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

1.分子筛中客体芳香族物种与稀土电荷补偿阳离子之间能量转移的动力学研究：通过测量脉冲激光激发客体分子~(5)D_4激发态发射随时间的升降，实时观察到客体芳香族物种二苯甲酮与萘之间的能量转移(Et)，以及Y型沸石分子中稀土电荷补偿性阳离子Tb~(2+)~(3+)的能量转移。客体物种在笼内的限制导致相对于溶液系统的发射强度大大增强，从而通过加强激发态络合物的形成来促进ET。此外，发射的动力学行为表明，当二苯甲酮分子被固定在笼子内的质子位置时，萘分子仍然可以移动，从而显著地观察到Tb^&lt；3+&gt；发射随负载的增加和衰减。一致的…在激发态络合物的假设下，直接激发Tb~(2+)~(3+)~(3+)的^7F_6→^5D_4能带(488 Nm)，在没有二苯甲酮或萘存在的情况下，导致了寿命为2.4ms的单指数发射衰减。吸附在沸石中的芳香族分子晶间迁移的直观和光谱演示：我们应用荧光显微镜方法研究了吸附在八面沸石分子筛中的芳香族分子的晶间迁移。利用特定电荷补偿阳离子辅助的体系间交叉和能量转移等光物理过程，以及分子筛中客体物种之间的电荷转移(CT)和三重三重态能量转移等光化学反应作为指示反应来提供单个沸石颗粒的发光颜色特征。在60~120℃的温度范围内，样品加热促进了两种类型的迁移机制：分子筛分离晶体之间的穿透空间扩散转移模式和从一个加载晶体到另一个未加载晶体的分子注入过程，两者都是接触的。在某些情况下，客体迁移存在一个优先方向：例如，萘、菲和黄烯等芳烃从钠形式的X沸石(Na^+-X)迁移到铊交换的X沸石(Tl^+-X)。另一方面，由于给电子体的迁移，给电子芳烃如菲、黄烯和接受电子的1，2，4，5-四氰基苯之间的CT络合物的形成也是由于给电子体的迁移而发生的。较少

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