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排序方式: 共有144条查询结果,搜索用时 15 毫秒
1.
Gunes Sibel Senyigit Ercan Karakaya Ersin Ozceyhan Veysel 《Journal of Thermal Analysis and Calorimetry》2019,136(4):1795-1806
Journal of Thermal Analysis and Calorimetry - This work introduces the determination of the optimum values of the design parameters in a tube with loose-fit perforated twisted tapes. The effects of... 相似文献
2.
Sevim?Hamamci Veysel?T.?YilmazEmail author William?T.?A.?Harrison 《Structural chemistry》2005,16(4):379-383
The first silver(I) complex of saccharinate (sac) with pyridine (py), [Ag(sac)(py)]n has been synthesized and characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffractometry. The complex crystallizes in chiral, trigonal space group P3121 (No. 152) with unit cell parameters of a = 11.2605(2) Å, c = 17.3300(4) Å, V = 1903.02(6) Å3 and Z = 6. [Ag(sac)(py)]n contains monomeric [Ag(sac)(py)] units linked into infinite helices by way of Ag⋅sAg interactions [d(Ag⋅sAg) = 2.909(2) and 2.985(1) Å]. The distorted square-planar environment of Ag is completed by an N-bonded sac [Ag—N = 2.084(2) Å] and a py molecule [Ag—N = 2.116(2) Å]. The Nsac—Ag—Npy angle is 173.85(10)∘. The one-dimensional chains are crosslinked by C—H⋅sO interactions involving the carbonyl and sulfonyl O atoms of sac and aromatic-ring hydrogen atoms of both sac and py. The thermal stability of the title complex was investigated using thermogravimetry and differential thermal analysis in a static atmosphere of air. The first decomposition stage between 90 and 160∘C corresponds to removal of the py molecule in a single stage, while the degradation of the sac moiety occurs at two stages in the temperature range 370–515∘C, giving an end product of metallic Ag. 相似文献
3.
Kayser V Turton DA Aggeli A Beevers A Reid GD Beddard GS 《Journal of the American Chemical Society》2004,126(1):336-343
Energy migration between tryptophan residues has been experimentally demonstrated in self-assembled peptide tapes. Each peptide contains 11 amino acids with a Trp at position 6. The peptide self-assembly is pH-sensitive and forms amphiphilic tapes, which further stack in ribbons (double tapes) and fibrils in water depending on the concentration. Fluorescence spectra, quenching, and anisotropy experiments showed that when the pH is lowered from 9 to 2, the peptide self-assembly buries the tryptophan in a hydrophobic and restricted environment in the interior of stable ribbons as expected on the basis of the peptide design. These fluorescence data support directly and for the first time the presence of such ribbons which are characterized by a highly packed and stable hydrophobic interior. In common with Trp in many proteins, fluorescence lifetimes are nonexponential, but the average lifetime is shorter at low pH, possibly due to quenching with neighboring Phe residues. Unexpectedly, time-resolved fluorescence anisotropy does not change significantly with self-assembly when in water. In highly viscous sucrose-water mixtures, the anisotropy decay at low pH was largely unchanged compared to that in water, whereas at high pH, the anisotropy decay increased significantly. We concluded that depolarization at low pH was not due to rotational diffusion but mainly due to energy migration between adjacent tryptophan residues. This was supported by a master equation kinetic model of Trp-Trp energy migration, which showed that the simulated and experimental results are in good agreement, although on average only three Trp residues were visited before emission. 相似文献
4.
Turan K. Yazicilar Omer Andac Yunus Bekdemir Halil Kutuk Veysel T. Yilmaz William T. A. Harrison 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(1):m21-m22
The title compound, alternatively named sodium 6‐nitro‐3H‐1,2,3‐benzoxathiazole 2,2‐dioxide monohydrate, Na+·C6H3N2O5S?·H2O, consists of chains of NaO7 units, with the seven donor‐O atoms coming from two water molecules and five p‐nitrobenzoxasulfamate anions. The seven‐coordinate geometry around the Na+ ion is described as monocapped trigonal prismatic, but with a large distortion from ideal geometry. Each triangular face is defined by one O atom each from a water molecule, a nitro group and a sulfonyl group. An O atom from a sulfonyl group caps one of the square faces of the trigonal prism in an unsymmetrical fashion. The water molecules and one sulfonyl O atom are involved in bridging adjacent units, as is the nitro group of the anion. The sulfamate ions adopt an antiparallel alignment between the NaO7 units and are connected to each other by C—H?O and π–π interactions. The three‐dimensional crystal structure is stabilized by a network of strong O—H?N hydrogen bonds. 相似文献
5.
Yildiray Topcu Omer Andac Veysel T. Yilmaz William T. A. Harrison 《Journal of Molecular Structure》2002,610(1-3):99-103
The synthesis, molecular and crystal structure of bis(triethanolamine)Mn(II) saccharinate, [Mn(tea)2](sac)2 are reported. The configuration of the tea ligands results in an unusual example of coordination number seven for the Mn(II) ion. The two triethanolamine (tea) ligands coordinate to the Mn(II) ion forming a monocapped trigonal prism geometry, in which one of the tea ligands behaves as a tridentate ligand, while the other one acts as a tetradentate donor. The free and coordinated hydroxyl hydrogens of the tea ligands are involved in hydrogen bonding with the amine nitrogen, carbonyl and sulfonyl oxygens of the neighbouring sac ions to form a three-dimensional infinite network. A weak π–π interaction between the phenyl rings of the sac ions also occurs. 相似文献
6.
