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991.
The apparent molal volumes and compressibilities of NaCl, KCl, and CsCl in mixtures of 18-Crown-6 and water have been calculated from density and speed-of-sound measurements at 25°C. The partial molal volumes and compressibilities of the salts when all cations have formed complexes with 18-Crown-6 molecules have been evaluated. The sign and magnitude of the volume and compressibility changes of complex formation strongly suggest that the charge of the cation becomes very effectively screened by the crown ether. 相似文献
992.
A new compound of 4,4'-diamino-N,N'-diethyl bisbenzenesulfamide (C18H26N4O4S2,Fw = 426.55) has been synthesized and its structure was determined by X-ray crystallography method. The crystal belongs to the monoclinic system, space group P21/c with a = 10.0623(9), b =13.6759(13), c =15.5309(14) (A),β = 100.482(2)°, V= 2101.6(3)(A)3, Dc = 1.348 g/cm3, F(000) = 904,μ = 0.285 mm-1, Z = 4, the final R = 0.0512 and wR = 0.1363 for 3485 observed reflections with I >2σ(Ⅰ). The structure of the title compound is pseudo secondary axisymmetric, and the two sulfamide-groups show distorted tetrahedral configurations. 相似文献
993.
0IntroductionCobaltcomplexeswithnonmacrocyclicchelatingligandscontainingtheamidefunctionalityhavere鄄ceivedmuchattentioninpastyears[1~3].Somestudieshaverevealedthatdeprotonatednitrogensoforganicamides,beinganionicinnature,arecapableofstabi鄄lizingthetriva… 相似文献
994.
Schiff碱双核Mn配合物的合成、结构和性能研究 总被引:3,自引:0,他引:3
Five manganese complexes of Schiff base were synthesized: [MnⅣ,Ⅳ(μ-O)(Salen)]2·DMF·H2O (1), [MnⅣ,Ⅳ(μ-O)(5-BrSalen)]2·DMF·0.5H2O (2), {MnⅣ,Ⅳ(μ-O)[Sal(1,2-pn)]}2·H2O (3), {MnⅣ,Ⅳ(μ-O)[5-Br-Sal(1,2-pn)]}2·H2O (4), {MnⅣ,Ⅳ(μ-O)[5-CH3-Sal(1,2-pn)]}2·2H2O (5), and were characterized by element analysis, IR and UV-Vis spectra. The results of cyclic voltammogram show that Schiff base ligands can drop the potential of manganese and steady high oxide state of manganese. The magnetic properties of 1 and 3 have also been studied. The results show that there is a weak ferromagnetically coupling of MnⅣ2 pair at room and low temperature, and the interactions of complex 3 are weaker than complex 1. 相似文献
995.
996.
Takeshi Shimomura Tatsuya Funaki Kohzo Ito Byoung-Ki Choi Tomihiro Hashizume 《Journal of inclusion phenomena and macrocyclic chemistry》2002,44(1-4):275-278
We have investigated the inclusion properties of molecular nanotubes composed ofcrosslinked -cyclodextrin. Induced circular dichroism was used to probe theformation and dissociation of complexes between the nanotubes and azobenzenemodified linear polymers. The polymer was poly(ethylene glycol) (PEG), either withor without a hydrophobic alkyl chain.It was found that the inclusion complex betweenthe nanotubes and polymers formed at room temperature, and that the polymers dissociated from the nanotubes with increasing temperature. Further, the polymer with hydrophobic alkyl chain was bound inside the nanotube more strongly and dissociated more abruptly with increasing temperature than its hydrophilic counterpart as expected theoretically. 相似文献
997.
In order to study the influence of the side-chain orientation on the peptide backbone conformation we have synthesised the model dipeptides t-BuCO-l-Pro-(1S,2R)-c6Phe-NHMe and t-BuCO-l-Pro-(1R,2S)-c6Phe-NHMe, incorporating each enantiomer of the trans cyclohexane analogue of phenylalanine (trans-1-amino-2-phenylcyclohexanecarboxylic acid). The orientation of the aromatic side-chain determines the β-turn type accommodated by these peptides to the point that the (1S,2R)-c6Phe derivative retains the type I β-turn in the crystalline state, in contrast to the behaviour exhibited by the natural counterpart t-BuCO-l-Pro-l-Phe-NHMe. 相似文献
998.
A new hydroxo‐bridged dimeric Cr(III) complex [Cr(saltn)OH]2·4H2O [H2saltn=N,N′‐bis(salicylidene)trimethylenediamine] has been synthesized and its structural and magnetic properties have been investigated. The complex crystallizes in the triclinic space group P‐1 with one dimeric formula unit in a cell of dimensions a=0.95828(19) nm, b=0.95926(19) nm, c=1.0437(2) nm, α=86.77(3)°, β=82.48(3)°, and γ=64.93(3)°. The geometry around each chromium(III) center is six‐coordinate, distorted‐octahedral. The bridging Cr2O2 unit is strictly planar, as required by the crystallographic symmetry. The Cr? O? Cr′ bridging angle is 99.94(16)°, and the distance between Cr…Cr′ is 0.3019 nm. The magnetic susceptibility of the complex has been examined in the range of 2‐300 K. By using the spin‐spin coupled model for an S1=S2=3/2 dimeric system , the magnetic data were fitted to give the parameters of g=2.01(1), J=‐0.85(2) cm‐1, and zJ' =0.18(3)cm‐1, indicating the presence of a weak antiferromagnetic spin‐exchange interaction between the Cr(III) ions in the binuclear complex. 相似文献
999.
1000.
Jun JIA Xing Wang WANG Yi Li ZHAO Yu ZHU Jing Chao TAO* Department of Chemistry Zhengzhou University Zhengzhou Chemical Engineering Institute of Henan Province Zhengzhou 《中国化学快报》2004,15(3):292-295
Proteins containing dinuclear Cu (II), Zn (II) centers play paramount roles in biology1. As mimetic of metal-dependent esterase, dinuclear Cu (II) and Zn (II) complexes have received a great deal of attentions2~6. They are of interest in the field of biomimetic chemistry to provide an improved understanding of the function of the biological sites and as potential catalysts for substrate oxidations. Schiff base type polydentate ligands which contain centeral hydroxyl group have been wid… 相似文献