Thermalization of Nuclear Spins in Lanthanide Molecular Magnets.

Single-molecule magnets (SMMs) distinguish themselves in the field of quantum magnetism through the ability to combine fundamental research with promising applications. The evolution of quantum spintronics in the last decade exemplifies the potential held by molecular-based quantum devices. Notably, the readout and manipulation of the nuclear spin states embedded in a lanthanide-based SMM hybrid device were employed in proof of principle studies of quantum computation at the single-molecule level. In the quest for further understanding of the relaxation behavior in SMMs for their integration in novel applications, herein, we study the relaxation dynamics of the 159Tb nuclear spins in a diluted molecular crystal employing the recently acquired understanding of the nonadiabatic dynamics of TbPc2 molecules. Through numerical simulation, we find that phonon-modulated hyperfine interaction opens a direct relaxation channel between the nuclear spins and the phonon bath. The mechanism is of potential importance for the theory of spin bath and the relaxation dynamics of the molecular spins.

Hilbert Space in Isotopologue Dy(III) SMM Dimers: Dipole Interaction Limit in [163/164Dy2(tmhd)6(tape)]0 Complexes.

Single-molecule magnets are molecular complexes proposed to be useful for information storage and quantum information processing applications. In the quest for multilevel systems that can act as Qudits, two dysprosium-based isotopologues were synthesized and characterized. The isotopologues are [164Dy2(tmhd)6(tape)] (1(I=0)) and [163Dy2(tmhd)6(tape)] (2(I=5/2)), where tmhd = 2,2,6,6-tetramethylheptandionate and tape = 1,6,7,12-tetraazaperylene. Both complexes showed slow relaxation at a zero applied magnetic field with dominant Orbach and Raman relaxation mechanisms. µSQUID studies at milli-Kelvin temperatures reveal quasi-single ion loops, in contrast with the expected S-shape (near zero field) butterfly loops, characteristic of antiferromagnetically coupled dimeric complexes. Through analysis of the low-temperature data, we find that the interaction operating between Dy(III) is small, leading to a small exchange biasing from the zero-field transition. The resulting indirectly coupled nuclear states are degenerate or possess a small energy difference between them. We, therefore, conclude that for the creation of Qudits with enlarged Hilbert spaces, shorter Dy(III)···Dy(III) distances are deemed essential.

Fe-Gd Ferromagnetic Cyclic Coordination Cluster [FeIII4GdIII4(teaH)8(N3)8(H2O)] with Magnetic Anisotropy─Theory and Experiment.

The synthesis, structural, and magnetic characterization of [FeIII4LnIII4(teaH)8(N3)8(H2O)] (Ln = Gd and Y) and the previously reported isostructural Dy analogue are discussed. The commonly held belief that both FeIII and GdIII can be regarded as isotropic ions is shown to be an oversimplification. This conclusion is derived from the magnetic data for the YIII analogue in terms of the zero-field splitting seen for FeIII and from the fact that the magnetic data for the new GdIII analogue can only be fit employing an additional anisotropy term for the GdIII ions. Furthermore, the Fe4Gd4 ring shows slow relaxation of magnetization. Our analysis of the experimental magnetic data employs both density functional theory as well as the finite-temperature Lanczos method which finally enables us to provide an almost perfect fit of magnetocaloric properties.

High-Performance Luminescence Thermometer with Field-Induced Slow Magnetic Relaxation Based on a Heterometallic Cyanido-Bridged 3d-4f Complex.

