Single-Crystal-to-Single-Crystal Installation of Ln4(OH)4 Cubanes in an Anionic Metallosupramolecular Framework

Postsynthetic installation of lanthanide cubanes into a metallosupramolecular framework via a single-crystal-to-single-crystal (SCSC) transformation is presented. Soaking single crystals of K₆[Rh₄Zn₄O(l -cys)₁₂] (K₆[ 1 ]; l -H₂cys=l -cysteine) in a water/ethanol solution containing Ln(OAc)₃ (Ln³⁺=lanthanide ion) results in the exchange of K⁺ by Ln³⁺ with retention of the single crystallinity, producing Ln₂[ 1 ] ( 2_Ln ) and Ln_0.33[Ln₄(OH)₄(OAc)₃(H₂O)₇][ 1 ] ( 3_Ln ) for early and late lanthanides, respectively. While the Ln³⁺ ions in 2_Ln exist as disordered aqua species, those in 3_Ln form ordered hydroxide-bridged cubane clusters that connect [ 1 ]⁶⁻ anions in a 3D metal-organic framework through coordination bonds with carboxylate groups. This study shows the utility of an anionic metallosupramolecular framework with carboxylate groups for the creation of a series of metal cubanes that have great potential for various applications, such as magnetic materials and heterogeneous catalysts.     

Single‐Crystal‐to‐Single‐Crystal Installation of Ln4(OH)4 Cubanes in an Anionic Metallosupramolecular Framework

Postsynthetic installation of lanthanide cubanes into a metallosupramolecular framework via a single‐crystal‐to‐single‐crystal (SCSC) transformation is presented. Soaking single crystals of K₆[Rh₄Zn₄O(l ‐cys)₁₂] (K₆[ 1 ]; l ‐H₂cys=l ‐cysteine) in a water/ethanol solution containing Ln(OAc)₃ (Ln³⁺=lanthanide ion) results in the exchange of K⁺ by Ln³⁺ with retention of the single crystallinity, producing Ln₂[ 1 ] ( 2_Ln ) and Ln_0.33[Ln₄(OH)₄(OAc)₃(H₂O)₇][ 1 ] ( 3_Ln ) for early and late lanthanides, respectively. While the Ln³⁺ ions in 2_Ln exist as disordered aqua species, those in 3_Ln form ordered hydroxide‐bridged cubane clusters that connect [ 1 ]^6? anions in a 3D metal‐organic framework through coordination bonds with carboxylate groups. This study shows the utility of an anionic metallosupramolecular framework with carboxylate groups for the creation of a series of metal cubanes that have great potential for various applications, such as magnetic materials and heterogeneous catalysts.     

Octanuclear Ni4Ln4 Coordination Aggregates from Schiff Base Anion Supports and Connecting of Two Ni2Ln2 Cubes: Syntheses,Structures, and Magnetic Properties

A family of 3d–4f aggregates have been reported through guiding the dual coordination modes of ligand anion (HL^?) and in situ generated ancillary bridge driven self‐assembly coordination responses toward two different types of metal ions. Reactions of lanthanide(III) nitrate (Ln=Gd, Tb, Dy, Ho and Yb), nickel(II) acetate and phenol‐based ditopic ligand anion of 2‐[{(2‐hydroxypropyl)imino}methyl]‐6‐methoxyphenol (H₂L) in MeCN‐MeOH (3 : 1) mixture and LiOH provided five new octanuclear Ni‐4f coordination aggregates from two Ni₂Ln₂ cubanes. Single‐crystal X‐ray diffraction analysis reveals that all the members of the family are isostructural, with the central core formed from the coupling of two distorted [Ni₂Ln₂O₄] heterometallic cubanes [Ni₂Ln₂(HL)₂(μ₃‐OH)₂(OH)(OAc)₄]⁺ (Ln=Gd ( 1 ), Tb ( 2 ), Dy ( 3 ), Ho ( 4 ) and Yb ( 5 )). Higher coordination demand of 4f ions induced the coupling of the two cubes by (OH)(OAc)₂ bridges. Variable temperature magnetic study reveals weak coupling between the Ni²⁺ and Ln³⁺ ions. For the Tb ( 2 ) and Dy ( 3 ) analogs, the compounds are SMMs without an applied dc field, whereas the Gd ( 1 ) analogue is not an SMM. The observation revealed thus that the anisotropy of the Ln³⁺ ions is central to display the SMM behavior within this structurally intriguing family of compounds.     

