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  • 451. Zhang, Pan
    et al.
    Wang, Mei
    Li, Caixia
    Li, Xueqiang
    Dong, Jingfeng
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Photochemical H-2 production with noble-metal-free molecular devices comprising a porphyrin photosensitizer and a cobaloxime catalyst2010Inngår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 46, nr 46, s. 8806-8808Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Among three noble-metal-free molecular devices (1-3) containing a porphyrin photosensitizer and a cobaloxime catalyst, the one with a zinc porphyrin unit displayed apparently higher efficiency for photoinduced H-2 production than complex 2 with a magnesium porphyrin and 3 with a free-base porphyrin, possibly due to the formation of a TEA center dot center dot center dot ZnPor-Co triad in solution.

  • 452. Zhang, Pan
    et al.
    Wang, Mei
    Li, XueQiang
    Cui, HongGuang
    Dong, JingFeng
    Sun, LiCheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Photochemical hydrogen production with molecular devices comprising a zinc porphyrin and a cobaloxime catalyst2012Inngår i: Science China Chemistry, ISSN 1674-7291, Vol. 55, nr 7, s. 1274-1282Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two new noble-metal-free molecular devices, [{Co(dmgH)(2)Cl}{Zn(PyTPP)}] (1, dmgH = dimethyloxime, PyTPP = 5-(4-pyridyl)-10,15,20-triphenylporphyrin) and [{Co(dmgH)(2)Cl}{Zn(apPyTPP)}] (2, apPyTPP = 5-[4-(isonicotinamidyl)phenyl]-10,15,20-triphenylporphyrin), for light-driven hydrogen generation were prepared and spectroscopically characterized. The zinc porphyrin photosensitizer and the Co-III-based catalyst unit are linked by axial coordination of a pyridyl group in the periphery of zinc-porphyrin to the cobalt centre of catalyst with different lengths of bridges. The apparent fluorescence quenching and lifetime decays of 1 and 2 were observed in comparison with their reference chromophores, Zn(PyTPP) (3) and Zn(apPyTPP) (4), suggesting a possibility for an intramolecular electron transfer from the singlet excited state of zinc porphyrin unit to the cobalt centre in the molecular devices. Photochemical H-2-evolving studies show that complexes 1 and 2 are efficient molecular photocatalysts for visible light-driven H-2 generation from water with triethylamine as a sacrificial electron donor in THF/H2O, with turnover numbers up to 46 and 35 for 1 and 2, respectively. In contrast to these molecular devices, the multicomponent catalyst of zinc porphyrin and [Co(dmgH)(2)PyCl] did not show any fluorescence quenching and as a consequence, no H-2 gas was detected by GC analysis in the presence of triethylamine with irradiation of visible light. The plausible mechanism for the photochemical H-2 generation with these molecular devices is discussed.

  • 453. Zhang, Pan
    et al.
    Wang, Mei
    Na, Yong
    Li, Xueqiang
    Jiang, Yi
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Homogeneous photocatalytic production of hydrogen from water by a bioinspired Fe2S2 catalyst with high turnover numbers2010Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 39, nr 5, s. 1204-1206Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A three-component homogeneous catalyst system, composed of a cyclometalated iridium(III) photosensitizer, a bioinspired diiron complex, and TEA in aqueous acetone, proved to be catalytically active for photoinduced H-2 production, with up to 660 turnovers over 8 h of irradiation.

  • 454.
    Zhang, Peili
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Chen, Hong
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Wang, Mei
    Yang, Yong
    Jiang, Jian
    Zhang, Biaobiao
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Duan, Lele
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Daniel, Quentin
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Li, Fusheng
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi. State Key Laboratory of Fine Chemicals, DUT-KTH Joint Education and Research Centre on Molecular Devices, Dalian University of Technology, 116023 Dalian, China .
    Gas-templating of hierarchically structured Ni-Co-P for efficient electrocatalytic hydrogen evolution2017Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 5, nr 16, s. 7564-7570Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    One of the grand challenges for developing scalable and sustainable hydrogen producing systems is the lack of efficient and robust earth-abundant element based catalysts for the hydrogen evolution reaction (HER). Herein, a hierarchically structured Ni-Co-P film was fabricated via a gas templating electro-deposition method. This film exhibits remarkably high catalytic performance for the HER in 1 M KOH with respective current densities of -10 and -500 mA cm(-2) at the overpotentials of -30 and -185 mV with a Tafel slope of 41 mV dec(-1). A controlled potential electrolysis experiment demonstrates that the as-prepared Ni-Co-P film is an efficient and robust catalyst with a faradaic efficiency close to 100%. Systematic characterization suggests that the unique hierarchical structure and the mutual participation of nano-sized Ni/Co based components are responsible for the high HER catalytic activity.

  • 455.
    Zhang, Peili
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi. State Key Laboratory of Fine Chemicals, Institute of Artificial Photosynthesis, DUT-KTH Joint Education and Research Centre on Molecular Devices, Dalian University of Technology, Dalian, 116024, China.
    Sheng, Xia
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Organisk kemi. State Key Laboratory of Fine Chemicals, Institute of Artificial Photosynthesis, DUT-KTH Joint Education and Research Centre on Molecular Devices, Dalian University of Technology, Dalian, 116024, China.
    Chen, Xiaoyu
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Fang, Zhiyong
    Jiang, Jian
    Wang, Mei
    Li, Fusheng
    Fan, Lizhou
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi.
    Ren, Yansong
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi.
    Zhang, Biaobiao
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi.
    Timmer, Brian J. J.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Organisk kemi.
    Ahlquist, Mårten S. G.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Sun, Licheng
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Organisk kemi. State Key Laboratory of Fine Chemicals, Institute of Artificial Photosynthesis, DUT-KTH Joint Education and Research Centre on Molecular Devices, Dalian University of Technology, Dalian, 116024, China.
    Paired Electrocatalytic Oxygenation and Hydrogenation of Organic Substrates with Water as the Oxygen and Hydrogen Source2019Inngår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 58, nr 27, s. 9155-9159Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The use of water as an oxygen and hydrogen source for the paired oxygenation and hydrogenation of organic substrates to produce valuable chemicals is of utmost importance as a means of establishing green chemical syntheses. Inspired by the active Ni3+ intermediates involved in electro-catalytic water oxidation by nickel-based materials, we prepared NiBx as a catalyst and used water as the oxygen source for the oxygenation of various organic compounds. NiBx was further employed as both an anode and a cathode in a paired electrosynthesis cell for the respective oxygenation and hydrogenation of organic compounds, with water as both the oxygen and hydrogen source. Conversion efficiency and selectivity of >= 99% were observed during the oxygenation of 5-hydroxy-methylfurfural to 2,5-furandicarboxylic acid and the simultaneous hydrogenation of p-nitrophenol to p-aminophenol. This paired electrosynthesis cell has also been coupled to a solar cell as a stand-alone reactor in response to sunlight.

