Syntheses,Structures, Photoluminescence,and Magnetism of a Series of Discrete Lanthanide Complexes based on 2,5‐Dichlorobenzoate and 1,10‐Phenanthroline

The syntheses and crystal structures of eight lanthanide complexes with formula [Ln(2,5‐DCB)_x(phen)_y] are reported, which are characterized via single‐crystal, powder X‐ray diffraction, elemental analysis, IR spectroscopy, thermogravimetric analysis, photoluminescence measurement, and DC/AC magnetic measurement. These eight complexes are isostructural, and possess a discrete dinuclear structure. The adjacent dinuclear molecules are linked by the hydrogen bonding interactions into a one‐dimensional (1D) supramolecular chain. The neighboring 1D chains are further extended into a two‐dimensional (2D) supramolecular layer by the π–π stacking interactions. The photoluminescent properties of complexes 1 (Nd^III), 2 (Sm^III), 3 (Eu^III), 5 (Tb^III), 6 (Dy^III), and 8 (Yb^III) were investigated. Magnetic investigations also reveal the presence of ferromagnetic interactions in complexes 4 (Gd^III), 6 (Dy^III), and 7 (Er^III). Additionally, complex 6 (Dy^III) demonstrates field‐induced slow magnetic relaxation behavior.     

Three Novel Rare-earth Complexes with Nitronyl Nitroxide Radical [RE(hfac)3 (NITPhOCH3)2] [RE = GdIII, YIII and ErIII]: Syntheses, Crystal Structures and Magnetic Properties

Three novel isomorphous complexes of formula [RE(hfac)₃(NITPhOCH₃)₂], where RE = Gd^III, Y^III and Er^III; hfac = hexafluoroacetylacetonate; NITPhOCH₃ = 4′-methoxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, were synthesized, structurally and magnetically characterized. The crystal structure consists of isolated molecules where the nitronyl nitroxide radicals act as monodentate ligands towards RE(III) through the oxygen atom of the N–O group. The magnetic properties of the complexes were studied by measuring their magnetic susceptibilities at various temperatures in the 5–300 K range. The analyses of these magnetic measurements showed that the spin coupling between the gadolinium ion and the radicals in the Gd^III complex is ferromagnetic, while antiferromagnetic superexchange interaction exists between the two radicals in the Gd^III and Y^III complexes. The Er^III complex reveals an overall intramolecular antiferromagnetic exchange interaction.     

Holmium(iii) molecular nanomagnets for optical thermometry exploring the luminescence re-absorption effect

Coordination complexes of lanthanide(3+) ions can combine Single-Molecule Magnetism (SMM) with thermally modulated luminescence applicable in optical thermometry. We report an innovative approach towards high performance SMM-based optical thermometers which explores tunable anisotropy and the luminescence re-absorption effect of Ho^III complexes. Our concept is shown in dinuclear cyanido-bridged molecules, {[Ho^III(4-pyridone)₄(H₂O)₂][M^III(CN)₆]}·nH₂O (M = Co, 1; Rh, 2; Ir, 3) and their magnetically diluted analogues, {[Ho^III_xY^III_1–x(4-pyridone)₄(H₂O)₂][M^III(CN)₆]}·nH₂O (M = Co, x = 0.11, 1@Y; Rh, x = 0.12, 2@Y; Ir, x = 0.10, 3@Y). They are built of pentagonal bipyramidal Ho^III complexes revealing the zero-dc-field SMM effect. Experimental studies and the ab initio calculations indicate an Orbach magnetic relaxation with energy barriers varying from 89.8 to 86.7 and 78.7 cm⁻¹ K for 1, 2, and 3, respectively. 1–3 also differ in the strength of quantum tunnelling of magnetization which is suppressed by hyperfine interactions, and, further, by the magnetic dilution. The Y^III-based dilution governs the optical properties as 1–3 exhibit poor emission due to the dominant re-absorption from Ho^III while 1@Y–3@Y show room-temperature blue emission of 4-pyridone. Within ligand emission bands, the sharp re-absorption lines of the Ho^III electronic transitions were observed. Their strong thermal variation was used in achieving highly sensitive ratiometric optical thermometers whose good performance ranges, lying between 25 and 205 K, are adjustable by using hexacyanidometallates. This work shows that Ho^III complexes are great prerequisites for advanced opto-magnetic systems linking slow magnetic relaxation with unique optical thermometry exploiting a luminescence re-absorption phenomenon.

Ho^III complexes bearing organic luminophores and inorganic metalloligands are an effective tool for achieving the unique conjunction of single-molecule magnetism and thermometric luminescence re-absorption phenomenon.     