Ionic Fluids Containing Both Strongly and Weakly Interacting Ions of the Same Charge Have Unique Ionic and Chemical Environments as a Function of Ion Concentration

Liquid multi‐ion systems made by combining two or more salts can exhibit charge ordering and interactions not found in the parent salts, leading to new sets of properties. This is investigated herein by examining a liquid comprised of a single cation, 1‐ethyl‐3‐methylimidazolium ([C₂mim]⁺), and two anions with different properties, acetate ([OAc]^?) and bis(trifluoromethylsulfonyl)imide ([NTf₂]^?). NMR and IR spectroscopy indicate that the electrostatic interactions are quite different from those in either [C₂mim][OAc] or [C₂mim][NTf₂]. This is attributed to the ability of [OAc]^? to form complexes with the [C₂mim]⁺ ions at greater than 1:1 stoichiometries by drawing [C₂mim]⁺ ions away from the less basic [NTf₂]^? ions. Solubility studies with molecular solvents (ethyl acetate, water) and pharmaceuticals (ibuprofen, diphenhydramine) show nonlinear trends as a function of ion content, which suggests that solubility can be tuned through changes in the ionic compositions.     

The undesirable acetylation of cellulose by the acetate ion of 1-ethyl-3-methylimidazolium acetate

Abstract  

The ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([C2mim]OAc) is considered to be an inert solvent of cellulose and lignocellulosic biomass. Acetylation (1.7% mol, or DS 0.017) of cellulose after dissolution in technical grade [C2mim]OAc (150 °C for 20 min), is demonstrated by compositional analysis, FTIR analysis and ¹³C NMR spectroscopy (in [C2mim]OAc with ¹³C enriched acetate). This acetylation, in the absence of added acylating agents, has not been reported before and may limit [C2mim]OAc utility in industrial scale biomass processing, even at this low extent. For example, cellulose acetylation may contribute to IL loss in processes where the IL is recovered and reused and inhibit enzyme saccharification of cellulose in lignocellulosic biofuel production processes based on saccharification and fermentation.     

Periodic Behavior of Lanthanide Coordination within Reverse Micelles

Trends in lanthanide(III) (Ln^III) coordination were investigated within nanoconfined solvation environments. Ln^III ions were incorporated into the cores of reverse micelles (RMs) formed with malonamide amphiphiles in n‐heptane by contact with aqueous phases containing nitrate and Ln^III; both insert into pre‐organized RM units built up of DMDOHEMA (N,N′‐dimethyl‐N,N′‐dioctylhexylethoxymalonamide) that are either relatively large and hydrated or small and dry, depending on whether the organic phase is acidic or neutral, respectively. Structural aspects of the Ln^III complex formation and the RM morphology were obtained by use of XAS (X‐ray absorption spectroscopy) and SAXS (small‐angle X‐ray scattering). The Ln^III coordination environments were determined through use of L₃‐edge XANES (X‐ray absorption near edge structure) and EXAFS (extended X‐ray absorption fine structure), which provide metrical insights into the chemistry across the period. Hydration numbers for the Eu species were measured using TRLIFS (time‐resolved laser‐induced fluorescence spectroscopy). The picture that emerges from a system‐wide perspective of the Ln? O interatomic distances and number of coordinating oxygen atoms for the extracted complexes of Ln^III in the first half of the series (i.e., Nd, Eu) is that they are different from those in the second half of the series (i.e., Tb, Yb): the number of coordinating oxygen atoms decrease from 9 O for early lanthanides to 8 O for the late ones—a trend that is consistent with the effect of the lanthanide contraction. The environment within the RM, altered by either the presence or absence of acid, also had a pronounced influence on the nitrate coordination mode; for example, the larger, more hydrated, acidic RM core favors monodentate coordination, whereas the small, dry, neutral core favors bidentate coordination to Ln^III. These findings show that the coordination chemistry of lanthanides within nanoconfined environments is neither equivalent to the solid nor bulk solution behaviors. Herein we address atomic‐ and mesoscale phenomena in the under‐explored field of lanthanide coordination and periodic behavior within RMs, providing a consilience of fundamental insights into the chemistry of growing importance in technologies as diverse as nanosynthesis and separations science.     

