Search

Sandwich complexes of lanthanides have recently attracted a considerable amount of interest due to their applications as Single Molecule Magnet (SMM). Herein, a comprehensive series of heteroleptic lanthanide sandwich complexes ligated by the cyclononatetraenyl (Cnt) and the cyclooctatetraenyl (Cot) ligand [Ln(Cot)(Cnt)] (Ln=Tb, Dy, Er, Ho, Yb, and Lu) is reported. The coordination behavior of the Cnt ligand has been investigated along the series and shows different coordination patterns in the solid-state depending on the size of the corresponding lanthanide ion without altering its overall anisotropy. Besides the characterization in the solid state by single-crystal X-ray diffraction and in solution by 1 H NMR, static magnetic studies and ab initio computational studies were performed.

Solvation of [(CNT)Ln(η8‐COT)] (Ln=La, Ce, Nd, Tb, Er; CNT=cyclononatetraenyl, i.e. C9H9−; COT=cyclooctatetraendiid, i.e. C8H82−) complexes with tetrahydrofuran (THF) gives rise to neutral [(η4‐CNT)Ln(thf)2(η8‐COT)] (Ln=La, Ce) and ionic [Ln(thf)x(η8‐COT)][CNT] (x=4 (Ce, Nd, Tb), 3 (Er)) species in a solid‐to‐solid transformation. Due to the severe distortion of the ligand sphere upon solvation, these species act as switchable luminophores and single‐molecule magnets. The desolvation of the coordinated solvents can be triggered by applying a dynamic vacuum, as well as a temperature gradient stimulus. Raman spectroscopic investigations revealed fast and fully reversible solvation and desolvation processes. Moreover, we also show that a Nd:YAG laser can induce the necessary temperature gradient for a self‐sufficient switching process of the Ce(III) analogue in a spatially resolved manner. [ABSTRACT FROM AUTHOR]

Sandwich complexes of lanthanides have recently attracted a considerable amount of interest due to their applications as Single Molecule Magnet (SMM). Herein, a comprehensive series of heteroleptic lanthanide sandwich complexes ligated by the cyclononatetraenyl (Cnt) and the cyclooctatetraenyl (Cot) ligand [Ln(Cot)(Cnt)] (Ln=Tb, Dy, Er, Ho, Yb, and Lu) is reported. The coordination behavior of the Cnt ligand has been investigated along the series and shows different coordination patterns in the solid‐state depending on the size of the corresponding lanthanide ion without altering its overall anisotropy. Besides the characterization in the solid state by single‐crystal X‐ray diffraction and in solution by 1H NMR, static magnetic studies and ab initio computational studies were performed. [ABSTRACT FROM AUTHOR]

Divalent lanthanide organometallics are well‐known highly reducing compounds usually used for single electron transfer reactivity and small molecule activation. Thus, their very reactive nature prevented for many years the study of their physical properties, such as magnetic studies on a reliable basis. Herein, the access to rare organometallic sandwich compounds of TmII with the cyclooctatetraenyl (Cot) ligand impacts on the use of divalent organolanthanide compounds as an additional strategy for the design of performing Single Molecule Magnets (SMM). The first divalent thulium sandwich complex with f13 configuration behaving as a single‐molecule magnet in absence of DC field is highlighted. [ABSTRACT FROM AUTHOR]

This Minireview covers the design and characterization of coordination lanthanide complexes involving TTF‐based ligands. The specific design of TTF‐based ligands allowed the isolation of complexes with magnetic properties such as Single‐Molecule Magnets (SMMs) behavior and the studies of magnetic modulations due to supramolecular interaction, molecular engineering, magnetic dilution as well as isotopic enrichment. A careful design leads to TTF‐based ligands displaying several coordination sites in order to rationally elaborate polynuclear systems with multi‐SMM behavior or to auto‐assembly SMMs. Their redox activity allowed the investigation of coordination lanthanide complexes in several oxidation states and their consequences on optical and magnetic properties. The complete experimental and theoretical studies of such systems contributed to the understanding of the magnetic properties of lanthanide ions for futures applications in high density storage and quantum computing. [ABSTRACT FROM AUTHOR]

