Engineering clock transitions in molecular lanthanide complexes

Stewart, R., Canaj, A. B. , Liu, S., Regincós Martí, E., Celmina, A., Nichol,, G., Cheng, H.-P., Murrie, M. and Hill, S. (2024) Engineering clock transitions in molecular lanthanide complexes. Journal of the American Chemical Society, (doi: 10.1021/jacs.3c09353) (PMID:38619978) (Early Online Publication)

Abstract

Molecular lanthanide (Ln) complexes are promising candidates for the development of next-generation quantum technologies. High-symmetry structures incorporating integer spin Ln ions can give rise to well-isolated crystal field quasi-doublet ground states, i.e., quantum two-level systems that may serve as the basis for magnetic qubits. Recent work has shown that symmetry lowering of the coordination environment around the Ln ion can produce an avoided crossing or clock transition within the ground doublet, leading to significantly enhanced coherence. Here, we employ single-crystal high-frequency electron paramagnetic resonance spectroscopy and high-level ab initio calculations to carry out a detailed investigation of the nine-coordinate complexes, [HoIIIL1L2], where L1 = 1,4,7,10-tetrakis(2-pyridylmethyl)-1,4,7,10-tetraaza-cyclododecane and L2 = F– (1) or [MeCN]0 (2). The pseudo-4-fold symmetry imposed by the neutral organic ligand scaffold (L1) and the apical anionic fluoride ion generates a strong axial anisotropy with an mJ = ±8 ground-state quasi-doublet in 1, where mJ denotes the projection of the J = 8 spin–orbital moment onto the ∼C4 axis. Meanwhile, off-diagonal crystal field interactions give rise to a giant 116.4 ± 1.0 GHz clock transition within this doublet. We then demonstrate targeted crystal field engineering of the clock transition by replacing F– with neutral MeCN (2), resulting in an increase in the clock transition frequency by a factor of 2.2. The experimental results are in broad agreement with quantum chemical calculations. This tunability is highly desirable because decoherence caused by second-order sensitivity to magnetic noise scales inversely with the clock transition frequency.

• Item Type: Articles
• Additional Information: The UK Engineering and Physical Sciences Research Council (grant ref EP/N01331X/1) and The University of Glasgow are thanked for the financial support. [...] Work performed at the National High Magnetic Field Laboratory is supported in part by the National Science Foundation (under DMR-1644779 and DMR-2128556) and the State of Florida
• Status: Early Online Publication
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Regincos Marti, Miss Emma and Tsanai, Dr Angelos and Murrie, Professor Mark
• Authors: Stewart, R., Canaj, A. B., Liu, S., Regincós Martí, E., Celmina, A., Nichol,, G., Cheng, H.-P., Murrie, M., and Hill, S.
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: Journal of the American Chemical Society
• Publisher: American Chemical Society
• ISSN: 0002-7863
• ISSN (Online): 1520-5126
• Published Online: 15 April 2024
• Copyright Holders: Copyright © 2024 American Chemical Society
• First Published: First published in Journal of the American Chemical Society 2024
• Publisher Policy: Reproduced in accordance with the publisher copyright policy

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
172637		Putting the Squeeze on Molecule-Based Magnets	Mark Murrie	Engineering and Physical Sciences Research Council (EPSRC)	035638	Chemistry