Mechanistic Aspects of the Gas‐Phase Reactions of Halobenzenes with Bare Lanthanide Cations: A Combined Experimental/Theoretical Investigation

The gas‐phase reactions of chlorobenzene with all atomic lanthanide cations Ln⁺ (except Pm⁺) have been investigated by using Fourier transform ion cyclotron resonance mass spectrometry in conjunction with density functional theory calculations. According to the latter, a direct chlorine transfer to the lanthanide cation, which has been observed previously for fluorine abstraction from fluorobenzene, is not operative for the C₆H₅Cl/Ln⁺ couples; rather, chlorine transfer proceeds through an initial coordination of the lanthanide cation to the aromatic ring of the substrate. Both, the product distribution and the chlorine abstraction efficiencies are affected by the bond dissociation energy (BDE(Ln⁺?Cl)) as well as the promotion energies of Ln⁺ to attain a 4fⁿ 5d¹ 6s¹ configuration. In addition, mechanistic aspects of some C?H and C?C bond activations are presented. Where appropriate, comparison with the previously studied C₆H₅F/Ln⁺ systems is made.     

Synthesis,Structure, and Magnetic Properties of a Series of Dinuclear Lanthanide Complexes Assembled by Acetate and a Schiff Base Ligand

Five dinuclear lanthanide complexes [Ln₂L₂(NO₃)₂(OAc)₄] · 2CH₃CN [Ln = Gd ( 1 ), Tb ( 2 ), Dy ( 3 ), Ho ( 4 ), and Er ( 5 )] [L = 2‐((2‐pyridinylmethylene)hydrazine)ethanol] were synthesized from the reactions of Ln(NO₃)₃ · 6H₂O with L and CH₃COOH in the presence of triethylamine. Their crystal structures were determined. They show similar dinuclear cores with the two lanthanide ions bridged by four acetate ligands in the μ₂‐η¹:η² and μ₂‐η¹:η¹ bridging modes. Each Ln^III ion in complexes 1 – 5 is further chelated by one L ligand and one nitrate ion, leading to the formation of a nine‐coordinated mono‐capped square antiprism arrangement. The dinuclear molecules in 1 – 5 are consolidated by hydrogen bonds and π ··· π stacking interactions to build a two‐dimensional sheet. Their magnetic properties were investigated. It revealed antiferromagnetic interactions between the Gd^III ions in 1 and ferromagnetic interactions between the Tb^III ions in 2 . The profiles of χ_mT vs. T curves of 3 – 5 reveal that the magnetic properties of 3 – 5 are probably dominated by the thermal depopulation of the Stark sublevels of Ln^III ions.     

Effect of Ionic Liquid Anion Type in the Performance of Solid Polymer Electrolytes Based on Poly(Vinylidene fluoride‐trifluoroethylene)

The effect of different anions within the ionic liquid in the characteristics of solid polymer electrolytes (SPEs) based on P(VDF‐TrFE) has been investigated. 1‐ethyl‐3‐methylimidazolium acetate, [C₂mim][OAc], 1‐ethyl‐3‐methylimidazolium triflate, [C₂mim][(CF₃SO₃)], 1‐ethyl‐3‐methylimidazolium lactate, [C₂mim][Lactate], 1‐ethyl‐3‐methylimidazolium thiocyanate, [C₂mim][SNC] and 1‐ethyl‐3‐methylimidazolium hydrogen sulfate [C₂mim][HSO₄] have been used in SPE prepared by solvent casting. The polymer phase, thermal and electrochemical properties of the SPE have been determined. The thermal and electrical properties of the SPEs strongly depend on the selected IL, as determined by their different interactions with the polymer matrix. The room temperature ionic conductivity increases in the following way for the different anions: [SNC]>[CF₃SO₃)]>[HSO₄]>[Lactate]>[OAc], which is mainly dependent on the viscosity of the ionic liquid.     

