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排序方式: 共有227条查询结果,搜索用时 15 毫秒
191.
Abdelwaheb Hamdi Mohamed Habib Noomen Rym Abidi A. Rim Woo Jeong Hwan Cho Yang Kim 《Journal of inclusion phenomena and macrocyclic chemistry》2011,71(3-4):287-291
The synthesis and complexation properties of three new derivatives, one spirobiscalix[4]azacrown (1) and two calix[4]azacrown (2 and 3), are reported. Complexation studies of the three ligands toward transition and heavy metal cations have been carried out and monitored by UV absorption spectrophotometry in acetonitrile. Mononuclear complexes were detected for all complexes, whereas binuclear species (M2L) were also formed in the case of ligand 1 with Cu2+ and Pb2+. The extraction properties of 1, 2 and 3 toward Cu2+, Zn2+, Pb2+, Ag2+ and Cd2+ are also reported. The results showed that complexation is the main factor affecting extraction with ligands 2 and 3, while with ligand 1 it is not. 相似文献
192.
Kwan Soo Kim Yung Hyup Joo In Wook Kim Kyoung Rim Lee Duk Young Cho Minjeong Kim 《合成通讯》2013,43(8):1157-1163
In their reactions with phosphines, cyclic sulfates 9, 10, 11, and 12 afforded corresponding olefins by way of phosphonium sulfate salts whereas sugar cyclic sulfates 21 and 22 gave anhydrosugar 23. 相似文献
193.
To characterize largazole's structural requirements for histone deacetylase (HDAC) inhibitory and antiproliferative activities, a series of analogues with modifications to the side chain or 16-membered macrocycle were prepared and biologically evaluated. Structure-activity relationships suggested that the four-atom linker between the macrocycle and octanoyl group in the side chain and the (S)-configuration at the C17 position are critical to repression of HDAC activity. However, the valine residue in the macrocycle can be replaced with alanine without significant loss of activity. 相似文献
194.
Kannappan K Werblowsky TL Rim KT Berne BJ Flynn GW 《The journal of physical chemistry. B》2007,111(24):6634-6642
The self-assembly of cyanuric acid into ordered nanostructures on a crystalline substrate, highly ordered pyrolytic graphite (HOPG), has been investigated at low temperature under ultrahigh vacuum (UHV) conditions by means of scanning tunneling microscopy in conjunction with theoretical simulations. Many domains with different self-assembly patterns were observed. One such domain represents the formation of an open 2D rosette (cyclic) structure from the self-assembly process, the first observation of this type of structure for pure cyanuric acid on a graphite substrate. Each self-assembled domain exhibits characteristic superstructures formed through different hydrogen bond networks at low coverage and low deposition rate. Experimental observation of coexistent, two-dimensional crystalline structures with distinct hydrogen bond patterns is supported by energy minimizations and molecular dynamics calculations, which show multiple stable structures for this molecule when self-assembled on graphite. 相似文献
195.
196.
Eun C Kim JH Lee J Bae JH Lim YR Lee S Sung J 《The journal of physical chemistry. B》2007,111(35):10468-10473
We investigate the first passage times for the contact between the ends of a Rouse chain, whose initial separation is greater than a predefined contact distance, sigma, and equilibrium-distributed. An approximate analytic expression for the mean first passage time is obtained and compared with the results of previous theories and Brownian dynamics simulations. We find that the results of the present theory are in better agreement with Brownian dynamics simulation results than those of previously reported theories. 相似文献
197.
Hui Bin Jeon Sehoon Park Kyeong Rim Ryu Suman Kr Ghosh Jaehoon Jung Kyeng Min Park Ji Won Ha 《Chemical science》2021,12(20):7115
Recently, chemical interface damping (CID) has been proposed as a new plasmon damping pathway based on interfacial hot-electron transfer from metal to adsorbate molecules. It has been considered essential, owing to its potential implications in efficient photochemical processes and sensing experiments. However, thus far, studies focusing on controlling CID in single gold nanoparticles have been very limited, and in situ reversible tuning has remained a considerable challenge. In these scanning electron microscopy-correlated dark-field spectroscopic measurements and density functional theory calculations, cucurbit[7]uril (CB[7])-based host–guest supramolecular interactions were employed to examine and control the CID process using monoamine-functionalized CB[7] (CB[7]-NH2) attached to single gold nanorods (AuNRs). In situ tuning of CID through the CB[7]–oxaliplatin complexation, which can result in the variation of the chemical nature and electronic properties of adsorbates, was presented. In addition, in situ tuning of CID was demonstrated through the competitive release of the oxaliplatin guest from the oxaliplatin@CB[7] complex, which was then replaced by a competitor guest of spermine in sufficient amounts. Furthermore, nuclear magnetic resonance experiments confirmed that the release of the guest is the consequence of adding salt (NaCl). Thus, in situ reversible tuning of CID in single AuNRs was achieved through successive steps of encapsulation and release of the guest on the same AuNR in a flow cell. Finally, single CB[7]-NH2@AuNRs were presented as a recyclable platform for CID investigations after the complete release of guest molecules from their host–guest inclusion complexes. Therefore, this study has paved a new route to achieve in situ reversible tuning of CID in the same AuNR and to investigate the CID process using CB-based host–guest chemistry with various guest molecules in single AuNRs for efficient hot-electron photochemistry and biosensing applications.This study has paved a new route to achieve in situ reversible tuning of chemical interface damping (CID) in the same gold nanorod (AuNR) and to investigate the CID process using cucurbituril (CB)-based host–guest chemistry with various guest molecules in single AuNRs. 相似文献
198.
Functionally dual gradient type of carbon fiber reinforced epoxy composites, in which crosslinking density of epoxies and content of carbon fibers are gradually varied through the thickness, were fabricated by using centrifugal force. The spatial variation of fiber content and the crosslinking density change of epoxies were confirmed by checking densities and glass transition temperatures, respectively, along the thickness. The mechanical properties of the polymer composites were also measured. 相似文献
199.
On the Bergman space of the unit polydisk in the complex n-space, we solve the zero-product problem for two Toeplitz operators with n-harmonic symbols that have local continuous extension property up to the distinguished boundary. In the case where symbols
have additional Lipschitz continuity up to the whole distinguished boundary, we solve the zero-product problem for products
with four factors. We also prove a local version of this result for products with three factors. 相似文献
200.
Chinwon Rim 《Tetrahedron letters》2009,50(28):4161-79
A facile and efficient synthetic approach to tripodal star-shaped oligomers is described. Several generations of hydroxyl-terminated tripodal star-shaped oligomers were prepared in high yield from 1,3,5-triacryloylhexahydro-1,3,5-triazine (TAT) as a core by alternating amine-catalyzed thiol-ene and acrylate esterification reactions. The compounds were fully characterized by 1D and 2D NMR spectroscopy, ESI-MS, and elemental analysis. The combination of thioether groups and hydrogen bonding moieties suggests that these products can be used as metal chelating ligands. 相似文献