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.
ASJC Scopus subject areas
- Colloid and Surface Chemistry