Synthesis, structures, and magnetic properties of face-sharing heterodinuclear Ni(II)-Ln(III) (Ln = Eu, Gd, Tb, Dy) complexes

Heterodinuclear [(Ni (II)L)Ln (III)(hfac) 2(EtOH)] (H 3L = 1,1,1-tris[(salicylideneamino)methyl]ethane; Ln = Eu, Gd, Tb, and Dy; hfac = hexafluoroacetylacetonate) complexes ( 1.Ln) were prepared by treating [Ni(H 1.5L)]Cl 0.5 ( 1) with [Ln(hfac) 3(H 2O) 2] and triethylamine in ethanol (1:1:1). All 1.Ln complexes ( 1.Eu, 1.Gd, 1.Tb, and 1.Dy) crystallized in the triclinic space group P1 (No. 2) with Z = 2 with very similar structures. Each complex is a face-sharing dinuclear molecule. The Ni (II) ion is coordinated by the L (3-) ligand in a N 3O 3 coordination sphere, and the three phenolate oxygen atoms coordinate to an Ln (III) ion as bridging atoms. The Ln (III) ion is eight-coordinate, with four oxygen atoms of two hfac (-)'s, three phenolate oxygen atoms of L (3-), and one ethanol oxygen atom coordinated. Temperature-dependent magnetic susceptibility and field-dependent magnetization measurements showed a ferromagnetic interaction between Ni (II) and Gd (III) in 1.Gd. The Ni (II)-Ln (III) magnetic interactions in 1.Eu, 1.Tb, and 1.Dy were evaluated by comparing their magnetic susceptibilities with those of the isostructural Zn (II)-Ln (III) complexes, [(ZnL)Ln(hfac) 2(EtOH)] ( 2.Ln) containing a diamagnetic Zn (II) ion. A ferromagnetic interaction was indicated in 1.Tb and 1.Dy, while the interaction between Ni (II) and Eu (III) was negligible in 1.Eu. The magnetic behaviors of 1.Dy and 2.Dy were analyzed theoretically to give insight into the sublevel structures of the Dy (III) ion and its coupling with Ni (II). Frequency dependence in the ac susceptibility signals was observed in 1.Dy.     

3d4f Heterobimetallic Dinuclear and Tetranuclear Complexes Involving Tetrathiafulvalene as Ligands: X-ray Structures and Magnetic and Photophysical Investigations

Six new 3d4f heterobimetallic dinuclear complexes, [(L(1))MLn(hfac)(3)] [M = Cu(II), Ni(II); Ln = Y(III), Er(III), Yb(III); L(1) = 4,5-bis(propylthio)tetrathiafulvalene-N,N'-phenylenebis(salicylideneimine) and hfac(-) = 1,1,1,5,5,5-hexafluoroacetylacetonate], and one tetranuclear complex, [(L(2))Cu(OH)Er(hfac)(3)](2) (where L(2) = 4,5-bis(propylthio)tetrathiafulvalene-N,N'-phenyleneaminosalicylideneimine), have been synthesized. All of the X-ray structures of the coordination complexes have been resolved from single-crystal diffraction. A quantitative magnetic approach has allowed one to determine the Cu-Ln ferromagnetic interaction for Gd(III) (1.29 cm(-1)) and Tb(III) (0.40 cm(-1)) and the antiferromagnetic interaction for Dy(III) (-0.46 cm(-1)) and Yb(III) (-2.25 cm(-1)), while in the case of Er(III), the magnetic interactions are negligible. The UV-visible absorption properties have been studied in a chloroform solution and rationalized by DFT and TD-DFT calculations. Upon oxidation, intramolecular SOMO → LUMO (20800 cm(-1)) and SOMO-n → SOMO (11350 cm(-1)) charge transfers appear, while the HOMO → LUMO charge transfers (20750 cm(-1)) disappear. The reversibility of the oxidation has been confirmed by electrochemistry and absorption properties upon the addition of a reducing agent. Irradiation at the HOMO → LUMO charge-transfer energy of the dinuclear complex [(L(1))NiY(hfac)(3)] induces a ligand-centered fluorescence at 14450 cm(-1).     

