Theoretical exploration of single-molecule magnetic and single-molecule toroic behaviors in peroxide-bridged double-triangular {MII3LnIII3} (M = Ni, Cu and Zn; Ln = Gd, Tb and Dy) complexes.

Detailed state-of-the-art and density functional theory (DFT) calculations have been undertaken to understand both Single-Molecule Magnetic (SMM) and Single-Molecule Toroic (SMT) behaviors of fascinating 3d-4f {MLn} triangular complexes having the molecular formula [MII3LnIII3(O)L(PyCO)](OH)(ClO)·8HO (with M = Zn; Ln = Dy (1), Tb (2) & Gd (3) and M = Cu; Ln = Dy (4), Tb (5) & Gd (6)) and [NiLn(HO)(mpko)(O)(NO)](ClO)3CHOH3CHCN (Ln = Dy (7), Tb (8), and Gd (9)) [mpkoH = 1-(pyrazin-2-yl)ethanone oxime]. All these complexes possess a peroxide ligand that bridges the {LnIII3} triangle in a μ-η:η fashion and the oxygen atoms/oxime of co-ligands that connect each M ion to the {LnIII3} triangle. Through our computational studies, we tried to find the key role of the peroxide bridge and how it affects the SMM and SMT behavior of these complexes.

Elevating the Performance of Heterometallic 3d/4f SMMs: The Role of Diamagnetic Co and Zn Ions in Magnetization Dynamics.

Recent advances in the synthesis of 3d/4f Single-Molecule Magnets (SMMs) have revealed the effective role of incorporating diamagnetic Co or Zn ions to enhance the magnetic properties of Ln ions. This concept highlights notable examples of Co/Ln and Zn/Ln SMMs documented in the recent literature, illustrating how the selection of various peripheral and/or bridging ligands can modulate the magnetic anisotropy of 4f metal ions, thereby increasing their energy barriers.

A combined theoretical and experimental approach to determine the right choice of co-ligand to impart spin crossover in Fe(II) complexes based on 1,3,4-oxadiazole ligands.

We present the synthesis of two new novel tetradentate ligands based on 1,3,4-oxadiazole, 2-(2-pyridyl)-5-[,-bis(2-pyridylmethyl)aminomethyl]-1,3,4-oxadiazole (LTetraPy-ODA) and 2-(2-phenyl)-5-[,-bis(2-pyridylmethyl)aminomethyl]-1,3,4-oxadiazole (LTetraPh-ODA). The ligands were used to prepare six mononuclear complexes [Fe(LTetraPy-ODA)(NCE)] (C1-C3) and [Fe(LTetraPh-ODA)(NCE)] (C4-C6) where E = S, Se or BH. In addition, the ligand LTetraPy-ODA was employed in the synthesis of a new di-nuclear complex [FeII2(LTetraPh)](ClO)·1 CHNO·1.

Slow Magnetization Relaxation in a Family of Triangular {Co Ln } Clusters: The Effect of Diamagnetic Co Ions on the Ln Magnetic Dynamics.

The first use of the Schiff base chelate N-naphthalidene-o-aminophenol (naphH ) in Co/Ln chemistry has afforded a family of isostructural [Co Ln (OMe) (naph) (O CMe) (MeOH) ] (Ln=Tb, Dy and Er) complexes, revealing a rare {Co Ln(μ -OMe)} triangular core composed of two diamagnetic Co ions and a 4f-ion with slightly distorted square antiprismatic geometry. Alternating current (ac) magnetic susceptibility studies revealed that {Co Dy}, and its magnetic diluted analogue {Co Dy Y }, behave as mononuclear single-molecule magnets (SMMs) with similar energy barriers for the magnetization reversal, U , of ~85-90 K. SMM properties were also detected for {Co Er}, with the compound exhibiting a U of 18.

Efficient synthetic route to heterobimetallic trinuclear complexes [Ln-Mn-Ln] and their single molecule magnetic properties.