  • 456. Zhang, Peili
    et al.
    Wang, Mei
    Gloaguen, Frederic
    Chen, Lin
    Quentelb, Francois
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Electrocatalytic hydrogen evolution from neutral water by molecular cobalt tripyridine-diamine complexes2013Inngår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 49, nr 82, s. 9455-9457Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A cobalt complex with a tripyridine-diamine pentadentate ligand was found to be a highly active catalyst for electrochemical H-2 production from neutral water, with an activity of 860 mol H-2 (mol cat)(-1) h(-1) (cm(2) Hg)(-1) over 60 h CPE experiment at-1.25 V in a pH 7 phosphate buffer solution, without considerable deactivation.

  • 457. Zhang, Peili
    et al.
    Wang, Mei
    Yang, Yong
    Yao, Tianyi
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    A Molecular Copper Catalyst for Electrochemical Water Reduction with a Large Hydrogen-Generation Rate Constant in Aqueous Solution2014Inngår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 53, nr 50, s. 13803-13807Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The copper complex [(bztpen)Cu](BF4)(2) (bztpen=N-benzyl-N,N,N-tris(pyridin-2-ylmethyl)ethylenediamine) displays high catalytic activity for electrochemical proton reduction in acidic aqueous solutions, with a calculated hydrogen-generation rate constant (k(obs)) of over 10000s(-1). A turnover frequency (TOF) of 7000h(-1)cm(-2) and a Faradaic efficiency of 96% were obtained from a controlled potential electrolysis (CPE) experiment with [(bztpen)Cu](2+) in pH2.5 buffer solution at -0.90V versus the standard hydrogen electrode (SHE) over two hours using a glassy carbon electrode. A mechanism involving two proton-coupled reduction steps was proposed for the dihydrogen generation reaction catalyzed by [(bztpen)Cu](2+).

  • 458. Zhang, Peili
    et al.
    Wang, Mei
    Yang, Yong
    Zheng, Dehua
    Han, Kai
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Highly efficient molecular nickel catalysts for electrochemical hydrogen production from neutral water2014Inngår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 50, nr 91, s. 14153-14156Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A series of nickel complexes containing N-5-pentadentate ligands with different amine-to-pyridine ratios were studied for electrochemical H-2 production in neutral water and the one with a diamine-tripyridine ligand displays a TON of up to 308000 over 60 h electrolysis at -1.25 V vs. SHE, with a Faradaic efficiency of similar to 91%.

  • 459. Zhang, Ting-Ting
    et al.
    Wang, Mei
    Wang, Ning
    Li, Ping
    Li, Zheng-Yi
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Protophilicity, electrochemical property, and desulfurization of diiron dithiolate complexes containing a functionalized C-2 bridge with two vicinal basic sites2009Inngår i: Polyhedron, ISSN 0277-5387, E-ISSN 1873-3719, Vol. 28, nr 6, s. 1138-1144Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two chiron dithiolate complexes [{mu-SC(NBn)CH(NHBn)S-mu)Fe-2(CO)(5)L] (L = PPh3, 2; P(Pyr)(3), 3) containing a functionlized C-2 bridge with two vicinal basic sites were prepared and characterized as models of the FeFe-hydrogenase active site. The molecular structures of 2 and its N-protonated form [(2H(N))(OTf)] were determined by X-ray analyses of single crystals. In the solid state of [(2HN)(OTf)]. Each asymmetric unit contains a molecule of [(2H(N))(OTf)] and a molecule of water. The molecule of water is close to the iron atom of the [Fe(CO)(3)] unit (Fe center dot center dot center dot O(H2O), 4J 99 angstrom). The complexes 2 and 3 are relatively protophilic. P-31 NMR spectra and cyclic voltammograms show that they can be protonated by the mild acids CCl3COOH and CF3COOH. Electrochemical studies show that the first reduction peak of 3 at - 1.51 V versus Fc(+)/Fc is 110 mV more positive than that (-1.62V) found for the analogous diiron azadithiolate complex [{(mu-SCH2)N(CH2C6H5)}Fe-2(CO)(5)P(Pyr)(3)] (7). Protonation of 2 and 3 leads to the anodic shifts of 610-650 mV for the (FeFe1)-Fe-1/(FeFe0)-Fe-1 reduction potentials. The shifts are apparently larger than that (450 mV) for protonation of 7. The reaction of the all-carbonyl complex [{(mu-SC(NBn)CH(NHBn)S-mu}Fe-2(CO)(5)L] with two equivalents of bis(diphenylphosphino)methane (dppm) in refluxing toluene affords a desulfurized complex 1(mu-S)(mu-dppm)(2)Fe-2(CO)(4)] (6). The reaction process was studied. A dppm mono-dentate intermediate [{mu-SC(NBn)CH(NHBn)S-mu)Fe-2(CO)(5)(kappa(1)-dppm)] (4) and a dppm mu-bridging species [{mu-SC(NBn)CH(NHBn)S-mu)Fe-2(CO)(4)(mu-dppm)] (5) have been isolated and spectroscopically characterized.

  • 460. Zhang, Tongyan
    et al.
    Sun, Shiguo
    Liu, Fengyu
    Fan, Jiangli
    Pang, Yi
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Peng, Xiaojun
    Redox-induced partner radical formation and its dynamic balance with radical dimer in cucurbit 8 uril2009Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 11, nr 47, s. 11134-11139Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    N-(4-Hydroxy-phenoxyethyl)-N'-ethyl-4,4'-bipyridium (1) can form a stable 1 : 1 inclusion complex with CB[8] in aqueous solution, in which the hydroxyphenol (HP) moiety is back-folded and inserted together with the viologen moiety into the cavity of CB[8]. When the ethyl viologen dication (EV2+) in 1 is reduced, chemically or electrochemically, an intramolecular partner radical (EV+center dot-HP)/CB[8] can be detected, meanwhile, a dynamic balance between the partner radical and the intermolecular radical dimer (EV+center dot-HP)(2)/CB[8] can be observed.

  • 461. Zhang, Wei
    et al.
    Liu, Jianhui
    Jin, Kun
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Synthesis of some new 4-substituted-3,5-bis(2-pyridyl)-1H-pyrazole2006Inngår i: Journal of Heterocyclic Chemistry, ISSN 0022-152X, E-ISSN 1943-5193, Vol. 43, nr 6, s. 1669-1672Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Several 4-substituted-3, 5-bis(2-pyridyl)-1H-pyrazoles, where the substituent is chloro, bromo, iodo, nitro, diazo, were synthesized under mild reaction conditions in high yields. The structures of the products were characterized by H-1 NMR, C-13 NMR, ESI-MS, IR and elemental analyses.