The 1:1:1 reaction of DyCl3·6H2O, K3[Co(CN)6] and bpyO2 in H2O has provided access to a complex with formula [DyCo(CN)6(bpyO2)2(H2O)3]·4H2O (1) in a very good yield, while [DyFe(CN)6(bpyO2)2 (H2O)3]·4H2O (2) was also precipitated (also in a high yield) using K3[Fe(CN)6] instead of K3[Co(CN)6]. Their structures have been determined by single-crystal X-ray crystallography and characterized based on elemental analyses and IR spectra. Combined direct current (dc) and alternating current (ac) magnetic susceptibility revealed slow magnetic relaxation upon application of a dc field. µ-SQUID measurements and CASSCF calculations revealed high-temperature relaxation dynamics for both compounds. Low-temperature magnetic studies show the relaxation characteristics for 1, while for compound 2 the dynamics corresponds to an antiferromagnetically coupled Dy···Fe pair. High-resolution optical studies have been carried out to investigate the performance of compounds 1 and 2 as luminescence thermometers. For 1, a maximum thermal sensitivity of 1.84% K-1 at 70 K has been calculated, which is higher than the acceptable sensitivity boundary of 1% K-1 for high-performance luminescence thermometers in a broad range of temperature between 40 and 140 K. Further optical studies focused on the chromaticity diagram of compound 1 revealed a temperature shift from warm white (3200 K) at 10 K toward a more natural white color near 4000 K at room temperature.

Lanthanide Luminescence Thermometry and Slow Magnetic Relaxation in 3-D Polycyanidometallate-Based Materials.

Two three-dimensional (3-D) polycyanidometallate-based luminescent thermometers with the general formula {Ln4Co4(CN)24(4-benpyo)17(H2O)·7H2O}n Ln = (Dy(III)(1), Eu(III)(2)), based on the red-emissive diamagnetic linker [Co(CN)6]3- and the bulky pyridine derivative that possesses the N-oxide moiety, 4-benzyloxy-pyridine N-oxide (benpyo), were prepared for the first time. The structure of compound 1 has been determined by single-crystal X-ray crystallography while the purity and structure of 2 have been confirmed by CHN, Fourier transform infrared spectroscopy (FT-IR), and powder X-ray diffraction (PXRD) analysis. Magnetic AC susceptibility measurements at zero field show no single-molecule magnet (SMM) behavior indicating fast relaxation operating in 1. Upon application of an optimal field of 2 kOe, the SMM character of compound 1 is revealed while the τ(Τ) can be reproduced solely considering the Raman process τ-1 = CTn with C = 7.0901(3) s-1 K-n and n = 3.58(1), indicating that a high density of low-lying states and optical as well as acoustic phonons play a major role in the relaxation mechanism. Micron-sized superconducting quantum interference device (µ-SQUID) loops show a very narrow opening in agreement with the AC susceptibility studies and complete active space self-consistent field (CASSCF) calculations. The interaction operating between the Dy(III) ions was quantified from CASSCF calculations. Good agreement is found by fitting the experimental DC χMΤ(Τ) and M(H), employing the Lines model, with JLines = -0.087 cm-1 (-0.125 K). The excitation spectra of compound 2 are used for temperature sensing in the 25-325 nm range with a maximum relative thermal sensitivity, Sr = 0.6% K-1 at 325 K, whereas compound 1 operates as a luminescent thermometer based on its emission features in the temperature range of 16-350 K with Sr ≈ 2.3% K-1 at 240 K.

Exchange-biased quantum tunnelling of magnetization in a [Mn3]2 dimer of single-molecule magnets with rare ferromagnetic inter-Mn3 coupling.

A covalently-linked dimer of two single-molecule magnets (SMMs), [Mn6O(O2CMe)6(1,3-ppmd)3](ClO4)2, has been synthesized from the reaction of [Mn3O(O2CMe)6(py)3](ClO4) with 1,3-phenylene-bis(pyridin-2-ylmethanone) dioxime (1,3-ppmdH2). It contains two [MnIII3O]+7 triangular units linked by three 1,3-ppmd2- groups into an [Mn3]2 dimer with D3 symmetry. Solid-state dc and ac magnetic susceptibility measurements showed that each Mn3 subunit retains its properties as an SMM with an S = 6 ground state. Magnetization vs. dc field sweeps on a single crystal reveal hysteresis loops below 1.3 K exhibiting exchange-biased quantum tunnelling of magnetization (QTM) steps with a bias field of +0.06 T. This is the first example of a dimer of SMMs showing a positive exchange bias of the QTM steps in the hysteresis loops, and it has therefore been subjected to a detailed analysis. Simulation of the loops determines that each Mn3 unit is exchange-coupled with its neighbour primarily through the 1,3-ppmd2- linkers, confirming a weak ferromagnetic inter-Mn3 interaction of J12≈ +6.5 mK (H = -2Jsi·sj convention). High-frequency EPR studies of a microcrystalline powder sample enable accurate determination of the zero-field splitting parameters of the uncoupled Mn3 SMMs, while also confirming the weak exchange interaction between the two SMMs within each [Mn3]2 dimer. The combined results emphasize the ability of designed covalent linkers to generate inter-SMM coupling of a particular sign and relative magnitude, and thus the ability of such linkers to modulate the quantum physics. As such, this work supports the feasibility of using designed covalent linkers to develop molecular oligomers of SMMs, or other magnetic molecules, as multi-qubit systems and/or other components of new quantum technologies.

