SINGLE MOLECULE MAGNETS:

The utilisation of quantum properties can largely impact how technological devices work. Up to date, the acquired knowledge of the quantum nature of several systems inspired the proposal of several novel technologies such as quantum sensing, quantum simulation and quantum computing. Single Molecule Magnets (SMMs) represent a class of quantum objects with promising properties to be exploited in quantum technologies. As of today, SMMs have been shown to possess bewildering quantum effects such as Quantum Tunnelling of the Magnetisation (QTM), quantisation of the energy manifold, coherence, spin parity effects and entanglement, among others. Furthermore, they have been successfully integrated into hybrid single-molecule spintronic devices, such as spin transistors and spin valves, hence, propitiating extensive investigation of technological applications. In this Review Article, some key quantum aspects, which make SMMs promising systems for technological proposals, are revised. Moreover, single-molecule devices, in which SMMs have been integrated in hybrid devices, as well as the technological applications such as quantum sensing, quantum simulation and quantum computing are described

Molecular Spin Qudits for Quantum Algorithms

Presently, one of the most ambitious technological goals is the development of devices working under the laws of quantum mechanics. One prominent target is the quantum computer, which would allow the processing of information at quantum level for purposes not achievable with even the most powerful computer resources. The large-scale implementation of quantum information would be a game changer for current technology, because it would allow unprecedented parallelised computation and secure encryption based on the principles of quantum superposition and entanglement. Currently, there are several physical platforms racing to achieve the level of performance required for the quantum hardware to step into the realm of practical quantum information applications. Several materials have been proposed to fulfil this task, ranging from quantum dots, Bose-Einstein condensates, spin impurities, superconducting circuits, molecules, amongst others. Magnetic molecules are among the list of promising building blocks, due to (i) their intrinsic monodispersity, (ii) discrete energy levels (iii) the possibility of chemical quantum state engineering, and (iv) their multilevel characteristics, leading to the so called Qudits (d > 2), amongst others. Herein we review how a molecular multilevel nuclear spin qubit (or qudit, where d = 4), known as TbPc2, gathers all the necessary requirements to perform as a molecular hardware platform with a first generation of molecular devices enabling even quantum algorithm operations.Comment: Chem. Soc. Rev., 2017, Advance Articl

Heteroleptic, polynuclear dysprosium(III_{III})-carbamato complexes throughin situcarbon dioxide capture

Amine groups are among the most effective systems for carbon dioxide capture. Reminiscent of the activation of nature\u27s most abundant enzyme RuBisCO, the treatment of amines with CO$_{2}$ in the presence of oxophilic metal ions, e.g. Mg$^{2+}$, results in the formation of carbamates. Here we report the synthesis, structure and magnetic properties of three new dysprosium-carbamato complexes. The reaction of gaseous CO$_{2}$ with N,N-diisopropylamine and DyCl$_{3}$(DME)$_{2}$ (DME = Dimethoxyethane) in toluene leads to the formation of the tetrametallic complex [Dy$_{4}$(O$_{2}$CNiPr$_{2}$)$_{10}$(O-C$_{2}$H$_{4}$–OMe)$_{2}$]. The addition of 2-hydroxy-3-methoxybenzaldehyde-N-methylimine yields the hexametallic compound [Dy$_{6}$(O$_{2}$CNiPr$_{2}$)$_{8}$(O-C$_{2}$H$_{4}$–OMe)$_{2}$(CO$_{3}$)$_{2}$(C$_{9}$O$_{2}$NH$_{10}$)$_{4}$] in which the metal sites form a chair-like configuration; The same hexanuclear motif is obtained using N,N-dibenzylamine. We show that by employing CO$_{2}$ as a feedstock, we are able to capture up to 2.5 molecules of CO$_{2}$ per Dy ion. Magnetic measurements show a decreasing χMT at low temperatures. Combining the experimental magnetic data with ab initio calculations reveils tilting of the easy axes and implies the presence of antiferromagnetic interactions between the Dy($_{III}$) metal ions

Very Anisotropic 2D Molecular Magnetic Materials Based on Pentagonal Bipyramidal Heptacyanidorhenate(IV)