A series of mononuclear lanthanoidate complexes isolated as [BuN][Ln(QCl)] 1Ln (QCl = 5-chloro-8-quinolinolate; Ln = Eu, Gd, Tb, Dy, Ho, and Er) have been prepared, characterised, and used as facile precursors to obtain a series of new heterobimetallic complexes as crystalline materials. Reaction of 1Ln with manganese nitrate forms [LnMn(QCl)] (2Ln, where Ln = Tb, Dy, Er and Yb) which have been structurally characterised in the cases of 2Tb and 2Yb. The heteroleptic trinuclear complex [Dy(QCl)Cl(OH)], 3, has also been obtained.

Strategies to Design Single-Molecule Toroics Using Triangular {Ln} Motifs.

In this mini-review, we highlight the research advanced in the field of single-molecule toroics (SMTs) with a specific focus on the triangular Ln-based SMTs. SMTs are molecules with a toroidal magnetic state and are insensitive to homogeneous magnetic fields but cooperate with charge and spin currents. The rapid growth in the area of SMTs witnessed in recent years is correlated not only to the interest to understand the fundamental physics of these molecules but also to the intriguing potential applications proposed, as the SMTs have several advantages compared to other classes of molecules such as single-molecule magnets (SMMs).

Enhancing the barrier height for magnetization reversal in 4d/4f RuIII2LnIII2 "butterfly" single molecule magnets (Ln = Gd, Dy) targeted structural alterations.

A series of 4d-4f {RuIII2DyIII2} and {RuIII2GdIII2} 'butterfly' (rhombohedral) complexes have been synthesized and characterized and their magnetic properties investigated. Earlier, we have reported the first 4d/4f SMM - [RuIII2DyIII2(OMe)(OCPh)(mdea)(NO)] (1Dy) with a value of 10.7 cm.

Quinoxaline radical-bridged transition metal complexes with very strong antiferromagnetic coupling.

A new family of radical-bridged compounds, (Cp*2Co)[M2Cl4(dpq)] (M = Fe (1), Co (2), Zn (3)), (dpq = 2,3-di(2-pyridyl)-quinoxaline) is reported. Magnetic studies, DFT and ab initio calculations reveal strong antiferromagnetic metal-radical interactions with coupling constants of J = -213.1 and -218.

Six-coordinate mononuclear dysprosium(iii) single-molecule magnets with the triphenylphosphine oxide ligand.

Structural, magnetic and theoretical studies of three octahedral mononuclear DyIII complexes with triphenylphosphine oxide and halide ligands are reported. The Cl- and Br- analogues exhibit SMM behavior with energy barriers of 49.1 K and 70.

A Co metallacycle stabilized by double anion-π interactions.

Self-assembly reactions of CoII ions in the presence of the 2,2-bipyrimidine (bpym) ligand produced both a dinuclear and an octanuclear cation with the nuclearity being governed by hydrogen-bonding versus anion-π interactions between the anions and the ligands.

New examples of triangular terbium(iii) and holmium(iii) and hexagonal dysprosium(iii) single molecule toroics.

The structural, magnetic and theoretical aspects are described for three triangular lanthanide complexes, [Tb(OH)(teaH)(paa)]Cl (1), [Dy(OH)(teaH)(paa)]Cl (2) and [Ho(OH)(teaH)(paa)]Cl (3), and a hexanuclear wheel of formula [Dy(pdeaH)(NO)] (4) [teaH = triethanolamine, paaH = N-(2-pyridyl)-acetoacetamide and pdeaH = 3-[bis(2-hydroxyethyl)amino]propan-1-ol]. Each complex displays single molecule toroidal behaviour as rationalised using high-level ab initio calculations. Complexes 2 and 3 are the first examples of mixed moment single molecule toroidal complexes featuring non-Kramers ions.

Switching on single-molecule magnet properties of homoleptic sandwich tris(pyrazolyl)borate dysprosium(iii) cations via intermolecular dipolar coupling.

Two new homoleptic DyIII compounds [Dy(TpMe2)2][DyCl3(TpMe2)]·CH2Cl2 (1) and [Dy(TpMe2)2]I (3) as well as a heteroleptic (NMe4)[DyCl3(TpMe2)] (2) (TpMe2 = tris(3,5-dimethylpyrazolyl)borate) species are reported. Magnetic studies revealed that 1 is a single-molecule magnet (SMM) with an energy barrier of Ueff = 80.7 K with τ0 = 6.