Exchange-Bias Quantum Tunneling of the Magnetization in a Dysprosium Dimer.

Single-molecule magnets (SMMs) have been shown to possess bewildering phenomena leading to their proposal in several futuristic applications ranging from data storage devices to the basic unit of quantum computers. The main characteristic for the proposal of SMMs in such schemes is their inherent and intriguing quantum mechanical properties, which in turn, could be exploited in novel devices with larger capacities, such as for data storage or enhanced properties, such as quantum computers. In the quest of SMMs displaying such intriguing quantum effects, herein, we explore the synthesis, structural, and magnetic characterization of a dimeric dysprosium-based SMM composed of a tetradentate Schiff-base ligand with formula [Dy2(HL)2(benz)2(NO3)2]. Magnetic studies show that the complex is an SMM, while sub-Kelvin µ-SQUID studies revealed the exchange-bias characteristics of the system attributed to the presence of exchange interaction between the Dy3+ pair.

Inorganic Approach to Stabilizing Nanoscale Toroidicity in a Tetraicosanuclear Fe18Dy6 Single Molecule Magnet.

Cyclic coordination clusters (CCCs) are proving to provide an extra dimension in terms of exotic magnetic behavior as a result of their finite but cyclized chain structures. The Fe18Dy6 CCC is a Single Molecule Magnet with the highest nuclearity among Ln containing clusters. The three isostructural compounds [Fe18Ln6(µ-OH)6(ampd)12(Hampd)12(PhCO2)24](NO3)6·38MeCN for Ln = DyIII (1), LuIII (2), or YIII (3), where H2ampd = 2-amino-2-methyl-1,3-propanediol, are reported. These can be described in terms of the cyclization of six {Fe3Ln(µOH)(ampd)2(Hampd)2(PhCO2)4}+ units with six nitrate counterions to give the neutral cluster. The overall structure consists of two giant Dy3 triangles sandwiching a strongly antiferromagnetically coupled Fe18 ring, leading to a toroidal arrangement of the anisotropy axis of the Dy ions, making this the biggest toroidal arrangement on a molecular level known so far.

Granular aluminium as a superconducting material for high-impedance quantum circuits.

Superconducting quantum information processing machines are predominantly based on microwave circuits with relatively low characteristic impedance, about 100 Ω, and small anharmonicity, which can limit their coherence and logic gate fidelity1,2. A promising alternative is circuits based on so-called superinductors3-6, with characteristic impedances exceeding the resistance quantum RQ = 6.4 kΩ. However, previous implementations of superinductors, consisting of mesoscopic Josephson junction arrays7,8, can introduce unintended nonlinearity or parasitic resonant modes in the qubit vicinity, degrading its coherence. Here, we present a fluxonium qubit design based on a granular aluminium superinductor strip9-11. We show that granular aluminium can form an effective junction array with high kinetic inductance and be in situ integrated with standard aluminium circuit processing. The measured qubit coherence time [Formula: see text] illustrates the potential of granular aluminium for applications ranging from protected qubit designs to quantum-limited amplifiers and detectors.

Manipulation of the Coordination Geometry along the C4 Rotation Axis in a Dinuclear Tb3+ Triple-Decker Complex via a Supramolecular Approach.

