Zeolite photochemistry : Investigation of cation-π interaction and diffusion of guest species

沸石光化学：阳离子-π相互作用和客体物质扩散的研究

基本信息

批准号：
14550796
负责人：
HASHIMOTO Shuichi
金额：
$ 2.37万
依托单位：
Gunma National College of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

项目摘要

1. A kinetic study on energy transfer between guest aromatic species and rare earth charge-compensating cations within zeolites :The real-time observation is made of energy transfer (ET) between guest aromatic species, benzophenone and naphthalene, and a rare-earth charge compensating cation, Tb^<3+> within a faujasite zeolite Y by the measurement of a time-dependent rise and decay of emission from the ^5D_4 excited-state of Tb^<3+> on excitation of the guest molecules with a pulsed-laser light. Confinement of the guest species within the cages leads to a greatly enhanced emission intensity relative to solution systems, thus facilitating the ET by enforcing the formation of excited-state complexes. Besides, the kinetic behavior of the emission reveals that while benzophenone molecules are immobilized at the protonic sites within the cages, naphthalene molecules are still mobile leading to a remarkable observation of the loading-dependent rise and decay of the Tb^<3+> emission. Consiste … More nt with the assumption of the excited-state complex, a direct excitation of the absorption band of ^7F_6→^5D_4 band (488 nm) of Tb^<3+> results in a single-exponential emission decay with a lifetime of 2.4 ms both in the absence and in the presence of benzophenone or naphthalene.2. Visual and spectroscopic demonstration of intercrystalline migration and resultant photochemical reactions of aromatic molecules adsorbed in zeolites :We applied a fluorescence microscopic method to investigate the intercrystalline migration of aromatic molecules adsorbed in faujasite zeolites. Photophysical processes such as intersystem crossing and energy transfer assisted by particular charge compensating cations, and photochemical reactions such as charge transfer (CT) and triplet-triplet energy transfer between guest species incorporated in the zeolites were exploited as indicator reactions to afford luminescence color characteristic to an individual zeolite particle. Two types of migration mechanism were evidenced assisted by sample heating at temperatures between 60 and 120℃ : a through space diffusional transfer mode between separated zeolite crystals and a molecular injection process from a loaded crystal to another unloaded crystal, both in contact. A preferential direction of guest migration was found to exist for a few cases : for instance, aromatics such as naphthalene, phenanthrene and chrysene migrate from sodium form of zeolite X (Na^+-X) to thallium-exchanged zeolite X (Tl^+-X). On the other hand, the migration-assisted formation of CT complexes between electron-donating arenes such as phenanthrene and chrysene, and electron-accepting 1,2,4,5-tetracyanobenzene, both incorporated into separate zeolite Na^+-X crystals, takes place as a result of the migration of the donors. Less

1. 沸石内客体芳香族与稀土电荷补偿阳离子之间能量转移的动力学研究：实时观察客体芳香族、二苯甲酮和萘与稀土电荷之间的能量转移（ET）通过测量 ^5D_4 激发态发射的时间依赖性上升和衰减来补偿八面沸石 Y 内的阳离子 Tb^<3+>用脉冲激光激发客体分子时，Tb ^ 3+ 将客体物质限制在笼内导致相对于溶液系统大大增强的发射强度，从而通过强制形成激发态来促进ET。此外，发射的动力学行为表明，虽然二苯甲酮分子固定在笼内的质子位点，但萘分子仍然是可移动的，从而导致了对负载依赖性上升和衰变的显着观察。 Tb^<3+> 发射的结果与激发态配合物的假设一致，直接激发 Tb^<3+> 结果的 ^7F_6→^5D_4 能带（488 nm）的吸收带在不存在或存在二苯甲酮或萘的情况下，单指数发射衰减的寿命均为 2.4 ms。2．吸附在沸石中的芳香分子的晶间迁移和由此产生的光化学反应：我们应用荧光显微镜方法研究了吸附在八面沸石中的芳香分子的晶间迁移，例如特定电荷补偿阳离子辅助的系间窜越和能量转移以及光化学。沸石中客体物质之间的电荷转移（CT）和三重态-三重态能量转移等反应被用作指示反应通过在 60 至 120℃ 之间加热样品，可以为单个沸石颗粒提供发光颜色特征：分离的沸石晶体之间的空间扩散转移模式和从负载晶体到另一个晶体的分子注入过程。在一些情况下，发现存在客体迁移的优先方向：例如，萘、菲和屈等芳香族化合物从钠形式迁移。另一方面，给电子芳烃（例如菲和屈）与电子-芳烃之间迁移辅助形成CT配合物。接受 1,2,4,5-四氰基苯，两者都合并到单独的沸石 Na^+-X 晶体中，这是由于迁移的结果而发生的捐助者较少。