TY - JOUR
T1 - Probing Nuclear Spin Effects on Electronic Spin Coherence via EPR Measurements of Vanadium(IV) Complexes
AU - Graham, Michael J.
AU - Krzyaniak, Matthew D.
AU - Wasielewski, Michael R.
AU - Freedman, Danna E.
N1 - Funding Information:
We thank Prof. J. Zadrozny for his ever-wonderful orthographic knowledge, and thank Dr. M. Nilges for experimental assistance. We acknowledge support from Northwestern University, the State of Illinois, and the National Science Foundation for CAREER Award No. CHE-1455017 (M.J.G. and D.E.F.) and Award No. CHE-1565925 (M.R.W.). M.J.G. acknowledges an NSF GRFP fellowship (DGE-1324585). The X-ray crystallography reported herein was performed at the IMSERC at Northwestern University, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF NNCI-1542205), the State of Illinois, and the International Institute for Nanotechnology (IIN).
PY - 2017/7/17
Y1 - 2017/7/17
N2 - Quantum information processing (QIP) has the potential to transform numerous fields from cryptography, to finance, to the simulation of quantum systems. A promising implementation of QIP employs unpaired electronic spins as qubits, the fundamental units of information. Though molecular electronic spins offer many advantages, including chemical tunability and facile addressability, the development of design principles for the synthesis of complexes that exhibit long qubit superposition lifetimes (also known as coherence times, or T2) remains a challenge. As nuclear spins in the local qubit environment are a primary cause of shortened superposition lifetimes, we recently conducted a study which employed a modular spin-free ligand scaffold to place a spin-laden propyl moiety at a series of fixed distances from an S = 1/2 vanadium(IV) ion in a series of vanadyl complexes. We found that, within a radius of 4.0(4)-6.6(6) Å from the metal center, nuclei did not contribute to decoherence. To assess the generality of this important design principle and test its efficacy in a different coordination geometry, we synthesized and investigated three vanadium tris(dithiolene) complexes with the same ligand set employed in our previous study: K2[V(C5H6S4)3] (1), K2[V(C7H6S6)3] (2), and K2[V(C9H6S8)3] (3). We specifically interrogated solutions of these complexes in DMF-d7/toluene-d8 with pulsed electron paramagnetic resonance spectroscopy and electron nuclear double resonance spectroscopy and found that the distance dependence present in the previously synthesized vanadyl complexes holds true in this series. We further examined the coherence properties of the series in a different solvent, MeCN-d3/toluene-d8, and found that an additional property, the charge density of the complex, also affects decoherence across the series. These results highlight a previously unknown design principle for augmenting T2 and open new pathways for the rational synthesis of complexes with long coherence times.
AB - Quantum information processing (QIP) has the potential to transform numerous fields from cryptography, to finance, to the simulation of quantum systems. A promising implementation of QIP employs unpaired electronic spins as qubits, the fundamental units of information. Though molecular electronic spins offer many advantages, including chemical tunability and facile addressability, the development of design principles for the synthesis of complexes that exhibit long qubit superposition lifetimes (also known as coherence times, or T2) remains a challenge. As nuclear spins in the local qubit environment are a primary cause of shortened superposition lifetimes, we recently conducted a study which employed a modular spin-free ligand scaffold to place a spin-laden propyl moiety at a series of fixed distances from an S = 1/2 vanadium(IV) ion in a series of vanadyl complexes. We found that, within a radius of 4.0(4)-6.6(6) Å from the metal center, nuclei did not contribute to decoherence. To assess the generality of this important design principle and test its efficacy in a different coordination geometry, we synthesized and investigated three vanadium tris(dithiolene) complexes with the same ligand set employed in our previous study: K2[V(C5H6S4)3] (1), K2[V(C7H6S6)3] (2), and K2[V(C9H6S8)3] (3). We specifically interrogated solutions of these complexes in DMF-d7/toluene-d8 with pulsed electron paramagnetic resonance spectroscopy and electron nuclear double resonance spectroscopy and found that the distance dependence present in the previously synthesized vanadyl complexes holds true in this series. We further examined the coherence properties of the series in a different solvent, MeCN-d3/toluene-d8, and found that an additional property, the charge density of the complex, also affects decoherence across the series. These results highlight a previously unknown design principle for augmenting T2 and open new pathways for the rational synthesis of complexes with long coherence times.
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U2 - 10.1021/acs.inorgchem.7b00794
DO - 10.1021/acs.inorgchem.7b00794
M3 - Article
C2 - 28657714
AN - SCOPUS:85024381743
VL - 56
SP - 8106
EP - 8113
JO - Inorganic Chemistry
JF - Inorganic Chemistry
SN - 0020-1669
IS - 14
ER -