Family of carboxylate- and nitrate-diphenoxo triply bridged dinuclear Ni(II)Ln(III) complexes (Ln = Eu, Gd, Tb, Ho, Er, Y): synthesis, experimental and theoretical magneto-structural studies, and single-molecule magnet behavior

Seven acetate-diphenoxo triply bridged M(II)-Ln(III) complexes (M(II) = Ni(II) and Ln(III) = Gd, Tb, Ho, Er, and Y; M(II) = Zn(II) and Ln(III) = Ho(III) and Er(III)) of formula [M(μ-L)(μ-OAc)Ln(NO(3))(2)], one nitrate-diphenoxo triply bridged Ni(II)-Tb(III) complex, [Ni(μ-L)(μ-NO(3))Tb(NO(3))(2)]·2CH(3)OH, and two diphenoxo doubly bridged Ni(II)-Ln(III) complexes (Ln(III) = Eu, Gd) of formula [Ni(H(2)O)(μ-L)Ln(NO(3))(3)]·2CH(3)OH have been prepared in one pot reaction from the compartmental ligand N,N',N"-trimethyl-N,N"-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine (H(2)L). Moreover, Ni(II)-Ln(III) complexes bearing benzoate or 9-anthracenecarboxylate bridging groups of formula [Ni(μ-L)(μ-BzO)Dy(NO(3))(2)] and [Ni(μ-L)(μ-9-An)Dy(9-An)(NO(3))(2)]·3CH(3)CN have also been successfully synthesized. In acetate-diphenoxo triply bridged complexes, the acetate bridging group forces the structure to be folded with an average hinge angle in the M(μ-O(2))Ln bridging fragment of ~22°, whereas nitrate-diphenoxo doubly bridged complexes and diphenoxo-doubly bridged complexes exhibit more planar structures with hinge angles of ~13° and ~2°, respectively. All Ni(II)-Ln(III) complexes exhibit ferromagnetic interactions between Ni(II) and Ln(III) ions and, in the case of the Gd(III) complexes, the J(NiGd) coupling increases weakly but significantly with the planarity of the M-(O)(2)-Gd bridging fragment and with the increase of the Ni-O-Gd angle. Density functional theory (DFT) theoretical calculations on the Ni(II)Gd(III) complexes and model compounds support these magneto-structural correlations as well as the experimental J(NiGd) values, which were found to be ~1.38 and ~2.1 cm(-1) for the folded [Ni(μ-L)(μ-OAc)Gd(NO(3))(2)] and planar [Ni(H(2)O)(μ-L)Gd(NO(3))(3)]·2CH(3)OH complexes, respectively. The Ni(II)Dy(III) complexes exhibit slow relaxation of the magnetization with Δ/k(B) energy barriers under 1000 Oe applied magnetic fields of 9.2 and 10.1 K for [Ni(μ-L)(μ-BzO)Dy(NO(3))(2)] and [Ni(μ-L)(μ-9-An)Dy(9-An)(NO(3))(2)]·3CH(3)CN, respectively.     

Heterometallic cubanes: syntheses, structures, and magnetic properties of lanthanide(III)-nickel(II) architectures

Reactions of lanthanide(III) perchlorate (Ln = Dy, Tb, and Gd), nickel(II) acetate, and ditopic ligand 2-(benzothiazol-2-ylhydrazonomethyl)-6-methoxyphenol (H(2)L) in a mixture of methanol and acetone in the presence of NaOH resulted in the successful assembly of novel Ln(2)Ni(2) heterometallic clusters representing a new heterometallic 3d-4f motif. Single-crystal X-ray diffraction reveals that all compounds are isostructural, with the central core composed of distorted [Ln(2)Ni(2)O(4)] cubanes of the general formula [Ln(2)Ni(2)(μ(3)-OH)(2)(OH)(OAc)(4)(HL)(2)(MeOH)(3)](ClO(4))·3MeOH [Ln = Dy (1), Tb (2), and Gd (3)]. The magnetic properties of all compounds have been investigated. Magnetic analysis on compound 3 indicates ferromagnetic Gd···Ni exchange interactions competing with antiferromagnetic Ni···Ni interactions. Compound 1 displays slow relaxation of magnetization, which is largely attributed to the presence of the anisotropic Dy(III) ions, and thus represents a new discrete [Dy(2)Ni(2)] heterometallic cubane exhibiting probable single-molecule magnetic behavior.     

