共查询到19条相似文献,搜索用时 156 毫秒
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本工作研究了冠醚化合物在外延乳剂生长过程中的调变作用。结果表明,1,4,7,10,13,16-六氧杂环十八烷对AgBr八面体乳剂无侵蚀作用,对非同晶系晶体之间的外延不起调变作用。1,7,10,16-四氟-4,13-二氮代杂环十八烷均使AgBr八面体乳剂的棱角产生了不同程度的侵蚀,可充当不同晶系晶体外延生长的调变剂,对晶体的溶解侵蚀能力依2S-18-C-6,2N-18-C-6,18-C-6的次序降低。这与它们同Ag+络合能力的强弱一致。2S-18-C-6,2N-18-C-6仅对非同晶系晶体之间的外延起调度作用,而对同晶系晶体的外延不起调查作用。冠醚化合物对晶体外延生长的调变作用与冠醚化合物对晶体的络合溶解作用有关。 相似文献
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镧系金属硫氰酸盐与‘四氧二氮’大环配合物 总被引:1,自引:0,他引:1
本文报道合成了‘四氧二氮’大环配体(1,7,10,16-四氧杂-4,13-二氮杂环十八烷)同La、Nd、Yb的硫氰酸盐的固体配合物。作配合物的合成中,为防止镧系金属离子的水解,加入原甲酸三乙酯作为脱水剂,而无需严格无水,因此操作方便。 所用试剂二乙腈为分析纯;镧系金属硫氰酸盐为本实验室制备,含4—5结晶水;原甲酸三乙酯为化学纯。 相似文献
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本文报道一类新型大环聚醚的合成.在以1,7-二氧杂-4,10-二氮杂环十二烷(1a)及1,7,10,16-四氧杂-4,13-二氮杂环十八烷(1b)中的两个仲胺上进行含醚键的卤代烷取代反应,获得一批带有两个含有侧链醚键的新型冠醚.以碳酸钾为缩合剂,所得冠醚碱金属配合物经酸分解及四甲基氢氧化铵处理后,得游离的大环聚醚. 用溶解度法初步测定了这类冠醚对碱金属的配位性能.结果指出,其母环及侧链上氧原子数的多少及碱金属离子半径的大小均影响配合物的稳定性,其中有些冠醚对碱金属有良好的配位能力,有的还具有优异的选择性,例如N,N′-β-甲氧基乙基-1,7-二氧杂-4,10-二氮杂环十二烷(13a)对钾及钠离子的选择比大于18-c-β,并比4,4′(5′)-二甲基苯并-30-c-10还高. 相似文献
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合成了四个Co(Ⅱ)离子同1,7,10,16-四氧杂-4,13-二氮杂环十八烷的固体配合物。经IR、电子光谱、电导、DTA-TG、磁性以及元素分析等推算了它们的组成,指派了谱带的归属,并从电子光谱数据用配位场方法计算了D_q值、B值和β值,计算结果与实验观察值相符。 相似文献
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本文研究了不同结构的季铵盐、季鏻盐、常用冠醚以及N,N'-二取代氦杂冠醚等相转移催化剂,催化产生的二溴卡宾与对-甲基苯乙烯的加成反应。结果证明,具有对称烷基结构的季铵盐的催化性能优于碳链较长、对称性较差的手铵盐。在冠醚类相转移催化剂中,新型N,N'-二取代氮杂冠醚优于常用冠醚及穴醚[2.2.2]。在十九种相转移催化剂中,以N,N'-双(3'、6'-二氧杂癸烷基)-1,7,10,16-四氧杂-4,13-二氮杂环十八烷[简称二丁基2.2(2.2)]的催化性能最佳。简要讨论了鎓盐及大环多醚的PTC反应机理及催化性能,还比较了氘代氯仿、氘代氢氧化钠重水体系进行的相转移催化反应。 相似文献
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由于冠醚化合物对碱金属和碱土金属离子有特异的配合能力而被广泛研究,但是它们对过渡金属离子的配合作用并不特征.根据路易斯酸碱理论,在冠醚环上以氮原子部分代替氧原子后,可预期改变它们对金属离子的配合能力和选择性.1969年Lehn等人首次合成了含氮原子的冠醚化合物——1,7,10,16-四氧杂-4,13-二氮杂环十八烷(以下简称四氧二氮大环).之后曾有人对其与碱金属和过渡金属离子在溶液中配合物的生成常数进行了测定,同时国内外又相继报道了以该配体为母体的带有不同侧链的一系列衍生物.这些工作的目的都在于提高它们对金属离子的选择性.迄今为止,该配体同过渡金属离子形成配合物的研究报道很少.我们合成了四氧二氮大环同NiCl_2·6H_2O和Ni(ClO_4)_2·4~5H_2O的配合物.经元素分析确定了它们的组成,测定了配合物的红外光谱、电导、差热-热重分析,电子光谱、磁性,并对中心离子的d-d跃迁谱带进行了指派,计算了D_q值和B值. 相似文献
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以水性聚乙烯醇(PVA)为粘合剂,以异位法制备的颗粒尺寸为140nm的AgBr乳剂作光敏元,考察了传统化学增感方法对PTG材料的光敏性影响.实验结果表明,分别将经过硫增感、金增感、硫加金增感以及还原增感的AgBr乳剂加入到PTG体系中,均提高了PTG体系的光敏性,而灰雾却没有明显的增长. 相似文献
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Xiaoyan Zheng Xueye Wang Shanfeng Yi Nuanqing Wang Yueming Peng 《Journal of computational chemistry》2009,30(16):2674-2683
In this work, a quantum mechanical research of five lariat crown ethers(LCEs), 2‐methoxy‐15‐crown‐5( A ), N‐methoxy‐4‐aza‐15‐crown‐5( B ), N‐methoxy‐4‐aza‐18‐crown‐6( C ), N‐methoxyethyl‐4‐aza‐18‐crown‐6( D ), N,N′‐bis(2‐metho xyethyl)‐4,13‐diaza‐18‐crown‐6( E ), which are based on either 15‐crown‐5 or 18‐crown‐6 frameworks and contain various pendant arms extending from either carbon or nitrogen atoms on the crown frameworks, had been done using