Significant effect of lanthanide doping on the texture and properties of nanocrystalline mesoporous TiO2

A systematic study of microstructure and photocatalytic properties of lanthanide doping of nanocrystalline mesoporous titanium dioxide is performed. The anatase-to-rutile (A-R) phase transformation of nanosized TiO₂ was significantly inhibited by lanthanide doping and the inhibitory effect was enhanced with the increase of the rare earth radius, i.e., La³⁺>Gd³⁺>Yb³⁺ for different lanthanide dopants. At high calcination temperatures, different texture lanthanide titanium oxides of Ln₄Ti₉O₂₄ (La³⁺, Pr³⁺, Nd³⁺), Ln₂Ti₂O₇ (Eu³⁺, Gd³⁺, Tb³⁺, Dy³⁺, Er³⁺), and Yb₂TiO₅ were developed, respectively, revealing that the structures of lanthanide titanium oxide developed in Ln/TiO₂ depend on the lanthanide radius. Larger radius lanthanides prefer to form higher coordination number lanthanide titanium oxide. In addition, the thermal stability of mesoporous structures of TiO₂ was remarkable improved by lanthanide doping. The photocatalytic properties were studied by employing the photodegradation of Rhodamine B (RB) as a probe reaction. The results indicate that the lanthanide doping could bring about significant improvement to the photoreactivity of TiO₂, and the improvement was sensitive to the atomic electronic configuration.     

Ionic liquid 1-ethyl-3-methylimidazolium acetate: an attractive solvent for native chemical ligation of peptides

The ionic liquid 1-ethyl-3-methylimidazolium acetate ([C₂mim][OAc]) was successfully used as alternative solvent for native chemical ligation of peptide fragments to produce model peptide LYRAXCRANK (X = G, A, L, N, Q, K, and F). The commonly used buffer system including thiol additives such as thiophenol and benzyl mercaptan can be replaced by the nontoxic ionic liquid [C₂mim][OAc]. In addition to improving the solubility of the peptides in [C₂mim][OAc], yields and rates of the ligation reactions were found to be efficiently enhanced.     

Photoluminescence Properties of Lanthanide‐Organic Frameworks (LnOFs) with Thiophene‐2,5‐Dicarboxylate and Acetate

S‐heterocyclic dicarboxylic acid, thiophene‐2,5‐dicarboxylic acid (H₂TDC), was employed to construct a series of lanthanide‐organic frameworks (LnOFs) with coligand acetate, formulated as [Ln(TDC)(OAc)(H₂O)]_n [Ln = Eu ( 1 ), Tb ( 2 ), Gd ( 3 ), Dy ( 4 ), Sm ( 5 )] under hydrothermal conditions. Structure analysis reveals that 1 – 5 have dinuclear 3D metal organic frameworks (MOFs), in which TDC^2– and OAc^– display (κ¹‐κ¹)‐(κ¹–κ¹)‐μ₄ and (κ²‐κ¹)‐μ₂ coordination fashions, respectively. The dehydrated products of all compounds show high thermal stability above 410 °C. As for 1 , 2 , 4 , and 5 , the photoluminescence analyses exhibit characteristic luminescence emission bands of the corresponding lanthanide ions in the visible region. In particular, compound 2 displays bright green luminescence in the solid state with ⁵D₄ lifetime of 0.510 ms and relative high overall quantum yield of 16 %, based on an ideal energy gap between the lowest triplet state energy level of H₂TDC ligand and the ⁵D₄ state energy level of Tb³⁺. The energy transfer mechanisms in compounds 1 and 2 were also discussed.     

Synthesis,structures and magnetic properties of a series of polynuclear copper(II)‐lanthanide( III) complexes assembled with carboxylate and hydroxide ligands

Heterometallic copper(II)‐lanthanide(III) complexes have been made with a variety of exclusively O‐donor ligands including betaines (zwitterionic carboxylates) and chloroacetate, which are dinuclear CuLn, tetranuclear Cu₂Ln₂, pentanuclear C_u3Ln₂, and octadecanuclear C_u12 complexes. The results show that subtle changes in both the carboxylates and acidity of the reaction solution can cause drastic changes in the structures of the products. Magnetic studies exhibit that shielding of the Ln³⁺ 4f electrons by the outer shell electrons is very effective to preclude significant coupling interaction between the Ln³⁺ 4f electrons and Cu²⁺ 3d electrons in either a mono‐atomic hydroxide‐bridged, or a carboxylate‐bridged system.     

