Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University , Evanston, Illinois 60208-3113, United States.
J Am Chem Soc. 2013 Sep 11;135(36):13322-5. doi: 10.1021/ja407648d. Epub 2013 Aug 29.
We report here a potassium-induced guanine quadruplex as a supramolecular platform for controlled assembly of electron donor-acceptor systems. A monodisperse, C4-symmetric octamer of a guanine-perylene-3,4,9,10-bis(dicarboximide) conjugate (GPDI) was prepared in tetrahydrofuran. The two layers of cyclic guanine tetramers have the same direction of rotation, and the PDI moiety between the layers adopts a nearly eclipsed relationship (H-aggregation), as revealed by small- and wide-angle X-ray scattering, NMR spectroscopy, and steady-state UV/vis absorption. Following photoexcitation of the PDI moiety in the quadruplex, charge separation occurs in τCS = 98 ± 12 ps to give G(+•)-PDI(-•) that recombines in τCR = 1.2 ± 0.2 ns, which is >100 times longer than that in the monomeric GPDI dyad. The transient absorption spectrum of G(+•)-PDI(-•) within the GPDI quadruplex suggests the formation of a radical anion delocalized over the neighboring PDI units, and this result is consistent with the more favorable electrochemical reduction potential for PDIs in the quadruplex relative to the monomer.
我们在此报告了一种钾诱导的鸟嘌呤四链体，它是用于控制电子给体-受体系统组装的超分子平台。在四氢呋喃中制备了具有单分散性、C4 对称性的鸟嘌呤-苝 3,4,9,10-二羧酸二酰亚胺（GPDI）八聚体。两层循环鸟嘌呤四聚体具有相同的旋转方向，层之间的 PDI 部分采用几乎重叠的关系（H-聚集），这一点通过小角和广角 X 射线散射、NMR 光谱和稳态 UV/vis 吸收得到证实。在四链体中 PDI 部分被光激发后，电荷分离发生在 τCS = 98 ± 12 ps 以产生 G(+•)-PDI(-•)，它在 τCR = 1.2 ± 0.2 ns 内重新结合，这比单体 GPDI 二聚体中的情况长 100 多倍。在 GPDI 四链体内 G(+•)-PDI(-•)的瞬态吸收光谱表明形成了一个自由基阴离子，在相邻的 PDI 单元之间离域，这一结果与四链体中 PDIs 的电化学还原电位相对于单体更有利的结果一致。
