There is a growing demand in quantum information science and sensing for electron spin purification and readout via a spin-optical interface. This technique, known as optically detected magnetic resonance (ODMR), has been applied to diamond-NV centers and transition-metal complexes. Metal-free counterparts of these optically addressable spin qubits promise to be cheaper, more sustainable color centers with prolonged polarization lifetimes. However, progress has been hindered by the low ODMR signals of carbon-based π-diradicals, partly due to the lack of a ground singlet-to-triplet intersystem crossing (ISC). In this work, we propose exploring organic systems that are even more electron-deficient: electron sextets. Using triplet carbenes as an example, we illustrate how the ground singlet-triplet gap can be widened beyond thermal energy with the associated singlet-to-triplet ISC made available by vibronic effects. Through careful molecular engineering, this ISC can occur at a rate similar to and with an opposite spin selectivity from the excited-state ISC well-established in π-diradicals, unlocking a new ODMR pathway with potential signal gains. Persistent triplet carbenes are a renascent field, with multiple stable molecules being isolated in the past five years. To motivate further development of its emissive properties, we illustrate our design in three realistic carbene candidates that incorporate existing strategies for carbene stabilization. Furthermore, we believe that a new realm of quantum materials can be uncovered by expanding our scope toward stable electron sextets.
Poh, Yong Rui, et al. "Electron Sextets as Optically Addressable Molecular Qubits: Triplet Carbenes." Journal of the American Chemical Society, vol. 147, no. 26, Jun. 2025. https://doi.org/10.1021/jacs.5c02672
Poh, Yong Rui, Chen, Xiao, Cheng, Hai-Ping, & Yuen-Zhou, Joel (2025). Electron Sextets as Optically Addressable Molecular Qubits: Triplet Carbenes. Journal of the American Chemical Society, 147(26). https://doi.org/10.1021/jacs.5c02672
Poh, Yong Rui, Chen, Xiao, Cheng, Hai-Ping, et al., "Electron Sextets as Optically Addressable Molecular Qubits: Triplet Carbenes," Journal of the American Chemical Society 147, no. 26 (2025), https://doi.org/10.1021/jacs.5c02672
@article{osti_2999596,
author = {Poh, Yong Rui and Chen, Xiao and Cheng, Hai-Ping and Yuen-Zhou, Joel},
title = {Electron Sextets as Optically Addressable Molecular Qubits: Triplet Carbenes},
annote = {There is a growing demand in quantum information science and sensing for electron spin purification and readout via a spin-optical interface. This technique, known as optically detected magnetic resonance (ODMR), has been applied to diamond-NV centers and transition-metal complexes. Metal-free counterparts of these optically addressable spin qubits promise to be cheaper, more sustainable color centers with prolonged polarization lifetimes. However, progress has been hindered by the low ODMR signals of carbon-based π-diradicals, partly due to the lack of a ground singlet-to-triplet intersystem crossing (ISC). In this work, we propose exploring organic systems that are even more electron-deficient: electron sextets. Using triplet carbenes as an example, we illustrate how the ground singlet-triplet gap can be widened beyond thermal energy with the associated singlet-to-triplet ISC made available by vibronic effects. Through careful molecular engineering, this ISC can occur at a rate similar to and with an opposite spin selectivity from the excited-state ISC well-established in π-diradicals, unlocking a new ODMR pathway with potential signal gains. Persistent triplet carbenes are a renascent field, with multiple stable molecules being isolated in the past five years. To motivate further development of its emissive properties, we illustrate our design in three realistic carbene candidates that incorporate existing strategies for carbene stabilization. Furthermore, we believe that a new realm of quantum materials can be uncovered by expanding our scope toward stable electron sextets.},
doi = {10.1021/jacs.5c02672},
url = {https://www.osti.gov/biblio/2999596},
journal = {Journal of the American Chemical Society},
issn = {ISSN 1520-5126},
number = {26},
volume = {147},
place = {United States},
publisher = {American Chemical Society (ACS)},
year = {2025},
month = {06}}
California Institute of Technology, Pasadena, CA (United States)
Sponsoring Organization:
USDOE
Grant/Contract Number:
SC0022089
OSTI ID:
2999596
Journal Information:
Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 26 Vol. 147; ISSN 0002-7863; ISSN 1520-5126
Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, Vol. 271, Issue 1https://doi.org/10.1080/10587259508034048