  • 462. Zhang, Wei
    et al.
    Liu, Jianhui
    Zhu, Hongjun
    Gao, Weiming
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Practical synthesis of new beta-diketone-connected bipyridine and its conversion to pyrazole-centered bipyridine ligand2007Inngår i: Synthetic Communications, ISSN 0039-7911, E-ISSN 1532-2432, Vol. 37, nr 19-21, s. 3393-3402Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two new polydentate ligands, 1-(6-hydroxymethyl-2-pyridyl)-3-(2-pyridyl)-propane-1,3-dione (6) and 1,3-bis(6-hydroxymethyl-2-pyridyl)-propane-1, 3-dione (8), have been synthesized starting from 2,6-pyridinedicarboxylic acid by conventional esterification, reduction, and condensation reactions. They were further converted to two new polydentate ligands, 3-(6-hydroxymethyl-2-pyridyl)-5-(2-pyridyl)-1H-pyrazole (7) and 3,5-bis(6-hydroxymethyl-2-pyridyl)-1H-pyrazole (9), by reaction with hydrazine hydrate. These four compounds were characterized by proton nuclear magnetic resonance (H-1 NMR), electrospray ionization-mass spectrum (ESI-MS), infrared spectrum (IR), and elemental analyses. The structure of 9 was also determined by X-ray diffraction.

  • 463. Zhang, Wei
    et al.
    Liu, Jian-Hul
    Pan, Jing-Xi
    Li, Ping
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Synthesis and characterization of some new mononuclear ruthenium complexes containing 4-(un) substituted dipyridylpyrazole ligands2008Inngår i: Polyhedron, ISSN 0277-5387, E-ISSN 1873-3719, Vol. 27, nr 4, s. 1168-1176Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A mononuclear ruthenium complex [Ru(bpy)(2)(bpp)](PF6) (1) and its halogenated and nitro derivatives [Ru(bpy)(2)(Xbpp)](PF6) (bpy = 2,2'-bipyridine; bpp = 3,5-bis(2-pyridyl)pyrazole; X = Cl, 2; X = Br, 3; X = I, 4; X = NO2, 5) have been synthesized and characterized by H-1 NMR, C-13 NMR, HRMS, elemental analysis. Complexes 2-5 have been further confirmed by X-ray diffraction. Their UV-Vis and emission spectroscopies, electrochemical measurements and acid-base properties are described. The results presented here reveal that the introduction of Cl, Br, I and NO2 groups to the coordinated bpp(-) ligand makes the absorption and emission maxima of the parent complex 1 blue-shifted, the oxidation potential of the Ru-II/Ru-III couple increased and the pK(a) value decreased obviously. In addition, significant quenching of the emission by these groups is also observed.

  • 464. Zhang, Xiang
    et al.
    Jia, Yin-Bao
    Lu, Xiao-Bing
    Li, Bo
    Wang, Hui
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Intramolecularly two-centered cooperation catalysis for the synthesis of cyclic carbonates from CO2 and epoxides2008Inngår i: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 49, nr 46, s. 6589-6592Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A catalyst systern containing an electrophilic center and a sterically hindered nUcleophilic center in one molecule was applied to the cycloaddition reaction of CO2 and epoxides. This intramolecularly two-centered cooperation catalyst showed activity even at a high [epoxide]/[catalyst] ratio up to 50000 under mild conditions such as solvent-free, ambient temperature, and low CO2 pressure. The reaction of CO2 with (S)-propylene oxide at 80 degrees C in the presence of the bifunctional catalyst gives (S)-propylene carbonate in 96% ee with retention of stereochemistry.

  • 465. Zhang, Xiang
    et al.
    Wang, Dong-Ping
    Jia, Yin-Bao
    Lu, Xiao-Bing
    Wang, Hui
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Asymmetric epoxidation of chromenes catalyzed by chiral pyrrolidine SalenMn(III) complexes with an anchored functional group2008Inngår i: Applied organometallic chemistry, ISSN 0268-2605, E-ISSN 1099-0739, Vol. 22, nr 10, s. 592-597Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Chiral pyrrolidine SalenMn(III) complexes with an anchored functional group at the N-aza-substituent in the pyrrolidine backbone were synthesized, and used as catalysts for asymmetric epoxidation of substituted chromenes. The complex 1 with an anchored imidazole as acceptor could effectively catalyze epoxidation of substituted chromenes in the absence of expensive additive 4-phenyl pyridine N-oxide (PPNO) by the coordination of the anchored organic base to the central manganese ion. Complexes 2 and 3 with a quaternary ammonium salt unit at the Naza-substituent in the pyrrolidine backbone displayed higher activities than Jacobsen catalyst and the analogous complex 4 without anchored functional group in the aforementioned reaction.

  • 466. Zhang, Yanyun
    et al.
    Yang, Xichuan
    Wang, Weihan
    Wang, Xiuna
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    DDQ as an effective p-type dopant for the hole-transport material X1 and its application in stable solid-state dye-sensitized solar cells2018Inngår i: Journal of Energy Challenges and Mechanics, ISSN 2095-4956, E-ISSN 2056-9386, Vol. 27, nr 2, s. 413-418Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    X1 (MeO-TPD) is an inexpensive and easily synthesized pi-conjugated molecule that has been used as a hole-transport material (HTM) in solid-state dye-sensitized solar cells (ssDSSCs), achieving relatively high efficiency. In this paper, we characterize the physicochemical properties of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and show that it is a promising p-dopant in a spin-coating solution with X1 as the HTM. The doped ssDSSCs showed an increase in short-circuit current density from 5.38 mA cm(-2) to 7.39 mA cm(-2), and their overall power conversion efficiency increased from 2.9% to 4.3%. Also, ssDSSCs with DDQ-doped X1 were more stable than the undoped samples, demonstrating that DDQ can act as a p-type dopant in X1 as an HTM for highly efficient, stable ssDSSCs.

  • 467.
    Zhang, Yongfei
    et al.
    DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Inst Artificial Photosynth, Dalian 116024, Peoples R China..
    Liang, Yongqi
    DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Inst Artificial Photosynth, Dalian 116024, Peoples R China..
    Wang, Yajuan
    DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Inst Artificial Photosynth, Dalian 116024, Peoples R China..
    Guo, Fengwan
    Peking Univ, Beijing Natl Lab Mol Sci, State Key Lab Struct Chem Unstable & Stable Speci, Coll Chem & Mol Engn, Beijing 100871, Peoples R China..
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi.
    Xu, Dongsheng
    Peking Univ, Beijing Natl Lab Mol Sci, State Key Lab Struct Chem Unstable & Stable Speci, Coll Chem & Mol Engn, Beijing 100871, Peoples R China..
    Planar FAPbBr(3) Solar Cells with Power Conversion Efficiency above 10%2018Inngår i: ACS ENERGY LETTERS, ISSN 2380-8195, Vol. 3, nr 8, s. 1808-1814Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bromide-based hybrid perovskites are of particular interest not only due to the fact that they offer a way to go beyond the Shockley-Queisser limit via the tandem cell scheme but single junction devices of them can also achieve reasonably high efficiency with high stability for solar energy conversion. However, the highest power conversion efficiency achieved up to now for FAPbBr(3) single-junction solar cells is only 8.2%, which is far below the efficiency of-17% predicted from detailed balance analysis. Here, a two-step method (the intermolecule exchange pathway) was systematically optimized for the fabrication of high quality FAPbBr(3) films. A molecule of urea, structurally similar to formamidinium, is introduced as an additive to tune the intermolecular ion exchange procedure. SnO2 is introduced as an electron-selective contact to the planar structured FAPbBr(3) solar cells. As a result, a power conversion efficiency of 10.61% and a V-oc of 1.56 V are achieved with planar structured solar cells, both of which represent the highest value ever reported for FAPbBr(3) solar cells.