A supramolecular complex (1⋅C60 ) was prepared by assembling (C60-Ih)[5,6]fullerene (C60 ) with the dinuclear Tb3+ triple-decker complex [(TPP)Tb(Pc)Tb(TPP)] (1: Tb3+ =trivalent terbium ion, Pc2- =phthalocyaninato, TPP2- =tetraphenylporphyrinato) with quasi-D4h symmetry to investigate the relationship between the coordination symmetry and single-molecule magnet (SMM) properties. Tb3+ -Pc triple-decker complexes (Tb2 Pc3 ) have an important advantage over Tb3+ -Pc double-decker complexes (TbPc2 ) since the magnetic relaxation processes correspond to the Zeeman splitting when there are two 4f spin systems. The two Tb3+ sites of 1 are equivalent, and the twist angle (φ) was determined to be 3.62°. On the other hand, the two Tb3+ sites of 1⋅C60 are not equivalent. The φ values for sites Tb1 and Tb2 were determined to be 3.67° and 33.8°, respectively, due to a change in the coordination symmetry of 1 upon association with C60 . At 1.8 K, 1 and 1⋅C60 undergo different magnetic relaxations, and the changes in the ground state affect the spin dynamics. Although 1 and 1⋅C60 relax via QTM in a zero applied magnetic field (H), H dependencies of the magnetic relaxation times (τ) for H>1500 Oe are similar. On the other hand, for H<1500 Oe, the τ values have different behaviors since the off-diagonal terms ( B k q ; q ≠ 0 ) affect the magnetic relaxation mechanism. From temperature (T) and H dependences of τ, spin-phonon interactions along with direct and Raman mechanisms explain the spin dynamics. We believe that a supramolecular method can be used to control the magnetic anisotropy along the C4 rotation axis and the spin dynamic properties in dinuclear Ln3+ -Pc multiple-decker complexes.

Highly Oxidized States of Phthalocyaninato Terbium(III) Multiple-Decker Complexes Showing Structural Deformations, Biradical Properties and Decreases in Magnetic Anisotropy.

Presented here is a comprehensive study of highly oxidized multiple-decker complexes composed of TbIII and CdII ions and two to five phthalocyaninato ligands, which are stabilized by electron-donating n-butoxy groups. From X-ray structural analyses, all the complexes become axially compressed upon ligand oxidation, resulting in bowl-shaped distortions of the ligands. In addition, unusual coexistence of square antiprism and square prism geometries around metal ions was observed in +4e charged species. From paramagnetic 1 H NMR studies on the resulting series of triple, quadruple and quintuple-decker complexes, ligand oxidation leads to a decrease in the magnetic anisotropy, as predicted from theoretical calculations. Unusual paramagnetic shifts were observed in the spectra of the +2e charged quadruple and quintuple-decker complexes, indicating that those two species are actually unexpected triplet biradicals. Magnetic measurements revealed that the series of complexes show single-molecule magnet properties, which are controlled by the multi-step redox induced structural changes.

Coexistence of Spin-Lattice Relaxation and Phonon-Bottleneck Processes in GdIII -Phthlocyaninato Triple-Decker Complexes under Highly Diluted Conditions.

Gd3+ complexes have been shown to undergo unusual slow magnetic relaxation processes similar to those of single-molecule magnets (SMMs), even though Gd3+ does not exhibit strong magnetic anisotropy. To reveal the origin of the slow magnetic relaxation of Gd3+ complexes, we have investigated the magnetic properties and heat capacities of two Gd3+ -phthalocyaninato triple-decker complexes, one of which has intramolecular Gd3+ -Gd3+ interactions and the other does not. It was found that the Gd3+ -Gd3+ interactions accelerate the magnetic relaxation processes. In addition, magnetically diluted samples, prepared by doping a small amount of the Gd3+ complexes into a large amount of diamagnetic Y3+ complexes, underwent dual magnetic relaxation processes. A detailed dynamic magnetic analysis revealed that the coexistence of spin-lattice relaxation and phonon-bottleneck processes is the origin of the dual magnetic relaxation processes.