Rare "Janus"-faced single-molecule magnet exhibiting intramolecular ferromagnetic interactions.

A rare disk-like single-molecule magnet (SMM) exclusively bridged by end-on azides with a spin ground state of = 14 was prepared by the reaction of a divalent Fe precursor with MeSiN under basic conditions. AC magnetic susceptibility studies revealed unusual, "Janus"-faced SMM behavior for the dried and pristine forms of the compound attributed to solvation/de-solvation effects of the coordinated MeCN ligands which leads to alterations in the crystal field and symmetry of the metal ions. DFT calculations confirmed the ferromagnetic nature of the interactions between the Fe spin carriers with the zero-field splitting parameters = -0.

Hard versus soft: zero-field dinuclear Dy(iii) oxygen bridged SMM and theoretical predictions of the sulfur and selenium analogues.

Two dinuclear lanthanide complexes (Gd and Dy) were prepared and characterized by X-ray, magnetic and computational methods. The Dy analogue shows SMM behavior with an energy barrier of 98.4 K in the absence of an applied dc field.

Oblate versus Prolate Electron Density of Lanthanide Ions: A Design Criterion for Engineering Toroidal Moments? A Case Study on {Ln } (Ln=Tb, Dy, Ho and Er) Wheels.

We report four new complexes based on a {Ln } wheel structure, three of which possess a net toroidal magnetic moment. The four examples consist of {Tb } and {Ho } wheels, which are rare examples of non Dy based complexes possessing a toroidal magnetic ground state, and a {Dy } complex which improves its toroidal structure upon lowering the crystallographic symmetry from trigonal (R ) to triclinic (P ). Notably the toroidal moment is lost for the trigonal {Er } analogue.

A cyanide-bridged wheel featuring a seven-coordinate Mo(iii) center.

A new cyclic molecule incorporating [MoIII(CN)7]4- has been characterized by single crystal X-ray methods, SQUID magnetometry and theoretical calculations. The wheel molecule [MoIII(CN)7]6[Ni(L)]12(H2O)6 exhibits ferromagnetic Mo-Ni coupling which did not exist for the previously reported octacyanometallate analogue [MoIV(CN)8]6[Ni(L)]12(H2O)6. These results indicate that known supramolecular architectures incorporating octacyanometallates can be used as platforms for making new molecules incorporating seven-coordinate cyanide precursors.

Effects of coordination sphere on unusually large zero field splitting and slow magnetic relaxation in trigonally symmetric molecules.

Geometric control in mononuclear complexes has come to the forefront in the field of molecular magnets due to its profound effects on relaxation pathways and blocking temperature in single molecule magnets (SMMs). Herein we report the synthesis and magnetic characterization of six trigonally symmetric, divalent Fe, Co, and Ni molecules, with the rigid geometry enforced the use of the tris-anionic, tetradentate ligand MST (,',''-[2,2',2''-nitrilotris-(ethane-2,1-diyl)]tris(2,4,6-trimethylbenzenesulfonamide)). A systematic study on the effect of converting between trigonal monopyramidal complexes, (MeN)[M(MST)], and trigonal bipyramidal complexes, (MeN)[M(MST)(OH)] was conducted experimentally and computationally.

Slow magnetic dynamics in a family of mononuclear lanthanide complexes exhibiting the rare cubic coordination geometry.

A new family of mononuclear lanthanide complexes, where the eight coordinate lanthanide ions adopt a very rare cubic coordination geometry is reported. The Dy analogue exhibits SMM behavior with a Ueff value 95.7 K under a 0.

Rationalizing the sign and magnitude of the magnetic coupling and anisotropy in dinuclear manganese(iii) complexes.

