Hybrid lanthanide double-deckers based on calixarene and polyoxometalate units

Complementarity of calixarene (H2L) and polyoxometalate ligands results in the first organic-inorganic [M(III)L{Mo5O13(OMe)4(NO)}]2– (M = Y, Gd and Dy) hybrid, directing the formation of a distorted square-antiprismatic MO8 ligand field,...

Rare-earth based tetrapyrrolic sandwiches: chemistry, materials and applications

This review summarises advances in chemistry of tetrapyrrole sandwiches with rare earth elements and highlights the current state of their use in single-molecule magnetism, organic field-effect transistors, conducting materials and nonlinear optics.

New Materials and Effects in Molecular Nanomagnets

Molecular magnets are a relatively new class of purely organic or metallo-organic materials, showing magnetism even without an external magnetic field. This interdisciplinary field between chemistry and physics has been gaining increased interest since the 1990s. While bulk molecular magnets are usually hard to build because of their molecular structures, low-dimensional molecular magnets are often easier to construct, down to dot-like (zero-dimensional) structures, which are investigated by different scanning probe technologies. On these scales, new effects such as superparamagnetic behavior or coherent switching during magnetization reversal can be recognized. Here, we give an overview of the recent advances in molecular nanomagnets, starting with single-molecule magnets (0D), typically based on Mn12, Fe8, or Mn4, going further to single-chain magnets (1D) and finally higher-dimensional molecular nanomagnets. This review does not aim to give a comprehensive overview of all research fields dealing with molecular nanomagnets, but instead aims at pointing out diverse possible materials and effects in order to stimulate new research in this broad field of nanomagnetism.

Macrocycle supported dimetallic lanthanide complexes with slow magnetic relaxation in Dy2 analogues

Six dimetallic lanthanide complexes, [Ln2(L')(acac)4] (1Dy-3Gd) (Ln = Dy (1Dy), Tb (2Tb) and Gd (3Gd)) and [Ln2(L')(tfac)4] (4Dy-6Gd) (Ln = Dy (4Dy), Tb (5Tb) and Gd (6Gd)) (H2L' = 1,9-dichloro-3,7,11,15-tetraaza-1,9(1,3)-dibenzenacyclohexadecaphane-2,10-diene-1,9-diol), have been synthesized by the reaction of lanthanide nitrates with the HL ligand in the presence of acetylacetonate (acac) (or trifluoroacetylacetonate (tfac) and triethylamine (HL = 4-chloro-2,6-bis(-((3-((3-(dimethylamino)propyl)amino)propyl)imino)methyl)phenol). Ln-Assisted modification of the Schiff base HL occurred and led to the formation of a new macrocyclic ligand (H2L'). X-ray crystallographic analysis revealed that the LnIII ions of complexes 1Dy-6Gd are all eight-coordinated in a square antiprismatic geometry with D4d local symmetry. Magnetic measurements of these complexes revealed that 1Dy and 4Dy show single-molecule magnet behaviour with energy barriers of 66.7 and 79.0 K, respectively, under a zero direct magnetic field. The orientations of the magnetic axes and crystal field parameters were obtained from theoretical calculations and an electrostatic model. The magneto-structural correlations of SMMs 1Dy and 4Dy are further discussed in detail.

Modulating magnetic dynamics through tailoring the terminal ligands in Dy2 single-molecule magnets

The alternation of terminal ligands leads to distinct arrangements of anisotropy axes and magnetic interactions in two Dy₂ complexes which present different dynamic magnetic behaviors.

Phthalocyanine-polyoxotungstate lanthanide double deckers

Two archetypal tetradentate ligands with square donor patterns, namely phthalocyanate and monolacunary Keggin-type polyoxotungstate, coordinate to rare earth ions to yield C_s-symmetric heteroleptic double-decker complexes.

