Reaction Control of Photochemical Processes in Liquid Crystalline Phases

已经尝试控制光化学过程的反应速率，例如液晶和双层膜系统中的能量转移和电子转移。(1)在含有敏化剂和受体分子（苝衍生物）作为客体分子的液晶盒上施加交流矩形波（最高可达10 <V_（0-p）>），观察到明显的电场效应，并对苝衍生物的敏化荧光强度进行了测量。敏化剂的荧光寿命的测量表明，能量转移的速率是独立的电场。当相对于液晶单元平面在垂直方向上检测到的强度变化与在水平方向上检测到的强度变化进行比较时，电场效应完全改变了符号。因此，电场对敏化荧光的影响归因于受体跃迁偶极矩的取向控制， ...更多信息 液晶的分子排列。(2)对于双层膜体系中的电子转移，利用卟啉-紫精交联体系研究了外加磁场对激光诱导电子转移速率的影响。在0.1T以上，紫精猝灭卟啉三重态所产生的光生分子内离子自由基对的反向电子转移速率受到明显抑制。此外，两亲性紫精分子组装体被发现有助于电荷分离的光诱导，分子内电子转移的敏化剂-受体连接系统纳入分子组装体。利用含咔唑基团的双链铵两亲物构建空穴传输体系，在激光激发下获得了极长寿命的电荷分离态。所有这些现象都归因于配向受体（或供体）单元的协同效应，它允许电子（或空穴）通过电子交换机制迁移。少

Attempts have been made to control reaction rates of photochemical processes, such as energy-transfer and electron-transfer, in liquid crystals and bilayer-membrane systems.(1) Remarkable electric field effects were observed with sensitized fluorescence intensities of a perylene derivative, when rectangular AC waves (up to 10 <V_(0-p)> ) were applied to liquid crystal cells containing a sensitizer and an acceptor (the perylene derivative) as the guest molecules. Measurements of the fluorescence lifetime of the sensitizer indicated that the rates of energy transfer were independent of the electric fields. The electric field effects completely changed the sign when the intensity variation detected at vertical direction was compared with that at the horizontal direction with respect to the plane of the liquid crystal cell. The observed electric field effects on the sensitized fluorescence were consequently ascribed to the orientation control of transition dipolemoment of the acceptor thro … More ugh molecular alignments of the liquid crystal.(2) As to the electron-transfer in bilayer membrane systems, effects of external magnetic fields on laser-induced electron-transfer rates were investigated by the use of porphyrin-viologen linked systems. Rates of reverse electron transfer in the photogenerated intramolecular ion radical pair, as originated from quenching of porphyrin triplet by viologen, were remarkably suppressed at above 0.1 T. In addition, amphiphilic viologen molecular assemblies were found to help charge-separation of the photoinduced, intramolecular electron transfer in sensitizer-acceptor linked system incorporated into the molecular assemblies. Construction of hole-transport system was also attempted by the use of double-chain ammonium amphiphile with carbazole moiety, which afforded extremely long-living charge-separated states on laser excitation. All of these phenomena were ascribed to cooperativity effects of aligned acceptor (or donor) units, which permit electron (or hole) migration via electron exchange mechanism. Less