The coordination of a helicene‐functionalized bipyridine to various lanthanide complexes (Ln = Y, Eu, Yb, Gd) led to the formation of an isostructural series. The photophysical study indicated that non‐emissive lanthanides act as heavy atoms strongly enhancing singlet oxygen generation. We also demonstrated that sensitization of the f‐f luminescence is in competition with singlet oxygen generation. The coordination of a helicene functionalized bipyridine to various lanthanide complexes (ln = Y, Eu, Yb, Gd) led to the formation of an isostructural series. The photophysical study indicated that lanthanides act as heavy atoms strongly enhancing the singlet oxygen generation. We also demonstrated that the sensitization of the f‐f luminescence is in competition with the singlet oxygen generation. [ABSTRACT FROM AUTHOR]

Molecular materials that possess a toroidal moment associated to a non‐magnetic ground state are known as single‐molecule toroics (SMTs) and are usually planar molecules. Herein, we report a Dy4 cubane, namely [Dy4(Bppd)4(μ3‐OH)4(Pa)4(H2O)4]⋅0.333 H2O (where BppdH=1,3‐Bis(pyridin‐4‐yl)propane‐1,3‐dione and PaH=2‐Picolinic acid) for which magnetometry measurements and state‐of‐art ab initio calculations highlight SMT behavior in a tridimensional structure (3D‐SMT). The in‐depth theoretical analysis on the resulting low‐lying energy states, along with their variation in function of the magnetic exchange pathways, allows further light to be shed on the description of single‐molecule toroics and identify the coupling scheme that better reproduces the observed data. 3D magnetic toroics: Molecular materials that have a toroidal moment associated to a non‐magnetic ground state are known as single‐molecule toroics (SMTs) and are usually planar molecules. Such a toroidal moment is observed in a Dy4 cubane, transposing this property to a tridimensional structure (3D‐SMT). [ABSTRACT FROM AUTHOR]

Abstract: We report the study of a Dy‐based metal–organic framework (MOF) with unprecedented magnetic properties. The compound is made of nine‐coordinated DyIII magnetic building blocks (MBBs) with poor intrinsic single‐molecule magnet behavior. However, the MOF architecture constrains the MBBs in a one‐dimensional structure that induces a ferromagnetic coupling between them. Overall, the material shows a magnetic slow relaxation in absence of external static field and a hysteretic behavior at 0.5 K. Low‐temperature magnetic studies, diamagnetic doping, and ab initio calculations highlight the crucial role played by the Dy–Dy ferromagnetic interaction. Overall, we report an original magnetic object at the frontier between single‐chain magnets and single‐molecule magnets that host intrachain couplings that cancel quantum tunneling between the MBBs. This compound is evidence that a bottom‐up approach through MOF design can induce spontaneous organization of MBBs able to produce remarkable molecular magnetic materials. [ABSTRACT FROM AUTHOR]

The two ligands 4‐[6‐(1,3‐benzothiazol‐2‐yl)pyridin‐3‐yl]‐4′,5′‐bis(methylthio)tetrathiafulvene (L1) and 4‐[6‐(1,3‐benzothiazol‐2‐yl)pyridin‐3‐yl]‐4′,5′‐(ethylenedithio)tetrathiafulvene (L2) were developed, and six new lanthanide coordination complexes, namely, [Ln2(hfac)6(L1)2]·C6H14·xCH2Cl2 [Ln = Dy and x = 0.25 (1); Ln = Yb and x = 0.30 (2); hfac– = 1,1,1,5,5,5‐hexafluoroacetylacetonate], [Ln(hfac)3(L2)] [Ln = Dy (3), Yb (4)] and [Ln(tta)3(L1)] [Ln = Yb (5), Er (6); tta– = 2‐thenoyltrifluoroacetylacetonate], were characterized by single‐crystal X‐ray diffraction. Compounds 1–6 were identified as mononuclear complexes, and the crystal packing depends on the natures of the ancillary and tetrathiafulvalene‐based ligands. The two dysprosium derivatives, 1 and 3, displayed single‐molecule‐magnet behaviour in zero applied magnetic field. Although the near‐infrared luminescence of 2 and 4 is almost undetectable, the change of ancillary ligand switched on the YbIII (5) and ErIII (6) luminescence. [ABSTRACT FROM AUTHOR]

