- Tunable photochromism of spirobenzopyran via selective metal ion coordination: An efficient visual and ratioing fluorescent probe for divalent copper ion
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In the present paper, a new spirobenzopyran derivative was synthesized and applied in simultaneously colorimetric and fluorescence ratiometric detections of Cu2+. In contrast to the virtually photochromic character of the common spirobenzopyrans in most organic solvents, this spirobenzopyran is colorless in organic aqueous solution even irradiating by ultraviolet light. The formation of red merocyanine in an ethanol-aqueous solution is only induced by Cu2+ coordination. Furthermore, the closed form of the spirobenzopyran is highly fluorescent. Upon complexation with Cu2+, it displays not only decreasing in the initial fluorescence emission band but also appearing in a new emission at long wavelength. Thus, the Cu2+ quantitative measure can be achieved by fluorescence ratiometry. With the optimum conditions described, the Cu2+ concentration can be determined from 5.13 × 10-7 M to 3.81 × 10-4 with a detection limit of 1.06 × 10-7 M. Both the color and the fluorescence changes of the spirobenzopyran are extremely specific for Cu 2+ over biologically relevant substrates, which meet the selectivity requirements for biomedical application. Serum divalent copper values were determined using this spirobenzopyran, which fell into the normal range of the content reported in the literature and were in good agreement with those obtained by atomic absorption spectroscopy. The combined data from fluorescence titrations and 1H NMR measurements indicate that the new emission of the spirobenzopyran generated by Cu2+ is the result of the metal-induced ring opening and conformation restriction by Cu2+ liganding with the opened merocyanine form and the subsequent reduction of the intramolecular charge transfer of the merocyanine.
- Shao, Na,Jian, Yu Jin,Wang, Hao,Zhang, Ying,Rong, Hua Yang,Wing, Hong Chan
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Read Online
- Schiff base aluminum catalysts containing morpholinomethyl groups in the ring opening polymerization of rac-lactide
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A series of Schiff base aluminum(III) complexes bearing morpholinomethyl substituents were synthesized. Comprehensive investigations on their stereoselective and kinetic features in the ring opening polymerization of lactide were carried out. The ring ope
- Guo, Zhijie,Duan, Ranlong,Deng, Mingxiao,Pang, Xuan,Hu, Chenyang,Chen, Xuesi
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p. 1741 - 1747
(2015/11/02)
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- METHOD OF PREPARING POLY(ALKYLENE CARBONATE) VIA COPOLYMERIZATION OF CARBON DIOXIDE/EPOXIDE IN THE PRESENCE OF NOVEL COMPLEX
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Provided is a method of preparing poly(alkylene carbonate) using a molecular weight regulator in a process of preparing a copolymer of carbon dioxide/epoxide using a novel complex synthesized from salen-type ligand including a quaternary ammonium salt as a catalyst. According to the present invention, even though the molecular weight regulator is used, an activity of the catalyst may be stably maintained, whereby the low molecular weight of poly(alkylene carbonate) having a desirable level may be effectively provided. In addition, it is expected that since the novel complex as the catalyst of the present invention has a simple structure as compared to the existing copolymerization catalyst, due to the economical preparation cost thereof, the novel complex may be effectively applied to a large-scale commercial process.
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Paragraph 258; 259; 260; 261
(2014/10/04)
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- Unsymmetric salen ligands bearing a Lewis base: Intramolecularly cooperative catalysis for cyanosilylation of aldehydes
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A series of unsymmetric salen ligands derived from 1,2-diaminocyclohexane bearing an appended Lewis base on the three-position of one aromatic ring were synthesized by the reaction of various functional salicyaldehydes with the condensation product of 1,2-diaminocyclohexane mono(hydrogen chloride) and 3,5-di-tert-butylsalicylaldehyde. These ligands in conjunction with Ti(O iPr)4 exhibited excellent activity in catalyzing the cyanosilylation of aldehydes with trimethylsilyl cyanide (TMSCN) at mild conditions. The highest activity was observed in the catalyst system with regard to the salen ligand bearing a diethylamino group, which proved to be active even at a high [aldehyde]/[catalyst] ratio up to 50000. In a low catalyst loading of 0.05 mol%, the quantitative conversion of benzaldehyde to the corresponding cyanosilylation product was found within 10 min. at ambient temperature. An intramolecularly cooperative catalysis was proposed wherein the central metal Ti(iv) is suggested to play a role of Lewis acid to activate aldehydes while the appended Lewis base to activate TMSCN.
