Experimental and Theoretical Studies towards the Charge Recombination of Organic Radicals in Inorganic Mesostructures

无机介观结构中有机自由基电荷复合的实验和理论研究

• 批准号: 5440448
• 负责人: Professor Dr. Jörg J. Schneider
• 金额: --
• 依托单位: Fachgebiet Anorganische Chemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2004
• 资助国家: 德国
• 起止时间: 2003-12-31 至 2007-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/5440448?language=en
• 关键词: Experimental; Theoretical; Studies; towards; Charge

The photoinduced charge separation between two redox centers is one of the basic steps in electron transfer (ET) processes. For this purpose the study of model processes of charge separation and recombination, as exemplified with large polycyclic aromatic hydrocarbons (PAH) as probe molecules for which stable radical centers are well documented, might allow fundamental insights into the kinetics of light conversion into chemically usable work, DG, and for charge recombination. Well defined compartmented reaction spaces where PAH probe molecule redox centers like e.g. dicoronenylene or quaterylene are held in intermolecular proximity to each other allow to study fundamental charge recombination processes under geometrically constrained conditions. Recombination parameters are dependent on the size of the given host space as well as the individual orientation of the inorganic radicals under study. As hosts, one dimensional nano- and mesoporous inorganic oxides like alumina or mesoporous hosts of the MCM 41 family that offer a highly ordered parallel pore arrangement will be used, making available a constrained reaction space for radical formation and recombination of large PAHs. To study the fate of charge separated species transient spectroscopic measurements are necessary. Timeresolved laser spectroscopy, will be used to investigate the kinetics of charge recombination by optical and/or conductivity detection. Within these experiments employed pulse widths of the lasers control the time resolution of the experiments. Radical properties like spin densities and g values as well as dynamic charge exchange phenomena are subjects of detailed ESR- and ENDOR studies. Understanding the microscopic situation and modeling the time-resolved spectra will be facilitated by theoretical studies employing quantum chemistry and molecular simulations. That part of the project is aimed towards a determination of structural and energetic characteristics of PAH adsorption on model surfaces of nano- and mesoporous zeolite- and aluminatype materials under various conditions mimicking the experimentally chosen geometrically constrained reaction spaces of porous alumina and MCM 41. Equilibrium surface density distributions of PAH guest molecules along with information about their orientational ordering are expected research results. Ultimately, chemical, geometrical (in the sense of utilizing the variable confinement conditions represented by the porous host material), as well as thermodynamic control of charge transfer kinetics based on microscopic insight is aspired.

两个氧化还原中心之间的光诱导电荷分离是电子转移过程的基本步骤之一。为了这个目的，电荷分离和重组的模型过程的研究，例如与大的多环芳烃（PAH）作为探针分子，稳定的自由基中心有据可查，可能会允许光转换成化学可用的工作，DG的动力学的基本见解，并为电荷重组。定义良好的分隔反应空间，其中PAH探针分子的氧化还原中心，如，例如，dicoronenylene或quaterylene被保持在分子间彼此接近，允许在几何约束条件下研究基本的电荷重组过程。结晶参数取决于给定的主机空间的大小以及所研究的无机自由基的个别取向。作为主机，一维纳米和介孔无机氧化物，如氧化铝或介孔主机的MCM 41家庭，提供了一个高度有序的平行孔排列将被使用，使大的多环芳烃的自由基形成和重组的约束反应空间。为了研究电荷分离物种的命运，瞬态光谱测量是必要的。时间分辨激光光谱，将被用来研究通过光学和/或电导率检测的电荷复合的动力学。在这些实验中，所采用的激光器的脉冲宽度控制实验的时间分辨率。自由基性质，如自旋密度和g值以及动态电荷交换现象是详细的ESR和ENDOR研究的主题。理解微观情况和建模的时间分辨光谱将促进采用量子化学和分子模拟的理论研究。该项目的这一部分旨在确定多环芳烃吸附在纳米和中孔沸石和aluminatype材料的模型表面上的结构和能量特征，在各种条件下模拟实验选择的多孔氧化铝和MCM 41的几何约束反应空间。PAH客体分子的平衡表面密度分布沿着与信息的取向有序是预期的研究结果。最终，化学，几何（在利用由多孔主体材料表示的可变限制条件的意义上），以及基于微观洞察力的电荷转移动力学的热力学控制是渴望的。