Nuclear-spin-pattern control of electron-spin dynamics in a series of V(iv) complexes.

Cassidy E Jackson,Spencer H Johnson,Joseph M Zadrozny,Chun-Yi Lin,Johan Van Tol

doi:10.1039/c9sc02899d

Cassidy E Jackson, Spencer H Johnson + Show 3 more

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https://doi.org/10.1039/c9sc02899d

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Abstract

Achieving control of phase memory relaxation times (T m) in metal ions is an important goal of molecular spintronics. Herein we provide the first evidence that nuclear-spin patterning in the ligand shell is an important handle to modulate T m in metal ions. We synthesized and studied a series of five V(iv) complexes with brominated catecholate ligands, [V(C6H4-n Br n O2)3]2- (n = 0, 1, 2, and 4), where the 79/81Br and 1H nuclear spins are arranged in different substitutional patterns. High-field, high-frequency (120 GHz) pulsed electron paramagnetic resonance spectroscopic analysis of this series reveals a pattern-dependent variation in T m for the V(iv) ion. Notably, we show that it is possible for two molecules to have starkly different (by 50%) T m values despite the same chemical composition. Nuclear magnetic resonance analyses of the protons on the ligand shell suggest that relative chemical shift (δ), controlled by the patterning of nuclear spins, is an important underlying design principle. Here, having multiple ligand-based protons with nearly identical chemical shift values in the ligand shell will, ultimately, engender a short T m for the bound metal ion.

Highlights

Magnetic molecules are next-generation components of many different technological arenas, ranging from magnetic resonance imaging (MRI)[1,2] to quantum information processing.[3,4,5,6,7,8,9,10,11] Utility in any of these applications requires long spin-lattice relaxation times (T1 > 1 ms) and phase-memory relaxation times (Tm§ > 100 ms)
Nuclear magnetic resonance analyses of the protons on the ligand shell suggest that relative chemical shift (d), controlled by the patterning of nuclear spins, is an important underlying design principle
Drawing inspiration from SiC, we address the questions: can patterning of nuclear spins on ligand shells in uence the electronic Tm of a ligated metal? Freedman and co-workers showed that separation between an open-shell ion and nuclear spins is important,[58] and there is signi cant literature demonstrating the impacts on replacement of 1H (m 1⁄4 2.79mN) with low-moment magnetic nuclei e.g. 2H (m 1⁄4 0.86mN).[19,42,46]

Summary

Introduction

Magnetic molecules are next-generation components of many different technological arenas, ranging from magnetic resonance imaging (MRI)[1,2] to quantum information processing.[3,4,5,6,7,8,9,10,11] Utility in any of these applications requires long spin-lattice relaxation times (T1 > 1 ms) and phase-memory relaxation times (Tm§ > 100 ms). Nuclear magnetic resonance analyses of the protons on the ligand shell suggest that relative chemical shift (d), controlled by the patterning of nuclear spins, is an important underlying design principle.

Results

Conclusion