  • 468. Zhang, Yuchen
    et al.
    Elawad, Mohammed
    Yu, Ze
    Jiang, Xiaoqing
    Lai, Jianbo
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. Dalian Univ Technol, Peoples R China.
    Enhanced performance of perovskite  solar cells with P3HT hole-transporting materials via molecular p-type doping2016Inngår i: RSC ADVANCES, ISSN 2046-2069, Vol. 6, nr 110, s. 108888-108895Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The conducting polymer poly(3-hexylthiophene-2,5-diyl) (P3HT) has been widely used as a polymeric hole-transporting material (HTM) in inorganic-organic perovskite solar cells (PSCs). However, pristine P3HT-based PSC devices typically exhibit mediocre overall performance, mainly due to its relatively low conductivity. Herein, we successfully introduced tetrafluoro-tetracyano-quinodimethane (F4TCNQ) as an efficient p-type dopant for P3HT as a HTM in mesoscopic PSCs. The overall performance was significantly enhanced after the introduction of F4TCNQ into P3HT. Under an optimal doping condition (1.0%, w/w), an impressive power conversion efficiency (PCE) of 14.4% was achieved, which was considerably higher than the pristine P3HT based devices (10.3%). The dramatic improvement of the PCE originated from the increase of the photocurrent density and fill factor, strongly correlated to the significant increase of the bulk conductivity of F4TCNQ doped P3HT. After doping with 1.0% F4TCNQ, the conductivity of the P3HT film was significantly increased by more than 50 times. UV-Vis and Fourier transform infrared spectroscopy (FTIR) measurements indicated that p-doping occurs via the electron transfer from the highest occupied molecular orbital (HOMO) level of P3HT to the lowest unoccupied molecular orbital (LUMO) level of the F4TCNQ, which led to a substantial increase of the bulk conductivity. Furthermore, PSCs based on the P3HT: F4TCNQ composite as a HTM also exhibited superior long-term stability under ambient conditions with a humidity of 40%. F4TCNQ was thus demonstrated to be an effective p-dopant for P3HT to improve the electrical properties and thereby the overall performance for highly efficient and stable PSCs.

  • 469. Zhao, Guang-Jiu
    et al.
    Chen, Rui-Kui
    Sun, Meng-Tao
    Liu, Jian-Yong
    Li, Guang-Yue
    Gao, Yun-Ling
    Han, Ke-Li
    Yang, Xi-Chuan
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Photoinduced intramolecular charge transfer and S-2 fluorescence in thiophene-pi-conjugated donor-acceptor systems: Experimental and TDDFT studies2008Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 14, nr 23, s. 6935-6947Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Experimental and theoretical methods were used to study newly synthesized thiophene-pi-cojugated donor-acceptor compounds, which were found to exhibit efficient intramolecular charge-transfer emission in polar solvents with relatively large Stokes shifts and strong solvatochromism. To gain insight into the solvatochromic behavior of these compounds, the dependence of the spectra on solvent polarity was studied on the basis of Lippert-Mataga models. We found that intramolecular charge transfer in these donor-acceptor systems is significantly dependent on the electron-with-drawing substituents at the thienyl 2-position. The dependence of the absorption and emission spectra of these compounds in methanol on the concentration of trifluoroacetic acid was used to confirm intramolecular charge-tranfer emission. Moreover, the calculated absorption and emission energies, which are in accordance with the experimental values, suggested that fluorescence can be emitted from different geometric confirmations. In addition, a novel S-2 fluorescence phenomenon for some of these compounds was also be observed. The fluorescence excitation spectra were used to confirm the S-2 fluorescence. We demonstrate that S-2 fluorescence can be explained by the calculated energy gap between the S-2 and S-1 states of these molecules. Furthermore, nonlinear optical behavior of the thiophene-pi-conjugated compound with diethylcyanomethylphosphonate substituents was predicted in theory.

  • 470. Zhao, Jianghua
    et al.
    Yang, Xichuan
    Cheng, Ming
    Li, Shifeng
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Molecular Design and Performance of Hydroxylpyridium Sensitizers for Dye-Sensitized Solar Cells2013Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 5, nr 11, s. 5227-5231Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Four hydroxylpyridium organic dyes were synthesized and applied in dye-sensitized solar cells (DSSCs). Hydroxylpyridium was introduced as an electron acceptor in donor-pi-conjugated bridge-acceptor (D-pi-A) system. The traditional anchoring groups, such as the carboxyl group, were replaced by hydroxyl group. It was found that the existence of the hydroxylpyridium exhibits a large effect on the absorption spectra of dyes JH401-JH404. For JH series of dyes, hexylthiophene was employed as the pi-conjugated bridge, and triphenylamine, phenothiazine, and their derivatives were used as the electron donor. The performances of the dyes with different structure were investigated by photophysical, photovoltaic, and electrochemical methods. When applied in the DSSCs, the sensitizer JH401 yields the best efficiency, 2.6% (J(sc) = 6.35 mA/cm(2), V-oc = 605 mV, FF = 67.696) under 100 mW/cm(2) light illumination. Its maximum incident photon-to-current conversion efficiency (IPCE) is 80% at 440 nm light wavelength, which is the highest IPCE value achieved with hydroxyl group adsorbent organic dyes so far.

  • 471. Zhao, Jianghua
    et al.
    Yang, Xichuan
    Cheng, Ming
    Li, Shifeng
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    New Organic Dyes with a Phenanthrenequinone Derivative as the pi-Conjugated Bridge for Dye-Sensitized Solar Cells2013Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 25, s. 12936-12941Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A series of organic dyes based on a phenanthrenequinone derivative have been employed for the first time as a it-conjugated bridge in the molecular design of D-pi-A structured organic dyes. Photophysical and electrochemical properties of dyes JH201-JH203 have been systematically investigated. The result shows that dye JH202 exhibits a higher molar extinction coefficient and widened absorption spectrum than dye JH201. Upon replacing the butoxyltriphenylamiine electron donor with phenothiazine, a bathochromic shift absorption spectrum for dye JH203 was observed. When applied in dye-sensitized solar cells (DSSCs), the device sensitized by JH203 yields the best photo-to-current conversion efficiency of 6.0% under standard AM 1.5G illumination (100 rnW/cm(2)) with a short-circuit photocurrent density (J(sc)) of 11.1 mA/cm(2), an open circuit photovoltage (V-oc) of 720 mV, and a fill factor (ff) of 74.9%. The maximum incident photo-to-current conversion efficiency reaches 87% at 460 nm.

