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991.
Steve Po‐Yam Li Tommy Siu‐Ming Tang Dr. Ken Shek‐Man Yiu Prof. Kenneth Kam‐Wing Lo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(42):13342-13354
A new class of phosphorescent cyclometalated iridium(III)–polyamine complexes [{Ir(N^C)2}n(bPEI)](PF6)n (bPEI=branched poly(ethyleneimine), average Mw=25 kDa, n=15.6–27.4; HN^C=2‐phenylpyridine Hppy ( 1 a ), 2‐((1,1′‐biphenyl)‐4‐yl)pyridine Hpppy ( 2 a ), 2‐phenylquinoline Hpq ( 3 a ), 2‐phenylbenzothiazole Hbt ( 4 a ), 2‐(1‐naphthyl)benzothiazole Hbsn ( 5 a )) and [Ir(N^C)2(en)](PF6) (en=ethylenediamine; HN^C=Hppy ( 1 b ), Hpppy ( 2 b ), Hpq ( 3 b ), Hbt ( 4 b ), Hbsn ( 5 b )) have been synthesized and characterized. The X‐ray crystal structure of complex 5 b was also determined. All of these complexes showed a reversible iridium(IV/III) oxidation couple at +1.01 to +1.26 V and a quasi‐reversible ligand‐based reduction couple at ?1.54 to ?2.08 V (versus SCE). Upon photoexcitation, the complexes displayed intense and long‐lived green to orange–red emission in fluid solutions at room temperature and in low‐temperature glass. Lipophilicity measurements indicated that bPEI played a dominant role in the polar nature of complexes 1 a – 5 a , thus rendering them very soluble in aqueous solutions. Inductively coupled plasma–mass spectrometry (ICP‐MS) and confocal laser scanning microscopy (CLSM) data indicated that an energy‐requiring process, such as endocytosis, was involved in the cellular uptake of all of the complexes. In addition, the cytotoxicity of the complexes toward human cervix epithelioid carcinoma (HeLa) and human embryonic kidney 293T (HEK293T) cell‐lines has been evaluated by the 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphenyltetrazolium bromide (MTT) assay. The DNA‐binding properties of complex 5 a have been investigated by gel‐retardation assays and the polyplexes that were formed from this complex with plasmid DNA (pDNA) were studied by zeta‐potential measurements and particle‐size estimation. Furthermore, complex 5 a was grafted with poly(ethylene glycol) (PEG, average Mw=2 kDa) to different extents, thereby yielding the phosphorescent copolymers PEG12.3‐g‐5 a , PEG25.4‐g‐5 a , and PEG62.1‐g‐5 a . Interestingly, these copolymers showed enhanced transfection activity, as revealed by in vitro transfection experiments with tissue‐culture‐based luciferase assays. 相似文献
992.
Agnieszka Bartoszewicz Dr. Rocío Marcos Dr. Suman Sahoo Dr. A. Ken Inge Prof. Xiaodong Zou Dr. Belén Martín‐Matute 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(45):14510-14519
A series of new iridium(III) complexes containing bidentate N‐heterocyclic carbenes (NHC) functionalized with an alcohol or ether group (NHC? OR, R=H, Me) were prepared. The complexes catalyzed the alkylation of anilines with alcohols as latent electrophiles. In particular, biscationic IrIII complexes of the type [Cp*(NHC‐OH)Ir(MeCN)]2+2[BF4?] afforded higher‐order amine products with very high efficiency; up to >99 % yield using a 1:1 ratio of reactants and 1–2.5 mol % of Ir, in short reaction times (2–16 h) and under base‐free conditions. Quantitative yields were also obtained at 50 °C, although longer reaction times (48–60 h) were needed. A large variety of aromatic amines have been alkylated with primary and secondary alcohols. The reactivity of structurally related iridium(III) complexes was also compared to obtain insights into the mechanism and into the structure of possible catalytic intermediates. The IrIII complexes were stable towards oxygen and moisture, and were characterized by NMR, HRMS, single‐crystal X‐ray diffraction, and elemental analyses. 相似文献
993.
User influence is generally considered as one of the most critical factors that affect information cascading spreading. Based on this common assumption, this paper proposes a theoretical model to examine user influence on the information multi-step communication in a micro-biog. The multi-steps of information communication are divided into first-step and non-first-step, and user influence is classified into five dimensions. Actual data from the Sina micro-blog is collected to construct the model by means of an approach based on structural equations that uses the Partial Least Squares (PLS) technique. Our experimental results indicate that the dimensions of the number of fans and their authority significantly impact the information of first-step conxrnunication. Leader rank has a positive impact on both first-step and non-first-step communication. Moreover, global centrality and weight of friends are positively related to the information non-first-step communication, but authority is found to have much less relation to it. 相似文献
994.