We have synthesised twelve manganese(iii) dinuclear complexes, 1-12, in order to understand the origin of magnetic exchange (J) between the metal centres and the magnetic anisotropy (D) of each metal ion using a combined experimental and theoretical approach. All twelve complexes contain the same bridging ligand environment of one μ-oxo and two μ-carboxylato, that helped us to probe how the structural parameters, such as bond distance, bond angle and especially Jahn-Teller dihedral angle affect the magnetic behaviour. Among the twelve complexes, we found ferromagnetic coupling for five and antiferromagnetic coupling for seven.

Understanding the Mechanism of Magnetic Relaxation in Pentanuclear {MnMnLn} Single-Molecule Magnets.

A new family of heterometallic pentanuclear complexes of formulas [MnMnLnO(benz)(mdea)(NO)(MeOH)] (Ln = Dy (1-Dy), Tb (2-Tb), Gd (3-Gd), Eu (4-Eu), Sm (5-Sm), Nd (6-Nd), Pr (7-Pr); benz(H) = benzoic acid; mdeaH= N-methyldiethanolamine) and [MnMnLnO(o-tol)(mdea)(NO)(MeOH)] (Ln = Gd (8-Gd), Eu (9-Eu); o-tol(H) = o-toluic acid) have been isolated and structurally, magnetically, and theoretically characterized. dc magnetic susceptibility measurements reveal dominant antiferromagnetic magnetic interactions for each complex, except for 2-Tb and 3-Gd, which reveal an upturn in the χT product at low temperatures. The magnetic interactions between the spin centers in the Gd derivatives, 3-Gd and 8-Gd, which display markedly different χT vs T profiles, were found to be due to the interactions of the Gd-Gd ions which change from ferromagnetic (3-Gd) to antiferromagnetic (8-Gd) due to structural differences.

Lanthanide Triangles Supported by Radical Bridging Ligands.

The first examples of metallacycles containing rare earth ions bridged by radicals are reported. The molecular triangles [Ln(hfac)(bptz)] (Ln = Dy, Y; hfac = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; bptz = 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine) consist of lanthanide ions bridged by bptz radical anion (bptz) ligands. Magnetic susceptibility measurements and CASSCF calculations performed on [Dy(hfac)(bptz)] reveal the presence of antiferromagnetic coupling between the Dy centers and the bptz ligands, with J = -6.

Slow Magnetic Relaxation and Single-Molecule Toroidal Behaviour in a Family of Heptanuclear {Cr Ln } (Ln=Tb, Ho, Er) Complexes.

The synthesis, magnetic properties, and theoretical studies of three heterometallic {Cr Ln } (Ln=Tb, Ho, Er) complexes, each containing a metal topology consisting of two Ln triangles connected via a Cr linker, are reported. The {CrTb } and {CrEr } analogues display slow relaxation of magnetization in a 3000 Oe static magnetic field. Single-crystal measurements reveal opening up of the hysteresis loop for {CrTb } and {CrHo } molecules at low temperatures.

Ferrotoroidic ground state in a heterometallic {CrDy} complex displaying slow magnetic relaxation.

Toroidal quantum states are most promising for building quantum computing and information storage devices, as they are insensitive to homogeneous magnetic fields, but interact with charge and spin currents, allowing this moment to be manipulated purely by electrical means. Coupling molecular toroids into larger toroidal moments via ferrotoroidic interactions can be pivotal not only to enhance ground state toroidicity, but also to develop materials displaying ferrotoroidic ordered phases, which sustain linear magneto-electric coupling and multiferroic behavior. However, engineering ferrotoroidic coupling is known to be a challenging task.

Strong Ferromagnetic Exchange Coupling Mediated by a Bridging Tetrazine Radical in a Dinuclear Nickel Complex.

The radical bridged compound [(Ni(TPMA))-μ-bmtz](BF)·3CHCN (bmtz = 3,6-bis(2'-pyrimidyl)-1,2,4,5-tetrazine, TPMA = tris(2-pyridylmethyl)amine) exhibits strong ferromagnetic exchange between the S = 1 Ni centers and the bridging S = 1/2 bmtz radical with J = 96 ± 5 cm (-2JSS). DFT calculations support the existence of strong ferromagnetic exchange.