  • 472. Zhao, Jianghua
    et al.
    Yang, Xichuan
    Cheng, Ming
    Li, Shifeng
    Wang, Xiuna
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Highly efficient iso-quinoline cationic organic dyes without vinyl groups for dye-sensitized solar cells2013Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 1, nr 7, s. 2441-2446Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Four organic dyes without a vinyl group are synthesized and applied in dye-sensitized solar cells (DSSCs). The iso-quinoline cation is employed firstly as an electron acceptor in the dye molecular structure. The effect of different dye structures on the photo-electrochemical properties and the performance of the DSSCs are systematically studied. The photovoltaic performances of the DSSCs sensitized by the JH304 dye exhibit the best conversion efficiency of 7.3% (under standard AM 1.5G illumination (100 mW cm(-2))) with a short-circuit current density (J(sc)) of 14.4 mA cm(-2), an open-circuit voltage (V-oc) of 684 mV and a fill factor (ff) of 74.4%. In comparison, the device sensitized by the N719 dye shows an efficiency of 7.9%. The DSSC device sensitized by JH304 also exhibits excellent soaking stability under sunlight for 1000 h.

  • 473. Zhao, Jianghua
    et al.
    Yang, Xichuan
    Cheng, Ming
    Wang, Weihan
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Influence of different methylene units on the performance of rhodanine organic dyes for dye-sensitized solar cells2014Inngår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, nr 10, s. 4811-4816Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In D-p-A structured organic dyes, rhodanine acetic acid and its derivates have served as electron acceptors successfully. In this work, two single rhodanine organic dyes with different methylene units have been synthesized and applied in dye-sensitized solar cells (DSSCs). The photophysical, electrochemical and photovoltaic properties have been studied systematically. The results show that dye with double methylene units produces a higher photon-to-electron conversion efficiency (eta) of 4.5% than that of a single methylene unit dye with a eta of 4.1%. Also, it is interesting to notice that the lengthened distance between electron acceptor and TiO2 surface does not decrease the short-circuit current density (J(sc)) and IPCE response for both structured dyes. On the contrary, rhodanine dye bearing double methylene units exhibits a better J(sc) and IPCE response than the single methylene unit. The explanation for this trend is probably due to the fact that increased methylene units could suppress regeneration between the injected electron and the oxidized dye effectively.

  • 474. Zhao, Jianghua
    et al.
    Yang, Xichuan
    Hao, Yan
    Cheng, Ming
    Tian, Jie
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Effect of Different Numbers of -CH2- Units on the Performance of Isoquinolinium Dyes2014Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, nr 6, s. 3907-3914Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Three new dyes have been synthesized to investigate the influence of the distance between the electron acceptor and TiO2 surface on the performance of dye-sensitized solar cells (DSSCs). In these dyes, the isoquinolinium acceptor, with a -(CH2)(n) COOH anchoring group, and a functionalized triphenylamine donor are separated by an oligothiophene bridge. The physical and electrochemical properties of the dyes were investigated systematically. The results prove that different numbers of -CH2- units between the isoquinolinium acceptor and the carboxyl anchoring group have a less pronounced effect on the physical and electrochemical properties of these dyes. However, when applied in DSSCs, a sharp decrease in the short-circuit current (J(SC)) was observed with increasing numbers of -CH2- units. For example, the device containing the organic dye bearing three -CH2- units produced the lowest J(SC) of 7.94 mA.cm(-2). In contrast, the device containing the dye bearing only one -CH2- unit exhibited the highest J(SC) of 13.88 mA.cm(-2). The higher photocurrent obtained with the device incorporating the dye with one -CH2- unit resulted in a higher power conversion efficiency of 6.8%.

  • 475.
    Zhao, Yawei
    et al.
    Dalian Univ Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, Inst Artificial Photosynth, Inst Energy Sci & Technol,State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Shen, Junyu
    Dalian Univ Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, Inst Artificial Photosynth, Inst Energy Sci & Technol,State Key Lab Fine Chem, Dalian 116024, Peoples R China.;Changshu Inst Technol, Sch Chem & Mat Engn, Jiangsu Lab Adv Funct Mat, Changshu 215500, Jiangsu, Peoples R China..
    Yu, Ze
    Dalian Univ Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, Inst Artificial Photosynth, Inst Energy Sci & Technol,State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Hu, Maowei
    Dalian Univ Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, Inst Artificial Photosynth, Inst Energy Sci & Technol,State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Liu, Chong
    Jinan Univ, Coll Informat Sci & Technol, Inst New Energy Technol, Guangzhou 510632, Guangdong, Peoples R China..
    Fan, Jiandong
    Jinan Univ, Coll Informat Sci & Technol, Inst New Energy Technol, Guangzhou 510632, Guangdong, Peoples R China..
    Han, Hongxian
    Chinese Acad Sci, Dalian Inst Chem Phys, State Key Lab Catalysis, Dalian Natl Lab Clean Energy, Dalian 116023, Peoples R China..
    Hagfeldt, Anders
    Ecole Polytech Fed Lausanne, Lab Photomol Sci, CH-1015 Lausanne, Switzerland..
    Wang, Mei
    Dalian Univ Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, Inst Artificial Photosynth, Inst Energy Sci & Technol,State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Sun, Licheng
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi. Dalian Univ Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, Inst Artificial Photosynth, Inst Energy Sci & Technol,State Key Lab Fine Chem, Dalian 116024, Peoples R China.
    Fine-tuning the coordination atoms of copper redox mediators: an effective strategy for boosting the photovoltage of dye-sensitized solar cells2019Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 7, nr 20, s. 12808-12814Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Natural systems have marvelously utilized copper complexes featuring sulfur-coordinating ligands, known as blue copper proteins, as efficient electron-transfer mediators in biological processes. Copper complexes with sulfur-coordinating ligands have been attempted as redox mediators in dye-sensitized solar cells (DSCs), the performance of which is not yet satisfactory and still remains less well explored. Herein, we report the application of new copper complexes bearing a tetradentate polythioether ligand, [(S-4)Cu](2+/+) (1(2+/+), S-4 = 1,4,8,11-tetrathiocyclotetradecane), as a redox mediator in DSCs in comparison with its N-4-tetradentate counterpart [(N-4)Cu](2+/+) (2(2+/+), N-4 = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane). Impressively, the changes of coordination atoms from N to S positively shift the formal redox potential of the copper complexes by 600 mV, leading to a remarkably high photovoltage approaching 1.0 V. This is one of the highest photovoltage values reported thus far for DSCs based on copper redox mediators.