Exchange coupling and magnetic anisotropy in a family of bipyrimidyl radical‐bridged dilanthanide complexes: Density functional theory and ab initio calculations

The origin of the magnetic anisotropy energy barriers in a series of bpym^? (bpym = 2,2′‐bipyrimidine) radical‐bridged dilanthanide complexes [(Cp*₂Ln)₂(μ‐bpym)]⁺ [Cp* = pentamethylcyclopentadienyl; Ln = Gd^III ( 1 ), Tb^III ( 2 ), Dy^III ( 3 ), Ho^III ( 4 ), Er^III ( 5 )] has been explored using density functional theory (DFT) and ab initio methods. DFT calculations show that the exchange coupling between the two lanthanide ions for each complex is very weak, but the antiferromagnetic Ln‐bpym^? couplings are strong. Ab initio calculations show that the effective energy barrier of 2 or 3 mainly comes from the contribution of a single Tb^III or Dy^III fragment, which is only about one third of a single Ln energy barrier. For 4 or 5 , however, both of the two Ho^III or Er^III fragments contribute to the total energy barrier. Thus, it is insufficient to only increase the magnetic anisotropy energy barrier of a single Ln ion, while enhancing the Ln‐bpym^? couplings is also very important. © 2014 Wiley Periodicals, Inc.     

Dinuclear Lanthanide(III) Complexes from the Use of Methyl 2-Pyridyl Ketoxime: Synthetic,Structural, and Physical Studies

The first use of methyl 2-pyridyl ketoxime (mepaoH) in homometallic lanthanide(III) [Ln(III)] chemistry is described. The 1:2 reactions of Ln(NO₃)₃·nH₂O (Ln = Nd, Eu, Gd, Tb, Dy; n = 5, 6) and mepaoH in MeCN have provided access to complexes [Ln₂(O₂CMe)₄(NO₃)₂(mepaoH)₂] (Ln = Nd, 1; Ln = Eu, 2; Ln = Gd, 3; Ln = Tb, 4; Ln = Dy, 5); the acetato ligands derive from the Ln^III—mediated hydrolysis of MeCN. The 1:1 and 1:2 reactions between Dy(O₂CMe)₃·4H₂O and mepaoH in MeOH/MeCN led to the all-acetato complex [Dy₂(O₂CMe)₆(mepaoH)₂] (6). Treatment of 6 with one equivalent of HNO₃ gave 5. The structures of 1, 5, and 6 were solved by single-crystal X-ray crystallography. Elemental analyses and IR spectroscopy provide strong evidence that 2–4 display similar structural characteristics with 1 and 5. The structures of 1–5 consist of dinuclear molecules in which the two Ln^III centers are bridged by two bidentate bridging (η¹:η¹:μ₂) and two chelating-bridging (η¹:η²:μ₂) acetate groups. The Ln^III atoms are each chelated by a N,N’-bidentate mepaoH ligand and a near-symmetrical bidentate nitrato group. The molecular structure of 6 is similar to that of 5, the main difference being the presence of two chelating acetato groups in the former instead of the two chelating nitrato groups in the latter. The geometry of the 9-coordinate Ln^III centers in 1, 5 and 6 can be best described as a muffin-type (MFF-9). The 3D lattices of the isomorphous 1 and 5 are built through H-bonding, π⋯π stacking and C-H⋯π interactions, while the 3D architecture of 6 is stabilized by H bonds. The IR spectra of the complexes are discussed in terms of the coordination modes of the organic and inorganic ligands involved. The Eu(III) complex 2 displays a red, metal-ion centered emission in the solid state; the Tb^III atom in solid 4 emits light in the same region with the ligand. Magnetic susceptibility studies in the 2.0–300 K range reveal weak antiferromagnetic intramolecular Gd^III…Gd^III exchange interactions in 3; the J value is −0.09(1) cm⁻¹ based on the spin Hamiltonian Ĥ = −J(Ŝ_Gd1·Ŝ_Gd2).     

