Quantum Sensing of Electric Fields Using Spin-Correlated Radical Ion Pairs

Fangbai Xie; Haochuan Mao; Chenjian Lin; Yuanning Feng; J Fraser Stoddart; Ryan M Young; Michael R Wasielewski

doi:10.1021/jacs.3c04212

Quantum Sensing of Electric Fields Using Spin-Correlated Radical Ion Pairs

J Am Chem Soc. 2023 Jul 12;145(27):14922-14931. doi: 10.1021/jacs.3c04212. Epub 2023 Jun 26.

Authors

Fangbai Xie^{1

2}, Haochuan Mao^{1

2}, Chenjian Lin^{1

2}, Yuanning Feng¹, J Fraser Stoddart^{1

3

4

5}, Ryan M Young^{1

2}, Michael R Wasielewski^{1

2}

Affiliations

¹ Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
² Center for Molecular Quantum Transduction and Institute for Sustainability and Energy at Northwestern, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
³ School of Chemistry, University of New South Wales, Sydney, New South Wales 2052, Australia.
⁴ Stoddart Institute of Molecular Science, Department of Chemistry, Zhejiang University, Hangzhou 310027, China.
⁵ ZJU-Hangzhou Global Scientific and Technological Innovation Center, Hangzhou 311215, China.

PMID: 37364237
DOI: 10.1021/jacs.3c04212

Abstract

Quantum sensing affords the possibility of using quantum entanglement to probe electromagnetic fields with exquisite sensitivity. In this work, we show that a photogenerated spin-correlated radical ion pair (SCRP) can be used to sense an electric field change created at one radical ion of the pair using molecular recognition. The SCRP is generated within a covalent donor-chromophore-acceptor system PXX-PMI-NDI, 1, where PXX = peri-xanthenoxanthene, PMI = 1,6-bis(p-t-butylphenoxy)perylene-3,4-dicarboximide, and NDI = naphthalene-1,8:4,5-bis(dicarboximide). The electron-rich PXX donor in 1 acts as a guest molecule that can be encapsulated selectively by a tetracationic cyclophane ExBox⁴⁺ host to give a supramolecular complex 1 ⊂ ExBox⁴⁺. Selective photoexcitation of the PMI chromophore results in ultrafast generation of the PXX^•+-PMI-NDI^•- SCRP. When PXX is encapsulated by ExBox⁴⁺, the cyclophane generates an electric field that repels the positive charge on PXX^•+ within PXX^•+-PMI-NDI^•-, reducing the SCRP distance, i.e., the distance between the centers-of-charge on the donor and acceptor. Pulse-EPR measurements are used to measure the coherent oscillations created primarily by the electron-electron dipolar coupling in the SCRP, which yields the distance between the two charges (spins) of PXX^•+-PMI-NDI^•-. The experimental results show that the distance between PXX^•+ and NDI^•- decreases when ExBox⁴⁺ encapsulates PXX^•+, which demonstrates that the SCRP can function as a quantum sensor to detect electric field changes in the vicinity of the radical ions.