  • 476. Zhao, Zhenbo
    et al.
    Wang, Mei
    Dong, Weibing
    Li, Ping
    Yu, Ze
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Synthesis and characterization of carboxy-functionalized diiron model complexes of FeFe -hydrogenases: Decarboxylation of Ph2PCH2COOH promoted by a diiron azadithiolate complex2009Inngår i: Journal of Organometallic Chemistry, ISSN 0022-328X, E-ISSN 1872-8561, Vol. 694, nr 15, s. 2309-2314Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two carboxy-functionalized diiron complexes [{(mu-SCH2)(2)X}{Fe(CO)(3)}{Fe(CO)(2)L}] (X = NC3H7, L = Ph2PCH2CH2COOH, 4; X = CH2, L = Ph2PCH2COOH, 5) were prepared, as biomimetic models of the [FeFe] hydrogenase active site, from the CO-replacement of [{(mu-SCH2)(2)NC3H7}Fe-2(CO)(6)] (1) and (mu-pdt)Fe-2(CO)(6) (2) by phosphine ligands in CH3CN at 40 degrees C, respectively. In contrast, the reaction of 1 with Ph2PCH2COOH under the same condition afforded complex [{(mu-SCH2)(2)NC3H7}{Fe(CO)(3)}{Fe- (CO)(2)(Ph2PCH3)}] (3) with a decarboxylated phosphine ligand. The molecular structures of complexes 3-5 were determined by X-ray crystallographic analyses, which show that they have similar frameworks with the phosphine ligand on the apical position. The interesting C-H center dot center dot center dot S contacts between the methylene hydrogen atoms of the PhCH2COOH ligand and the mu-S atoms of the pdt-bridge are found in the crystal of 5. According to the experimental evidence, a plausible mechanism, via sequential phosphine coordination, N-protonation, and decarboxylation steps, is proposed for the formation of 3 and for explanation of the contrastive reactivities of the adt- (2-aza-1,3-propanedithiolato) and the pdt-(1,3-propanedithiolato) bridged diiron complexes toward decarboxylation of the Ph2PCH2COOH ligand.

  • 477. Zheng, D.
    et al.
    Wang, M.
    Chen, L.
    Wang, N.
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Redox reactions of [FeFe]-hydrogenase models containing an internal amine and a pendant phosphine2014Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 53, nr 3, s. 1555-1561Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A diiron dithiolate complex with a pendant phosphine coordinated to one of the iron centers, [(μ-SCH2)2N(CH2C 6H4-o-PPh2){Fe2(CO)5}] (1), was prepared and structurally characterized. The pendant phosphine is dissociated together with a CO ligand in the presence of excess PMe3, to afford [(μ-SCH2)2N(CH2C 6H4-o-PPh2){Fe(CO)2(PMe 3)}2] (2). Redox reactions of 2 and related complexes were studied in detail by in situ IR spectroscopy. A series of new Fe IIFeI ([3]+ and [6]+), Fe IIFeII ([4]2+), and FeIFe I (5) complexes relevant to Hox, Hox CO, and Hred states of the [FeFe]-hydrogenase active site were detected. Among these complexes, the molecular structures of the diferrous complex [4]2+ with the internal amine and the pendant phosphine co-coordinated to the same iron center and the triphosphine diiron complex 5 were determined by X-ray crystallography. To make a comparison, the redox reactions of an analogous complex, [(μ-SCH2)2N(CH 2C6H5){Fe(CO)2(PMe 3)}2] (7), were also investigated by in situ IR spectroscopy in the absence or presence of extrinsic PPh3, which has no influence on the oxidation reaction of 7. The pendant phosphine in the second coordination sphere makes the redox reaction of 2 different from that of its analogue 7.

  • 478. Zheng, Dehua
    et al.
    Wang, Mei
    Chen, Lin
    Wang, Ning
    Cheng, Minglun
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. Dalian Univ Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, China.
    The influence of a S-to-S bridge in diiron dithiolate models on the oxidation reaction: a mimic of the H-ox(air) state of [FeFe]-hydrogenases2014Inngår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 50, nr 66, s. 9255-9258Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two-electron oxidation of a diiron complex (1) containing a bulky S-to-S bridge with an exocyclic carbonyl group affords [1(OH)](+), which replicates the coordination structure and electronic configuration of H-ox(air), and the chemically reversible reaction between 1 and [1(OH)](+) mimics the bioprocess of interconversion of the inactive H-ox(air) and the active H-red states of the [FeFe]-hydrogenases.

  • 479. Zheng, Dehua
    et al.
    Wang, Mei
    Wang, Ning
    Cheng, Minglun
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. Dalian University of Technology (DUT), China.
    Effect of Bridgehead Steric Bulk on the Intramolecular C-H Heterolysis of [FeFe]-Hydrogenase Active Site Models Containing a P2N2 Pendant Amine Ligand2016Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 55, nr 2, s. 411-418Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A series of pendant amine-containing [FeFe]-hydrogenase models, [X(CH2S-μ)2{Fe(CO)3}{Fe(CO)(P2 PhN2 Bn)}] (1H, X = CH2; 2Me, C(CH3)2; 3Et, C(CH2CH3)2; and P2 PhN2 Bn = 1,5-dibenzyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane) with different groups at the bridgehead carbon of the S-to-S linker were synthesized. The oxidations of these complexes as well as the reverse reduction reaction were studied by cyclic voltammetry and in situ IR spectroscopy. Regardless of the bridgehead steric bulk, all three complexes demonstrate intramolecular iron-mediated C(sp3)-H bond heterolytic cleavage with the assistance of the pendant amine base within the chelating diphosphine ligand in the two-electron oxidation process. X-ray crystallographic analysis shows that the doubly oxidized products, [1′H]+, [2′Me]+, and [3′Et]+, all have a rigid FeSC three-membered ring at the open apical site of the rotated iron center. The most noticeable difference in structures of the oxidized complexes is that the single CO ligand of the rotated Fe(P2 PhN2 Bn)(CO) unit in [1′H]+ and [2′Me]+ is found below the Fe⋯Fe vector, while in [3′Et]+ an unusually rotated Fe(P2 PhN2 Bn)(CO) moiety positions one of the P donors within the bidentate ligand under the Fe⋯Fe vector. The starting FeIFeI complexes can be recovered from their corresponding doubly oxidized complexes by reduction in the presence of Brönsted acid.