Reversible tuning of luminescence and magnetism in a structurally flexible erbium–anilato MOF

By combining 3,6-N-ditriazolyl-2,5-dihydroxy-1,4-benzoquinone (H₂trz₂An) with NIR-emitting Er^III ions, two different 3D neutral polymorphic frameworks (1a and 1b), differing in the number of uncoordinated water molecules, formulated as [Er₂(trz₂An)₃(H₂O)₄]_n·xH₂O (x = 10, a; x = 7, b), have been obtained. The structure of 1a shows layers with (6,3) topology forming six-membered rings with distorted hexagonal cavities along the bc plane. These 2D layers are interconnected through the N4 atoms of the two pendant arms of the trz₂An linkers, leading to a 3D framework, where neighboring layers are eclipsed along the a axis, with hexagonal channels filled with water molecules. In 1b, layers with (6,3) topology in the [101] plane are present, each Er^III ion being connected to three other Er^III ions through bis-bidentate trz₂An linkers, forming rectangular six-membered cavities. 1a and 1b are multifunctional materials showing coexistence of NIR emission and field-induced slow relaxation of the magnetization. Remarkably, 1a is a flexible MOF, showing a reversible structural phase transition involving shrinkage/expansion from a distorted hexagonal 2D framework to a distorted 3,6-brickwall rectangular 3D structure in [Er₂(trz₂An)₃(H₂O)₂]_n·2H₂O (1a_des). This transition is triggered by a dehydration/hydration process under mild conditions (vacuum/heating to 360 K). The partially dehydrated compound shows a sizeable change in the emission properties and an improvement of the magnetic blocking temperature with respect to the hydrated compound, mainly related to the loss of one water coordination molecule. Theoretical calculations support the experimental findings, indicating that the slight improvement observed in the magnetic properties has its origin in the change of the ligand field around the Er^III ion due to the loss of a water molecule.

Tuning of luminescent and SIM properties is herein reported, in a novel flexible 3D anilato-based Er^III-MOF, displaying reversible shrinkage/expansion from a distorted hexagonal to a 3,6-brickwall rectangular structure.     

Rational enhancement of the energy barrier of bis(tetrapyrrole) dysprosium SMMs via replacing atom of porphyrin core

With the coordination geometry of Dy^III being relatively fixed, oxygen and sulfur atoms were used to replace one porphyrin pyrrole nitrogen atom of sandwich complex [(Bu)₄N][Dy^III(Pc)(TBPP)] [Pc = dianion of phthalocyanine, TBPP = 5,10,15,20-tetrakis[(4-tert-butyl)phenyl]porphyrin]. The energy barrier of the compounds was enhanced three times, with the order of Dy^III(Pc)(STBPP) > Dy^III(Pc)(OTBPP) > [(Bu)₄N][Dy^III(Pc)(TBPP)] [STBPP = monoanion of 5,10,15,20-(4-tert-butyl)phenyl-21-thiaporphyrin, OTBPP = monoanion of 5,10,15,20-(4-tert-butyl)phenyl-21-oxaporphyrin]. Theoretical calculations offer reasonable explanations of such a significant enhancement. The energy barrier of 194 K for Dy^III(Pc)(STBPP) represents the highest one among all the bis(tetrapyrrole) dysprosium SMMs, providing a strategy to rationally enhance the anisotropy and energy barrier via atom replacement.     

Characterization and chemical reactivity of room-temperature-stable MnIII–alkylperoxo complexes

While alkylperoxomanganese(iii) (Mn^III–OOR) intermediates are proposed in the catalytic cycles of several manganese-dependent enzymes, their characterization has proven to be a challenge due to their inherent thermal instability. Fundamental understanding of the structural and electronic properties of these important intermediates is limited to a series of complexes with thiolate-containing N₄S⁻ ligands. These well-characterized complexes are metastable yet unreactive in the direct oxidation of organic substrates. Because the stability and reactivity of Mn^III–OOR complexes are likely to be highly dependent on their local coordination environment, we have generated two new Mn^III–OOR complexes using a new amide-containing N₅⁻ ligand. Using the 2-(bis((6-methylpyridin-2-yl)methyl)amino)-N-(quinolin-8-yl)acetamide (H^6Medpaq) ligand, we generated the [Mn^III(OO^tBu)(^6Medpaq)]OTf and [Mn^III(OOCm)(^6Medpaq)]OTf complexes through reaction of their Mn^II or Mn^III precursors with ^tBuOOH and CmOOH, respectively. Both of the new Mn^III–OOR complexes are stable at room-temperature (t_1/2 = 5 and 8 days, respectively, at 298 K in CH₃CN) and capable of reacting directly with phosphine substrates. The stability of these Mn^III–OOR adducts render them amenable for detailed characterization, including by X-ray crystallography for [Mn^III(OOCm)(^6Medpaq)]OTf. Thermal decomposition studies support a decay pathway of the Mn^III–OOR complexes by O–O bond homolysis. In contrast, direct reaction of [Mn^III(OOCm)(^6Medpaq)]⁺ with PPh₃ provided evidence of heterolytic cleavage of the O–O bond. These studies reveal that both the stability and chemical reactivity of Mn^III–OOR complexes can be tuned by the local coordination sphere.

