共查询到20条相似文献,搜索用时 10 毫秒
1.
2.
Cooke G 《Angewandte Chemie (International ed. in English)》2003,42(40):4860-4870
The application of electrochemistry or photochemistry to modulate supramolecular interactions between host-guest systems in solution is a burgeoning field. In particular, the speed and reversibility associated with electrochemically or photochemically actuated supramolecular interactions has allowed the creation and modulation of novel solution-based devices. In recent years, great advances have been made in transferring these systems from the solution to the solid state, to facilitate the development of molecular-electronics components that can operate in unison under the influence of an externally applied stimulus. These studies pave the way for the creation of responsive surfaces with advanced materials and nanotechnology applications. 相似文献
3.
4.
5.
6.
7.
8.
D'Souza F Chitta R Gadde S Zandler ME McCarty AL Sandanayaka AS Araki Y Ito O 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(15):4416-4428
Two types of structurally well-defined, self-assembled zinc porphyrin-fullerene conjugates were formed by "two-point" binding strategies to probe the effect of axial ligation or pi-pi-type interactions on the photochemical charge stabilization in the supramolecular dyads. To achieve this, meso-tetraphenylporphyrin was functionalized to possess one or four [18]crown-6 moieties at different locations on the porphyrin macrocycle while fullerene was functionalized to possess an alkyl ammonium cation, and a pyridine or phenyl entities. As a result of the crown ether-ammonium cation complexation, and zinc-pyridine coordination or pi-pi-type interactions, stable zinc porphyrin-fullerene conjugates with defined distance and orientation were formed. Evidence for the zinc-pyridine complexation or pi-pi-type interactions was obtained from the spectral and computational studies. Steady-state and time-resolved emission studies revealed efficient quenching of the zinc-porphyrin singlet excited state in these dyads, and the measured rates of charge separation, k(CS) were found to be slightly better in the case of the dyads held by axial coordination and crown ether-cation complexation. Nanosecond transient absorption studies provided evidence for the electron transfer reactions, and these studies also revealed charge stabilization in these dyads. The lifetimes of the radical ion pairs were found to depend upon the type of porphyrins utilized to form the dyads, that is, porphyrin possessing the crown ether moiety at the ortho position of one of the phenyl rings yielded prolonged charge stabilized states. Addition of pyridine to the supramolecular dyads eliminated the zinc-pyridine coordination or pi-pi-type interactions of the "two-point" bound systems due to the formation of a new zinc-pyridine axial bond thus giving a unique opportunity to probe the effect of axial coordination or pi-pi interactions on k(CS) and k(CR). Under these conditions, the measured electron transfer rates revealed faster k(CS) and slower k(CR) as compared to those obtained in the absence of added pyridine. The evaluated lifetimes of the radical ion-pairs were found to be hundreds of nanoseconds and were longer in the presence of pyridine. 相似文献
9.
Xin Bin Alireza Azizi Tianlv Xu Steven R. Kirk Michael Filatov Samantha Jenkins 《International journal of quantum chemistry》2019,119(16):e25957
The conical intersections corresponding to the C─O and C─C ring opening were optimized and the reaction paths traversing these intersections were obtained. Investigation of the C─O ring opening revealed that when traversing the lowest energy conical intersection, the reaction path returns to the closed ring geometry. The C─O path traversing the intersection featuring torsion of terminal CH2 group however, led to a ring-opened geometry, an H-shift and the formation of acetaldehyde that can undergo further dissociation. The observation of different reaction paths was explained by the 3-D paths from quantum theory of atoms in molecules (QTAIM) that defined the most preferred direction of electronic motion that precisely tracked the mechanisms of bond breaking and formation throughout the photo-reactions. The size, orientation, and location of these most preferred 3-D paths indicated the extent and direction of motion of atoms, bonds, and the degree of torsion or planarity of a bond indicating a predictive ability. 相似文献
10.
11.