Erste Pyridylbenzimidazolate der Lanthanide: Synthese,Kristallstruktur und thermischer Abbau von NH4[Ln(N3C12H8)4] mit Ln = Nd,Yb

The First Pyridylbenzimidazolates of the Lanthanides: Syntheses, Crystal Structure and Thermal Decomposition of NH₄[Ln(N₃C₁₂H₈)₄] with Ln = Nd, Yb Transparent yellow crystals of the compounds NH₄ [Ln^III (N₃C₁₂H₈)₄] with Ln = Nd, Yb were obtained by solvent‐free reactions of the lanthanides neodymium and ytterbium with 2‐(2‐Pyridyl)‐benzimidazole. The bulk syntheses lead to isotypic compounds despite the different ionic radii of Nd^III and Yb^III exhibiting nitrogen coordination of the lanthanides only. Both compounds were investigated IR‐ and Raman‐spectroscopically and in regard to their thermal behaviour. They are the first examples of completely solvent‐free (coordinating and non‐coordinating) compounds of the lanthanides with a complete N‐coordination that were obtained via a solid‐state reaction method.     

Syntheses,Structures, and Photoluminescence of Lanthanide Coordination Polymers Based on 4‐Oxo‐1,4‐dihydro‐2,6‐pyridinedicarboxylic acid

Investigating the coordination chemistry of H₂CDA (4‐oxo‐1,4‐dihydro‐2,6‐pyridinedicarboxylic acid) with rare earth salts Ln(NO₃)₃ under hydrothermal conditions, structure transformation phenomenon was observed. The ligand, H₂CDA charged to its position isomer, enol type structure, H₃CAM (4‐hydroxypyridine‐2,6‐dicarboxylic acid). Six new lanthanide(III) coordination polymers with the formulas [Ln(CAM)(H₂O)₃]_n [Ln = La ( 1 ), Pr, ( 2 )] and {[Ln(CAM)(H₂O)₃] · H₂O}_n [Ln = Nd, ( 3 ), Sm, ( 4 ), Eu, ( 5 ), Y, ( 6 )] were synthesized and characterized. The X‐ray structure analyses show two kinds of coordination structures. The complexes 1 and 2 and 3 – 6 are isostructural. Complexes 1 and 2 crystallize in the monoclinic C₂/c space group, whereas 3 – 6 crystallize in the monoclinic system with space group P2₁/n. In the two kinds of structures, H₃CAM displays two different coordination modes. The Sm^III and Eu^III complexes exhibit the corresponding characteristic luminescence in the visible region at an excitation of 376 nm.     

A structural study of ternary lanthanide orthoscandate perovskites

Ternary lanthanide scandates (Ln=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, and Ho) have been synthesized at ambient pressure. Their structure has been investigated at room temperature by Rietveld analysis of powder X-ray diffraction data. The Ln-scandates are orthorhombic perovskites, adopting space group Pbnm (? 62), a≈b≈√2a_p, c≈2a_p, Z=4. Heavy lanthanides (Er-Lu), and Y do not form perovskites at ambient conditions. Compositionally driven phase transitions were not observed. The unit-cell parameters decrease with increasing ScO₆ octahedron rotation and atomic number of the Ln cation. In common with lanthanide orthoferrites, the uniform structural evolution is interrupted at the middle-heavy part of the lanthanide sequence. This is probably due to an interplay between: (i) enlargement of the ScO₆ octahedra relative to BO₆ in other perovskites (e.g., FeO₆ in GdFeO₃); (ii) reduction in size of the first coordination sphere of Ln³⁺ coincident with the lanthanide contraction; (iii) coincident expansion of the second coordination sphere due to screening effects of O^I1 on O^I2, and entry of Sc to the lanthanide coordination sphere; (iv) complex mixing between oxygen and lanthanide lanthanide f- and scandium d-orbitals. In the series studied, Ln³⁺ are in eight-fold coordination (tetragonal antiprism), and are considerably displaced from the center of the LnO₈ polyhedron along [001]. Evolution of the crystallochemical characteristics through the Ln orthoscandate series is complex due to both the antipathetic distortions of A- and B-site coordination polyhedra and interaction of the orbitals of oxygen, Ln and Sc. Empirically obtained limits of Goldschmidt and observed ^viiit_o tolerance factors for ternary LnBO₃ compounds adopting the Pbnm structure are 0.795 and 0.841, respectively.     