  • 480. Zheng, Dehua
    et al.
    Wang, Ning
    Wang, Mei
    Ding, Shengda
    Ma, Chengbing
    Darensbourg, Marcetta Y.
    Hall, Michael B.
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Intramolecular Iron-Mediated C-H Bond Heterolysis with an Assist of Pendant Base in a [FeFe]-Hydrogenase Model2014Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 136, nr 48, s. 16817-16823Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although many metalloenzymes containing iron play a prominent role in biological C-H activation processes, to date iron-mediated C(sp(3-)H heterolysis has not been reported for synthetic models of Fe/S-metalloenzymes. In contrast, ample precedent has established that nature's design for reversible hydrogen activation by the diiron hydrogenase ([FeFe]-H(2)ase) active site involves multiple irons, sulfur bridges, a redox switch, and a pendant amine base, in an intricate arrangement to perform H-H heterolytic cleavage. In response to whether this strategy might be extended to C-H activation, we report that a [FeFe]-H2ase model demonstrates iron-mediated intramolecular C-H heterolytic cleavage via an agostic C-H interaction, with proton removal by a nearby pendant amine, affording Fe-II-[ Fe'(II)-CH- S] three-membered-ring products, which can be reduced back to 1 by (CpCo)-Co-2 in the presence of HBF4. The function of the pendant base as a proton shuttle was confirmed by the crystal structures of the N-protonated intermediate and the final deprotonated product in comparison with that of a similar but pendant-amine-free complex that does not show evidence of C-H activation. The mechanism of the process was backed up by DFT calculations.

  • 481. Zhou, Xu
    et al.
    Li, Fei
    Li, Hua
    Zhang, Biaobiao
    Yu, Fengshou
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Photocatalytic Water Oxidation by Molecular Assemblies Based on Cobalt Catalysts2014Inngår i: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 7, nr 9, s. 2453-2456Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Chromophore-catalyst molecular assemblies towards visible light-driven water oxidation were synthesized by covalent integration of a light-harvesting complex [Ru(bpy)(3)](2+) (bpy= 2,2'-bipyridine) and a Co4O4 cubane water oxidation catalyst. The two components were assembled either in linear or macrocyclic configurations. In the presence of the sacrificial reagent, the Ru-Co metallocycle exhibits remarkable photocatalytic activity for oxygen evolution, which is one order of magnitude higher than that of a multicomponent system and exceeds that of a linear assembly by a factor of five, offering access to highly active photocatalyst through molecular design.

  • 482. Zhou, Xu
    et al.
    Li, Fei
    Li, Xiaona
    Li, Hua
    Wang, Yong
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Photocatalytic oxidation of organic compounds in a hybrid system composed of a molecular catalyst and visible light-absorbing semiconductor2015Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 44, nr 2, s. 475-479Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Photocatalytic oxidation of organic compounds proceeded efficiently in a hybrid system with ruthenium aqua complexes as catalysts, BiVO4 as a light absorber, [Co(NH3)(5)Cl](2+) as a sacrificial electron acceptor and water as an oxygen source. The photogenerated holes in the semiconductor are used to oxidize molecular catalysts into the high-valent Ru-IV=O intermediates for 2e(-) oxidation.

  • 483. Zietz, Burkhard
    et al.
    Gabrielsson, Erik
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Johansson, Viktor
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    El-Zohry, Ahmed M.
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Photoisomerization of the cyanoacrylic acid acceptor group - a potential problem for organic dyes in solar cells2014Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, nr 6, s. 2251-2255Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Organic solar cell dyes containing the most common anchoring group, cyanoacrylic acid, are shown to be photolabile and undergo photoisomerization. This may have significant consequences for dye-sensitized solar cells, as isomerisation competes with electron injection and leads to modifications of the dye and surface arrangement.

  • 484. Ziolek, Marcin
    et al.
    Cohen, Boiko
    Yang, Xichuan
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Paulose, Maggie
    Varghese, Oomman K.
    Grimes, Craig A.
    Douhal, Abderrazzak
    Femtosecond to millisecond studies of electron transfer processes in a donor-(pi-spacer)-acceptor series of organic dyes for solar cells interacting with titania nanoparticles and ordered nanotube array films2012Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 14, nr 8, s. 2816-2831Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Time-resolved emission and absorption spectroscopy are used to study the photoinduced dynamics of forward and back electron transfer processes taking place between a recently synthesized series of donor-(pi-spacer)-acceptor organic dyes and semiconductor films. Results are obtained for vertically oriented titania nanotube arrays (inner diameters 36 nm and 70 nm), standard titania nanoparticles (25 nm diameter) and, as a reference, alumina nanoparticle (13 nm diameter) films. The studied dyes contain a triphenylamine group as an electron donor, cyanoacrylic acid part as an electron acceptor, and differ by the substituents in a spacer group that causes a shift of its absorption spectra. Despite a red-shift of the dye absorption band resulting in an improved response to the solar spectrum, smaller electron injection rates and smaller extinction coefficients result in reduced dye sensitized solar cell (DSSC) conversion efficiencies. For the most efficient dye, TPC1, electron injection from the hot locally excited state to titania on a time scale of about 100 fs is suggested, while from the relaxed charge transfer state it proceeds in a non-exponential way with time constants from 1 ps to 50 ps. Our results imply that the latter process involves the trap states below the conduction band edge (or the sub-bandgap tail of the acceptor states), localized close to the dye radical cation, and is accompanied by fast electron recombination to the parent dye's ground state. This process should limit the efficiency of DSSCs made using these types of organic dyes. The residual, slower recombination can be described by a stretched exponential decay with a characteristic time of 0.5 ms and a dispersion parameter of 0.33. Both the electron injection and back electron transfer dynamics are similar in titania nanoparticles and nanotubes. Variations between the two film types are only found in the time resolved emission transients, which are explained in terms of the difference in local electric fields affecting the position of the emission bands.

  • 485. Ziolek, Marcin
    et al.
    Tacchini, Ignacio
    Martinez, M. Teresa
    Yang, Xichuan
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Douhal, Abderrazzak
    A photo-induced electron transfer study of an organic dye anchored on the surfaces of TiO2 nanotubes and nanoparticles2011Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, nr 9, s. 4032-4044Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on femtosecond-nanosecond (fs-ns) studies of the triphenylamine organic dye (TPC1) interacting with titania nanoparticles of different sizes, nanotubes and nanorods. We used time-resolved emission and absorption spectroscopy to measure the photoinduced dynamics of forward and back electron transfer processes taking place in TPC1-titania complexes in acetonitrile (ACN) and dichloromethane (DCM) solutions. We observed that the electron injection from the dye to titania occurs in a multi-exponential way with the main contribution of 100 fs from the hot excited charge-transfer state of anchored TPC1. This process competes with the relaxation of the excited state, mainly governed by solvation, that takes place with average time constants of 400 fs in ACN and 1.3 ps in DCM solutions. A minor contribution to the electron injection process takes place with longer time constants of about 1-10 ps from the relaxed excited state of TPC1. The latter times and their contribution do not depend on the size of the nanoparticles, but are substantially smaller in the case of nanotubes (1-3 ps), probably due to the caging effect. The contribution is also smaller in DCM than in ACN. The efficient back recombination takes place also in a multi-exponential way with times of 1 ps, 15 ps and 1 ns, and only 20-30% of the initial injected electrons in the conduction band are left within the first 1 ns after excitation. The faster recombination rates are suggested due to those originating from the free electrons in the conduction band of titania or the electrons in the shallow trap states, while the slower recombination is due to the electrons in the deep trap states. The results reported here should be relevant to a better understanding of the photobehaviour of an organic dye with promising potential for use in solar cells. They should also help to determine the important factors that limit the efficiency of solar cells based on the triphenylamine-based dyes for solar energy conversion.