Single‐molecule magnet (SMM) behavior of dysprosium‐based dimers was optimized by substitution of a DyIII ancillary ligand (hfac– in the previously reported DyPyNO and tta– in Dy). A clear hysteresis opening is visible at 0.5 K for Dy that allows for the determination of an antiferromagnetic (AF) coupling of –2.92 cm–1 (S = 1/2, gz = 19.58) which was confirmed by ab initio calculations. Comparison with the results of DyPyNO shows that stronger AF coupling correlates with better SMM behavior. This is further demonstrated by diamagnetic substitution, and a Y–Dy species (YDy) highlights that the strong AF magnetic interaction in Dy significantly enhances magnetic relaxation at low temperature. This coupling is also expected to be at the origin of the unexpectedly weak isotopic effect observed for the isotopically pure parents of Dy, namely 161Dy and 164Dy. [ABSTRACT FROM AUTHOR]

Keywords: Lanthanides; Magnetism; Molecular Switches; Photoluminescence; Sandwich Compounds EN Lanthanides Magnetism Molecular Switches Photoluminescence Sandwich Compounds 1 1 1 04/19/23 20230424 NES 230424 B Sandwich Compounds b . Lanthanides, Magnetism, Molecular Switches, Photoluminescence, Sandwich Compounds. [Extracted from the article]

Since the 1990s and the discovery of the first Single Molecule Magnets (SMMs), chemists and physicists have been working in concert to elaborate such molecular systems and understand their peculiar properties. Especially the use of lanthanide ions in the design of SMMs exploded with the discovery of the first example of mononuclear Tb III -based complex which displayed a slow magnetic relaxation in 2003. This high-degree of interest comes from the diverse potential applications in quantum computing, high-density data storage devices and spintronics. Recently, the specific luminescence properties of the lanthanide ions were correlated to the magnetic ones. Even if the most common lanthanide ions used in the elaboration of SMMs are the Dy III , Tb III and Er III ions, new SMMs involving others lanthanide ions (Yb III , Ce III , Nd III , Ho III and Tm III ) started to emerge. This review presents the research endeavour in the area of these uncommon lanthanide-based SMMs and underlines the different approaches to better understand their physical properties. [ABSTRACT FROM AUTHOR]

The reactions between the chiral helicene-like ligand (L) and either Ln(hfac)3·2H2O (hfac– = 1,1,1,5,5,5-hexafluoroacetylacetonate), Ln(tta)3·2H2O (tta– = 2-tenoyltrifluoroacetonate), iron(II) sulfate or chloride, or a combination of them led to the formation of five chiral 4f compounds of formula [HL][Ln(hfac)4]·nCH2Cl2 [Ln = Dy, n = 0.5 (1) and Ln = Yb, n = 1 (2)], [HL][Ln(tta)4]·nC6H14 [Ln = Dy, n = 0 (3) and Ln = Yb, n = 2.5 (4)], and [HL]2[Yb8(hfac)12(OH)12(O)]·0.5C6H14·H2O (5), a chiral 3d complex of formula [Fe(NCS)2(L)]·CH3NO2 (6), and a chiral 3d/4f heterodimetallic compound of formula [Fe(tta)(L)]- [Dy(tta)4]·2.5CH2Cl2 (7). The influence of the nature of the ancillary ligand and the presence or absence of base during the synthesis on the homochiral or heterochiral arrangement of the ligands as well as the dimensionality and nuclearity of the complexes were studied. Ytterbium-based compounds 2, 4, and 5 display near-infrared (NIR) luminescence under irradiation at λ = 350 nm owing to the 2F5/2 → 2F7/2 YbIII transition (centered at λ = 1000 nm). Complex 2 displays a second NIR emission at λ = 1278 nm, which is attributed to singlet-oxygen phosphorescence (a1Δg → X3Σg -) at both room temperature and 77 K. Dynamic magnetic measurements show an out-of-phase signal for the magnetic susceptibility of 7, which can be depicted as a 3d/4f chiral heterodimetallic single-molecule magnet. [ABSTRACT FROM AUTHOR]