Selective Coordination of Self-Assembled Hexanuclear [Ni4Ln2] and [Ni2Mn2Ln2] (Ln = DyIII, TbIII, and HoIII) Complexes: Stepwise Synthesis, Structures, and Magnetic Properties.

The versatility for a unique aggregation of heterometallic 3d-4f and 3d-3d'-4f ions by the new Schiff base ligand 2-{[(2-hydroxy-3-methoxybenzyl)imino]methyl}phenol (H2L) providing O3N donors has been examined. A series of complexes having the general formula [Ln2Ni4(L)4(µ1,3-CH3CO2)2(µ3-OH)4(MeOH)2]·xCH3OH·yH2O [where Ln = DyIII, x = 4, y = 0 (1), Ln = TbIII, x = 0, y = 4 (2), and Ln = HoIII, x = 4, y = 0 (3)] were obtained from the sequential use of lanthanide(III) nitrate salts and Ni(CH3CO2)2·4H2O. The incorporation of two different 3d ions and one 4f ion in the same coordination aggregate was achieved through the isomorphic replacement of two NiII centers by MnIII ions as second group of cationic complexes, [Ln2Ni2Mn2(L)4(µ1,3-CH3CO2)2(µ3-OH)4(MeOH)2](NO3)2·2CH3OH [where Ln = DyIII (4), TbIII (5), and HoIII (6)]. Direct-current (dc) magnetic susceptibility studies hint to the possibility of ferromagnetic interactions occurring in the aggregates, whereas alternating-current susceptibility measurements find both the DyIII analogues, 1 and 4, to show out-of-phase components at zero applied dc field, characteristic of single-molecule-magnet (SMM) behavior. Micro-SQUID studies reveal open hysteresis loops for 1, corroborating its SMM character. Further detailed complete-active-space self-consistent-field and density functional theory calculations were also performed, supporting the experimental findings in complexes 1 and 4.

Magnetic Properties and Electronic Structure of the S = 2 Complex [MnIII{(OPPh2)2N}3] Showing Field-Induced Slow Magnetization Relaxation.

The high-spin S = 2 Mn(III) complex [Mn{(OPPh2)2N}3] (1Mn) exhibits field-induced slow relaxation of magnetization (Inorg. Chem. 2013, 52, 12869). Magnetic susceptibility and dual-mode X-band electron paramagnetic resonance (EPR) studies revealed a negative value of the zero-field-splitting (zfs) parameter D. In order to explore the magnetic and electronic properties of 1Mn in detail, a combination of experimental and computational studies is presented herein. Alternating-current magnetometry on magnetically diluted samples (1Mn/1Ga) of 1Mn in the diamagnetic gallium analogue, [Ga{(OPPh2)2N}3], indicates that the slow relaxation behavior of 1Mn is due to the intrinsic properties of the individual molecules of 1Mn. Investigation of the single-crystal magnetization of both 1Mn and 1Mn/1Ga by a micro-SQUID device reveals hysteresis loops below 1 K. Closed hysteresis loops at a zero direct-current magnetic field are observed and attributed to fast quantum tunneling of magnetization. High-frequency and -field EPR (HFEPR) spectroscopic studies reveal that, apart from the second-order zfs terms (D and E), fourth-order terms (B4m) are required in order to appropriately describe the magnetic properties of 1Mn. These studies provide accurate spin-Hamiltonian (sH) parameters of 1Mn, i.e., zfs parameters |D| = 3.917(5) cm-1, |E| = 0.018(4) cm-1, B04 = B42 = 0, and B44 = (3.6 ± 1.7) × 10-3 cm-1 and g = [1.994(5), 1.996(4), 1.985(4)], and confirm the negative sign of D. Parallel-mode X-band EPR studies on 1Mn/1Ga and CH2Cl2 solutions of 1Mn probe the electronic-nuclear hyperfine interactions in the solid state and solution. The electronic structure of 1Mn is investigated by quantum-chemical calculations by employing recently developed computational protocols that are grounded on ab initio wave function theory. From computational analysis, the contributions of spin-spin and spin-orbit coupling to the magnitude of D are obtained. The calculations provide also computed values of the fourth-order zfs terms B4m, as well as those of the g and hyperfine interaction tensor components. In all cases, a very good agreement between the computed and experimentally determined sH parameters is observed. The magnetization relaxation properties of 1Mn are rationalized on the basis of the composition of the ground-state wave functions in the absence or presence of an external magnetic field.

