- Development of non-enzymatic strip for simple and selective determination of urea in water and biological samples
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A simple and selective method for the determination of urea based on the paptode technique is described. The sensor was constructed by immobilizing an ionophore on a TLC strip. The procedure is based on the nucleophilic displacement of urea with tetrachlorop-benzoquinone (chloranil) as an ionophore, and the formed violet-color product was detected using a flatbed scanner. The color of each spot was analyzed to red (R), green (G) and blue (B) values from 0 to 255 using a program written in visual basic (VB) programming language. The calibration graph obtained with the proposed sensor was linear over the range of 0.05-10.00 mg L-1 with a detection limit of 0.01 mg L-1 for urea. Parameters such as pH and concentration of chloranil were optimized. The proposed sensor was successfully applied for the determination of urea in bovine serum, urine and tap water samples.
- Abbaspour,Norouz-Sarvestani,Mirahmadi
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- Metal-Diamidobenzoquinone Frameworks via Post-Synthetic Linker Exchange
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Metal-organic frameworks with amidic linkers often exhibit exceptional physical properties, but, owing to their strong metal-nitrogen bonds, are exceedingly challenging to isolate through direct synthesis. Here, we report a route to access metal-diamidobenzoquinone frameworks from their dihydroxobenzoquinone counterparts via postsynthetic linker exchange. The parent compounds (Me2NH2)2[M2L3] (M = Zn, Mn; H2L = 2,5-dichloro-3,6-dihydroxo-1,4-benzoquinone) undergo linker exchange upon exposure to a solution of monodeprotonated 2,5-diamino-3,6-dibromo-1,4-benzoquinone or 2,5-diamino-3,6-dichloro-1,4-benzoquinone, proceeding through single-crystal-to-single-crystal reactions. The presence of both types of linker in the resulting frameworks is confirmed by a combination of NMR, Raman, and energy-dispersive X-ray (EDX) spectroscopies. Moreover, the extent of linker exchange in the Zn frameworks is quantified using 13C NMR spectroscopy, and spatially resolved EDX spectroscopy reveals the two types of linker to be homogeneously distributed within a crystal. Finally, we propose a tentative mechanism of linker exchange based on pKa measurements, considerations of framework solubility, and powder X-ray diffraction analysis. This work provides the first method to exchange organic linkers with different donor atoms in metal-organic frameworks and in doing so demonstrates exchange between linkers with donor atoms differing in acidity by a remarkable 11 units of pKa. Together, these results offer a potentially general synthetic strategy toward new materials with exotic metal-linker coordination modes.
- Liu, Lujia,Li, Liang,Ziebel, Michael E.,Harris, T. David
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supporting information
p. 4705 - 4713
(2020/03/31)
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- Method for synthesizing 2,5-diaminohydroquinone dihydrochloride
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The invention discloses a method for synthesizing 2,5-diaminohydroquinone dihydrochloride. The method for synthesizing 2,5-diaminohydroquinone dihydrochloride includes the steps that under normal temperature, raw materials including chloranil and a reaction solvent are added into a reaction container, stirring is conducted, ammonium hydroxide is dropwise added, after dropwise addition is completed, temperature is increased to 50-80 DEG C, an ammonolysis reaction is conducted for 2-8 h, then reaction liquid is subjected to after-treatment, and finally an intermediate which is 2,5-diamino-3,6- dichloro-benzoquinone is obtained; 2,5-diamino-3,6-dichloro-benzoquinone, water and Pd/C are added into a reaction kettle for a reduction reaction for 1-8 h at the temperature of 40-80 DEG C and underhydrogen pressure of 0.1-0.6 MPa, then reaction liquid is subjected to after-treatment, and finally the 2,5-diaminohydroquinone dihydrochloride is obtained. Reaction technology parameters are easy tocontrol, energy consumption is low, no toxic side products are generated, the yield is good, purity is high, and industrial feasibility is high.
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Paragraph 0024-0028; 0036; 0037; 0039; 0040; 0042; 0043
(2019/04/26)
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- Tuning the optical and electronic properties of 4,8-disubstituted benzobisoxazoles via alkyne substitution
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In an effort to design new electron-deficient building blocks for the synthesis of conjugated materials, a series of new trans-benzobisoxazoles bearing halogen or alkynyl substituents at the 4,8-positions was synthesized. Additionally, the impact of these modifications on the optical and electronic properties was investigated. Theoretical calculations predicted that the incorporation of various alkynes can be used to tune the energy levels and band gaps of these small molecules. The targeted 4,8-disubstituted benzobisoxazoles were easily prepared in good yields using a two-step reaction sequence: Lewis acid catalyzed orthoester cyclization followed by Sonogashira cross-coupling. The experimentally determined HOMO values for these 4,8-disubstituted benzobisoxazoles ranged from -4.97 to -6.20 eV and showed reasonable correlation to the theoretically predicted values, with a percent deviation that ranged from 2.4-12.8%. However, the deviation between actual and predicted HOMO values was reduced to less than 3.5% when the theoretical values were extrapolated to the long-chain limit and compared to copolymers containing the 4,8-disubstituted benzobisoxazoles. Collectively, these results indicate that these 4,8-disubstituted trans-benzobisoxazoles can be used for the synthesis of new conjugated materials with electronic properties that are variable and predictable.
- Tlach, Brian C.,Tomlinson, Aimee L.,Bhuwalka, Achala,Jeffries-El, Malika
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scheme or table
p. 8670 - 8681
(2011/12/22)
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- An efficient synthesis of 2,6-disubstituted benzobisoxazoles: New building blocks for organic semiconductors
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(Chemical Equation Presented) 2,6-Disubstituted benzobisoxazoles have been synthesized by a highly efficient reaction of diaminobenzene diols with various orthoesters. The scope of this new reaction for the synthesis of substituted benzobisoxazoles has been investigated using four different orthoesters. The utility of these compounds as building blocks for the synthesis of conjugated polymers is demonstrated.
- Mike, Jared F.,Makowski, Andrew J.,Jeffries-El, Malika
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supporting information; experimental part
p. 4915 - 4918
(2009/05/31)
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- Method for producing 3,6-bis(carboethoxyamino)-2,5-diaziridinyl-1,4-benzoquinone
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A method is described of preparing a diaziridinyl diaminobenzoquinone-N, N'-dicarboxylate compound selected from dialkyl, di(arylalkyl), or diphenyl diaminobenzoquinone-N, N'-dicarboxylates, said method comprising: reacting a diaminohydroquinone of the formula: STR1 wherein X is selected from the group consisting of chlorine, fluorine, bromine, iodine or alkoxy groups with a molar excess of a pyrocarbonate di-substituted with alkyl groups, arylalkyl groups, or phenyl groups to produce a dialkyl, a di(arylalkyl), or a diphenyl diaminohydroquinone-N,N'-dicarboxylate; oxidizing said hydroquinone to the respective benzoquinone; reacting said benzonquinone with an aziridine having no substitution on the nitrogen and having substituents on the carbons selected from the group consisting of hydrogen and alkyl; and recovering the resultant diazirindinyl diaminobenzoquinone-N,N'-dicarboxylate.
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