Komplexe von 2,6-Dimethylpyridin-1-oxid mit Lanthanidjodiden

Complexes of 2,6-dimethylpyridine 1-oxide with lanthanide iodides of the formulaeLn(2,6-LTNO)₅I₃ whereLn=La, Tb and Yb,Ln(2,6-LTNO)₄I₃ whereLn=Pr and Nd and Er(2,6-LTNO)_4.5I₃ have been prepared and characterised by chemical analysis, infrared and conductance studies. Infrared and conductance data have been interpreted in terms of dimeric (or polymeric) structures involving bridging amine oxide groups.

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Mit 2 Abbildungen     

Thermal,spectral and magnetic behaviour of 4-chloro-2-methoxybenzoates of light lanthanides(III)

4-Chloro-2-methoxybenzoates of light lanthanides(III) were obtained as mono-, di-or trihydrates with metal to ligand ratio of 1:3 and general formula Ln(C₈H₆ClO₃)₃·nH₂O, where n=1 for Ln=Ce, Pr, n=2 for Ln=Nd, Sm, Eu, Gd and n=3 for Ln=La. The complexes were characterized by elemental analysis, IR spectra, thermogravimetric studies, X-ray diffraction and magnetic measurements. The carboxylate group appears to be a symmetrical bidentate, chelating ligand. All complexes seem polycrystalline compounds. Their thermal stabilities were determined in air. When heated they dehydrate to form anhydrous salts which next are decomposed to the oxides of the respective metals. The solubilities of light lanthanide(III) 4-chloro-2-methoxybenzoates in water at 293 K are of the order of 10⁻⁵ mol dm⁻³. The magnetic moments were determined over the range of 77–300 K. They obey the Curie-Weiss law. The values of μ_eff calculated for all compounds are close to those obtained for Ln³⁺ by Hund and Van Vleck. The results indicate that there is no influence of the ligand field of 4f electrons on lanthanide ions and the metal ligand bonding is mainly electrostatic in nature.     

Syntheses and Crystal Structures of LnIII–CuI Coordination Polymers

Four three‐dimensional heterometallic coordination polymers, [Ln₂Cu₄I₃(IN)₇(H₂O)]_n ( 1 , 2 ) and [LnCu_3.5I₃(IN)_3.5(H₂O)₃]_n · nH₂O ( 3 , 4 ) [HIN = isonicotinic acid, Ln = Nd ( 1 ), Gd ( 2 ), La ( 3 ), Eu ( 4 )] were hydrothermally synthesized by using lanthanide oxides, isonicotinic acid, copper chloride, and potassium iodide. The different molar ratio of raw materials results in two distinct types of three‐dimensional frameworks of compounds 1 – 4 . The structure of compounds 1 and 2 are constructed by the layer modules of [Ln₂(IN)₇(H₂O)]_n^n– and Cu₄I₃ clusters, whereas that of compounds 3 and 4 are built by dimeric Ln₂(IN)₆(H₂O)₆ and layered polymeric [Cu₇I₆]_nⁿ⁺ units.     

Organic‐inorganic Hybrid Lanthanide‐Silver Heterometallic Coordination Frameworks Constructed from Oxalate and Sulfate Anion: Syntheses,Structures, and Photoluminescent Properties

The first four examples of organic‐inorganic hybrid lanthanide‐silver heterometallic frameworks, namely, [AgLn(μ₅‐C₂O₄)(SO₄)(H₂O)₂] [Ln = Eu ( 1 ) and Sm ( 2 )] and [AgLn(μ₄‐C₂O₄)_0.5(μ₆‐C₂O₄)_0.5(SO₄)(H₂O)] [Ln = Tb ( 3 ) and Dy ( 4 )] based on oxalate and sulfate anions were synthesized by hydrothermal reactions of lanthanide oxide, silver nitrate, oxalic acid and sulfuric acid. All structures contain ladder‐like inorganic lanthanide sulfato chains, which are further connected together through silver atoms by oxalate anions with different coordination behavior (μ₅‐C₂O₄: 1 and 2 , μ₆‐C₂O₄ mixed μ₄‐C₂O₄: 3 and 4 ) to generate two types of 3D networks. The luminescent properties of these compounds were also studied.