title: Photoselective DNA hairpin spin switches.
abstract: DNA hairpins having both a tethered anthraquinone (Aq) end-capping group and a perylenediimide (PDI) base surrogate were synthesized, wherein Aq and PDI are each separated from a G-C base pair hole trap by A-T and I-C base pairs (G = guanine, A = adenine, T= thymine, C = cytosine, I = inosine). Selective photoexcitation of PDI at 532 nm generates a singlet radical ion pair (RP), (1)(G(+•)-PDI(-•)), while selective photoexcitation of Aq at 355 nm generates the corresponding triplet RP, (3)(G(+•)-Aq(-•)). Subsequent radical pair intersystem crossing within these spin-correlated RPs leads to mixed spin states that exhibit spin-polarized, time-resolved EPR spectra in which the singlet- and triplet-initiated RPs have opposite phases. These results demonstrate that a carefully designed DNA hairpin can serve as a photodriven molecular spin switch based on wavelength-selective formation of the singlet or triplet RP without significant competition from undesired energy transfer processes.
authors.affiliation: Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, USA. r-carmielli@northwestern.edu
authors.forename: Raanan
authors.initials: R
authors.lastname: Carmieli
authors.forename: Arun K
authors.initials: AK
authors.lastname: Thazhathveetil
authors.forename: Frederick D
authors.initials: FD
authors.lastname: Lewis
authors.forename: Michael R
authors.initials: MR
authors.lastname: Wasielewski
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry* / Q000235:genetics; D055029:Inverted Repeat Sequences / Q000528:radiation effects*; D007834:Lasers; D008027:Light; D013696:Temperature
chemical_list: D004247:DNA