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首页> 外文期刊>Chemistry: A European journal >Anionic Organic Guests Incorporated in Zeolites:Adsorption and Reactivity of a Meisenheimer Complex in Faujasites
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Anionic Organic Guests Incorporated in Zeolites:Adsorption and Reactivity of a Meisenheimer Complex in Faujasites

机译：沸石中掺入的阴离子有机客体：八面沸石中Meisenheimer配合物的吸附和反应性

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摘要

Zeolites are suitable micro-porous hosts for positively charged organic species,but it is believed that they cannot adsorb organic anions.Pure Meisenheimer complex,derived from reduction of 2,4-dinitroaniline with NaBH_4,was adsorbed inside fau-jasite cavities.Evidence for the internal incorporation of this negatively charged reaction intermediate comes from 1) XPS elemental analysis as a function of the depth of penetration into the particle,2) the remarkable blue shift in lambda_(max) of the Meisenheimer complex adsorbed on zeolite (ca.470 nm) as compared to that in acetonitrile (580 nm) and 3) from the lack of reactivity with size-excluded hydride-acceptor reagents.Evidence is provided in support of an adsorption mechanism in which a neutral ion pair (alkali metal ion+Meisenheimer anion) is the actual species being adsorbed.In fact it appears that there is remarkable increase in the association constant for the ion-pair complex within the zeolite cavities as compared to DMF solution.Although this mechanism of adsorption as an ion-pair complex has precedents in the adsorption of some inorganic salts,what is novel is the notable increase in the stability and persistence of the Meisenheimer anion (a anionic reaction intermediate) as a result of zeolite inclusion.Adsorbed Meisenheimer complex exhibits much lower reactivity towards electron acceptors,oxygen,and water.Cyclic voltammetry of zeolite-modified electrodes reveals for the Meisenheimer complex adsorbed on LiY a reversible redox peak that is not observed in solution and has been interpreted as arising from site isolation and stabilisation of the electrochemically generated species.
机译：沸石是带正电的有机物的合适微孔基质，但据信它们不能吸附有机阴离子。纯的Meisenheimer络合物被吸附在八面体腔内，该络合物是由NaBH_4还原2,4-二硝基苯胺所衍生的。这种带负电荷的反应中间体的内部结合来自于1）XPS元素分析与渗透到颗粒中的深度有关，2）吸附在沸石上的迈森海默配合物的λ（max）的显着蓝移（约470）与乙腈（580 nm）和3）相比，由于与尺寸排除的氢化物-受体试剂缺乏反应性，提供了支持中性离子对（碱金属离子+迈森海默（Meisenheimer）的吸附机理的证据。阴离子）是被吸附的实际物质。事实上，与DMF溶液相比，沸石腔内离子对络合物的缔合常数似乎显着增加尽管这种作为离子对络合物的吸附机理在某些无机盐的吸附方面具有先例，但新颖的是由于沸石的包埋，Meisenheimer阴离子（阴离子反应中间体）的稳定性和持久性显着提高。吸附的Meisenheimer络合物对电子受体，氧和水的反应性低得多。沸石修饰电极的循环伏安法显示，吸附在LiY上的Meisenheimer络合物在溶液中未观察到可逆的氧化还原峰，并被解释为是由位点产生的分离和稳定电化学生成的物质。

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