The first neutral 2D heterometallic assemblies based on orbitally degenerate heptacyanidorhenate(IV) were prepared and structurally characterized. An analysis of the magnetic data for the polycrystalline samples of Ph$_4$P[{Mn(acacen)}$_2$Re(CN)$_7$]·Solv (1) and PPN[{Mn(acacen)}$_2$Re(CN)$_7$]·Solv (2) have shown that both materials display slow magnetic relaxation at temperatures below 10 and 21 K for 1 and 2, respectively. Despite the presence of the same molecular magnetic modules that make up the anionic layers, the studied 2D networks differ significantly in magnetic anisotropy, having a small coercive field (0.115 T) for 1 and a large one (~2.5 T) for 2 at 2 K. In addition, for both polymers a M(H) value does not saturate at the maximum available field of 7 T, and the material 2 is a metamagnet. This intriguing difference originates from the cooperative anisotropic spin interaction in Re$^{IV}$−CN−Mn$^{III}$ pairs and the zero field splitting (ZFS) effect of Mn$^{III}$ ions with a noncollinear alignment of the local magnetic axes in crystals of the compounds

Quantum tunnelling of the magnetisation in single-molecule magnet isotopologue dimers

Quantum tunnelling of the magnetisation plays a major role in the magnetic properties of lanthanide Single-Molecule Magnets: while it is considered a problem for data storage device applications since it leads to information loss, it is an essential pre-requisite for the read-out and manipulation of the nuclear states in Quantum Information Processing schemes. Here we describe two isotopologue dysprosium dimers, i.e. [($^{163}$Dy(tmhd)$_{3}$)$_{2}$(bpym)] and [($^{164}$Dy(tmhd)$_{3}$)$_{2}$(bpym)] (tmd = tris(tetramethylheptanedionato) and bpym = bipyrimidine), where the nuclear spin presence or absence clearly affects the magnetic properties of the systems. Through μ-SQUID studies at milli-Kelvin temperatures and alternating current magnetic measurements, we find significant differences in the magnetic behaviour of both complexes. While simulation of the hysteresis loops at 30 mK reveals that the presence of nuclear spin does not influence the tunnelling rate, we find that it facilitates the coupling to the phonon bath enhancing the direct relaxation process; an observation reflected in the temperature and field dependence of the relaxation rates

Direct determination of high-order transverse ligand field parameters via µSQUID-EPR in a Et4_{4}N[160^{160}GdPc2_{2}] SMM

The development of quantum technologies requires a thorough understanding of systems possessing quantum effects that can ultimately be manipulated. In the field of molecular magnetism, one of the main challenges is to measure high-order ligand field parameters, which play an essential role in the relaxation properties of SMMs. The development of highly advanced theoretical calculations has allowed the ab-initio determination of such parameters; however, currently, there is a lack of quantitative assessment of how good the ab-initio parameters are. In our quest for technologies that can allow the extraction of such elusive parameters, we develop an experimental technique that combines the EPR spectroscopy and µSQUID magnetometry. We demonstrate the power of the technique by performing EPR-µSQUID measurement of a magnetically diluted single crystal of Et4N[GdPc2], by sweeping the magnetic field and applying a range of multifrequency microwave pulses. As a result, we were able to directly determine the high-order ligand field parameters of the system, enabling us to test theoretical predictions made by state-of-the-art ab-initio methods

g-engineering in hybrid rotaxanes to create AB and AB2 electron spin systems: EPR spectroscopic studies of weak interactions between dissimilar electron spin qubits

Hybrid [2]rotaxanes and pseudorotaxanes are reported where the magnetic interaction between dissimilar spins is controlled to create AB and AB2 electron spin systems,allowing independent control of weakly interacting S =1=2 centers

Synthesis and Characterization of a Heterometallic Extended Architecture Based on a Manganese(II)-Substituted Sandwich-Type Polyoxotungstate

The reaction of [α-P2W15O56]12− with MnII and DyIII in an aqueous basic solution led to the isolation of an all inorganic heterometallic aggregate Na10(OH2)42[{Dy(H2O)6}2Mn4P4W30O112(H2O)2]·17H2O (Dy2Mn4-P2W15). Single-crystal X-ray diffraction revealed that Dy2Mn4-P2W15 crystallizes in the triclinic system with space group P 1 ¯ , and consists of a tetranuclear manganese(II)-substituted sandwich-type phosphotungstate [Mn4(H2O)2(P2W15O56)2]16− (Mn4-P2W15), Na, and DyIII cations. Compound Dy2Mn4-P2W15 exhibits a 1D ladder-like chain structure based on sandwich-type segments and dysprosium cations as linkers, which are further connected into a three-dimensional open framework by sodium cations. The title compound was structurally and compositionally characterized in solid state by single-crystal XRD, powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric (TGA), and elemental analyses. Further, the absorption and emission electronic spectra in aqueous solutions of Dy2Mn4-P2W15 and Mn4-P2W15 were studied. Also, magnetic properties were studied and compared with the magnetic behavior of [Mn4(H2O)2(P2W15O56)2]16−