltammograms in MeCN (0.1 M [NBu4]PF6) display a reversible ReVI/V couple at E1/2 =3D 0.39-0.49 V vs SCE. In aqueous media, three proton-coupled electron transfer reactions corresponding to ReVI/V, ReV/III, and ReIII/II couples were observed at pH 1. The Pourbaix diagrams of 1=C2=B7OTf, 3=C2=B7OTf, and 5=C2=B7OTf have been examined. The electronic absorption spectra of the cis-dioxorhenium(V) complexes show three absorption bands at around 800 nm (600-1730 dm3 mol-1 cm-1), 580 nm (1700-5580 dm3 mol-1 cm-1), and 462-523 nm (3170-6000 dm3 mol-1 cm-1). Reaction of 1 with Lewis acids (or protic acids) gave cis-[ReV(O)(OH)(pyxn)]2+ (1=C2=B7H+), in which the Re-O distances are lengthened to 1.788(5) A. Complex cis-2 resulted from isomerization of trans-2 at elevated temperature. cis-[ReVI(O)2(pyxn)](PF6)2 (1'=C2=B7(PF6)2) was obtained by constant-potential electrolysis of 1=C2=B7PF6 in MeCN (0.1 M [NBu4]PF6) at 0.56 V vs SCE; it displays shorter Re-O distances (1.722(4), 1.726(4) A) and a smaller O-Re-O angle (114.88(18)=C2=B0) relative to 1 and shows a d-d transition absorption band at 591 nm (epsilon =3D 77 dm3 mol-1 cm-1). With a driving force of ca. 75 kcal mol-1, 1' oxidizes hydrocarbons with weak C-H bonds (75.5-76.3 kcal mol-1) via hydrogen atom abstraction. DFT and TDDFT calculations on the electronic structures and spectroscopic properties of the cis-dioxorhenium(V/VI) complexes were performed.=20
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  • Highly phosphorescent organopalladium(ii) complexes with metal-metal-to-ligand charge-transfer excited states in fluid solutions

    Lin, Jinqiang   Zou, Chao   Zhang, Xiaobao   Gao, Qin   Suo, Sa   Zhuo, Qihang   Chang, Xiaoyong   Xie, Mo   Lu, Wei  

    Dinuclear pincer-type cyclometalated Pd(ii) complexes with foldable diacetylide ligands show crystallographically determined intramolecular PdMIDLINE HORIZONTAL ELLIPSISPd contacts of 3.203-3.380 angstrom. In deoxygenated fluid solutions, these Pd(ii) complexes are highly phosphorescent in the red region with emission quantum yields up to 48%, which has been ascribed to metal-metal-to-ligand charge-transfer (MMLCT) excited states in nature.
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  • Controlling Metallophilic Interactions in Chiral Gold(I) Double Salts towards Excitation Wavelength-Tunable Circularly Polarized Luminescence

    Yang, Jian-Gong   Li, Kai   Wang, Jian   Sun, Shanshan   Chi, Weijie   Wang, Chao   Chang, Xiaoyong   Zou, Chao   To, Wai-Pong   Li, Ming-De   Liu, Xiaogang   Lu, Wei   Zhang, Hong-Xing   Che, Chi-Ming   Chen, Yong  

    Materials exhibiting excitation wavelength-dependent photoluminescence (Ex-De PL) in the visible region have potential applications in bioimaging, optoelectronics and anti-counterfeiting. Two multifunctional, chiral [Au(NHC)(2)][Au(CN)(2)] (NHC=3D(4R,5R)/(4S,5S)-1,3-dimethyl-4,5-diphenyl-4,5-dihydro-imidazolin-2-ylidene) complex double salts display Ex-De circularly polarized luminescence (CPL) in doped polymer films and in ground powder. Emission maxima can be dynamically tuned from 440 to 530 nm by changing the excitation wavelength. The continuously tunable photoluminescence is proposed to originate from multiple emissive excited states as a result of the existence of varied Au-1...Au-1 distances in ground state. The steric properties of the NHC ligand are crucial to the tuning of Au-1...Au-1 distances. An anti-counterfeiting application using these two salts is demonstrated.
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