density functional theory with B3LYP/6‐31G* method to obtain the electronic and geometrical structures of the LCEs and their complexes with alkali metal ions: Na+ and K+. The nucleophilicity of LCEs had been investigated by the Fukui functions. For complexes, the match between the cation and cavity size, the status of interaction between alkali metal ions and donor atoms in the LCEs, and the sidearm effect of the LCEs had been analyzed through the other calculated parameters, such as, highest occupied molecular orbital energy, lowest unoccupied molecular orbital energy, and energy gaps. In addition, the enthalpies of complexation reaction had been studied by the calculated thermodynamic data (298 K). The calculated results are all in a good agreement with the experimental data for the complexes. © 2009 Wiley Periodicals, Inc. J Comput Chem 2009 相似文献
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Esteban D Avecilla F Platas-Iglesias C Mahía J de Blas A Rodríguez-Blas T 《Inorganic chemistry》2002,41(17):4337-4347
The complexation properties of three related macrocycles derived from 4,13-diaza-18-crown-6 toward lead(II) are reported. The flexible macrocycle N,N'-bis(2-aminobenzyl)-4,13-diaza-18-crown-6 (L(2)) forms stable complexes with this metal ion in the presence of different counterions (perchlorate and thiocyanate). The X-ray crystal structure of [PbL(2)](SCN)(2) indicates that, in the solid state, the lead(II) ion is eight-coordinated and fits quite well into the crown hole favoring an anti arrangement of the organic receptor, which generates a very infrequent cubic coordination polyhedron around the Pb(II) ion. In solution both complexes are fluxional and the nature of the counterion seems to affect the dynamic behavior. Ligand L(3), N,N'-bis[(2-salicylaldimino)benzyl]-4,13-diaza-18-crown-6, derives from L(2) by condensation of salicylaldehyde with the amine group of each side arm. It can be deprotonated to yield cationic complexes of formula [Pb(L(3)-H)](+) where the metal ion lies asymmetrically on the cavity of the ligand, being seven-coordinated and pushed out from the crown hole, the bibracchial lariat ether presents a syn arrangement, and one of the arms remains uncoordinated. The lead(II) ion also lies asymmetrically on the cavity of the third macrocycle (L(7)), a lateral macrobicycle incorporating a phenolyl Schiff-base spacer. Spectrophotometric titrations of L(2) and (L(3)-2H)(2)(-) with lead(II) perchlorate in acetonitrile gave values of log K[PbL(2)] = 7.7(5) and log K[Pb(L(3)-2H)] = 7.2(3), demonstrating that the stability of the lead(II) complexes with these two ligands is very similar. 相似文献
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希土冠醚配合物的电子结构 总被引:4,自引:0,他引:4
本文用INDO方法计算了希土冠醚配合物的分子构型、电子结构、电荷分布和键级,讨论了配位前后电荷分布特征,以及由于配位引起L→L_n电荷转移跟配合物电子结合能化学位移和配位活化的关系,解释了因冠醚内腔不同希土冠醚配合物呈现不同构型的内在原因。希土冠醚配合物的占据分子轨道以配位体轨道成分为主体(4f轨道除外),低空轨道以希土原子轨道成分为主体。其占据分子轨道可分为六组。冠醚环上引入苯环后配合物前线轨道呈现π键性质。其价键的主要贡献部份是5d轨道,其次是6p和6s。4f轨道基本上不参与成键。讨论了配合物的化学键性质及高配位数时稳定的因素。 相似文献
