Charge-transfer complexation and photoreduction of viologen derivatives bearing the para-substituted benzophenone group in dimethyl sulfoxide
摘要:
New viologen derivatives having the various para-substituted benzophenone groups connected with a -(CH2)3- linkage were effectively photoreduced by dimethyl sulfoxide by the intramolecular charge transfer complex formation between the viologen and benzophenone groups through effective stacking. The photoreduction was enhanced by the introduction of electron-donating para-substituents on the benzophenone units which were favorable for the intramolecular charge transfer complexation.
Synthesis of ruthenium tris(2,2′-bipyridine)-type complexes tethered to peptides at 5,5′-positions
作者:Yoshimi Shiina、Shigero Oishi、Hitoshi Ishida
DOI:10.1016/j.tetlet.2011.12.117
日期:2012.3
design of rutheniumtris(bipyridine)-type complexes bearing two different functional groups. In this study, a novel rutheniumtris(bipyridine) derivative bearing viologen and tyrosine as an electron acceptor and donor, respectively, is synthesized. This synthesis exemplifies the effectiveness of the molecular design for functionalizing ruthenium bipyridine-type complexes. The photophysical properties
Thermodynamic Parameters for Formation of Through-Ring<i>α</i>-Cyclodextrin Complexes of Donor–Acceptor Linked Compounds: Comparison between D<sub>2</sub>O and H<sub>2</sub>O Solutions of Anthracene–Viologen Systems with Intramolecular Charge-Transfer Absorption Spectra
作者:Akira Toki、Hiroaki Yonemura、Taku Matsuo
DOI:10.1246/bcsj.66.3382
日期:1993.11
intramolecular charge-transfer absorption band of an anthracene-viologen linked compound rapidly disappeared with elapsed time. The reason was ascribed to formation of a through-ring CD complex, which hinders direct interaction between the donor- and acceptor moieties. Thermodynamic parameters, including the energy of activation for complexation of α-CD, were evaluated by the use of the charge-transfer absorption
添加α-环糊精(CD)后,蒽-紫精连接化合物的分子内电荷转移吸收带随着时间的推移迅速消失。原因归因于形成通环 CD 复合物,这阻碍了供体和受体部分之间的直接相互作用。通过使用 D2O-和 H2O 溶液中的电荷转移吸收带来评估热力学参数,包括 α-CD 络合的活化能。观察到溶剂氘同位素效应随络合时的自由能变化而变化,但未随形成通环 CD 络合物的活化能变化而观察到。连接化合物的开放、扩展构象异构体被提议作为形成通环 CD 复合物的激活状态模型。
Spectroscopic studies on exchange properties in through-ring cyclodextrin complexes of carbazole-viologen linked compounds: effects of spacer chain length
Analysis of H-1 NMR spectra (400 MHz) revealed a novel mode of interaction between cyclodextrin (CD) and carbazole-viologen linked compounds (CACnV), where the spacer chain was consisted of n methylene units (n = 4, 6, 8, 10, and 12). In the case of alpha-CD, the complexed species lived long enough to afford distinct proton signals, when the spacer chain was relatively long (n greater-than-or-equal-to 8). As to CAC12V, the equilibrium constant for the 1:1 complex was 4.9 X 10(4) M-1 at 30-degrees-C and coalescence temperatures for the proton signals exceeded 100-degrees-C. Clear NOEs were observed to prove strong interaction between the protons in the CD cavity and the spacer methylene groups of CAC12V. The spacer was concluded to be encased in the cavity of alpha-CD. In the caw of beta-CD, essentially the same ''through-ring CD complex'' was formed. The line shape analysis indicated that thc free energies of activation at 70-degrees-C for complexation and decomplexation were 11.6 and 17.2 kcal/mol, respectively. Activation parameters for the alpha-CD complexes were evaluated by the rate of disappearance of intramolecular charge-transfer absorption (420 nm) on the addition of alpha-CD. The free energy of activation for decomplexation was found to exceed 22 kcal/mol in the alpha-CD complexes for CACnV (n = 8, 10, and 12). The viologen moiety of CACnV was concluded to be the site of entrance for forming ''through-ring CD complex'', and the large activation energies were ascribed to dehydration of viologen units to go through the CD cavity.
Rapid Communication Effect of Alkali Metal Ions on Photochromic Behavior of Bisviologen-incorporated Oligo-oxyethylene Units¶
Two bisviologen derivatives, 1,11-bis(N-propyl-4,4'-bipyridinium)-3,6,9-trioxaundecane tetrakis-(hexafluorophosphate) (1) and 1,8-bis(N-propyl-4,4'-bipyridinium)-3,6-dioxaoctane tetrakis-(hexafluorophosphate) (2), each incorporating trioxaundecane and dioxaoctane groups between two viologen units, respectively, were prepared so that their photochromic behavior in the absence and the presence of alkali metal ions in a thin polymer film could be investigated. Photoirradiation of the films containing 1 and 2 caused color changes from pale yellow to blue, associated with the photoinduced reduction of the viologen units from the dication to the radical cation. The addition of alkali metal ions, especially, K+ and Na+, caused change in the spectra of the photoreduced viologen radical cation for 1 and 2, respectively, because of the increase in the fractional amplitude for the dimer component of the radical cation rather than the monomer one. This may be related to the guest-induced conformational change of 1 and 2, in which the alkali metal ion is surrounded by the oligo-oxyethylene unit of 1 and 2. The regulation in photochromic properties of viologen derivatives can be achieved by addition of alkali metal ions.
A bistable electrochromic device based on poly(viologen)s