A silver(I)-saccharinato (sac) complex with nicotinamide (nia), [Ag(sac)(nia)]
n
has been synthesized and characterized by elemental analysis, IR spectroscopy, DTA-TG analyses and single crystal X-ray diffractometry. The complex crystallizes in monoclinic space group P21/n with unit cell parameters of a=7.0258(4) Å, b=24.3784(10) Å, c=8.4301(5) Å, β=109.407(5)°, V=1361.85(13) Å3 and Z=4. [Ag(sac)(nia)]
n
contains [Ag(sac)(nia)] units, which are doubly bridged by both nia and sac ligands, leading to a linear one-dimensional polymeric chains running along the a axis. The silver(I) ion has a highly distorted AgN2O2 tetrahedral geometry and the coordination polymer exhibits relatively short intra-chain ligand supported Ag···Ag separations of 3.1593(4) Å. The one-dimensional chains are crosslinked by N–H···O hydrogen bonds and aromatic π(sac)···π(nia) stacking interactions to generate a two-dimensional layer structure. IR spectra and thermal analysis data are in agreement with the crystal structure. 相似文献
7.
Veysel T. Yilmaz Serkan Guney Omer Andac William T. A. Harrison 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(8):m427-m430
The title complexes [M(sac)2(mpy)2] [sac is saccharinate (C7H4NO3S) and mpy is 2‐pyridylmethanol (C6H7NO)], with M = ZnII and CdII, are isostructural and consist of neutral molecules. The ZnII or CdII cations are octahedrally coordinated by the two neutral mpy and two anionic sac ligands. The mpy ligand acts as a bidentate donor through the amine N and hydroxyl O atoms. The sac ligands exhibit an ambidentate coordination behaviour; one is N‐coordinated and the other is O‐coordinated within the same coordination octahedron. The crystal packing is determined by C—H?O‐type hydrogen bonding, as well as by weak py–py and sac–sac aromatic π–π‐stacking interactions. 相似文献
8.
A new assembly [Cu2(sac)2(μ‐dmea)2(μ‐H2O)]n (sac = saccharinate and Hdmea = 2‐dimethylaminoethanol) has been synthesized and characterized by elemental analysis, IR spectroscopy, thermal analysis and single crystal X‐ray diffraction. The complex crystallizes in the monoclinic space group C2/c and consists of dinuclear modules of [Cu2(sac)2(dmea)2]. The sac ligand is N‐coordinated, while the dmea ligand is in the deprotanated form by losing the ethanol hydrogen atom and acts as a bidentate donor through the alkoxo group and N atom. The alkoxo group also serves as a bridge between two copper(II) ions, leading to an intra‐dimer Cu···Cu separation of 3.0229(7) Å. The dimeric units are bridged by aqua ligands to generate a one‐dimensional water‐bridged helical chain, in which the copper(II) ions exhibit a distorted square‐pyramidal CuN2O3 coordination. The Cu–Cu distance in the chain separated by the bridging aqua ligands is 5.297Å. The polymeric chains are further linked by π(sac)···π(sac) and C–H···π(sac) interactions into a two‐dimensional supramolecular network. 相似文献
9.
H. Göktürk C. Eylem S. Hatipoĝlu H. N. Erten 《Journal of Radioanalytical and Nuclear Chemistry》1995,198(2):449-456
The sorption behavior of strontium and barium on kaolinite, bentonite and chlorite-illite mixed clay was studied by radioanalytical techniques using the batch method.90Sr (29.1 y) and133Ba (10.5 y) were used as radiotracers. Characterization of the solid matrices was done by FTIR and XRD spectrometries and specific surface area measurements. Synthetic groundwater was used as the aqueous phase. The variation of the distribution ratioR
d, as a function of metal ion loading was examined. The sorption isotherms were fitted to various isotherm models. The sorption energies were calculated to be in the range of 8–10 kJ/mol suggesting an ion exchange type of sorption mechanism. In detailed experiments, chlorite-illite mixed clay was first presaturated with K+, Sr2+, Ca2+ and Al3+ ions, respectively, prior to sorption studies with Ba2+ ions. The results of Ca2+ pretreated chlorite-illite were very similar to those of natural chlorite-illite, suggesting that the Ba2+ ion exchanges primarily with the Ca2+ ion on the clay minerals. 相似文献
10.
A new mercury(II) complex of 1,2‐bis(4‐pyridyle)ethene (bpe) with anionic acetate and thiocyanate ligands has been synthesized and characterized by elemental analysis, IR, 1H NMR and 13C NMR spectroscopy. The single crystal X‐ray analysis shows that the complex is a two‐dimensional polymer with simultaneously bridging 1,2‐bis(4‐pyridyle)ethane, acetate and thiocyanate ligands and basic repeating dimeric [Hg2(μ‐bpe)(μ‐OAc)2(μ‐SCN)2] units. The two‐dimensional system forms a three‐dimensional network by packing via π‐π stacking interactions. 相似文献