排序方式: 共有92条查询结果,搜索用时 15 毫秒
81.
Zhan Xian LI Mei Gong FAN Wen Fu FU Ming Ming YU Xi Juan ZHAO De Hui WANG 《中国化学快报》2006,17(8):1017-1020
Much attention has been paid to new polydentate ligands usually formed by a central heteroaromatic ring conveniently linked to one or two arms bearing heteroatoms (these arms can be heterocycles). For ligands N?N?N, C?N?N, N?C?N, O?N?N, O?N?O and O?N?N?O … 相似文献
82.
Herein, we report the structural analysis of a novel family of iron-chelating dendrimers and their synthetic intermediates utilizing matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and electrospray ionization ion trap (ESI IT) MS. These dendrimers share a benzene tricarbonyl core moiety attached to three tripodal branching units, each linking to three terminal groups, ranging from carboxyl, catechol and 3-hydroxy-6-methyl-pyran-4-one moieties and their protected analogs. In order to monitor the progression of dendrimer synthesis, all intermediates and final products were mass analyzed by conventional MALDI-TOF MS with and without alkali metal spiking. For structural characterization, interpretable post-source decay (PSD) and electrospray ionization ion trap MS/MS spectra were obtained from proton, sodium and potassium adducts of the dendrimers. One major route of dendrimer fragmentation was at or adjacent to the amide bonds either of the terminal chelating groups or near the core moiety. Fragmentation in the latter case was primarily at the N-terminal side of the amide bond and was directed by the proximity of a tertiary carbon of the branching unit. Furthermore, it was found that terminal ester, ether and amide linkages to the protecting and chelating groups could be sequentially broken in a single MS/MS spectrum through multiple cleavages resulting in product ions of decreasing intensity. Moreover, such cleavages could also be induced in a stepwise manner in a multistage ion trap MS(n) experiment. 相似文献
83.
Anand Ramanathan Dirk Klomp Joop A. Peters Ulf Hanefeld 《Journal of molecular catalysis. A, Chemical》2006,260(1-2):62-69
A series of Schiff-base complexes has been synthesized by the condensation of 1,2-diaminocyclohexane with salicylaldehyde, 2-pyridinecarboxaldehyde, and 2-hydroxy-1-naphthaldehyde, followed by the metallation with manganese (1, 2, 3a), cobalt (3b), copper (3c) and iron (3d) salts. These Schiff-base ligands L1–L3 and complexes 1, 2, 3a–d were then characterized by IR, 1H NMR, 13C NMR, UV–vis spectra, and DSC measurement. Schiff-base Mn complex (3a) resulting from N,N′-bis(2-hydroxy-1-naphthalidene)cyclohexanediamine (L3) ligand was considerably active for the catalytic epoxidation of styrene under mild conditions, in which the highest yield of styrene oxide reached 91.2 mol%, notably higher than those achieved from simple salt catalysts Mn(Ac)2·4H2O and MnSO4·H2O. However, another two salen–Mn complexes 1 and 2 derived from ligands N,N′-bis(salicylidene)cyclohexanediamine (L1) and N,N′-bis(2-pyridine carboxalidene)cyclohexanediamine (L2) exhibited relatively poor activity under identical experimental conditions. 相似文献
84.
Holis Abdul Holik Faisal Maulana Ibrahim Angela Alysia Elaine Bernap Dwi Putra Arifudin Achmad Achmad Hussein Sundawa Kartamihardja 《Molecules (Basel, Switzerland)》2022,27(10)
Therapeutic radiopharmaceuticals have been researched extensively in the last decade as a result of the growing research interest in personalized medicine to improve diagnostic accuracy and intensify intensive therapy while limiting side effects. Radiometal-based drugs are of substantial interest because of their greater versatility for clinical translation compared to non-metal radionuclides. This paper comprehensively discusses various components commonly used as chemical scaffolds to build radiopharmaceutical agents, i.e., radionuclides, pharmacokinetic-modifying linkers, and chelators, whose characteristics are explained and can be used as a guide for the researcher. 相似文献
85.
《印度化学会志》2021,98(4):100049
The new azo-imine ligands 2,4-di-tert-butyl-6-((2-((2-hydroxyphenyl)diazenyl) phenylimino)methyl)phenol, H2L1, 1a, and 2,4-di-tert-butyl-6-((2-((2-hydroxyphenyl) diazenyl)p-chlorophenylimino)phenol, H2L2, 1b, were prepared. Reaction of H2L1;1a, and H2L2;1b, with uranyl nitrate hexahydrate afforded the mononuclear complexes of compositions [U(O)2(L1)(H2O)]; 2a, and [U(O)2(L2)(H2O)]; 2b, complexes respectively. The newly synthesised ligands (1a and 1b) and the complexes (2a and 2b) were characterised unequivocally. The x-ray structure of 2a was determined. The tetradentate dianionic ligand (L1)2- coordinated the uranium ion equatorially with a water molecule in the same plane. Two axially coordinated oxo ligands completed the overall pentagonal bipyramid geometry around U(VI) ion. Structural pattern, electron transfer properties (oxidation near 1.32 V vs Ag/AgCl) and electronic transitions of [U(O)2(L1)(H2O)]; 2a, and [U(O)2(L2)(H2O)]; 2b have been rationalized by DFT calculations. 相似文献
86.
