Self-Assembled Phenylethynylene Bis-urea Macrocycles Facilitate the Selective Photodimerization of Coumarin
摘要:
There is much interest in designing molecular sized containers that influence and facilitate chemical reactions within their nanocavities. On top of the advantages of improved yield and selectivity, the studies of reactions in confinement also give important clues that extend our basic understanding of chemical processes. We report here, the synthesis and self-assembly of an expanded bis-urea macrocycle to give crystals with columnar channels. Constructed from two C-shaped phenylethynylene units and two urea groups, the macrocycle affords a large pore with a diameter of similar to 9 angstrom. Despite its increased size, the macrocycles assemble into columns with high fidelity to afford porous crystals. The porosity and accessibility of these channels have been demonstrated by gas adsorption studies and by the uptake of coumarin to afford solid inclusion complexes. Upon UV-irradiation, these inclusion complexes facilitate the conversion of coumarin to its anti-head-to-head (HH) photodimer with high selectivity. This is contrary to what is observed upon the solid-state irradiation of coumarin, which affords photodimers with low selectivity and conversion.
Self-Assembled Phenylethynylene Bis-urea Macrocycles Facilitate the Selective Photodimerization of Coumarin
摘要:
There is much interest in designing molecular sized containers that influence and facilitate chemical reactions within their nanocavities. On top of the advantages of improved yield and selectivity, the studies of reactions in confinement also give important clues that extend our basic understanding of chemical processes. We report here, the synthesis and self-assembly of an expanded bis-urea macrocycle to give crystals with columnar channels. Constructed from two C-shaped phenylethynylene units and two urea groups, the macrocycle affords a large pore with a diameter of similar to 9 angstrom. Despite its increased size, the macrocycles assemble into columns with high fidelity to afford porous crystals. The porosity and accessibility of these channels have been demonstrated by gas adsorption studies and by the uptake of coumarin to afford solid inclusion complexes. Upon UV-irradiation, these inclusion complexes facilitate the conversion of coumarin to its anti-head-to-head (HH) photodimer with high selectivity. This is contrary to what is observed upon the solid-state irradiation of coumarin, which affords photodimers with low selectivity and conversion.
Modulating the reactivity of chromone and its derivatives through encapsulation in a self-assembled phenylethynylene bis-urea host
作者:Sahan R. Salpage、Logan S. Donevant、Mark D. Smith、Andreas Bick、Linda S. Shimizu
DOI:10.1016/j.jphotochem.2015.09.003
日期:2016.1
This manuscript reports on the modulation of the photoreactivity of a series of chromones, also known as benzo-gamma-pyrones, by absorption into a porous self-assembled host formed from phenylethynylene bis-urea macrocycles. Chromone and four derivatives namely 6-fluorochromone, 6-bromochromone, 7-hydroxy-4-chromone, and 3-cyanochromone are unreactive in the solid-state. Each of these derivatives was loaded into the nanochannels of self-assembled phenylethynylene his-urea macrocycles to form solid host.guest complexes, which were subsequently UV-irradiated at room temperature under argon atmosphere. We observed that chromone and 6-fluorochromone underwent selective [2+2] photo-dimerization reactions to produce anti-HT dimers in high selectivity and conversion. The 6-bromochromone also reacted in high selectivity and conversion to afford an aryl coupling adduct. In each case, the products were extracted, and the crystalline host recovered. In comparison, 7-hydroxy-4-chromone, and 3-cyanochromone were unreactive within the complex. Simple GCMC simulation studies suggest that chromone, 6-fluorochromone, and 6-bromochromone were loaded in orientations that facilitate photoreaction, and correctly predicted that the anti-HT dimer would be favored in the chromone case. In contrast, syn-HH dimers were predicted by GCMC simulations for the halogen containing derivatives but were not observed. The simulations with 7-hydroxy-4-chromone were in agreement with the observed reactivity. We compare these computational and experimental findings and suggest future methods for optimizing simulation parameters. Our goal is to expand the scope and accuracy of the simulations to be able to predict the reactivity of guests encapsulated within columnar nanotubes. (C) 2015 Elsevier B.V. All rights reserved.
Applications of a Bis-Urea Phenylethynylene Self-Assembled Nanoreactor for [2 + 2] Photodimerizations
作者:Sandipan Dawn、Sahan R. Salpage、Brent A. Koscher、Andreas Bick、Arief C. Wibowo、Perry J. Pellechia、Linda S. Shimizu
DOI:10.1021/jp505304n
日期:2014.11.13
potentially photoreactive guests to interrogate the utility of the one-dimensional nanochannels of a porous host to absorb and facilitate the reaction of encapsulated guests. The host is a columnar self-assembled phenylethynylene bis-urea macrocycle, which absorbs guests, including coumarin, 6-methyl coumarin, 7-methyl coumarin, 7-methoxy coumarin, acenaphthylene, cis-stilbene, trans-stilbene, and trans-β-methylstyrene
密闭环境可用于通过影响反应物的组织,改变被捕获分子的迁移率,促进一个反应途径或选择性稳定产物来改变反应的选择性。该手稿利用了一系列潜在的光反应性客体来询问多孔主体的一维纳米通道的效用,以吸收并促进被包封的客体的反应。宿主是柱状自组装的苯基乙炔基双脲大环化合物,可吸收来宾,包括香豆素,6-甲基香豆素,7-甲基香豆素,7-甲氧基香豆素,,顺式-sti,反式-二苯乙烯和反式的-β-甲基苯乙烯,得到结晶包合物。我们使用粉末X射线衍射检查了主体:客体复合物的结构,这表明它们是有序的高度结晶的材料。使用固态交叉极化幻角旋转13 C 1的研究1 H-CP-MAS NMR光谱表明,客人相对于宿主是可移动的。在紫外线照射下,我们观察到香豆素,6-甲基香豆素,7-甲基香豆素和ena的选择性光二聚反应,而其他底物即使在长时间紫外线照射下也没有反应。蒙特卡洛大法则的模拟结果表明,反应性宾客是紧密配对的,并以有
Self-Assembled Phenylethynylene Bis-urea Macrocycles Facilitate the Selective Photodimerization of Coumarin
作者:Sandipan Dawn、Mahender B. Dewal、David Sobransingh、Monissa C. Paderes、Arief C. Wibowo、Mark D. Smith、Jeanette A. Krause、Perry J. Pellechia、Linda S. Shimizu
DOI:10.1021/ja110779h
日期:2011.5.11
There is much interest in designing molecular sized containers that influence and facilitate chemical reactions within their nanocavities. On top of the advantages of improved yield and selectivity, the studies of reactions in confinement also give important clues that extend our basic understanding of chemical processes. We report here, the synthesis and self-assembly of an expanded bis-urea macrocycle to give crystals with columnar channels. Constructed from two C-shaped phenylethynylene units and two urea groups, the macrocycle affords a large pore with a diameter of similar to 9 angstrom. Despite its increased size, the macrocycles assemble into columns with high fidelity to afford porous crystals. The porosity and accessibility of these channels have been demonstrated by gas adsorption studies and by the uptake of coumarin to afford solid inclusion complexes. Upon UV-irradiation, these inclusion complexes facilitate the conversion of coumarin to its anti-head-to-head (HH) photodimer with high selectivity. This is contrary to what is observed upon the solid-state irradiation of coumarin, which affords photodimers with low selectivity and conversion.