排序方式: 共有130条查询结果,搜索用时 140 毫秒
31.
Preechaworapun A Chuanuwatanakul S Einaga Y Grudpan K Motomizu S Chailapakul O 《Talanta》2006,68(5):1726-1731
Sulfonamides (SAs) were electrochemically investigated using cyclic voltammetry at a boron-doped diamond (BDD) electrode. Comparison experiments were carried out using a glassy carbon electrode. The BDD electrode provided well-resolved oxidation, irreversible cyclic voltammograms and higher current signals when compared to the glassy carbon electrode. Results obtained from using the BDD electrode in a flow injection system coupled with amperometric detection were illustrated. The optimum potential from a hydrodynamic voltammogram was found to be 1100 mV versus Ag/AgCl, which was chosen for the HPLC-amperometric system. Excellent results of linear range and detection limit were obtained. This method was also used for determination of sulfonamides in egg samples. The standard solutions of 5, 10, and 15 ppm were spiked in a real sample, and percentage of recoveries was found to be between 90.0 and 107.7. 相似文献
32.
Treetepvijit S Preechaworapun A Praphairaksit N Chuanuwatanakul S Einaga Y Chailapakul O 《Talanta》2006,68(4):1329-1335
The electrochemical analysis of tetracyclines was investigated using nickel-implanted boron-doped diamond thin film electrode (Ni-DIA) by cyclic voltammetry and high performance liquid chromatographic with amperometry. Cyclic voltammetry was used to study the electrochemical oxidation of tetracyclines. Comparison experiments were carried out utilizing as-deposited BDD and glassy carbon electrodes. Ni-DIA electrode provided well-resolved oxidative irreversible cyclic voltammograms and the highest current signals among the electrode studied. High performance liquid chromatography (HPLC) with amperometric detection was also studied. The chromatography was performed using a commercially available Inertsil C18 column, with the mobile phase being: 80% phosphate buffer (pH 2.5)-20% acetonitrile and detected at 1.55 V. The methods were validated over the concentration range 0.05-100 ppm with the overall average recoveries from 83.3 to 102.5% and R.S.D. of less than 10%. The proposed method was further applied to analyse shrimp samples. 相似文献
33.
Rajca A Boratyński PJ Olankitwanit A Shiraishi K Pink M Rajca S 《The Journal of organic chemistry》2012,77(5):2107-2120
We describe the synthesis and electronic properties of ladder oligomers of poly(m-aniline) that may be considered as derivatives of azaacenes with cross-conjugated π-systems. Syntheses of ladder oligo(m-aniline)s with 9 and 13 collinearly fused six-membered rings employed Pd-catalyzed aminations and Friedel-Crafts-based ring closures. Structures were confirmed by either X-ray crystallography or correlations between DFT-computed and experimental spectroscopic data such as (1)H, (13)C, and (15)N NMR chemical shifts and electronic absorption spectra. All compounds have planar "azaacene" moieties. The experimental band gaps E(g) ≈ 3.5-3.65 eV, determined by the UV-vis absorption onsets, were in agreement with the TD-DFT-computed vertical excitation energies to the S(1) state. Fluorescence quantum yields of up to 20% were found. Electrochemically estimated HOMO energies of -4.8 eV suggested propensity for a facile one-electron oxidation and just sufficient environmental stability toward oxygen (O(2)). For two oligomers with "tetraazanonacene" moieties, potentials of E(4+/3+) ≈ 1.6-1.7 V vs SCE were determined for four-electron oxidation to the corresponding tetraradical tetracations. 相似文献
34.
间苯二甲酸连接的氢键导致的二维锌配位聚合物的合成及晶体结构 总被引:3,自引:0,他引:3
由于配位聚合物在催化材料,磁性材料和光学材料等领域内具有广泛的 应用价值,近年来人们已经合成了不少多维配位聚合物,并对其进行了结构鉴定和性质研究。配位聚合物一般都是通过体系内的配位键、氢键,和金属-金属间相互作用等作用力形成。在大多数的体系中,一般采用含氮基团,如4,4-联吡啶,2,4,6-三(4-吡啶基)-1,3,5-三嗪,1,4-二咪唑丁胺等作为桥连配体合成具有各种不同拓扑结构的无限伸展体系。同时,利用含氧基团作为桥基合成各类配位聚合物也是一个重要的途径,一般为多酸体系,如1,3,5-三苯甲酸,马来酸等。我们通过分子自组装作用,合成了一例由间苯二甲酸作桥基通过氢键导致的金属锌的二维配位聚合物,通过单晶X-射线衍射,研究了它的结构。 相似文献
35.