A pair of room-temperature-stable Mn^III–alkylperoxo complexes were characterized and shown to oxidize PPh₃. Thermal decomposition studies provide evidence of both homolysis and heterolysis of the Mn^III–alkylperoxo O–O bond.     

Syntheses and structures of nine-coordinate K3[DyIII(nta)2(H2O)]·5H2O and eight-coordinate (NH4)3[DyIII(nta)2] complexes

K₃[Dy^III(nta)₂(H₂O)]·5H₂O and (NH₄)₃[Dy^III(nta)₂] have been synthesized in aqueous solution and characterized by IR, elemental analysis and single-crystal X-ray diffraction techniques. In K₃[Dy^III(nta)₂(H₂O)]·5H₂O the Dy^III ion is nine coordinated yielding a tricapped trigonal prismatic conformation, and its crystal belongs to monoclinic system and C2/c space group. The crystal data are as follows: a = 15.373(5) Å, b = 12.896(4) Å, c = 26.202(9) Å; β = 96.122(5)°, V = 5165(3) ų, Z = 8, D _c = 1.965 g·cm^?3, μ = 3.458 mm^?1, F(000) = 3016, R ₁ = 0.0452 and wR ₂ = 0.1025 for 4550 observed reflections with I ≥ 2σ(I). In (NH₄)₃[Dy^III(nta)₂] the Dy^III ion is eight coordinated yielding a usual dicapped trigonal anti-prismatic conformation, and its crystal belongs to monoclinic system and C2/c space group. The crystal data are as follows: a = 13.736(3) Å, b = 7.9389(16) Å, c = 18.781(4) Å; β = 104.099(3)°, V = 1986.3(7) ų, Z = 2, D _c = 1.983 g·cm^?3, μ = 3.834 mm^?1, F(000) = 1172, R ₁ = 0.0208 and wR ₂ = 0.0500 for 2022 observed reflections with I ≥ 2σ(I). The results indicate that the difference in counter ion also influences coordination numbers and structures of rare earth metal complexes with aminopolycarboxylic acid ligands.     

A Series of High‐nuclear 3d‐4f (FeIII8LnIII2) Complexes: Syntheses,Structures, and Magnetic Properties

Six novel decanuclear clusters with formula of {[Fe₈Ln₂(O)₄(OH)₄(EtO)₂(dhbp)₄(dhbpH)₂(piv)₆]·4EtOH} (Ln = Y ( 1 ), Gd ( 2 ), Tb ( 3 ), Dy ( 4 ), Ho ( 5 ), Er ( 6 ), dhbpH₂ = 6,6′‐dihydroxyl‐2,2′‐bipyridine, Hpiv = pivalic acid, EtOH = ethanol) have been synthesized and characterized. Single‐crystal and powder X‐ray diffraction analyses reveal that complexes 1 – 6 are isostructural and show a sandwich‐like Fe^III₈Ln^III₂ structure, in which the [Ln₂] unit is sandwiched by two planar [Fe₄] units. Magnetic properties of complexes 1 – 6 have been investigated and display dominant antiferromagnetic interactions, thereinto, complexes 4 and 6 display weak ferromagnetic behaviors associated with Ln^III ions, while others are antiferromagnetic‐like features. Furthermore, complex 4 (Fe^III₈Dy^III₂) shows temperature/frequency‐dependent ac signals with an energy barrier of 4.1 K, indicating that complex 4 should be a single‐molecule magnet (SMM)     

Metal–metal bonded alkaline-earth distannyls

The first families of alkaline-earth stannylides [Ae(SnPh₃)₂·(thf)_x] (Ae = Ca, x = 3, 1; Sr, x = 3, 2; Ba, x = 4, 3) and [Ae{Sn(SiMe₃)₃}₂·(thf)_x] (Ae = Ca, x = 4, 4; Sr, x = 4, 5; Ba, x = 4, 6), where Ae is a large alkaline earth with direct Ae–Sn bonds, are presented. All complexes have been characterised by high-resolution solution NMR spectroscopy, including ¹¹⁹Sn NMR, and by X-ray diffraction crystallography. The molecular structures of [Ca(SnPh₃)₂·(thf)₄] (1′), [Sr(SnPh₃)₂·(thf)₄] (2′), [Ba(SnPh₃)₂·(thf)₅] (3′), 4, 5 and [Ba{Sn(SiMe₃)₃}₂·(thf)₅] (6′), most of which crystallised as higher thf solvates than their parents 1–6, were established by XRD analysis; the experimentally determined Sn–Ae–Sn′ angles lie in the range 158.10(3)–179.33(4)°. In a given series, the ¹¹⁹Sn NMR chemical shifts are slightly deshielded upon descending group 2 from Ca to Ba, while the silyl-substituted stannyls are much more shielded than the phenyl ones (δ¹¹⁹Sn/ppm: 1′, −133.4; 2′, −123.6; 3′, −95.5; 4, −856.8; 5, −848.2; 6′, −792.7). The bonding and electronic properties of these complexes were also analysed by DFT calculations. The combined spectroscopic, crystallographic and computational analysis of these complexes provide some insight into the main features of these unique families of homoleptic complexes. A comprehensive DFT study (Wiberg bond index, QTAIM and energy decomposition analysis) points at a primarily ionic Ae–Sn bonding, with a small covalent contribution, in these series of complexes; the Sn–Ae–Sn′ angle is associated with a flat energy potential surface around its minimum, consistent with the broad range of values determined by experimental and computational methods.