Synthesis, structure and magnetic properties of a novel family of heterometallic nonanuclear Na(I)2Mn(III)6Ln(III) (Ln = Eu, Gd, Tb, Dy) complexes

The structures and magnetic properties of four isomorphous nonanuclear heterometallic complexes [Na(2){Mn(3)(III)(μ(3)-O(2-))}(2)Ln(III)(hmmp)(6)(O(2)CPh)(4)(N(3))(2)]OH·0.5 CH(3)CN·1.5H(2)O are reported, where Ln(III) = Eu (1), Gd (2), Tb (3) and Dy (4), H(2)hmmp = 2-[(2-hydroxyethylimino)methyl]-6-methoxyphenol. Complexes 1-4 were prepared by the reactions of hmmpH(2) with a manganese salt and the respective lanthanide salt together with NaO(2)CPh and NaN(3). Single-crystal X-ray diffraction analyses reveal that the six Mn(III) and one Ln(III) metal topology in the aggregate can be described as a bitetrahedron. The two peripheral [Mn(III)(3)(μ(3)-O(2-))](7+) triangles are each bonded to a central Ln(III) ion with rare distorted octahedral geometry. The magnetic properties of all the complexes were investigated using variable temperature magnetic susceptibility and both antiferromagnetic and ferromagnetic interactions exist in the [Mn(III)(3)(μ(3)-O(2-))](7+) triangle. Weak ferromagnetic exchange between the Ln(III) and Mn(III) ions has been established for the corresponding Gd derivative. The Gd, Tb and Dy complexes show no evidence of slow relaxation behaviour above 2.0 K.     

Structure, magnetism and theory of a family of nonanuclear Cu(II)5Ln(III)4-triethanolamine clusters displaying single-molecule magnet behaviour

Synthesis, crystal structures and magnetic studies are reported for four new heterometallic Cu(II)-Ln(III) clusters. The reaction of Cu(NO(3))(2)·3H(2)O with triethanolamine (teaH(3)), pivalic acid, triethylamine and Ln(NO(3))(3)·6H(2)O (Ln=Gd, Tb, Dy and Ho) results in the formation of four isostructural nonanuclear complexes of general formula [Cu(II)(5)Ln(III)(4)O(2)(teaH)(4){O(2)CC(CH(3))(3)}(2)(NO(3))(4)(OMe)(4)]·2MeOH·2Et(2)O [Ln=Gd (1), Tb (2), Dy (3) and Ho (4)]. The metal core of each cluster is made up of four face- and vertex-sharing tetrahedral units. Solid-state DC magnetic susceptibility studies reveal competing anti- and ferromagnetic interactions within each cluster leading to large-spin ground states for 1-4. Solid-state AC magnetic susceptibility studies show frequency-dependent out-of-phase (χ'(M)) signals for 2-4 below 4 K, suggestive of single-molecule magnet behaviour. Ab initio calculations on one of the anisotropic examples (3) provided a rare set of J values for Dy-Cu and Cu-Cu exchange interactions (Dy-Dy zero), some ferro- and some antiferromagnetic in character, that explain its magnetic behaviour.     