The first molecular TmII luminescence measurements are reported along with rare magnetic, X and Q bands EPR studies. Access to simple and soluble molecular divalent lanthanide complexes is highly sought for small-molecule activation studies and organic transformations using single-electron transfer processes. However, owing to their low stability and propensity to disproportionate, these complexes are hard to synthetize and their electronic properties are therefore almost unexplored. Herein we present the synthesis of [Tm(μ-OTf)2(dme)2] n, a rare and simple coordination compound of divalent thulium that can be seen as a promising starting material for the synthesis of more elaborated complexes. This reactive complex was structurally characterized by X-ray diffraction analysis and its electronic structure has been compared with that of its halide cousin TmI2(dme)3. [ABSTRACT FROM AUTHOR]

Two new tetrathiafulvalene-based ligands { L1 = 4,5-bis[2,6-di(pyrazol-1-yl)-4-pyridylmethylthio]-4′,5′-bis(methylthio)tetrathiafulvene, L3 = 4-(4′-methyl-2,2′-bypiridin-4-ylmethylthio)-5-(2-cyanoethylthio)-4′,5′-ethylenedithiotetrathiafulvene} have been elaborated and four new lanthanide coordination complexes, namely [Dy2(hfac)6( L1)] ·C6H14 ( 1; hfac- = 1,1,1,5,5,5-hexafluoroacetylacetonate), [Ln(hfac)3( L2)] ·CH2Cl2 {Ln = Dy ( 2) and Yb ( 3); L2 = 4,5-bis[2,6-di(pyrazol-1-yl)-4-pyridylmethylthio]-4′,5′-ethylenedithiotetrathiafulvene} and [Yb(hfac)3( L3)] ( 4) were isolated as single crystals. The lanthanide ions adopt an N3O6 nine-coordination with either a spherical tricapped trigonal prism ( D3 h) or spherical capped square antiprism ( C4 v) as coordination polyhedra in complexes 1- 3. In 4, the YbIII ion adopts an N2O6 eight-coordination with a square antiprism ( D4 d) coordination sphere. The photophysical properties of the ligands L1 and L3 were studied in both solution and solid state and rationalised by time-dependent density functional theory. Complex 2, in which the DyIII ion has the most regular C4 v symmetry, behaves as a field-induced single-molecule magnet. [ABSTRACT FROM AUTHOR]

Ligand L was synthesized and then coordinated to [Ln(hfac)3] ⋅2 H2O (LnIII=Tb, Dy, Er; hfac−=1,1,1,5,5,5-hexafluoroacetylacetonate anion) and [Ln(tta)3]⋅2 H2O (LnIII=Eu, Gd, Tb, Dy, Er, Yb; tta−=2-thenoyltrifluoroacetonate) to give two families of dinuclear complexes [Ln2(hfac)6( L)] ⋅C6H14 and [Ln2(tta)6( L)] ⋅2 CH2Cl2. Irradiation of the ligand at 37 040 cm−1 and 29 410 cm−1 leads to tetrathiafulvalene-centered and 2,6-di(pyrazol-1-yl)-4-pyridine-centered fluorescence, respectively. The ligand acts as an organic chromophore for the sensitization of the infrared ErIII (6535 cm−1) and YbIII (10 200 cm−1) luminescence. The energies of the singlet and triplet states of L are high enough to guarantee an efficient sensitization of the visible EuIII luminescence (17 300-14 100 cm−1). The EuIII luminescence decay can be nicely fitted by a monoexponential function that allows a lifetime estimation of (0.49±0.01) ms. Finally, the magnetic and luminescence properties of [Yb2(hfac)6( L)] ⋅C6H14 were correlated, which allowed the determination of the crystal field splitting of the 2F7/2 multiplet state with MJ=±1/2 as ground states. [ABSTRACT FROM AUTHOR]