The complete series of heterobimetallic alkaline-earth distannyls [Ae{SnR₃}₂·(thf)_x] (Ae = Ca, Sr, Ba) have been prepared for R = Ph and SiMe₃, and their bonding and electronic properties have been comprehensively investigated.     

Control of the Single‐Molecule Magnet Behavior of Lanthanide‐Diarylethene Photochromic Assemblies by Irradiation with Light

Lanthanide‐based extended coordination frameworks showing photocontrolled single‐molecule magnet (SMM) behavior were prepared by combining highly anisotropic Dy^III and Ho^III ions with the carboxylato‐functionalized photochromic molecule 1,2‐bis(5‐carboxyl‐2‐methyl‐3‐thienyl)perfluorocyclopentene (H₂dae), which acts as a bridging ligand. As a result, two new compounds of the general formula [{Ln^III₂(dae)₃(DMSO)₃(MeOH)} ? 10 M eOH]_n (M=Dy for 1 a and Ho for 2 ) and two additional pseudo‐polymorphs [{Dy^III₂(dae)₃(DMSO)₃(H₂O)} ? x MeOH]_n ( 1 b ) and [{Dy^III₂(dae)₃(DMSO)₃(DMSO)} ? x MeOH]_n ( 1 c ) were obtained. All four compounds have 2D coordination‐layer topologies, in which carboxylate‐bridged Ln₂ units are linked together by dae^2? anions into grid‐like frameworks. All four compounds exhibited a strong reversible photochromic response to UV/Vis light. Moreover, both 1 a and 2 show field‐induced SMM behavior. The slow magnetic relaxation of 1 a is influenced by the photoisomerization reaction leading to the observation of the cross‐effect: photocontrolled SMM behavior.     

Magnetic dilution effect on the charge transfer phase transition and the ferromagnetic transition for an iron mixed-valence complex, (n-C3H7)4N[FeII1−xZnIIxFeIII(dto)3] (dto = C2O2S2)

Iron mixed-valence complex, (n-C₃H₇)₄N[Fe^IIFe^III(dto)₃] (dto = C₂O₂S₂) shows a new-type of phase transition coupled with spin and charge around 120 K, where the charge transfer between the Fe^II and Fe^III sites occurs reversibly, and shows the ferromagnetic transition at 7 K. To investigate the magnetic structure and its dimensionality of (n-C₃H₇)₄N[Fe^IIFe^III(dto)₃], we have synthesized a mixed crystal system, (n-C₃H₇)₄N[Fe^II_1?xZn^II_xFe^III(dto)₃], and measured its magnetic properties. In this system, the magnetic moment is reduced with increasing of Zn ratio. Moreover, the ferromagnetic interaction changes to the antiferromagnetic one and the remnant magnetization disappears between x = 0.48 and 0.96, while the charge transfer between the Fe^II and Fe^III sites disappears above x = 0.26. In this paper, we present the magnetic dilution effect on the charge transfer phase transition and the ferromagnetic transition by means of magnetic susceptibility measurement and ⁵⁷Fe Mössbauer spectroscopy.     