Heterometallic cubane-like {M2Ln2} (M = Ni, Zn; Ln =, Gd, Dy) and {Ni2Y2} aggregates. Synthesis, structures and magnetic properties

The syntheses, structural determinations and magnetic studies of tetranuclear M(II)Ln(III) complexes (M = Ni, Zn; Ln = Y, Gd, Dy) involving an in situ compartmentalized schiff base ligand HL derived from the condensation of o-vanillin and 2-hydrazinopyridine as main ligand are described. Single-crystal X-ray diffraction reveals that all complexes are closely isostructural, with the central core composed of distorted {M(2)Ln(2)O(4)} cubes of the formulas [Ni(2)Ln(2)(μ(3)-OH)(2)(L)(2)(OAc)(4)(H(2)O)(3.5)](ClO(4))(2)·3H(2)O (Ln = Y 1 and Gd 2), [Ni(2)Dy(2)(μ(3)-OH)(2)(L)(2)(OAc)(5)(EtOH)(H(2)O)(1.5)](ClO(4))·EtOH·H(2)O (3) and [Zn(2)Ln(2)(μ(3)-OH)(2)(L)(2)(OAc)(5)(EtOH)(H(2)O)](ClO(4))·2EtOH·1.5H(2)O (Gd 4 and Dy 5). The Ln(III) ions are linked by two hydroxo bridges and each M(II) ion is also involved in a double phenoxo-hydroxo bridge with the two Ln(III) ions, so that each hydroxo group is triply linked to the two Ln(III) and one M(II) ions. The magnetic properties of all complexes have been investigated. Ni(2)Y(2) (1) has a ferromagnetic Ni(II)Ni(II) interaction. A weak ferromagnetic Ni(II)Ln(III) interaction is observed in the Ni(2)Ln(2) complexes (Ln = Gd 2, Dy 3), along with a weak antiferromagnetic Ln(III)Ln(III) interaction, a D zero-field splitting term for the nickel ion and a ferromagnetic Ni(II)Ni(II) interaction. The isomorphous Zn(2)Ln(2) (Ln = Gd 4, Dy 5) does confirm the presence of a weak antiferromagnetic Ln(III)Ln(III) interaction. The Ni(2)Dy(2) complex (3) does not behave as a SMM, which could result from a subtractive combination of the Dy and Ni anisotropies and an increased transverse anisotropy, leading to large tunnel splittings and quantum tunneling of magnetization. On the other hand, Zn(2)Dy(2) (5) exhibits a possible SMM behavior, where its slow relaxation of magnetization is probably attributed to the presence of the anisotropic Dy(III) ions.     

Single-molecule magnet behaviour in a tetrathiafulvalene-based electroactive antiferromagnetically coupled dinuclear dysprosium(III) complex

The reactions between the [Ln(tta)(3)]·2H(2)O precursors (tta(-)=2-thenoyltrifluoroacetonate anion) and the tetrathiafulvalene-3-pyridine-N-oxide ligands (L(1)) lead to dinuclear complexes of formula [{Ln(tta)(3)(L(1))}(2)]·xCH(2)Cl(2) (x=0.5 for Ln=Dy(III) (1) and x=0 for Ln=Gd(III) (2)). The crystal structure reveals that two {Ln(tta)(3)} moieties are bridged by two donors through the nitroxide groups. The Dy(III) centre adopts a distorted square antiprismatic oxygenated polyhedron structure. The antiferromagnetic nature of the exchange interaction between the two Dy(III) ions has been determined by two methods: 1) an empirical method using the [Dy(hfac)(3)(L(2))(2)] mononuclear complex as a model (3) (hfac(-)=1,1,1,5,5,5-hexafluoroacetylacetonate anion, L(2)=tetrathiafulvaleneamido-2-pyridine-N-oxide ligand), and 2) assuming an Ising model for the Dy(III) ion giving an exchange energy of -2.30 cm(-1), g=19.2 in the temperature range of 2-10 K. The antiferromagnetic interactions have been confirmed by a quantitative determination of J for the isotropic Gd(III) derivative (J=-0.031 cm(-1), g=2.003). Compound 1 displays a slow magnetisation relaxation without applied external magnetic fields. Alternating current susceptibility shows a thermally activated behaviour with pre-exponential factors of 5.48(4)×10(-7) s and an energy barrier of 87(1) K. The application of an external field of 1.6 kOe compensates the antiferromagnetic interactions and opens a new quantum tunnelling path.     