The association of the two 4,5-bis(thiomethyl)-4′-carboxytetrathiafulvalene (H L1) and 4,5-bis(thiomethyl)-4′-(2-pyridyl- N-oxide)carbamoyltetrathiafulvalene ( L2) with the metalloprecursor [Dy(tta)3] ·2H2O (tta = 2-thenoyltrifluoroacetonate) leads to the formation of the dinuclear complex of formula [Dy(tta)2( L1)( L2)]2 ·2CH2Cl2. Static magnetic measurements highlight significant ferromagnetic interactions between the DyIII ions, and dynamic magnetic measurements demonstrate single-molecule-magnet behaviour with an energy barrier of 20 cm-1 and a relaxation time of 8.6(9) × 10-6 s. The thermal dependence of the magnetic susceptibility was evaluated by using a crystal field approach (Stevens operators), which confirmed the Ising character of the system. Finally, electrochemistry shows a complex multiredox system with the successive oxidations of the two tetrathiafulvalene (TTF) ligands. [ABSTRACT FROM AUTHOR]

The two mononuclear complexes [Ln(tta)3(L)] ·C6H14 {Ln = DyIII and YbIII} (tta- = 2-thenoyltrifluoroacetonate, L = 2-{1-methylpyridyl-4,5-[4,5-bis(propylthio)tetrathiafulvalenyl]-1 H-benzimidazol-2-yl}pyridine) are isostructural. The lanthanide ions adopt a distorted-square-antiprism coordination polyhedron ( D4d symmetry). The DyIII compound behaves like a single-molecule magnet (SMM), whereas no out-of-phase component of the magnetic susceptibility is measured for YbIII. The crystal-field splitting of the 2F7/2 and 6H15/2 ground multiplets of YbIII and DyIII, respectively, were determined by means of ab initio calculations and confirmed by the emission energy lines of the 2F5/2→2F7/2 luminescence spectrum in the case of YbIII. The nature of the MJ ground states indicates that YbIII is not an Ising system, whereas DyIII is. The experimental and calculated anisotropy axes for DyIII lie along the most negatively charged direction, whereas those for YbIII lie almost perpendicularly. Finally, the gz values corroborate the uniaxiality of the anisotropy axis for DyIII. [ABSTRACT FROM AUTHOR]

Herein, we provide some structural evidence of the complexation color-change of murexide solutions in presence of lanthanide, which has been used for decades in complexometric studies. For Ln=Sm to Lu and Y, the compounds crystallize as monomeric [Ln(Murex)3] ⋅11 H2O with an N3O6 tricapped square-antiprism environment, which are stable up to 250 °C. Single-ion magnet (SIM) behavior is then observed on the YbIII derivative in an original nine-coordinated environment. In-field slow relaxation (Δ=(15.6±1) K; τ0=2.73×10−6 s) is observed with a very narrow distribution of the relaxation time ( αmax=0.09). Magnetic and photophysical properties can be correlated. On one hand the analysis of NIR emission spectrum permits to have access to crystal field parameters and to compare them with those extracted from dc measurements. On the other hand, magnetic measurements permit to identify the nature of the MJ states involved in the 2F5/2→2F7/2 luminescence spectrum. The gap between the low-lying states is in agreement with the energy barrier obtained from magnetic slow-relaxation measurement. [ABSTRACT FROM AUTHOR]