Oligonuclear 3d–4f Complexes as Tectons in Designing Supramolecular Solid‐State Architectures: Impact of the Nature of Linkers on the Structural Diversity

Heteronuclear cationic complexes, [LCuLn]³⁺ and [(LCu)₂Ln]³⁺, were employed as nodes in designing high‐nuclearity complexes and coordination polymers with a rich variety of network topologies (L is the dianion of the Schiff base resulting from the 2:1 condensation of 3‐methoxysalycilaldehyde with 1,3‐propanediamine). Two families of linkers have been chosen: the first consists of exo‐dentate ligands bearing nitrogen‐donor atoms (bipyridine (bipy), dicyanamido (dca)), whereas the second consists of exo‐dentate ligands with oxygen‐donor atoms (anions derived from the acetylenedicarboxylic (H₂acdca), fumaric (H₂fum), trimesic (H₃trim), and oxalic (H₂ox) acids). The ligands belonging to the first family prefer copper(II ) ions, whereas the ligands from the second family interact preferentially with oxophilic rare‐earth cations. The following complexes have been obtained and crystallographically characterized: [LCu^II(OH₂)Gd^III(NO₃)₃] ( 1 ), [{LCu^IIGd^III(NO₃)₃}₂(μ‐4,4′‐bipy)] ( 2 ), [LCu^IIGd^III(acdca)_1.5(H₂O)₂] ? 13 H₂O ( 3 ), [LCu^IIGd^III(fum)_1.5(H₂O)₂] ? 4 H₂O ? C₂H₅OH ( 4 ), [LCu^IISm^III(H₂O)(Hfum)(fum)] ( 5 ), [LCu^IIEr^III(H₂O)₂(fum)]NO₃ ? 3 H₂O ( 6 ), [LCu^IISm^III(fum)_1.5(H₂O)₂] ? 4 H₂O ? C₂H₅OH ( 7 ), [{(LCu^II)₂Sm^III}₂fum₂](OH)₂ ( 8 ), [LCu^IIGd^III(trim)(H₂O)₂] ? H₂O ( 9 ), [{(LCu^II)₂Pr^III}(C₂O₄)_0.5(dca)]dca ? 2 H₂O ( 10 ), [LCu^IIGd^III(ox)(H₂O)₃][Cr^III(2,2′‐bipy)(ox)₂] ? 9 H₂O ( 11 ), and [LCuGd(H₂O)₄{Cr(CN)₆}] ? 3 H₂O ( 12 ). Compound 1 is representative of the whole family of binuclear Cu^II–Ln^III complexes which have been used as precursors in constructing heteropolymetallic complexes. The rich variety of the resulting structures is due to several factors: 1) the nature of the donor atoms of the linkers, 2) the preference of the copper(II ) ion for nitrogen atoms, 3) the oxophilicity of the lanthanides, 4) the degree of deprotonation of the polycarboxylic acids, 5) the various connectivity modes exhibited by the carboxylato groups, and 6) the stoichiometry of the final products, that is, the Cu^II/Ln^III/linker molar ratio. A unique cluster formed by 24 water molecules was found in crystal 11 . In compounds 2 , 3 , 4 , 9 , and 11 the Cu^II–Gd^III exchange interaction was found to be ferromagnetic, with J values in the range of 3.53–8.96 cm^?1. Compound 12 represents a new example of a polynuclear complex containing three different paramagnetic ions. The intranode Cu^II–Gd^III ferromagnetic interaction is overwhelmed by the antiferromagnetic interactions occurring between the cyanobridged Gd^III and Cr^III ions.     

Syntheses and structural determinations of the nine-coordinate rare earth metal: Na4[DyIII(dtpa)(H2O)]2·16H2O,Na[DyIII(edta)(H2O)3]·3.25H2O and Na3[DyIII(nta)2(H2O)]·5.5H2O