Heptanuclear heterometallic [Cu6Ln] clusters: trapping lanthanides into copper cages with artificial amino acids

Employment of the artificial amino acid 2-amino-isobutyric acid, aibH, in Cu(II) and Cu(II)/Ln(III) chemistry led to the isolation and characterization of 12 new heterometallic heptanuclear [Cu(6)Ln(aib)(6)(OH)(3)(OAc)(3)(NO(3))(3)] complexes consisting of trivalent lanthanide centers within a hexanuclear copper trigonal prism (aibH = 2-amino-butyric acid; Ln = Ce (1), Pr (2), Nd (3), Sm (4), Eu (5), Gd (6), Tb (7), Dy (8), Ho (9), Er (10), Tm (11), and Yb (12)). Direct curent magnetic susceptibility studies have been carried out in the 5-300 K range for all complexes, revealing the different nature of the magnetic interactions between the 3d-4f metallic pairs: dominant antiferromagnetic interactions for the majority of the pairs and dominant ferromagnetic interactions for when the lanthanide center is Gd(III) and Dy(III). Furthermore, alternating current magnetic susceptibility studies reveal the possibility of single-molecule magnetism behavior for complexes 7 and 8. Finally, complexes 2, 5-8, 10, and 12 were analyzed using positive ion electrospray mass spectrometry (ES-MS), establishing the structural integrity of the heterometallic heptanuclear cage structure in acetonitrile.     

Synthesis, structures, and magnetic properties of heteronuclear Cu(II)-Ln(III) (Ln = La, Gd, or Tb) complexes

Facile one-pot reactions led to the formations of dinuclear [CuLn(hmp)2(NO3)3(H2O)2] (Ln = Tb (1.Tb), Gd (1.Gd), or La (1.La)), and trinuclear [Cu2Ln(mmi)4(NO3)(H2O)2](ClO4)(NO3).2H2O (Ln = Tb (2.Tb) or Gd (2.Gd)) and [Cu2La(mmi)4(NO3)2(H2O)](ClO4).2H2O (2.La) with polydentate ligands 2-(hydroxymethyl)-pyridine and 2-hydroxymethyl-1-methyl-imidazole. In these complexes, each pair of Cu(II) and Ln(III) ions is linked by a double mu-alkoxo bridge. The temperature dependences of the magnetic susceptibilities of 1 and 2 were investigated in the range of 2-300 K. The dinuclear and trinuclear Cu-Gd complexes exhibit ferromagnetic interaction. The coupling constant J values in the heterodinuclear Cu-Gd complexes are correlated to values of the dihedral angles alpha between the two O-Cu-O and O-Gd-O fragments of the bridging CuO2Gd networks, with the largest J value associated with the smallest alpha value. The occurrence of a ferromagnetic interaction between Cu(II) and Gd(III) ions of the trinuclear entity is supported by the field dependence of the magnetization. The field dependence of the magnetization at 2 K of 1.Gd and 2.Gd confirms the nature of the ground state and of the Cu(II)-Gd(III) interaction, while alternating current susceptibility measurements demonstrates out-of-phase ac susceptibility signals of 1.Tb, which is the molecule-based magnetic material of the smallest nuclearity which exhibits frequency-dependent behavior within the 3d-4f mixed-metal systems.     

Fluoride-bridged {Ln(2)Cr(2)} polynuclear complexes from semi-labile mer-[CrF(3)(py)(3)] and [Ln(hfac)(3)(H(2)O)(2)

The trifluorido complex mer-[CrF(3)(py)(3)] (py = pyridine) reacts with 1 equiv. of [Ln(hfac)(3)(H(2)O)(2)] and depending on the solvent forms the tetranuclear clusters [Cr(2)Ln(2)(μ-F)(4)(μ-OH)(2)(py)(4)(hfac)(6)], 1Ln, and [Cr(2)Ln(2)(μ-F)(4)F(2)(py)(6)(hfac)(6)], 2Ln, in acetonitrile and 1,2-dichloroethane, respectively (Ln = Y, Gd, Tb, Dy, Ho, and Er; hfacH = 1,1,1,5,5,5-hexafluoroacetylacetone). Reaction with [Dy(hfac)(3)(H(2)O)(2)] in dichloromethane produces the dinuclear cluster [CrDy(μ-F)F(OH(2))(py)(3)(hfac)(4)], 3Dy. All the clusters feature fluoride bridges between the chromium(iii) and lanthanide(iii) centres. Fits of susceptibility data for 1Gd and 2Gd reveal the fluoride-mediated chromium(iii)-lanthanide(iii) exchange interactions to be 0.43(5) cm(-1) and 0.57(7) cm(-1), respectively (in the convention). Heat capacity measurements on 2Gd reveal a moderate magneto-caloric effect (MCE) reaching -ΔS(m)(T) = 11.4 J kg(-1) K(-1) for ΔB(0) = 9 T → 0 T at T = 4.1 K. Out-of-phase alternating-current susceptibility (χ') signals are observed for 1Dy, 2Dy and 2Tb, demonstrating slow relaxation of the magnetization.     