Jie‐Ying Wu Suchada Chantrapromma Dong‐Wen Chen Yu‐Peng Tian Ping Yang Hoong‐Kun Fun 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(5):523-525
The tetradentate N2S2 Schiff base ligand 3,3′‐[2,2′‐(ethylenedioxy)dibenzylidene]bis(S‐methyl dithiocarbazate) (H2L), prepared by the condensation of S‐methyl dithiocarbazate with 1,4‐bis(2‐formylphenyl)‐1,4‐dioxabutane in a 1:2 molar ratio, reacts with nickel acetate to form the title neutral metal complex, [Ni(C20H20N4O2S4)]. The X‐ray structure of the complex shows a distorted square‐planar geometry around the Ni atom. The monomeric units are weakly associated into dimers via a long Ni?S interaction [3.569 (1) Å]. These dimeric units are then linked by C—H?S intermolecular contacts to form a polymeric chain along the a axis. 相似文献
36.
Qingli Hao Hoong‐Kun Fun Suchada Chantrapromma Ibrahim Abdul Razak Fangfang Jian Xujie Yang Lude Lu Xin Wang 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(6):717-718
The title coordination complex, [Ni(C14H14O2PS2)2(C12H8N2)] or [Ni(pMePh‐dtp)2(phen)] (phen is 1,10‐phenanthroline; dtp is diaryldithiophosphate), has a non‐crystallographic twofold axis of symmetry through the Ni atom and the phen moiety. Two O,O‐di‐p‐tolyldithiophosphate (dtp) ions act as bidentate ligands. The central metal atom is coordinated by four S atoms from two dtp groups and two N atoms from the phen ligand. The title compound displays distorted octahedral geometry around the central Ni atom. 相似文献
37.
Anwar Usman Ibrahim Abdul Razak Hoong‐Kun Fun Suchada Chantrapromma Bao‐Guo Zhao Jian‐Hua Xu 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(2):o57-o58
In the title compound, C26H22O4, the pyranone ring adopts a twisted boat conformation, while the cyclohexane ring is close to an envelope conformation. The dihedral angle between the mean planes of the coumarin and naphthalene systems is 78.8 (1)°. The attached phenyl ring is in an equatorial position with respect to the cyclohexane ring. 相似文献
38.
Suchada Chantrapromma Anwar Usman Hoong‐Kun Fun 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(11):m531-m533
In the title compound [systematic name: triaqua(1,4,7,10,13,16‐hexaoxacyclooctadecane‐κ6O)(2‐nitrophenolato‐κO)barium(II)–aqua(1,4,7,10,13,16‐hexaoxacyclooctadecane‐κ6O)‐ bis(2‐nitrophenolato‐κ2O,O′)barium(II)–2‐nitrophenolate (1/1/1)], [Ba(C12H24O6)(C6H4NO3)(H2O)3][Ba(C12H24O6)(C6H4NO3)2(H2O)](C6H4NO3), the two BaII atoms encapsulated by the 18‐crown‐6 rings have different coordinations. Although both BaII atoms are coordinated to the six O atoms of the crowns, in the neutral moiety, the BaII atom is coordinated to one terminal O atom from a water molecule, two phenolate O atoms and two nitro‐group O atoms, while in the cationic moiety, the BaII atom is coordinated to three terminal O atoms from water molecules and one phenolate O atom. Both the crowns are eclipsed and translated along the b direction. In the asymmetric unit, the three components are interconnected by four O—H?O interactions. The packing is stabilized by two intermolecular C—H?O interactions and by one O—H?O interaction. 相似文献
39.
Rajca A Shiraishi K Vale M Han H Rajca S 《Journal of the American Chemical Society》2005,127(25):9014-9020
Hydrocarbon diradical 1, a new stable, 3-fold symmetric analogue of trimethylenemethane (TMM) with no heteroatom perturbation, is prepared and studied. Such diradicals should provide new building blocks for high-spin hydrocarbon polyradicals with very strong net ferromagnetic coupling. Magnetic studies (SQUID) and EPR spectroscopy indicate that 1 in tetrahydrofuran-d8 (THF-d8) possesses a triplet (S = 1) ground state, with strong ferromagnetic coupling. After annealing at room temperature, the EPR spectra of 1 (approximately 0.02 M in frozen THF-d8) consist of a single narrow resonance (deltaH(pp) < 1 G), and intermolecular antiferromagnetic coupling is increased by 1 order of magnitude. This behavior is consistent with the presence of exchange narrowing, thus suggesting aggregation of 1 in THF-d8. Blue solutions of 1 in THF-d8 possess a strong UV-vis absorption band at lambda(max) approximately 640 nm. Diradical 1 in THF-d8 is stable (or persistent) at room temperature, with no detectable decomposition for at least 2 days. 相似文献
40.
Anwar Usman Ibrahim Abdul Razak Hoong‐Kun Fun Suchada Chantrapromma Yan Zhang Jian‐Hua Xu 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(2):o59-o62
In the syn‐ and anticlinal isomers of the title compound, C22H18N2O6, the indole moiety is not completely planar, with the pyrrolidine ring being distorted very slightly towards a conformation intermediate between half‐chair and envelope. The molecular and packing structures in the crystals of these isomers are stabilized by C—H?O interactions. 相似文献