Three complexes, Na₄[Dy^III(dtpa)(H₂O)]₂?·?16H₂O, Na[Dy^III(edta)(H₂O)₃]?·?3.25H₂O and Na₃[Dy^III (nta)₂(H₂O)]?·?5.5H₂O, have been synthesized in aqueous solution and characterized by FT–IR, elemental analyses, TG–DTA and single-crystal X-ray diffraction. Na₄[Dy^III(dtpa)(H₂O)]₂?·?16H₂O crystallizes in the monoclinic system with P2₁/n space group, a?=?18.158(10)?Å, b?=?14.968(9)?Å, c?=?20.769(12)?Å, β?=?108.552(9)°, V?=?5351(5)?ų, Z?=?4, M?=?1517.87?g?mol^?1, D _c?=?1.879?g?cm^?3, μ?=?2.914?mm^?1, F(000)?=?3032, and its structure is refined to R ₁(F)?=?0.0500 for 9384 observed reflections [I?>?2σ(I)]. Na[Dy^III(edta)(H₂O)₃]?·?3.25H₂O crystallizes in the orthorhombic system with Fdd2 space group, a?=?19.338(7)?Å, b?=?35.378(13)?Å, c?=?12.137(5)?Å, β?=?90°, V?=?8303(5)?ų, Z?=?16, M?=?586.31?g?mol^?1, D _c?=?1.876?g?cm^?3, μ?=?3.690?mm^?1, F(000)?=?4632, and its structure is refined to R ₁(F)?=?0.0307 for 4027 observed reflections [I?>?2σ(I)]. Na₃[Dy^III(nta)₂(H₂O)]?·?5.5H₂O crystallizes in the orthorhombic system with Pccn space group, a?=?15.964(12)?Å, b?=?19.665(15)?Å, c?=?14.552(11)?Å, β?=?90°, V?=?4568(6)?ų, Z?=?8, M?=?724.81?g?mol^?1, D _c?=?2.102?g?cm^?3, μ?=?3.422?mm^?1, F(000)?=?2848, and its structure is refined to R ₁(F)?=?0.0449 for 4033 observed reflections [I?>?2?σ(I)]. The coordination polyhedra are tricapped trigonal prism for Na₄[Dy^III(dtpa)(H₂O)]₂?·?16H₂O and Na₃[Dy^III(nta)₂(H₂O)]?·?5.5H₂O, but monocapped square antiprism for Na[Dy^III(edta)(H₂O)₃]?·?3.25H₂O. The crystal structures of these three complexes are completely different from one another. The three-dimensional geometries of three polymers are 3-D layer-shaped structure for Na₄[Dy^III(dtpa)(H₂O)]₂?·?16H₂O, 1-D zigzag type structure for Na[Dy^III(edta)(H₂O)₃]?·?3.25H₂O and a 2-D parallelogram for Na₃[Dy^III(nta)₂(H₂O)]?·?5.5H₂O. According to thermal analyses, the collapsing temperatures are 356°C for Na₄[Dy^III(dtpa)(H₂O)]₂?·?16H₂O, 371°C for Na[Dy^III(edta)(H₂O)₃]?·?3.25H₂O and 387°C for Na₃[Dy^III(nta)₂(H₂O)]?·?5.5H₂O, which indicates that their crystal structures are very stable.     

Cadmium-Inspired Self-Polymerization of {LnIIICd2} Units: Structure,Magnetic and Photoluminescent Properties of Novel Trimethylacetate 1D-Polymers (Ln = Sm,Eu, Tb,Dy, Ho,Er, Yb)

A series of heterometallic carboxylate 1D polymers of the general formula [Ln^IIICd₂(piv)₇(H₂O)₂]_n·nMeCN (Ln^III = Sm (1), Eu (2), Tb (3), Dy (4), Ho (5), Er (6), Yb (7); piv = anion of trimethylacetic acid) was synthesized and structurally characterized. The use of Cd^II instead of Zn^II under similar synthetic conditions resulted in the formation of 1D polymers, in contrast to molecular trinuclear complexes with Ln^IIIZn₂ cores. All complexes 1–7 are isostructural. The luminescent emission and excitation spectra for 2–4 have been studied, the luminescence decay kinetics for 2 and 3 was measured. Magnetic properties of the complexes 3–5 and 7 have been studied; 4 and 7 exhibited the properties of field-induced single-molecule magnets in an applied external magnetic field. Magnetic properties of 4 and 7 were modelled using results of SA-CASSCF/SO-RASSI calculations and SINGLE_ANISO procedure. Based on the analysis of the magnetization relaxation and the results of ab initio calculations, it was found that relaxation in 4 predominantly occurred by the sum of the Raman and QTM mechanisms, and by the sum of the direct and Raman mechanisms in the case of 7.     

White Light Emissive DyIII Single‐Molecule Magnets Sensitized by Diamagnetic [CoIII(CN)6]3− Linkers

The self‐assembly of Dy^III–3‐hydroxypyridine (3‐OHpy) complexes with hexacyanidocobaltate(III) anions in water produces cyanido‐bridged {[Dy^III(3‐OHpy)₂(H₂O)₄] [Co^III(CN)₆]}?H₂O ( 1 ) chains. They reveal a single‐molecule magnet (SMM) behavior with a large zero direct current (dc) field energy barrier, ΔE=266(12) cm^?1 (≈385 K), originating from the single‐ion property of eight‐coordinated Dy^III of an elongated dodecahedral geometry, which are embedded with diamagnetic [Co^III(CN)₆]^3? ions into zig‐zag coordination chains. The SMM character is enhanced by the external dc magnetic field, which results in the ΔE of 320(23) cm^?1 (≈460 K) at H_dc=1 kOe, and the opening of a butterfly hysteresis loop below 6 K. Complex 1 exhibits white Dy^III‐based emission realized by energy transfer from Co^III and 3‐OHpy to Dy^III. Low temperature emission spectra were correlated with SMM property giving the estimation of the zero field ΔE. 1 is a unique example of bifunctional magneto‐luminescent material combining white emission and slow magnetic relaxation with a large energy barrier, both controlled by rich structural and electronic interplay between Dy^III, 3‐OHpy, and [Co^III(CN)₆]^3?.     