Ahmed Oueslati Hatem Ben Romdhane Vincent Martin Fréderic Schiets Régis Mercier Refaât Chaâbouni 《Journal of polymer science. Part A, Polymer chemistry》2011,49(9):1988-1998
A novel pentamethylated norbornadiene (NBD) based dianhydride, α,α′‐bis‐(3,4,5,6,7‐pentamethylcyclopenta‐2,4‐dienyl)meta‐xylene‐1,2‐dianhydride (3), was prepared from α,α′‐bis‐(pentamethylcyclopentadienyl)meta‐xylene (1) and acetylene dicarboxylic acid. The bis‐adduct formed via Diels–Alder reaction afforded tetra‐acid (2), which was chemically cyclodehydrated to lead the targeted dianhydride (3). New polyimides containing NBD moieties in the main chain were prepared from the dianhydride monomer (3) and various aromatic diamines. The chemical structure of the polymers was confirmed by both 1H and 13C NMR analysis. Their Molecular weights were also measured by SEC. All of these polyimides are soluble at room temperature in common organic solvents, such as chloroform, dichloromethane, THF, DMSO, DMF, and NMP, and show good thermal stabilities. The photochemical isomerization of the NBD into quadricyclane (QC) was investigated by UV/vis spectrophotometry from polymer films using visible sunlight as irradiation source. It was found that the kinetic rate of the conversion NBD‐QC which proceeded smoothly is a first kinetic order. The stored energies released by the transformation of QC groups into NBD ones of the irradiated polymer films were also evaluated by DSC measurement and were found to be around 90 kJ mol?1. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
12.
利用254 nm紫外光对[2.2]对环蕃氯仿溶液进行辐照,得到两种主要产物4-醛基-[2.2]-对环蕃和4,4'-(乙基-1,2-二取代)二苯甲醛,利用核磁共振波谱仪(NMR)和气相色谱-质谱联用(GC-MS)技术手段对产物的结构进行分析研究。 同时对反应条件进行探究,发现当氯仿和水同时存在时才能生成醛基,并由此提出了提出了可能的反应机理:通过瑞默-提曼反应使CHCl2·自由基加成到苯环上并进一步生成醛基。 相似文献
13.
14.
HAN Jun DENG Chao FANG Ru LI YiZhi WANG LeYong& PAN Yi Key Laboratory of Mesoscopic Chemistry Ministry of Education School of Chemistry Chemical Engineering Nanjing University Nanjing China State Key Laboratory of Coordination Chemistry 《中国科学:化学》2010,(4)
Three tripod molecules, tris(2-methoxy-5-nitrobenzyl)phosphine oxide (1), tris(2-butoxy-3-methyl-5-nitrobenzyl)phosphine oxide (2), and tris(3-nitrobenzyl)amine (TNBA), were synthesized and crystallized. The structures of 1, 2, and their comparison (TNBA) were determined by X-ray crystallography. It is noteworthy that compound 1 interacted with adjacent molecules via π-π stacking and C-H···π interactions to yield an open supramolecular network with the porosity P in 8.9%, whereas compound 2 gathered closely... 相似文献
15.
Jun Wang Cui Qin Li Shu Yan Zhang Fang Sun Teng Jie Ge 《中国化学快报》2008,19(1):43-46
Dendritic molecules with dodecyl groups as the hyperbranchs were synthesized in methanol by Michael addition with dodecylamine and methyl acrylate as raw materials. This new-type dendritic molecules were called vividly "broom molecules" in this report. The surface tension of the aqueous solution of broom molecule terminated amino group was measured by using the dropvolume method. The demulsification performance of the broom molecules for the oil/water (O/W) simulated crude oil emulsion was examined. The experimental results revealed that, as a new-type of surfactants, the broom molecules terminated amino groups showed demulsification for the O/W simulated crude oil emulsion. 2007 Jun Wang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All fights reserved. 相似文献
16.
17.
