- Facile C-N bond cleavage promoted by cuprous oxide: Formation of C-C-coupled biimidazole from its methylene-bridged congener
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The methylenebis(N-alkylimidazolium) halides are converted to dialkylbiimidazoles by cuprous oxide with concurrent C-N bond cleavage and C-C bond formation. This unusual C-N bond cleavage is proposed to involve a Cu(I)-NHC (N-heterocyclic carbene) complex. The reaction is unique, as it involves C-H bond activation, C-N bond cleavage, and C-C bond formation.
- Sabiah, Shahulhameed,Lee, Chen-Shiang,Hwang, Wen-Shu,Lin, Ivan J. B.
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- Cyclometalated IrIII Complexes as Mitochondria-Targeted Photodynamic Anticancer Agents
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Photodynamic therapy (PDT) is an attractive therapeutic modality with high therapeutic efficacy and less side effects compared with other therapies. Herein, we developed a series of cyclometalated IrIII complexes based on 2,2′-biimidazole with different alkyl substitutions (methyl, ethyl, propyl, and butyl). These complexes can efficiently produce singlet oxygen upon light irradiation. In vitro photocytotoxicity towards four cell lines (HeLa, A549, A549R, and LO2) was examined. Ir1–Ir5 show quick penetration of cells, remarkable mitochondrial accumulation, strong phototoxicity, and they exhibit high selectivity between tumor cells and normal cells. With the highest 1O2 quantum yields, Ir5 presents the best PDT efficiency with a high phototoxicity index (PI) value (PI = 150) towards HeLa cells. This work provides a valuable avenue to improve the PDT effect by tuning the lipophilicity and other properties with variation of the alkyl substitution on the photosensitizer. In addition, their satisfying PDT effect to a cisplatin-resistant cell line (A549R) may contribute to the future development of improved chemotherapeutics.
- Ouyang, Miao,Zeng, Leli,Qiu, Kangqiang,Chen, Yu,Ji, Liangnian,Chao, Hui
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- Incrementing Stokes Shifts through the Formation of 2,2′-Biimidazoldiium Salts
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The formation of biimidazoldiium structures by the introduction of methyl substituents on the N atoms at the 3 and 3′ positions of 2,2′-biimidazoles led to increments in the Stokes shift of these structures. Based on time-dependent density functional theory (TDDFT) calculations, the imidazolium rings become distorted and the N atoms of the imidazolium rings underwent structural changes through sp2 to sp3 rehybridization in the excited states.
- Matsumoto, Shoji,Watanabe, Mei,Akazome, Motohiro
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- Mixing divalent ionic liquids: effects of charge and side-chains
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We have prepared novel divalent ionic liquids (ILs) based on the bis(trifluoromethylsulfonyl)imide anion where two charged imidazolium groups in the cations are either directly bound to each other or linked by a single atom. We assessed the influence of the side-chain functionality and divalency on their physical properties and on the thermodynamics of mixing. The results indicate that shortening the spacer of a divalent IL reduces its thermal stability and increases its viscosity. Mixtures of divalent and monovalent ILs show small but significant deviations from ideality upon mixing. These deviations appear to depend primarily on the (mis)match of the nature and length of the cation side-chain. The non-ideality imposed by mixing ILs with different side-chains appears to be enhanced by the increase in formal charge of the cations in the mixture.
- Bakis, Eduards,van den Bruinhorst, Adriaan,Pison, Laure,Palazzo, Ivan,Chang, Thomas,Kjellberg, Marianne,Weber, Cameron C.,Costa Gomes, Margarida,Welton, Tom
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p. 4624 - 4635
(2021/03/15)
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- Effect of ancillary ligands on the properties of diphenylphosphoryl-substituted cationic Ir(iii) complexes
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A new class of diphenylphosphoryl-substituted cationic cyclometalated Ir(iii) complexes [Ir(POFdFppy)2(N^N)]+PF6- (dFppy = 2-(2,4-difluorophenyl)pyridine) (POF1-POF6) with different N^N ancillary ligands have been synthesized and characterized. The influences of N^N ancillary ligands on the photophysical and electrochemical properties of the Ir(iii) complexes have been investigated systematically. The results demonstrate that the photoluminescence quantum yields (ΦPL) of the complexes are dependent on the N^N ancillary ligands. POF1-POF3 equipped with phenanthroline or bipyridine ancillary ligands exhibit intense emission bands at 465-497 nm and high ΦPL in the range of 56-61% in CH2Cl2. The biimidazole-type complexes POF4-POF6 exhibit an obvious substituent effect on the photophysical and electrochemical properties. Although the emission spectra of POF4 and POF5 show similar fine structures, the ΦPL of POF5 bearing two methyl groups at the biimidazole moiety is remarkably lower (5%) than that of POF4 (45%, unmodified biimidazole). POF6 bearing two phenyl groups at the biimidazole moiety exhibits a red-shift and a weak emission band, and an extremely low ΦPL (3%). However, the photoluminescence quantum yields of POF5 and POF6 (35% and 41% in EC film, 40% and 65% in neat film, respectively) in the film increase effectively in comparison to those in solution. Cyclic voltammetry shows further that the structure of the ancillary ligand affects the redox properties. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were performed to provide insights into the electronic structures of POF1-POF6. POF1 bearing a 1,10-phenanthroline moiety demonstrates the highest oxygen sensitivity.
