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Molecular qubits are a promising platform for future quantum information science technologies; however, to find success in novel devices requires that the molecules exhibit long spin relaxation times. Understanding and optimizing these relaxation times has been shown to be challenging and much experimental work has been done to understand how various chemical features of the molecular qubit influence relaxation times. Here we have curated a data set of relaxation times of metal complex molecular qubits and formulated systems design charts to provide a hierarchical organization of how chemical variables affect relaxation times via known physical processes. We demonstrate the utility of the systems charts by combining examples from the literature with calculated descriptors for molecules in the dataset. This approach helps reduce the complexity associated with de novo molecular design by providing a map of interdependencies and identifying features to prioritize during synthesis. [ABSTRACT FROM AUTHOR]

The emerging field of quantum information science promises to transform a diverse range of scientific fields, ranging from computation to sensing and metrology. The interdisciplinary scientific community laid the groundwork for the next generation of quantum technologies through key advances in understanding the fundamental unit of quantum information science, the qubit. Electronic spin is a promising platform for qubits, demonstrating suitably long coherence times, optical initialization, and single spin addressability. Herein, we discuss recent accomplishments and future progress from our group targeted at imbuing transition metal complexes with the aforementioned properties, creating a pathway to fusing spatial precision with long coherence times. A strong emphasis of this feature article is progressing towards single spin measurements via a chemical approach for imbuing molecular qubits with an optically-induced spin polarization mechanism. [ABSTRACT FROM AUTHOR]

We report the temperature dependence of the spin dynamics of the octacyanometallates [Mo(CN)8]3− and [W(CN)8]3−. At 5 K, these complexes display remarkably long spin–lattice relaxation times of 1.05 s, and 0.63 s, respectively. We probe the contributing factors to the spin relaxation and demonstrate the impact of spin–orbit coupling as a handle to tune vibrationally mediated spin–lattice relaxation. [ABSTRACT FROM AUTHOR]

A novel Mn2+…Bi3+ heterobimetallic complex, featuring the closest Mn…Bi interaction for a paramagnetic molecular species, exhibits unusually large axial zero-field splitting. We attribute this enhancement to the proximity of Mn2+ to a heavy main group element, namely, bismuth. [ABSTRACT FROM AUTHOR]

A counterintuitive three-order of magnitude slowing of the spin–lattice relaxation rate is observed in a high spin qubit at high magnetic field via multifrequency pulsed electron paramagnetic resonance measurements. [ABSTRACT FROM AUTHOR]

We report the first tris(alkoxide)V(iii) complex to bind dinitrogen. Removal of THF from V(OR)3THF furnishes the highly reactive V(OR)3fragment, which binds dinitrogen to form [V(OR)3]2(μ-N2) in the solid state. Dinitrogen is readily released upon dissolution of the complex. Structural and DFT studies are consistent with significant activation of N2when bound by the vanadium tris(alkoxide) platform. [ABSTRACT FROM AUTHOR]

Reaction of [(PY5Me2)V(MeCN)]2+ with [M(CN)6]3- (M = Cr, Mo) affords the star-like clusters [(PY5Me2)4- V4M(CN)6]5+, exhibiting S = 9/2 ground states that are exceptionally well-isolated in energy. [ABSTRACT FROM AUTHOR]

Reaction of [(PY5Me2)V(MeCN)]2+with [M(CN)6]3−(M = Cr, Mo) affords the star-like clusters [(PY5Me2)4V4M(CN)6]5+, exhibiting S= 9/2 ground states that are exceptionally well-isolated in energy. [ABSTRACT FROM AUTHOR]

Molecular qubits are a promising platform for future quantum information science technologies; however, to find success in novel devices requires that the molecules exhibit long spin relaxation times. Understanding and optimizing these relaxation times has been shown to be challenging and much experimental work has been done to understand how various chemical features of the molecular qubit influence relaxation times. Here we have curated a data set of relaxation times of metal complex molecular qubits and formulated systems design charts to provide a hierarchical organization of how chemical variables affect relaxation times via known physical processes. We demonstrate the utility of the systems charts by combining examples from the literature with calculated descriptors for molecules in the dataset. This approach helps reduce the complexity associated with de novo molecular design by providing a map of interdependencies and identifying features to prioritize during synthesis.