  • 486. Ziolek, Marcin
    et al.
    Yang, Xichuan
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Douhal, Abderrazzak
    Interrogating the ultrafast dynamics of an efficient dye for sunlight conversion2010Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 12, nr 28, s. 8098-8107Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on studies of the recently synthesized compound (TPC1) with a promising potential use in dye-sensitized solar cells. We used steady-state as well as femtosecond (fs) to nanosecond (ns) time-resolved emission techniques to understand its behaviour under different conditions of solvation and light excitation. In polar solvents the equilibrium between TPC1 normal and anion structures was found to depend on solvent H-bond acceptor ability and concentration of the dye. We observed a correlation between the contribution of the normal form in the total absorption spectrum and solar energy conversion efficiency of the photovoltaic devices prepared in different baths, which are high in dichloromethane and low in tetrahydrofurane. Both forms exhibit a large charge transfer character in the excited state manifested by a large Stokes shift between absorption and emission maxima (up to 9000 cm(-1) in acetonitrile). The lifetime of the relaxed state of the normal structure varies significantly with the solvent polarity (from 80 ps in acetonitrile to 1.8 ns in n-hexane), and it is considerably shorter than that of the anion one (1.2-2.6 ns). The ultrafast relaxation processes are dominated by the solvation dynamics which is the fastest in acetonitrile (below 1 ps) and the slowest in ethanol (about 25 ps, the amplitude-averaged time). The results reported here should be relevant to a better understanding of the photobehaviour of metal-free dyes for solar cells and help in the design of new and more efficient dyes for conversion of light to electricity.

  • 487. Ziółek, M.
    et al.
    Martín, C.
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Douhal, A.
    Effect of electrolyte composition on electron injection and dye regeneration dynamics in complete organic dye sensitized solar cells probed by time-resolved laser spectroscopy2012Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, nr 50, s. 26227-26238Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Femtosecond time-gated fluorescence and nanosecond flash photolysis studies of seven complete, real titania nanoparticle solar cells sensitized with an efficient organic dye (TH305) were performed in order to investigate the role of the electrolyte composition on the charge transfer dynamics. The electron injection rate constants were found to range from 0.4 to 3.5 ps-1 in iodide-based electrolyte, and they well correlate with the shift of the conduction band edge potential of titania. The lithium cation additives resulted in 2 times faster electron injection rate constant (3.55 ps-1) with respect to that when larger sodium cations were used (1.86 ps-1). However, in the presence of a pyridine derivative component in the electrolyte solution, the electron injection rate constant decreased several times (0.38 ps-1 for Li+ and 0.54 ps-1 for Na+), while the electron injection efficiency was found to be still very high, 96-100%. The dye regeneration by the redox couple under relatively low fluence of excitation beam (0.4 mJ/cm2 giving about 4 electrons per titania nanoparticle) proceeds with an average rate constant of about 40 × 10 3 s-1 and efficiency close to 100%, independent of the electron composition. However, for a larger fluence (2 mJ/cm2) excitation, a titania-dye electron recombination process competes with the dye regeneration and lowers the solar cell efficiency. The effect of self-quenching, high vibrational levels of the dye excited state, and the neat solvent on the electron injection process are also discussed. This study clearly shows that for TH350-based DSSCs the best performance is obtained using Li+ and TBP as additives to the iodide electrolyte, giving the highest open circuit voltage and almost 100% efficiency of electron injection and dye regeneration.

  • 488. Zong, Xu
    et al.
    Na, Yong
    Wen, Fuyu
    Ma, Guijun
    Yang, Jinhui
    Wang, Donge
    Ma, Yi
    Wang, Mei
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Li, Can
    Visible light driven H-2 production in molecular systems employing colloidal MoS2 nanoparticles as catalyst2009Inngår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, nr 30, s. 4536-4538Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Colloidal MoS2 nanoparticles with diameters of less than 10 nm were prepared with a simple solvothermal method and demonstrated high efficiency in catalyzing H-2 evolution in Ru(bpy)(3)(2+)-based molecular systems under visible light.

  • 489.
    Zou, Dapeng
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Andersson, Samir
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Zhang, Rong
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Sun, Shiguo
    Åkermark, Björn
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Selective binding of cucurbit 7 uril and beta-cyclodextrin with a redox-active molecular triad Ru(bpy)(3)-MV2+-naphthol2007Inngår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, nr 45, s. 4734-4736Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A 1:1:1 inclusion complex is formed by the binding interactions among beta-CD, CB[ 7] hosts, and Ru(bpy)(3)-terminated viologen naphthalene guest in aqueous solution, in which the positions of both CB[7] and beta-CD are closer to the Ru stopper than in the respective 1:1 inclusion complexes, forming a tightened nut on bolt'' structural mode.

  • 490.
    Zou, Dapeng
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Andersson, Samir
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Zhang, Rong
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Sun, Shiguo
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Åkerrnark, Björn
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    A host-induced intramolecular charge-transfer complex and light-driven radical cation formation of a molecular triad with cucurbit 8 uril2008Inngår i: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 73, nr 10, s. 3775-3783Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The host-guest chemistry of systems containing a molecular triad Ru(bpy)(3)-MV2+-naphthol complex (denoted as Ru2+-MV2+-Np, 1) and cucurbit[8]uril (CB[8]) is investigated by NMR, EST-MS, UV-vis, and electrochemistry. The Ru2+-MV2+-Np guest and CB [8] host can form a stable 1:1 inclusion complex, in which the naphthalene residue is back-folded and inserted together with the viologen residue into the cavity of CB[8]. The selective binding of Ru2+-MV2+-Np guest with beta-CD and CB[8] host is also investigated. We find that CB[8] binds the Ru2+-MV2+-Np guest stronger than beta-CD. Upon light irradiation, a MV+center dot radical cation stabilized in the cavity of CB[8] accompanied by the naphthalene residue has been observed. This novel system may open a new way for design and synthesis of photoactive molecular devices.

78910 451 - 490 of 490
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