- Yu, Hongcui,Liu, Chun,Yu, Zhenni,Zhang, Liyan,Xiu, Jinghai
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supporting information
p. 3519 - 3527
(2017/04/13)
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- Synthesis of 2,2′-bIImidazole-based platinum(II) polymetallaynes and tuning their fluorescent response behaviors to Cu2+ ions through optimizing the configuration of the organic spacers and steric effect
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Under controlled conditions, platinum(ii) polymetallaynes with different 2,2′-biimidazole-based organic spacers have been synthesized readily. Their photophysical properties and fluorescent response behaviors to Cu2+ ions have been investigated in detail. By adjusting both the configuration of the 2,2′-biimidazole-based spacers and the steric effect, the fluorescent response behaviors of the polymetallaynes to Cu2+ ions can be tuned dramatically. The fluorescent signal from the polymetallayne with an optimized structure can be quenched rapidly by Cu2+ ions with a high Stern-Volmer constant KSV of ca. 6.8 × 104 M-1 and a low detecting limit (DL) of ca. 0.99 ppm. These results not only highlight the great potential of these polymetallaynes as novel Cu2+ sensors, but also provide new strategies for optimizing the sensing abilities of the 2,2′-biimidazole-based ion sensors.
- Zhang, Huiming,Yan, Xiaogang,Zhao, Jiang,Yang, Xiaolong,Huang, Zuan,Zhou, Guijiang,Wu, Yong
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p. 88758 - 88766
(2015/11/09)
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- Synthesis of cationic iridium(III) complexes with high quantum yield via enhancing the steric hindrance of ligands
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A series of cationic Ir(III) complexes 1a-4a functionalized with carbazole-9-yl-n-butyl group (CZB) were designed and synthesized. An investigation of their photophysical properties showed that the attachment of CZB moiety into the complexes resulted in large improvement in the photoluminescence quantum yield (PLQY) of solid film although the emission spectra and excited-state character presented little change compared with those of the parent complexes. Besides, the functionalized complexes also exhibited good thermal stability and film-forming property. In light of our quantum chemical calculations and X-ray data, these advantages of functionalized complexes mainly derived from the CZB moiety which was superior in reducing the intermolecular interaction and inhibiting the quenching process. Furthermore, to verify our results and design cationic Ir(III) complexes with much higher efficiency, four Ir(III) complexes G0-G3 were synthesized, in which different number of CZB moieties (from 0 to 3) were introduced into the complexes, respectively. Noticeably, in case of G3, the obvious high neat film PLQY of 43% was obtained. In comparison with its dispersed film, a large retaining percentage (90%) was realized, indicating that the CZB moiety could suppress the quenching of luminescence effectively.
- Shan, Guo-Gang,Li, Hai-Bin,Mu, Zhong-Cheng,Zhu, Dong-Xia,Su, Zhong-Min,Liao, Yi
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supporting information; scheme or table
p. 27 - 35
(2012/03/13)
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- Efficient synthesis of biazoles by aerobic oxidative homocoupling of azoles catalyzed by a copper(i)/2-pyridonate catalytic system
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A highly efficient and convenient CuCl/2-pyridonate catalytic system for oxidative homocoupling of azoles affording a biazole product has been developed. With this system, a variety of biazoles have been effectively synthesized in good to excellent yields
- Zhu, Mingwen,Fujita, Ken-Ichi,Yamaguchi, Ryohei
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supporting information; experimental part
p. 12876 - 12878
(2012/02/03)
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- An efficient and convenient Cu(OAc)2/air mediated oxidative coupling of azoles via C-H activation
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An efficient and convenient approach to construct C-C bonds at the 2-position of azoles via Cu(OAc)2/air mediated oxidative homo- and cross-coupling reaction was reported. The corresponding products were obtained in good to excellent yield.
