Liddell Paul A, Kodis Gerdenis, Andréasson Joakim, de la Garza Linda, Bandyopadhyay Subhajit, Mitchell Reginald H, Moore Thomas A, Moore Ana L, Gust Devens
Department of Chemistry, Arizona State University, Tempe, Arizona 85287-1604, USA.
J Am Chem Soc. 2004 Apr 21;126(15):4803-11. doi: 10.1021/ja039800a.
Photonic control of photoinduced electron transfer has been demonstrated in a dimethyldihydropyrene (DHP) porphyrin (P) fullerene (C(60)) molecular triad. In the DHP-P-C(60) form of the triad, excitation of the porphyrin moiety is followed by photoinduced electron transfer to give a DHP-P()(+)-C(60)()(-) charge-separated state, which evolves by a charge shift reaction to DHP()(+)-P-C(60)()(-). This final state has a lifetime of 2 micros and is formed in an overall yield of 94%. Visible (>or=300 nm) irradiation of the triad leads to photoisomerization of the DHP moiety to the cyclophanediene (CPD). Excitation of the porphyrin moiety of CPD-P-C(60) produces a short-lived (<10 ns) CPD-P()(+)-C(60)()(-) state, but charge shift to the CPD moiety does not occur, due to the relatively high oxidation potential of the CPD group. Long-lived charge separation is not observed. Irradiation of CPD-P-C(60) with UV (254 nm) light converts the triad back to the DHP form. Thermal interconversion of the DHP and CPD forms is very slow, photochemical cycling is facile, and in the absence of oxygen, many cycles may be performed without substantial degradation. Thus, light is used to switch long-lived photoinduced charge separation on or off. The principles demonstrated by the triad may be useful for the design of molecule-based optoelectronic systems.
在二甲基二氢芘（DHP）-卟啉（P）-富勒烯（C60）分子三联体中已证明了对光致电子转移的光子控制。在三联体的DHP-P-C60形式中，卟啉部分的激发之后是光致电子转移，产生DHP-P(+)-C60()-电荷分离态，该态通过电荷转移反应演变为DHP()+-P-C60()-。这个最终态的寿命为2微秒，形成的总产率为94%。三联体在可见光（≥300nm）照射下会导致DHP部分光异构化为环二烯（CPD）。CPD-P-C60中卟啉部分的激发产生一个短寿命（<10纳秒）的CPD-P(+)-C60()-态，但由于CPD基团相对较高的氧化电位，电荷不会转移到CPD部分。未观察到长寿命的电荷分离。用紫外线（254nm）照射CPD-P-C60会使三联体变回DHP形式。DHP和CPD形式的热相互转化非常缓慢，光化学循环很容易进行，并且在无氧条件下，可以进行许多循环而不会有实质性降解。因此，光被用于开启或关闭长寿命的光致电荷分离。三联体所证明的原理可能对基于分子的光电子系统的设计有用。