Effects of the Exchange Coupling on Dynamic Properties in a Series of CoGdCo Complexes.

Reaction of 2-hydroxy3-methoxybenzaldehyde ( o-vanillin) with 1,1,1-tris(aminomethyl)ethane, Me-C(CH2NH2)3, or with N, N', N''-trimethylphosphorothioic trihydrazide, P(S)[NMe-NH2]3, yields two tripodal LH3 and L1H3 ligands which are able to give cationic heterotrinuclear [LCoGdCoL]+ or [L1CoGdCoL1]+ complexes. The CoII ions are coordinated to these deprotonated ligands in the inner N3O3 site, while the GdIII ion is linked to three deprotonated phenoxo oxygen atoms of two anionic [LCo]- or [L1Co]- units. Air oxidation of these trinuclear complexes does not yield complexes associating CoIII and GdIII ions. With the first ligand, the structurally characterized resulting complex is the neutral mononuclear LCoIII compound, while in the second case, oxidation of the CoII ions turned out to be impossible. The [L1CoLnCoL1]+ complexes behave as single-molecule magnets with effective energy barriers for the reversal of magnetization varying from Ueff = 51.3 K, τo = 2 × 10-6 s for the yttrium complex to Ueff = 29.5, 29.4, 27.4 K and τo = 1.3 × 10-7, 1.47 × 10-7, 1.50 × 10-7 s for the gadolinium ones, depending on the used counteranions. The energy decrease is compensated by the suppression of quantum tunneling of magnetization in absence of applied field, thanks to the introduction of a ferromagnetic Co-Gd interaction. Current work also shows that uncritical use of conventional spin Hamiltonians, based on quenched orbital momenta, can be misleading and that ab initio calculations are indispensable for establishing the picture of real magnetic interaction. Ab initio calculations show that the CoII sites in the investigated compounds possess large unquenched orbital moments due to the first-order spin-orbit coupling resulting in strongly axial magnetic anisotropy. Although the CoII ions are not axial enough for showing slow relaxation of magnetization by themselves, blocking barriers of exchange type are obtained thanks to the exchange interaction with GdIII ions.

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 that lead to Qudits, where the dimension of the Hilbert space is d > 2. Herein we review how a molecular nuclear spin qudit, (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.

Proximity-Induced Superconductivity and Quantum Interference in Topological Crystalline Insulator SnTe Thin-Film Devices.

Topological crystalline insulators represent a new state of matter, in which the electronic transport is governed by mirror-symmetry protected Dirac surface states. Due to the helical spin-polarization of these surface states, the proximity of topological crystalline matter to a nearby superconductor is predicted to induce unconventional superconductivity and, thus, to host Majorana physics. We report on the preparation and characterization of Nb-based superconducting quantum interference devices patterned on top of topological crystalline insulator SnTe thin films. The SnTe films show weak anti-localization, and the weak links of the superconducting quantum interference devices (SQUID) exhibit fully gapped proximity-induced superconductivity. Both properties give a coinciding coherence length of 120 nm. The SQUID oscillations induced by a magnetic field show 2π periodicity, possibly dominated by the bulk conductivity.

Comparison of the Magnetic Anisotropy and Spin Relaxation Phenomenon of Dinuclear Terbium(III) Phthalocyaninato Single-Molecule Magnets Using the Geometric Spin Arrangement.