Ferromagnetic NiII-GdIII interactions in complexes with NiGd, NiGdNi, and NiGdGdNi cores supported by tripodal ligands

Dinuclear [(NiL)Gd(hfac)(2)(EtOH)](H(3)L = 1,1,1-tris(N-salicylideneaminomethyl)ethane, Hhfac = hexafluoroacetylacetone), trinuclear [(NiL)(2)Gd(NO(3))], and tetranuclear [(NiL)Gd(CH(3)CO(2))(2)(MeOH)](2) complexes, were prepared by treating [Ni(HL)] with [Gd(hfac)(3)(H(2)O)(2)], Gd(NO(3))(3).6H(2)O, and Gd(CH(3)CO(2))(3).4H(2)O, respectively, in the presence of Et(3)N. All the complexes show that ferromagnetic interactions occur between the Ni(II) and Gd(III) ions.     

Two new lanthanide–radical complexes: synthesis,structure, and magnetic properties

Two new lanthanide–radical complexes, [Tb(hfac)₃(EtVNIT)₂] (1) and [Dy(hfac)₃(EtVNIT)₂] (2) (EtVNIT?=?2-(4′-ethoxy-3′-methoxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, hfac?=?1,1,1,5,5,5-hexafluoroacetylacetonate), were synthesized; both display radical–Ln(III)–radical (Ln=Tb (1), Dy (2)) tri-spin structures. Magnetic studies reveal that interactions between the lanthanide ions and radicals are ferromagnetic.     

Family of double-cubane Mn4Ln2 (Ln = Gd, Tb, Dy, Ho) and Mn4Y2 complexes: a new Mn4Tb2 single-molecule magnet

The synthesis and characterization of a family of Mn(2)(III)Mn(2)(II)Ln(III)(2) complexes (Ln = Gd (1), Tb (2), Dy (3), and Ho (4)) of formula [Mn(4)Ln(2)O(2)(O(2)CBu(t))(6)(edteH(2))(2)(NO(3))(2)] are reported, where edteH(4) is N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine. The analogous Mn(4)Y(2) (5) complex has also been prepared. They were obtained from reaction of Ln(NO(3))(3) or Y(NO(3))(3) with Mn(O(2)CBu(t))(2), edteH(4), and NEt(3) in a 2:3:1:2 molar ratio. The crystal structures of representative 1 and 2 were obtained, and their core consists of a face-fused double-cubane [Mn(4)Ln(2)(μ(4)-O(2-))(2)(μ(3)-OR)(4)] unit. Such double-cubane units are extremely rare in 3d metal chemistry and unprecedented in 3d-4f chemistry. Variable-temperature, solid-state dc and ac magnetic susceptibility studies on 1-5 were carried out. Fitting of dc χ(M)T vs T data for 5 gave J(bb) (Mn(III)···Mn(III)) = -32.6(9) cm(-1), J(wb) (Mn(II)···Mn(III)) = +0.5(2) cm(-1), and g = 1.96(1), indicating a |n, 0, n> (n = 0-5) 6-fold-degenerate ground state. The data for 1 indicate an S = 12 ground state, confirmed by fitting of magnetization data, which gave S = 12, D = 0.00(1) cm(-1), and g = 1.93(1) (D is the axial zero-field splitting parameter). This ground state identifies the Mn(II)···Gd(III) interactions to be ferromagnetic. The ac susceptibility data independently confirmed the conclusions about 1 and 5 and revealed that 2 displays slow relaxation of the magnetization vector for the Mn(4)Tb(2) analogue 2. The latter was confirmed as a single-molecule magnet by observation of hysteresis below 0.9 K in magnetization vs dc field scans on a single crystal of 2·MeCN on a micro-SQUID apparatus. The hysteresis loops also displayed well-resolved quantum tunneling of magnetization steps, only the second 3d-4f SMM to do so.     