- Wen, Ye-Qian,Ren, Wei-Min,Lu, Xiao-Bing
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scheme or table
p. 6323 - 6330
(2011/10/09)
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- Direct C-H bond arylation of 2-hydroxybenzaldehydes with arylboronic acids via ligand-free palladium catalysis
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A mild and efficient ligand-free palladium-catalyzed direct C-H bond arylation reaction was developed to afford 2-hydroxybenzophenones in good to excellent yields from easily available 2-hydroxybenzaldehydes and arylboronic acids. The given reaction provided one of the easiest pathways for accessing 2-hydroxybenzophenones, and a variety of functional groups could be tolerated in this process.
- Weng, Fei,Wang, Chengming,Xu, Bin
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supporting information; experimental part
p. 2593 - 2596
(2010/07/04)
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- Mechanism and scope of salen bifunctional catalysts in asymmetric aldehyde and α-ketoester alkylation
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Metal complexes of C2-symmetric Lewis acid/Lewis base salen ligands provide bifunctional activation resulting in rapid rates in the enantioselective addition of diethylzinc to aldehydes (up to 92% ee). Further experiments probed the reactivity of the individual Lewis acid and Lewis base components of the catalyst and established that both moieties are essential for asymmetric catalysis. These catalysts are also effective in the asymmetric addition of diethylzinc to α-ketoesters. This finding is significant because α-ketoesters alone serve as their own ligands to accelerate racemic 1,2-carbonyl addition of Et2Zn and racemic carbonyl reduction. The latter proceeds via a metalloene pathway, and often accounts for the predominant product. Singular Lewis acid catalysts do not accelerate enantioselective 1,2-addition over these two competing paths. The bifunctional amino salen catalysts, however, rapidly provide enantioenriched 1,2-addition products in excellent yield, complete chemoselectivity, and good enantioselectivity (up to 88% ee). A library of the bifunctional amino salens was synthesized and evaluated in this reaction. The utility of the α-ketoester method has been demonstrated in the synthesis of an opiate antagonist.
- Fennie, Michael W.,DiMauro, Erin F.,O'Brien, Erin M.,Annamalai, Venkatachalam,Kozlowski, Marisa C.
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p. 6249 - 6265
(2007/10/03)
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- Salen-derived catalysts containing secondary basic groups in the addition of diethylzinc to aldehydes
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matrix presented A set of modular bifunctional salen catalysts which contain Lewis acid and Lewis base activating groups is described. These groups can be altered independently to control nucleophilic and electrophilic activation of the reacting substrates. These salen-derived catalysts show enhanced reactivity in the addition of diethylzinc to aldehydes with respect to most other salen, amino alcohol, and diamine derived catalysts and reactivity comparable to that of Ti complexes of bis-sulfonamides and diols.
- DiMauro, Erin F.,Kozlowski, Marisa C.
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p. 3053 - 3056
(2007/10/03)
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- Supramolecular assemblies from ditopic ligands and transition metal salts
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Tetradentate salicylaldimine ligands of the H2salen-type bearing ort/io-A'-morpholinomethyl substituents function as ditopic ligands, bonding to Ni" or Cu" with the [N2O2]2" donor set of the salen unit and a sulfate or two nitrate anions with the protonat
- Miller, Hamish A.,Laing, Norman,Parsons, Simon,Parkin, Andrew,Tasker, Peter A.,White, David J.
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p. 3773 - 3782
(2007/10/03)
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