Herein we report the synthesis and characterization of a dinuclear TbIII single-molecule magnet (SMM) with two [TbPc2]0 units connected via a fused-phthalocyaninato ligand. The stable and robust complex [(obPc)Tb(Fused-Pc)Tb(obPc)] (1) was characterized by using synchrotron radiation measurements and other spectroscopic techniques (ESI-MS, FT-IR, UV). The magnetic couplings between the TbIII ions and the two π radicals present in 1 were explored by means of density functional theory (DFT). Direct and alternating current magnetic susceptibility measurements were conducted on magnetically diluted and nondiluted samples of 1, indicating this compound to be an SMM with improved properties compared to those of the well-known [TbPc2]-/0/+ and the axially symmetric dinuclear TbIII phthalocyaninato triple-decker complex (Tb2(obPc)3). Assuming that the probability of quantum tunneling of the magnetization (QTM) occurring in one TbPc2 unit is PQTM, the probability of QTM simultaneously occurring in 1 is PQTM2, meaning that QTM is effectively suppressed. Furthermore, nondiluted samples of 1 underwent slow magnetic relaxation times (τ ≈ 1000 s at 0.1 K), and the blocking temperature (TB) was determined to be ca. 16 K with an energy barrier for spin reversal (Ueff) of 588 cm-1 (847 K) due to D4d geometry and weak inter- and intramolecular magnetic interactions as an exchange bias (Hbias), reducing QTM. Four hyperfine steps were observed by micro-SQUID measurement. Furthermore, solution NMR measurements (one-dimensional, two-dimensional, and dynamic) were done on 1, which led to the determination of the high rotation barrier (83 ± 10 kJ/mol) of the obPc ligand. A comparison with previously reported TbIII triple-decker compounds shows that ambient temperature NMR measurements can indicate improvements in the design of coordination environments for SMMs. A large Ueff causes strong uniaxial magnetic anisotropy in 1, leading to a χax value (1.39 × 10-30 m3) that is larger than that for Tb2(obPc)3 (0.86 × 10-30 m3). Controlling the coordination environment and spin arrangement is an effective technique for suppressing QTM in TbPc2-based SMMs.

Tetranuclear Dysprosium(III) Quintuple-Decker Single-Molecule Magnet Prepared Using a π-Extended Phthalocyaninato Ligand with Two Coordination Sites.

The magnetic properties and spin relaxation processes of a tetranuclear dysprosium(III) fused phthalocyaninato (Pc4- ) quintuple-decker single-molecule magnet (SMM) (1) with non-equivalent octa-coordination geometries are reported. The structure of 1 is regarded as a dimer of Dy3+ -Pc triple-decker SMMs with different magnetic relaxation characteristics, corresponding to the octa-coordination geometry sites Dy1 with C4 symmetry (ϕ1 =23°) and Dy2 with D4d symmetry (ϕ2 =45°). In an Hdc of 1750 Oe and T range of 1.8-3.75 K, the quantum tunnelling of the magnetization was suppressed, and the direct process was enhanced. The effects of the coordination geometry on the spin relaxation phenomena are examined.

Slow Magnetic Relaxation in a Palladium-Gadolinium Complex Induced by Electron Density Donation from the Palladium Ion.

Incorporating palladium in the first coordination sphere of acetato-bridged lanthanoid complexes, [Pd2 Ln2 (H2 O)2 (AcO)10 ]⋅2 AcOH (Ln=Gd (1), Y (2), Gd0.4 Y1.6 (3), Eu (4)), led to significant bonding interactions between the palladium and the lanthanoid ions, which were demonstrated by experimental and theoretical methods. We found that electron density was donated from the d8 Pd2+ ion to Gd3+ ion in 1 and 3, leading to the observed slow magnetic relaxation by using local orbital locator (LOL) and X-ray absorption near-edge structure (XANES) analysis. Field-induced dual slow magnetic relaxation was observed for 1 up to 20 K. Complex 3 and frozen aqueous and acetonitrile solutions of 1 showed only one relaxation peak, which confirms the role of intermolecular dipolar interactions in slowing the magnetic relaxation of 1. The slow magnetic relaxation occurred through a combination of Orbach and Direct processes with the highest pre-exponential factor (τo =0.06 s) reported so far for a gadolinium complex exhibiting slow magnetic relaxation. The results revealed that transition metal-lanthanoid (TM-Ln) axial interactions indeed could lead to new physical properties by affecting both the electronic and magnetic states of the compounds.