Interaction of Photogenerated Spin Qubit Pairs with a Third Electron Spin in DNA Hairpins
Emmaline R. Lorenzo, Jacob H. Olshansky, Daniel S. D. Abia, Matthew D. Krzyaniak, Ryan M. Young, Michael R. Wasielewski
Abstract
The designing of tunable molecular systems that can host spin qubits is a promising strategy for advancing the development of quantum information science (QIS) applications. Photogenerated radical pairs are good spin qubit pair (SQP) candidates because they can be initialized in a pure quantum state that exhibits relatively long coherence times. DNA is a well-studied molecular system that allows for control of energetics and spatial specificity through careful design and thus serves as a tunable scaffold on which to control multispin interactions. Here, we examine a series of DNA hairpins that use naphthalenediimide (NDI) as the hairpin linker. Photoexcitation of the NDI leads to subnanosecond oxidation of guanine (G) within the duplex or a stilbenediether (Sd) end-cap to give NDI•–-G•+ or NDI•–-Sd•+ SQPs, respectively. A 2,2,6,6-tetramethylpiperdinyl-1-oxyl (TEMPO) stable radical is covalently attached to the hairpin at varying distances from the SQP spins. While TEMPO has a minimal effect on the SQP formation and decay dynamics, EPR spectroscopy indicates that there are significant spin–spin dipolar interactions between the SQP and TEMPO. We also demonstrate the ability to implement more complex spin manipulations of the NDI•–-Sd•+-TEMPO system using pulse-EPR techniques, which is important for developing DNA hairpins for QIS applications.