Mononuclear complexes with the formula [Ln(hfac)3( L1)] and [Ln(hfac)3( L2)] with hfac- = 1,1,1,5,5,5-hexafluoroacetylacetonate, L1 = 2-{4,5-[4,5-bis(propylthio)tetrathiafulvalenyl]-1 H-benzimidazol-2-yl}pyridine and L2 = 2-{1-methylpyridyl-4,5-[4,5-bis(propylthio)tetrathiafulvalenyl]-1 H-benzimidazol-2-yl}pyridine are reported for Ln = YIII, ErIII and YbIII. The X-ray structures reveal that the Ln(hfac)3 moieties are coordinated to the bidentate 1-(2-pyridylmethyl)benzimidazole acceptor. The coordination polyhedron is described as a more or less distorted triangular dodecahedron prism ( D2 d symmetry), depending on the degree of alkylation of the ligand. The influence of this distortion on the magnetic and photophysical properties is determined by the fit of the static magnetic measurements and luminescence spectra. Irradiation of the lowest-energy intraligand charge transfer (ILCTs) bands (21740 cm-1) induces the metal-centred 4I13/2 → 4I15/2 and 2F5/2 → 2F7/2 luminescence for the ErIII and YbIII complexes, respectively. The alkylation enhances both the intensity and lifetime of the YbIII luminescence. The ErIII luminescence can be sensitised by the antenna effect, whereas the YbIII luminescence could involve a photoinduced electron transfer (PET). Finally, the evolution of the YbIII luminescence spectra shape due to the alkylation is directly correlated to the energy splitting of the MJ states that stem from the 2F7/2 multiplet ground state. Ab initio calculations give evidence of the nature of the MJ ground state as well as the orientation of the associated magnetic anisotropy axis (i.e., the one that lies along the less electronegative direction). The key role of the imidazole proton of L2 is highlighted. The calculated energy splitting of the 2F5/2 multiplet state perfectly matches the emission lines. [ABSTRACT FROM AUTHOR]

Reaction of the ligands 4,5-bis(propylthio)tetrathiafulvalene-2-(2-pyridyl)benzimidazole ( L1) and 4,5-bis(propylthio)tetrathiafulvalene-2-(2-pyridyl)-3-(2-pyridinylmethyl)benzimidazole ( L2) with Dy(hfac)3 ⋅2 H2O (hfac=1,1,1,5,5,5-hexafluoroacetylacetonate) gave mononuclear complexes [Dy(hfac)3( L1)] ( 1) and [Dy(hfac)3( L2)] ( 2). In both compounds the DyIII ion is surrounded by six oxygen and two nitrogen atoms. Complex 1 displays single-ion magnet (SIM) behaviour only in solution ( Δ=12(1) K and τ0=1.9(4)×10−6 s), while complex 2 is a SIM in both solution ( Δ=15(2) K and τ0=1.5(3)×10−6 s) and solid state ( Δ=17(2) K and τ0=9.5(2)×10−6 s). The SIM behaviour is obtained if the hydrogen bond is broken by dissolution ( 1 in solution) or by alkylation ( 2). Multiple relaxation processes were identified for 2 with two competing processes: a fast one in zero field and a slow one for fields higher than 500 Oe. The two processes coexist for intermediate applied magnetic field. Magnetic-dilution and frozen-solution measurements led to the conclusion that the origin of these multiple relaxation processes is not due to the property of a single molecule. [ABSTRACT FROM AUTHOR]

