The development of quantum information processing has the potential to create new frontiers of quantum technology. Quantum information processing relies on the manipulation and lifetime of quantum bits (or “qubits”), such as electronic spin. Although electronic spins are the most studied qubit candidates, they suffer from short superposition times due to strong interactions with their environment. Here, we show that the high sensitivity of the electron spins can be combined with the robust spin coherence of nuclear spins in a series of Co(III) complexes with various alkyl group substituents, ([CpCo(OP(OR2))3]2Co)+ SbCl6- (R = Me, Et, i-Pr and t-Bu). The nuclear spin properties of the Co(III) ion are studied via 59Co NMR, a technique that utilizes a high chemical shift resolution to detect minute differences in the chemical environment of Co atoms. Additionally, the Co(III) ion has two electronic configurations, the non-magnetic (S = 0) low-spin and the magnetic (S = 2) high-spin configuration. External control of the Co(III) spin state is possible by utilizing an external stimulus, such as temperature. This phenomenon is known as spin crossover (SCO), and by combining this property with our unique molecular design, we may enhance the sensitivity of the temperature dependence of the chemical shift for this 59Co nuclei. For the first time, we will demonstrate the effect of the SCO process on the Co(III) ion chemical shift and the relaxation times (T1, T2 and T2*).

Record chemical shift sensitivity and robust coherence time in spin crossover Co(III) nuclear spin qubits

ACS Spring 2022

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