Sang-deok Mun Junseong Lee So Han Kim Young-ho Ko Jeong Hak Lim Youngkyu Do 《Journal of organometallic chemistry》2007,692(16):3519-3525
New monomeric titanatranes (Ar = 2,6-di-i-Pr-phenyl; x = 0, 5; x = 1, 6; x = 2, 7; x = 3, 8) were synthesized from the corresponding tetradentate ligands 1-4, respectively, using an equimolar mixture of Ti(O-i-Pr)4 and 2,6-di-i-Pr-phenol. These compounds show the catalytic activity for the ring opening polymerization of l-lactide. 相似文献
87.
A series of new 1,2-bis-(2-aminophenoxyethane) N,N,N′,N′-tetraacetic acid (BAPTA) chelators were designed and synthesized to form novel and improved fluorescent indicators. Substituted 2-nitrophenol, acting as the material, reacted in five steps to give BAPTA-derived chelators. The Ca2+ affinity of BAPTA chelators could increase significantly by addition of electron-donating groups and decrease by electron-withdrawing groups. Compounds 3a–e were treated with iron powder instead of hydrogenation, obtaining a satisfying yield. The structures of all compounds were characterized by infrared, 1H NMR, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) spectra. 相似文献
88.
Jeong Hee Kim Sungwoo Yoon Sang-deok Mun Junseong Lee Soo Han Kwon Chanhong Lee 《Journal of organometallic chemistry》2011,696(9):1729-670
A series of monomeric pentamethylcyclopentadienyltitanatranes, [n = 0, 1; n = 1, 2; n = 2, 3], were synthesized by the reaction of Cp∗TiCl3 with corresponding triethanolamines such as (HOCH2CH2)nN(CH2CMe2OH)3 − n (n = 0, L1H3; n = 1, L2H3; n = 2, L3H3), which varied by the number of CMe2 groups adjacent to an OH functionality from 3 (L1H3) to 2 (L2H3) to 1 (L3H3), in the presence of NEt3. All complexes were characterized by elemental analysis and solution 1H and 13C{1H} NMR spectroscopy. Moreover, their solid state structures, which are slightly distorted three-legged piano stool geometry, have been confirmed by single crystal X-ray diffraction analysis. On activation with methylaluminoxane (MAO), these complexes showed good catalytic activity for the polymerization of styrene producing syndiotactic polystyrene (SPS) with high molecular weights. Compounds 1 and 2 bearing more than two pairs of methyl substituents on the side arms of triethanolamines showed the enhanced catalytic activities as the polymerization temperature went up from 50 °C to 110 °C, whereas less bulky complexes 3 and Cp∗Ti(OCH2CH2)3N (4) gave the decreased activities as polymerization temperature rose. Unlike 3 and 4, complexes 1 and 2 in the presence of MAO as a cocatalyst gave SPS with controlled bimodal molecular weight distribution. Bimodal properties were much distinct at low polymerization temperature. 相似文献
89.
采用密度泛函的B3LYP和UB3LYP方法分别优化了一系列[Ru(iph)(L)2]2+ (L=cpy (1), mpy (2), npy (3); 其中iph为2,9-双(1′-甲基-2′-咪唑)-1,10-邻二氮杂菲, cpy为4-氰基嘧啶, mpy为4-甲基嘧啶, npy为4-氮二甲基嘧啶)配合物的基态和激发态结构. 利用含时密度泛函理论(TD-DFT)方法, 结合极化连续介质(PCM)模型计算了它们在丙酮溶液中的吸收和发射光谱. 研究结果表明: 优化得到的几何结构参数和相应的实验值符合得非常好. 1和2的最高占据分子轨道主要由金属的d轨道和iph配体的π轨道构成, 但是3主要占据在npy配体上, 而它们的最低空轨道主要由iph配体的π反键轨道占据. 因此, 1和2的最低能吸收和发射属于金属到配体(MLCT)和配体内部(ILCT)的电荷转移跃迁, 而3属于两个配体之间的电荷转移(LLCT)跃迁. 三个配合物的最低能吸收分别在509 nm (1), 527 nm (2)和563 nm (3), 其磷光发射分别在683 nm (1), 852 nm (2)和757 nm (3). 这显示出通过调节L配体的π电子给予能力可以改变最低能吸收和发射的跃迁性质和发光颜色. 相似文献
90.