Louis Nadelson Cheryl Jorcyk Dazhi Yang Mary Jarratt Smith Sam Matson Ken Cornell Virginia Husting 《School science and mathematics》2014,114(2):76-86
Trust in science and scientists can greatly influence consideration of scientific developments and activities. Yet, trust is a nebulous construct based on emotions, knowledge, beliefs, and relationships. As we explored the literature regarding trust in science and scientists we discovered that no instruments were available to assess the construct, and therefore, we developed one. Using a process of data collection from science faculty members and undergraduate students, field testing, expert feedback, and an iterative process of design, we developed, validated, and established the reliability of the Trust in Science and Scientist Inventory. Our 21‐item instrument has a reliability of Cronbach's alpha of .86, and we have successfully field‐tested it with a range of undergraduate college students. We discuss implications and possible applications of the instrument, and include it in the appendix. 相似文献
995.
Robert R. Milburn Ken McRae Johann Chan Jason Tedrow Robert Larsen Margaret Faul 《Tetrahedron letters》2009,50(8):870-9099
The condensation of alkyl phosphonates with aryl esters to give β-ketophosphonates may be carried out at elevated temperatures mediated by LiHMDS under Barbier type conditions. The reaction is scalable, does not require specialized cryogenic equipment, and is general for all aryl and heteroaryl esters examined. 相似文献
996.
Ken Kamikawa Takayuki Shiromoto Jun Yamaguchi Shin Takemoto Hiroyuki Matsuzaka 《Research on Chemical Intermediates》2009,35(8-9):931-937
Peptide-based organocatalysts with a helical structure induced by a terminal l-histidine derivative were synthesized. These organocatalysts were applied to the kinetic resolution of secondary alcohol. 相似文献
997.
Ritsuki Masuo Ken Ohmori Dr. Lukas Hintermann Dr. Saki Yoshida Keisuke Suzuki Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(19):3462-3465
Stereocontrolled access to the hexacyclic core of FD‐594 has been achieved. The key steps include the intramolecular SNAr reaction for construction of the densely functionalized xanthone skeleton, the stereoselective lactone cleavage using a chiral nucleophile to induce the axial stereochemistry, and the SmI2‐mediated pinacol cyclization for the stereocontrolled conversion of axially chiral biaryl dialdehyde into the corresponding trans diol.
998.
Shi Li Dr. Zhiping Li Dr. Kiyohiko Nakajima Prof. Dr. Ken‐ichiro Kanno Dr. Tamotsu Takahashi Prof. Dr. 《化学:亚洲杂志》2009,4(2):294-301
Double up : A zirconium‐mediated double homologation method was successfully applied for the synthesis of multi‐substituted pentacene derivatives from 1,2,4,5‐tetrakis(propargyl)benzenes. The bis(zirconacyclopentadiene) intermediates were also characterized. Among these symmetrical derivatives, tetra‐ and octa‐substituted pentacenes undergo reversible conversion between monomeric and dimeric forms.
999.
Jasimuddin S Yamada T Fukuju K Otsuki J Sakai K 《Chemical communications (Cambridge, England)》2010,46(44):8466-8468
Supramolecular photosynthetic systems made up of the [Ir(ppy)(2)(bpy)](+) and [Co(bpy)(3)](2+) cores (ppy = 2-phenylpyridinate, bpy = 2,2'-bipyridine) are in situ self-assembled in aqueous media to generate H(2) upon visible light irradiation, where one of them recorded a relatively high turnover number of 20. 相似文献
1000.
Zhu KY Fu Q Xie HQ Xu SL Cheung AW Zheng KY Luk WK Choi RC Lau DT Dong TT Jiang ZY Chen JJ Tsim KW 《Journal of separation science》2010,33(23-24):3666-3674
Kaixinsan is an ancient Chinese herbal decoction mainly prescribed for patients suffering from mental depression. This decoction was created by Sun Si-miao of Tang Dynasty (A.D. 600) in ancient China, and was composed of four herbs: Radix and Rhizome Ginseng, Radix Polygalae, Rhizoma Acori Tatarinowii and Poria. Historically, this decoction has three different formulations, each recorded at a different point in time. In this study, the chemical compositions of all three Kaixinsan formulae were analyzed. By using rapid resolution LC coupled with a diode-array detector and an ESI triple quadrupole tandem MS (QQQ-MS/MS), the Radix and Rhizome Ginseng-derived ginsenosides including Rb(1), Rd, Re, Rg(1), the Radix Polygalae-derived 3,6'-disinapoyl sucrose, the Rhizoma Acori Tatarinowii-derived α- and β-asarone and the Poria-derived pachymic acid were compared among the three different formulations. The results showed variations in the solubility of different chemicals between one formula and the others. This systematic method developed could be used for the quality assessment of this herbal decoction. 相似文献