Preparation, crystal structures, and magnetic features for a series of dinuclear [Ni(II)Ln(III)] Schiff-base complexes: evidence for slow relaxation of the magnetization for the Dy(III) derivative

A series of dinuclear [Ni(II)Ln(III)] Schiff-base complexes (using a Schiff-base dicompartmental ligand derived from o-vanillin [H(2)valpn = 1,3-propanediylbis(2-iminomethylene-6-methoxy-phenol)]) with Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and a hydroxo-bridged tetranuclear [Ni(II)Yb(III)] are reported. The crystal structures have been solved for 10 dinuclear complexes revealing four arrangements for the dinuclear units, which are modulated by the coordinated solvent molecules and the nitrato-anion interactions. The magnetic behaviors have been investigated, and the nature of the Ni(II)-Ln(III) exchange interaction has been emphasized by comparison with the behavior of the related [Zn(II)Ln(III)] derivatives. This allowed for establishing that the interaction within these compounds is antiferromagnetic with the 4f ions of the beginning of the Ln series and turns ferromagnetic from Gd(III) toward the end of the series. AC susceptibility investigations clearly show the occurrence of slow relaxation processes of the magnetization close to 2 K for the dinuclear [Ni(II)Dy(III)] complex.     

Structural and Magnetic Properties of 2p‐3d‐4f Hetero‐Tri‐Spin Chains Comprising [{Cu(hfac)2‐Radical}2] Dimers and Ln(hfac)3 (hfac=hexafluoroacetylacetonate)

A new family of 2p‐3d‐4f hetero‐tri‐spin complexes [Ln(hfac)₃{Cu(hfac)₂(NIT‐3 PyPh)}₂] (Ln=Gd ( 1 ), Tb ( 2 ), Dy ( 3 ), Ho ( 4 ); NIT‐3 PyPh=2‐[4‐(3‐pyridinylmethoxy)phenyl]‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide; hfac=hexafluoroacetylacetonate) have been synthesized. Four complexes possess a 1D chain structure in which two radical ligands join two Cu(hfac)₂ molecules to form a [{Cu(hfac)₂‐rad)}₂] dimer cycle and the dimer rings are linked by Ln(hfac)₃ units. Magnetic studies show that ferromagnetic exchange couplings exist between the coordinated NO groups of radical ligands and metal ions. Field‐induced slow relaxation of the magnetization was observed in the Tb and Dy compounds.     

Synthesis,Crystal Structure,and Magnetic Property of New Trispin Ln(III)‐Nitronyl Nitroxide Complexes

Four Ln(III) complexes based on a new nitronyl nitroxide radical have been synthesized and structurally characterized: {Ln(hfac)₃[NITPh(MeO)₂]₂} (Ln = Eu( 1 ), Gd( 2 ), Tb( 3 ), Dy( 4 ); NITPh(MeO)₂ = 2‐(3′,4′‐dimethoxyphenyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide; hfac = hexafluoroacetylacetonate). The single‐crystal X‐ray diffraction analysis shows that these complexes have similar mononuclear trispin structures, in which central Ln(III) ion is eight‐coordinated by two O‐atoms from two nitroxide groups and six O‐atoms from three hfac anions. The variable temperature magnetic susceptibility study reveals that there exist ferromagnetic interactions between Gd(III) and the radicals, and antiferromagnetic interactions between two radicals (J_Gd‐Rad = 3.40 cm^?1, J_Rad‐Rad = ?9.99 cm^?1) in complex 2 . Meanwhile, antiferromagnetic interactions are estimated between Eu(III) (or Dy(III)) and radicals in complexes 1 and 4 , and ferromagnetic interaction between Tb(III) and radicals in complex 3 , respectively.     