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本文应用反相纸色层法和静态吸附平衡法检测了王冠化合物与稀土离子之间的络合能力和水相阴离子类型对络合能力的影响。所用的王冠化合物有:B-15-C-5,DB-18-C-6,四氢呋喃丙酮四聚体,DB-18-C-6-甲醛缩聚物和B-15-C-5-甲醛缩聚物。得到如下主要结果:1.不同王冠化合物的络合能力顺序是;B-15-C-5>DB-18-C-6》四氢呋喃丙酮吗聚体,另B-15-C-5-甲醛缩聚物>DB-18-C-6-甲醛缩聚物。2.稀土离子络合能力的顺序是:Sm3+Er3+=La3+(反相纸色层法),Er3+>Eu3+>La3+(吸附平衡法)。3.与不同阴离子缔合的离子对的稳定性顺序是:苦味酸根>三氯代乙酸根>磺基水杨酸根》Cl-、NO3-、ClO4-及SO4=。 相似文献
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Dutot L Gaucher A Elkassimi K Drapeau J Wakselman M Mazaleyrat JP Peggion C Formaggio F Toniolo C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(10):3154-3163
A new set of beta-amino acids that carry various crown ether receptors on their side chains of the general formula (S)-beta(3)-HDOPA(crown ether) (HDOPA: homo-3,4-dihydroxyphenylalanine; (crown ether): [15]crown-5 ([15-C-5]), [18]crown-6 ([18-C-6]), [21]crown-7 ([21-C-7]), 1,2-Benzo-[24]crown-8 ([Benzo-24-C-8]) and (R)-Binol-[20]crown-6 ([(R)-Binol-20-C-6])) was prepared. Peptides that are based on these new crowned beta-amino acids combined with (1S,2S)-ACHC (2-aminocyclohexanecarboxylic acid), which is known to be a potent 3(14)-helix inducer, to the hexamer level, with two crowned residues at the i and i+3 positions of the main-chain, were synthesized in solution by stepwise coupling using Boc-N(alpha)-protection (Boc: tert-butoxycarbonyl) and the EDC/HOAt C-activation method. Their conformational analysis was performed by using FTIR absorption, NMR and CD spectroscopy techniques. Our results are in full agreement with a 3(14)-helix conformation. 相似文献
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L. A. Kartsova O. V. Markova A. I. Amel’chenko N. D. Ostryanina 《Journal of Analytical Chemistry》2000,55(3):270-279
The use of crown compounds (18-crown-6, benzo-18-crown-6, dibenzo-18-crown-6, benzo-15-crown-5, dibenzo-24-crown-8, 4,13-diaza-18-crown-6,4,13-dibenzyl-diaza-18-crown-6,
and cryptand [2.2.2]) as components of stationary phases in the determination of organic compounds by gas chromatography is
studied. The polarity, selectivity, efficiency, and working temperature ranges of stationary phases based on crown ethers
and cryptand as well as conventional stationary phases for gas chromatography are compared. The influence of the type and
number of heteroatoms, the conformational lability of the cavity, and the presence of substituents on the polarity and selectivity
of the stationary phases under study is revealed. Preferable types of interactions of stationary phases containing crown compounds
with organic compounds of different classes are discussed. It is concluded that phases of the mixed type based on crown ethers
are promising for improving the selectivity and efficiency of gas-chromatographic separation 相似文献