Six dinuclear complexes, [Ln2(hfac)6(H2O)2( L)] [Ln = Y ( 1) and Er ( 2)], [Yb2(hfac)6( L)] ( 3), [Ln2(tta)6( L)] ·3CH2Cl2 [Ln = Y ( 4) and Er ( 5)] and [Yb2(tta)6( L)] ·2C6H14 ( 6), have been prepared by coordination reactions between the [Ln(β-diketonate)3] ·2H2O (Ln = YIII, ErIII and YbIII; β-diketonate = hfac- or tta-) building blocks and 4,4′,7,7′-tetra- tert-butyl-2,2′-bi-1,3-benzodithiole-5,5′,6,6′-tetrone ligand ( L), which acts as a bridge between the two metal centres. Their X-ray structures reveal that the symmetries around the lanthanide atoms depend on the β-diketonate anions and the size of the 4f ions. The dc magnetic measurements showed paramagnetic behaviour with thermal variations of the χM T products that depend on the crystal-field symmetry around the 4f ions. The photophysical properties of the coordination complexes were studied by solid-state absorption spectroscopy, and DFT calculations were carried out on the free ligand L and the diamagnetic YIII derivatives 1 and 4. Irradiation of the charge-transfer (ILCT) band of L [ λex = 700 nm (14285 cm-1)], 1 and 4 [ λex = 750 nm (13335 cm-1)] induced weak fluorescence in L at 12500 cm-1 (for free L) and in 1 at 12200 cm-1, whereas in the case of 3, irradiation at 13335 cm-1 induced weak line-shape emission assigned to the 2F5/2 → 2F7/2 (9880 cm-1) ytterbium-centred transition. No residual charge-transfer emission was observed in this last case attesting the efficient energy transfer from the excited charge-transfer state to the 2F5/2 state. The weak intensity of the emissions should mainly be attributed to energy back-transfer between the relaxed CT excited state and the CT state. Nevertheless, sensitisation of the YbIII luminescence in 3 was achieved through the lowest-energy donor excited state (13585 cm-1) reported until now. [ABSTRACT FROM AUTHOR]

Keywords: cyclononatetraenyl; lanthanides; organometallics; magnetism; single molecule magnets EN cyclononatetraenyl lanthanides organometallics magnetism single molecule magnets 13480 13480 1 09/28/21 20210924 NES 210924 B High-symmetry organometallic sandwiches b of lanthanides are of current high interest because of their magnetic and optical properties. Cyclononatetraenyl, lanthanides, organometallics, magnetism, single molecule magnets When trivalent lanthanide complexes feature the large monoanionic cyclononatetraenyl (Cnt) ligand, an interesting hapticity switching is observed along with a decrease in the size of the metal center. [Extracted from the article]

The reactions between the bis(1,10-phenantro[5,6-b])tetrathiafulvalene triad (L) and the metallo-precursors Yb(hfac)3(H2O)2 (hfac− = 1,1,1,5,5,5-hexafluoroacetylacetonato anion) and Dy(facam)3 (facam− = 3-trifluoro-acetyl-(+)-camphorato anion) lead to the formation of two dinuclear complexes of formula [Yb2(hfac)6(L)]·2(C7H16) ((1)·2(C7H16)) and [Dy2((+)facam)6(L)]·2(C6H14) ((2)·2(C6H14)). The X-ray structures reveal that the L triad bridges two terminal Yb(hfac)3 or Dy(facam)3 units. (1)·2(C7H16) behaved as a near infrared YbIII centered emitter and a field-induced Single-Molecule Magnet (SMM) while (2)·2(C6H14) displayed SMM behavior in both zero- and in-dc field. The magnetization mainly relaxes through a Raman process for both complexes under an optimal applied magnetic field. [ABSTRACT FROM AUTHOR]

The reaction between the 2,2′-benzene-1,4-diylbis(6-hydroxy-4,7-di-tert-butyl-1,3-benzodithiol-2-ylium-5-olate biradical triad (L) and the metallo-precursor [Dy(hfac)3]·2H2O leads to the formation of a one-dimensional coordination polymer with the formula {[Dy(hfac)3(L)]·2C6H14}n (1). The X-ray structure reveals that the polymeric structure is formed by the bridging of the Dy(hfac)3 units with the multi-redox triad L. Single-crystal X-ray diffraction and UltraViolet-visible absorption spectroscopy confirm that the triad L in 1 is bound as a direduced, diprotonated form of o-quinone-extended tetrathiafulvalene-o-quinone (Q-exTTF-Q). Alternate Current (AC) measurements highlight a field-induced single-molecule magnet (SMM) behavior with an energy barrier of 20 K, and thus 1 can be described as a one-dimensional assembly of mononuclear SMMs bridged by the L triad. [ABSTRACT FROM AUTHOR]