Wentao Liu Wenfang Qin Xiaobei Wang Dr. Fei Xue Prof. Xiao‐Yu Liu Prof. Yong Qin 《Angewandte Chemie (International ed. in English)》2018,57(38):12299-12302
The development of efficient syntheses of complex natural products has long been a major challenge in synthetic chemistry. Designing cascade reactions and employing bioinspired transformations are an important and reliable means of achieving this goal. Presented here is a combination of these two strategies, which allow efficient asymmetric synthesis of the cinchona alkaloid (+)‐cinchonidine. The key steps of this synthesis are a controllable, visible‐light‐induced photoredox radical cascade reaction to efficiently access the tetracyclic monoterpenoid indole alkaloid core, as well as a practical biomimetic cascade rearrangement for the indole to quinoline transformation. The use of stereoselective chemical transformations in this work makes it an efficient synthesis of (+)‐cinchonidine. 相似文献
18.
Yasuhide Nakayama Takehisa Matsuda 《Journal of polymer science. Part A, Polymer chemistry》1993,31(4):977-982
This article reports a novel photoinduced surface process technology enabling simultaneous hydrogel formation and its surface fixation on polymeric substrates. The process consists of layering two different types of photoreactive coatings on a polymeric surface, an azidophenyl-bearing polymer as an adhesive layer and cinnamoylated copolymer as a hydrogel layer, and subsequent UV irradiation. The photoreactive adhesive polymer coated on a substrate is poly(m-azidostyrene), in which photoreaction of phenyl azido groups is responsible for the chemical bonding between the substrate and hydrogel. N,N-dimethylacrylamide copolymer containing cinnamate moieties in their side chains, which undergo photocrosslinking via intermolecular dimerization, was applied as an overcoat on the adhesive layer. UV irradiation resulted in the formation of hydrogel chemically bonded onto the substrate. This was confirmed by ESCA measurements. A heparin-immobilized hydrogelated surface with controlled release characteristics was demonstrated. © 1993 John Wiley & Sons, Inc. 相似文献
19.
Optical emission diagnostics in cascade arc plasma polymerization and surface modification processes
Q. S. Yu E. Krentsel H. K. Yasuda 《Journal of polymer science. Part A, Polymer chemistry》1998,36(10):1583-1592
Optical Emission Spectroscopy (OES) was used to identify reactive species and their excitation states in low-temperature cascade arc plasmas of N2, CF4, C2F4, CH4, and CH3OH. In a cascade arc plasma, the plasma gas (argon or helium) was excited in the cascade arc generator and injected into a reactor in vacuum. A reactive gas was injected into the cascade arc torch (CAT) that was expanding in the reactor. What kind of species of a reactive gas, for example, nitrogen, are created in the reactor is dependent on the electronic energy levels of the plasma gas in the cascade arc plasma jet. OES revealed that no ion of nitrogen was found when argon was used as the plasma gas of which metastable species had energy less than the ionization energy of nitrogen. When helium was used, ions of nitrogen were found. While OES is a powerful tool to identify the products of the cascade arc generation (activation process), it is less useful to identify the reactive species that are responsible for surface modification of polymers and also for plasma polymerization. The plasma surface modification and plasma polymerization are deactivation processes that cannot be identified by photoemission, which is also a deactivation process. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1583–1592, 1998 相似文献
20.
De Novo Synthesis of Imidazoles by Visible‐Light‐Induced Photocatalytic Aerobic Oxidation/[3+2] Cycloaddition/Aromatization Cascade 下载免费PDF全文
Qiao‐Hui Deng You‐Quan Zou Dr. Liang‐Qiu Lu Prof. Dr. Zi‐Long Tang Dr. Jia‐Rong Chen Prof. Dr. Wen‐Jing Xiao 《化学:亚洲杂志》2014,9(9):2432-2435
A visible‐light‐induced photocatalytic aerobic oxidation/[3+2] cycloaddition/aromatization cascade between secondary amines and isocyanides has been successfully developed. The reaction provides a general and efficient access to diversely substituted imidazoles and imidazo[1,5‐a]quinoxalin‐4(5 H)‐ones in good yields under mild conditions. 相似文献