Creating the next generation of quantum systems requires control and tunability, which are key features of molecules. To design these systems, one must consider the ground-state and excited-state manifolds. One class of systems with promise for quantum sensing applications, which require water solubility, are d 8 Ni 2+ ions in octahedral symmetry. Yet, most Ni 2+ complexes feature large zero-field splitting, precluding manipulation by commercial microwave sources due to the relatively large spin-orbit coupling constant of Ni 2+ (630 cm -1 ). Since low lying excited states also influence axial zero-field splitting, D , a combination of strong field ligands and rigidly held octahedral symmetry can ameliorate these challenges. Towards these ends, we performed a theoretical and computational analysis of the electronic and magnetic structure of a molecular qubit, focusing on the impact of ligand field strength on D . Based on those results, we synthesized 1, [Ni(ttcn) 2 ](BF 4 ) 2 (ttcn = 1,4,7-trithiacyclononane), which we computationally predict will have a small D ( D calc = +1.15 cm -1 ). High-field high-frequency electron paramagnetic resonance (EPR) data yield spin Hamiltonian parameters: g x = 2.1018(15), g x = 2.1079(15), g x = 2.0964(14), D = +0.555(8) cm -1 and E = +0.072(5) cm -1 , which confirm the expected weak zero-field splitting. Dilution of 1 in the diamagnetic Zn analogue, [Ni 0.01 Zn 0.99 (ttcn) 2 ](BF 4 ) 2 (1') led to a slight increase in D to ∼0.9 cm -1 . The design criteria in minimizing D in 1 via combined computational and experimental methods demonstrates a path forward for EPR and optical addressability of a general class of S = 1 spins., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

We report the temperature dependence of the spin dynamics of the octacyanometallates [Mo(CN)8]3- and [W(CN)8]3-. At 5 K, these complexes display remarkably long spin-lattice relaxation times of 1.05 s, and 0.63 s, respectively. We probe the contributing factors to the spin relaxation and demonstrate the impact of spin-orbit coupling as a handle to tune vibrationally mediated spin-lattice relaxation.

Mononuclear transition metal complexes demonstrate significant potential in the divergent applications of spintronics and quantum information processing. The facile tunability of these complexes enables structure function correlations for a plethora of relevant magnetic quantities. We present a series of pseudotetrahedral [Co(C 3 S 5 ) 2 ] 2- complexes with varying deviations from D 2d symmetry to investigate the influence of structural distortions on spin relaxation dynamics and qubit viability, as tuned by the variable transverse magnetic anisotropy, E . To overcome the traditional challenge of measuring E in species where D ≫ E , we employed a different approach of harnessing ac magnetic susceptibility to probe the emergence of quantum tunneling of magnetization as a proxy for E . Across the range of values for E in the series, we observe magnetic hysteresis for the smallest value of E . The hysteresis disappears with increasing E , concomitant with the appearance of an observable, low frequency (L-band) electron paramagnetic resonance (EPR) signal, indicating the potential to controllably shift the molecule's utilization from classical to quantum information processing applications. The development of design principles for molecular magnet information processing requires separate design principles for classical versus quantum regimes. Here we show for the first time how subtle structural changes can switch the utility of a complex between these two types of applications.

Frustrated magnets with integer spin are predicted to have exotic physical properties including spin nematicity, yet few are known to exist. We report a new, frustrated S = 1 magnet, BaNi(3)(OH)(2)(VO(4))(2), which is the structural analogue of the mineral vesignieite. Magnetic frustration arises from a competition between ferromagnetic and antiferromagnetic ordering leading to a glassy transition at 19 K., (This journal is © The Royal Society of Chemistry 2012)

The diamagnetic complex [Re(CN)8]3- is shown to react with Mn2+ ions in methanol to generate the centered, face-capped octahedral cluster (CH3OH)24Mn9Re6(CN)48, which is structurally analogous to (CH3OH)24Mn9Mo6(CN)48. Related reactions involving stoichiometric mixtures of octacyanometalate complexes generate the substituted species (CH3OH)24Mn9Mo5Re(CN)48, (CH3OH)24Co9Mo5Re(CN)48, (CH3OH)24Mn9Mo3Re3(CN)48, (CH3OH)24Mn9W5Re(CN)48 and (CH3OH)24Co9W5Re(CN)48, in which the O(h) symmetry of the cluster core is broken. Reassessment of the magnetic properties of the Mn9Mo6(CN)48 cluster confirm that it possesses a ground state spin of S = 39/2, but does not exhibit single-molecule-magnet behavior. Lowering the symmetry of the molecule by substitutions of ReV at one or three of the MoV sites does not lead to an overall increase in the magnetic anisotropy, as probed by ac magnetic susceptibility measurements. A similar result occurs for the other substituted species, with the important exception of the new single-molecule magnet (CH3OH)24Co9W5Re(CN)48, for which the spin reversal barrier is significantly reduced relative to that observed previously in (CH3OH)24Co9W6(CN)48.