- Li, Yan,Jin, Jun,Qian, Weixing,Bao, Weiliang
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supporting information; experimental part
p. 326 - 330
(2010/02/16)
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- New asymmetric synthesis of protein farnesyltransferase inhibitors via palladium-catalyzed cross-coupling reactions of 2-iodo-imidazoles
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Palladium catalyzed cross-coupling reactions of 2-iodoimidazole have been studied to synthesize imidazole-containing protein farnesyltransferase inhibitors. The Suzuki coupling reaction proved to be very efficient to introduce functionalized alkyl chains at the 2-position of the imidazole ring and a new synthesis of the required alkenylboronates was realised by a reaction of cross metathesis. Asymmetric synthesis of allyl succinic derivatives allowed us to synthesize chiral protein farnesyltransferase inhibitors through Suzuki coupling and to determine the influence of the stereochemistry of our inhibitors on the enzymatic activity.
- Kerherve, Jennifer,Botuha, Candice,Dubois, Joelle
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supporting information; experimental part
p. 2214 - 2222
(2009/09/04)
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- Synthesis, characterization, and surface studies of conjugated polymers possessing 2,2'-biimidazole moieties
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Two novel 2,2'-biimidazole-thiophene structures, 5,5'-bis(2,2'-bithiophene- 5-yl)-1,1'-dimethyl-2,2'-biimidazole and 5,5'-bis(3,4-ethylenedioxythiophene-2- yl)-1,1'-dimethyl-2,2'-biimidazole, have been synthesized and electrochemically polymerized. These materials underwent facile oxidation on Pt and ITO surfaces in CH2Cl2/Bu4NPF6 to yield conjugated, electroactive polymer films. The films were characterized with cyclic voltammetry, electronic absorption spectroscopy, and atomic force microscopy.
- Walker,Douglas,Mac Lean
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experimental part
p. 729 - 737
(2009/12/04)
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- ELECTROCHEMICAL AFFINITY BIOSENSOR SYSTEM AND METHODS
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The present invention provides novel osmium-based electrochemical species for the detection of wide variety of analytes using immunological techniques. The present invention also provides diagnostic kits and test sensors supporting electrode structures that can be used with the osmium-based electrochemical species. The test sensor can be fabricated to support interdigitated arrays of electrodes that have been designed to provide amplification of the electrical signal amplification desired to analyze analytes that may be present at low concentrations.
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Page/Page column 77-78; Sheet 31
(2010/02/11)
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- Recyclable Sonogashira coupling reactions in an ionic liquid, effected in the absence of both a copper salt and a phosphine
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(Bisimidazole)Pd(Me)Cl catalyzes an efficient and recyclable Sonogashira coupling reaction without copper salts or bulky phosphine ligands, in an ionic liquid.
- Park, Soon Bong,Alper, Howard
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p. 1306 - 1307
(2007/10/03)
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- Highly efficient, recyclable Pd(II) catalysts with bisimidazole ligands for the heck reaction in ionic liquids
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(Matrix presented) New Pd(II) complexes with bisimidazole ligands were prepared and proved to be effective catalysts for the Heck reaction under phosphine-free conditions using ionic liquids as solvents. This system could be recycled five times without any loss of catalytic activity.
- Park, Soon Bong,Alper, Howard
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p. 3209 - 3212
(2007/10/03)
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- Long tethers binding redox centers to polymer backbones enhance electron transport in enzyme "wiring" hydrogels
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A redox hydrogel with an apparent electron diffusion coefficient (Dapp) of (5.8 ± 0.5) × 10-6 cm2 s-1 is described. The order of magnitude increase in Dapp relative to previously studied redox hydrogels results from the tethering of redox centers to the backbone of the cross-linked redox polymer backbone through 13 atom spacer arms. The long and flexible tethers allow the redox centers to sweep electrons from large-volume elements and to collect electrons of glucose oxidase efficiently. The spacer arms make the collection of electrons from glucose oxidase so efficient that glucose is electrooxidized already at -0.36 V versus Ag/AgCl, the reversible potential of the redox potential of the FAD/FADH2 centers of the enzyme at pH 7.2. The limiting current density of 1.15 mA cm-2 is reached at a potential as low as -0.1 V versus Ag/AgCl. The novel redox center of the polymer is a tris-dialkylated N,N′-biimidazole Os2+/3+ complex. Its redox potential, -0.195 V versus Ag/AgCl, is 0.8 V reducing relative to that of Os(bpy)2+/3+, its 2,2′-bipyridine analogue.