Ligand field-tuned single-molecule magnet behaviour of 2p-4f complexes

Three new 2p-4f complexes of [Ln(acac)(3)(NIT-2Py)]·0.5NIT-2Py [Ln(III) = Gd(1), Dy(2)] and [Dy(tfa)(3)(NIT-2Py)]·0.5C(7)H(16) (3) (NIT-2Py = 2-(2'-pyridyl)- 4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; acac = acetylacetonate and tfa = trifluoroacetylacetonate) have been synthesized, and structurally and magnetically characterized. The X-ray structural analysis exhibits that the three complexes show similar mononuclear structures, in which NIT-2Py radical chelates the Ln(III) ion through the oxygen atom of the NO group and the nitrogen atom from the pyridine ring. The static magnetic measurements on the three complexes exhibit ferromagnetic coupling between the lanthanide ion and the radical. Compared to the silence of the out-of-phase ac susceptibility of complex 3, the magnetic relaxation behavior of complex 2 is observed, suggesting single-molecule magnet behavior. The different magnetic relaxation behaviours of 2 and 3 are due to their slightly different crystal structure around the Dy(III) ions. It was demonstrated that the spin dynamic can be modified by the careful adjustment of the ligand field around the metal center.     

Syntheses and crystal structures of anhydrous Ln(hfac)3(monoglyme). Ln = La, Ce, Pr, Sm, Eu, Gd, Tb, Dy, Er, Tm

The crystal structures of a broad series of anhydrous Ln(hfac)(3)(monoglyme) complexes, prepared in moderate to high yield, are presented: hfac = 1,1,1,5,5,5-hexafluoroacetylacetonato-; Ln = La, Ce, Pr, Sm, Eu, Gd, Tb, Dy, Er, Tm. This study contradicts the general assumption that monoglyme is too small a polyether to act as a partitioning agent displacing coordinated water on the larger lanthanide(III) ions. The structures of an intermediate La(hfac)(3)(monoglyme)(2) species and the hydrated Ce(hfac)(3)(monoglyme)(H(2)O) species are also included. The crystallographic evidence presented herein is supplemented by other characterization techniques (melting point, IR, etc.) and trends are delineated.     

Three-dimensional open-frameworks based on Ln(III) ions and open-/closed-shell PTM ligands: synthesis, structure, luminescence, and magnetic properties

A series of isostructural open-framework coordination polymers formulated as [Ln(dmf)(3)(ptmtc)] (Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5); PTMTC = polychlorotriphenylmethyl tricarboxylate) and [Ln(dmf)(2)H(2)O(αH-ptmtc)] (Ln = Sm (1'), Eu (2'), Gd (3'), Tb (4'), Dy (5')) have been obtained by treating Ln(III) ions with PTMTC ligands with a radical (PTMTC(3-)) or a closed-shell character (αH-PTMTC(3-)). X-ray diffraction analyses reveal that these coordination polymers possess 3D architectures that combine large channels and fairly rare lattice complex T connectivity. In addition, these compounds show selective framework dynamic sorption properties. For both classes of ligands, the ability to act as an antenna in Ln sensitization processes has been investigated. No luminescence was observed for compounds 1-5, and 3' because of the PTMTC(3-) ligand and/or Gd(III) ion characteristics. Conversely, photoluminescence measurements show that 1', 2', 4', and 5' emit dark orange, red, green, and dark cyan metal-centered luminescence. The magnetic properties of all of these compounds have been investigated. The nature of the {Ln-radical} exchange interaction in these compounds has been assessed by comparing the behavior of the radical-based coordination polymers 1-5 with those of the compounds with the diamagnetic ligand set. While antiferromagnetic {Sm-radical} interactions are found in 1, ferromagnetic {Ln-radical} interactions propagate in the 3D architectures of 3, 4, and 5 (Ln = Gd, Tb, and Dy, respectively). This procedure also provided access to information on the {Ln-Ln} exchange existing in these magnetic systems.