Hemiporphyrazine-Involved Sandwich Dysprosium Double-Decker Single-Ion Magnets

Both heteroleptic (phthalocyaninato)(hemiporphyrazinato) and homoleptic bis(hemiporphyrazinato) dysprosium double-decker complexes, Dy[H(Hp)₂] (1) and Dy[H(Pc)(Hp)] (2) (H₂Pc = metal-free phthalocyanine; H₂Hp = metal-free hemiporphyrazine), were designed, synthesized, and structurally characterized. The dysprosium center in both double-deckers are octa-coordinated with a nearly ideal square-antiprismatic coordination geometry, which provides an increased molecular anisotropy for the dysprosium ion and ensures the strengthened magnetic properties of both single-ion magnets (SIMs) in terms of coordination geometry. Magnetic studies reveal that both double-deckers exhibit typical SIM behavior with a spin reversal energy barrier of 80.1 ± 6.3 K for 1 and 57.3 ± 3.8 K for 2 as well as the hysteresis loops emerging at 3 K. In particular, introduction of two Hp ligands with four pyridine nitrogen atoms coordinated with the dysprosium spin center endows Dy[H(Hp)₂] (1) with the thus far highest energy barrier among the sandwich-type dysprosium SIMs with N₄-macrocyclic ligands, revealing the potential applications of sandwich-type lanthanide complexes with Hp ligands in molecular-based information storage.

Syntheses, structures and magnetic properties of macrocyclic Schiff base-supported homodinuclear lanthanide complexes

Five new homodinuclear lanthanide complexes with the general formula [(acac)4Ln2(L)] (Ln3+ = Dy3+ (1), Tb3+ (2), Ho3+ (3), Er3+ (4), and Gd (5)) were synthesized by one-pot [2 + 2] condensation of 2,6-diformyl-4-methylphenol and 1,3-diaminopropane in the presence of various lanthanide acetylacetonates. The eight-coordinate Ln(iii) centre adopts a slightly distorted square antiprism geometry with D4d symmetry. Theoretical analysis and magnetic measurements reveal that the corresponding Dy complex 1 exhibits slow magnetic relaxation behavior, characteristic of a typical SMM with the intramolecular ferromagnetic Dy3+Dy3+ interaction.

A W-Shaped Ga-Dy-Dy-Dy-Ga Cluster: Synthesis, Characterization, and Magnetic Properties

A W-shaped {Ga-Dy-Dy-Dy-Ga} coordination cluster, [Ga₂ Dy₃ (L)₆ (MeO)₂ (MeOH)₃ ]⋅NO₃ ⋅7 MeOH (1) with H₂ L, (E)-2-(2-hydroxy-3-methoxy-benzylideneamino)phenol was synthesized, characterized, and the magnetic properties investigated. The magnetic measurements indicate that the compound shows single-molecule magnet (SMM) behavior under zero dc field. This suggests that the combination of Ga^III ions and Dy^III ions (4 f) is a successful strategy to assemble SMM clusters. The combination of these metal ions also offers prospects in dual functionality therapeutics for medical applications.

Thiacalix[4]arene-supported mononuclear lanthanide compounds: slow magnetic relaxation in dysprosium and erbium analogues

Four mononuclear Ln^III compounds have been synthesized, and the dysprosium and erbium analogues exhibit typical field-induced SMM behavior.

Single molecule magnetic behaviour in lanthanide naphthalenesulfonate complexes

A family of mononuclear lanthanide complexes exhibiting slow magnetic relaxation is reported, providing the first examples of pure 4f sulfonate-based single molecule magnets.

Half-sandwich lanthanide crown ether complexes with the slow relaxation of magnetization and photoluminescence behaviors

Four half-sandwich lanthanide crown ether complexes were successfully synthesized and structurally characterized. Dysprosium complexes show both the slow relaxation of magnetization and photoluminescence behaviors.

Phthalocyanine supported dinuclear LnIIIcomplexes: the solvent-induced change of magnetic properties in dysprosium(iii) analogues

Three phthalocyanine-supported dinuclear Ln^IIIcomplexes were obtained and characterized. The Dy^IIIanalogue exhibits reversible solvent dependent single-molecule magnetic properties between a single relaxation and a dual relaxation process.