- Mao, Fei,Mano, Nicolas,Heller, Adam
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p. 4951 - 4957
(2007/10/03)
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- Polymeric transition metal complexes and uses thereof
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Novel polymeric transition metal complexes of iron, cobalt, ruthenium, osmium, and vanadium are described. The polymeric transition metal complexes can be electron transfer mediators in enzyme-based electrochemical sensors. In such instances, transition metal complexes accept electrons from, or transfer electrons to, enzymes at a high rate and also exchange electrons rapidly with the sensor.
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- Dimerizations of ?-Rich N-Heteroaromatic Compounds and Xantin Derivatives
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Dimerization reactions of six ?-rich N-heteroaromatic compounds (2-7) and five xantin derivatives (8-12) in the presence of platinated palladium-carbon (Pd-Py/C) catalyst were investigated.N-Methylimidazole (2), benzimidazole (4) and N-methylbenzimidazole (5) condensed dehydrogenatively to afford the corresponding symmetric dimers when heated in the presence of Pd-Pt/C catalyst and pyridine oxide (1).On the other hand, imidazole (3), pyrazole (6) and N-methylpyrazole (7) did not dimerize under the same conditions.The same reactions using caffeine (10), 1,7-dimethylhypoxanthine (9) gave the corresponding dimers.
- Sekine, Toshikazu,Higuchi, Yoshihiro,Yamada, Tomoko,Murakoshi, Isamu
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p. 1987 - 1989
(2007/10/02)
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- Reactions of C-imidazolyllithium derivatives with Group Ib compounds: tris3,C2)>tri-gold(I) and -silver(I). Crystal structure of bis (1-benzylimidazolin-2-yliden)gold(I) chloride
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Upon reaction of LMX (M=Au, X=Cl, L=PPh3 or Me2S; M=Ag, X=NO3, L=Me2S) with 1-R-2-lithiumimidazole the lithium is replaced by a noble metal to give the species (1-R-2-M-imidazole)n (M=Au, R=methyl or benzyl, n=3; M=Ag, R=benzyl).From Me2SCuBr the compound bis(1-R-imidazol-2-yl) was obtained (R=methyl or benzyl).The unexpected formation during work up of , a carbene derivative, was confirmed by an X-ray crystal structural study which showed the presence of two independent molecules where C-Au-C is 175.2(4) or 176.6(4) deg, average Au-C is 2.027(7) Angstroem, and there is an Au...Au interaction at 3.2630(5) Angstroem.
- Bonati, Flavio,Burini, Alfredo,Pietroni, Bianca Rosa,Bovio, Bruna
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p. 147 - 160
(2007/10/02)
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- Constantes d'acidite de quelques biheterocycles
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The pKa1 and pKa2 of 19 biheterocycles A-(CH2)-n-B (in which A and B represent pyrazole, imidazole, or pyridine rings, and n = 0 or 1) were determined in water at 25 deg C using potentiometry and UV spectroscopy methods.
- Tjiou, El Mostafa,Fruchier, Alain,Pellegrin, Valdo,Tarrago, Georges
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p. 893 - 898
(2007/10/02)
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- Palladium-Catalyzed Reactions of Terminal Acetylenes and Olefins with Halo-1,3-azoles
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The palladium-catalyzed reactions of 4-bromo- and 5-bromothiazoles, as well as 4-bromo and 5-bromooxazoles with terminal acetylenes gave ethynyl derivatives in 43-89percent yields, whereas the reactions of 2-bromothiazoles and iodo-N-methylimidazoles affo
- Sakamoto, Takao,Nagata, Hideo,Kondo, Yoshinori,Shiraiwa, Masafumi,Yamanaka, Hiroshi
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p. 823 - 828
(2007/10/02)
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