The synthesis, structural characterization, magnetochemistry and Mössbauer spectroscopy of [Fe3LnO2(CCl3COO)8H2O(THF)3] (Ln = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Lu and Y)

The new tetranuclear complexes [Fe₃Ln(μ₃-O)₂(CCl₃COO)₈(H₂O)(THF)₃]·THF (Ln = Ce^III (1), Pr^III (2), Nd^III (3)) and [Fe₃Ln(μ₃-O)₂(CCl₃COO)₈(H₂O)(THF)₃]·THF·C₇H₁₆ (Ln = Sm^III (4), Eu^III (5), Gd^III (6), Tb^III (7), Dy^III (8), Ho^III (9), Lu^III (10) and Y^III (11)) have been prepared. All compounds were prepared by the reaction between [Fe₂BaO(CCl₃COO)₆(THF)₆] and the corresponding Ln^III nitrate salt. The crystal structures of 1–4, 8 and 9 have been determined; these isostructural molecules have a non-planar {Fe₃Ln(μ₃-O)₂} “butterfly” core. Magnetic susceptibility measurements show dominant intramolecular antiferromagnetic exchange interactions for all the complexes. ⁵⁷Fe Mössbauer spectroscopy shows three different environments for the Fe^III metal ions, all in their high-spin state S = 5/2 (confirming that no electron transfer from Ce^III to Fe^III occurs in 1). At the time scale of the Mössbauer spectroscopy (about 10⁻⁷ s), evidence of magnetization blocking, i.e. slow relaxation of the magnetization, is observed below 3 K for 7, which was confirmed by ac susceptibility measurements.     

Syntheses,Structures, Magnetic Properties,and NIR Emission Properties of a Series of Novel 1, 2, 4, 5‐Cyclohexanetetracarboxylate‐bridged Lanthanide Complexes with 3D Framework Structures

Solvothermal combination of trivalent lanthanide metal precursors with 1, 2, 4, 5‐cyclohexanetetracarboxylic acid (L) ligand has afforded the preparation of a family of eight new coordination polymers [Ln₄(L)₃(H₂O)₁₀] · 7H₂O (Ln = Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) ( 1 – 8 ). Structural analyses reveal that the 1, 2, 4, 5‐cyclohexanetetracarboxylic acid ligand with e,a,a,e (L^I) conformation displays a μ₄‐(κ³O, O, O⁵)(κ²O²,O²)(κ²O⁴,O⁴)‐bridging mode to generate 3D frameworks of complexes 1 – 8 and the α‐Po topology with the short Schläfli symbol {4¹².6³} could be observed in complexes 1 – 8 . The near‐infrared luminescence properties were studied, and the results have shown that the Ho^III, Er^III, and Yb^III complexes emit typical near‐infrared luminescence in the solid‐state. Variable‐temperature magnetic susceptibility measurements of complexes 2 – 7 have shown that complex 2 (Gd) shows the ferromagnetic coupling between magnetic centers, whereas the complexes 3 – 7 show the antiferromagnetic coupling between magnetic centers. Additionally, the thermogravimetric analyses were discussed.     

Synthesis and photophysical properties of Ir<Superscript>III</Superscript>-Ln<Superscript>III</Superscript> (Ln = Nd,Yb, Er) bimetallic complexes containing bipyrimidines as bridging ligands

Bipyrimidines have been chosen as (N∧N)(N∧N) bridging ligands for connecting metal centers. Ir^III-Ln^III (Ln = Nd, Yb, Er) bimetallic complexes [Ir(dfppy)₂(μ-bpm)Ln(TTA)₃]Cl were synthesized by using Ir(dfppy)₂(bpm)Cl as the ligand coordinating to lanthanide complexes Ln(TTA)₃·2H₂O. The stability constants between Ir(dfppy)₂(bpm)Cl and lanthanide ions were measured by fluorescence titration. The obvious quenching of visible emission from Ir^III complex in the Ir^III-Ln^III (Ln = Nd, Yb, Er) bimetallic complexes indicates that energy transfer occurred from Ir^III center to lanthanides. NIR emissions from Nd^III, Yb^III, and Er^III were obtained under the excitation of visible light by selective excitation of the Ir^III-based chromophore. It was proven that Ir(dfppy)₂(bpm)Cl as the ligand could effectively sensitize NIR emission from Nd^III, Yb^III, and Er^III.