Rational Design of a Lanthanide‐Based Complex Featuring Different Single‐Molecule Magnets

The rational synthesis of the 2‐{1‐methylpyridine‐N‐oxide‐4,5‐[4,5‐bis(propylthio)tetrathiafulvalenyl]‐1H‐benzimidazol‐2‐yl}pyridine ligand ( L ) is described. It led to the tetranuclear complex [Dy₄(tta)₁₂( L )₂] ( Dy‐Dy₂‐Dy ) after coordination reaction with the precursor Dy(tta)₃?2 H₂O (tta^?=2‐thenoyltrifluoroacetonate). The X‐ray structure of Dy‐Dy₂‐Dy can be described as two terminal mononuclear units bridged by a central antiferromagnetically coupled dinuclear complex. The terminal N₂O₆ and central O₈ environments are described as distorted square antiprisms. The ac magnetism measurements revealed a strong out‐of‐phase signal of the magnetic susceptibility with two distinct sets of data. The high‐ and low‐frequency components were attributed to the two terminal mononuclear single‐molecule magnets (SMMs) and the central dinuclear SMM, respectively. A magnetic hysteresis loop was detected at very low temperature. From both structural and magnetic points of view, the tetranuclear SMM Dy‐Dy₂‐Dy is a self‐assembly of two known mononuclear SMMs bridged by a known dinuclear SMM.     

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.     

Effects of substituents on bridging ligands on the single‐molecule magnet properties of Zn2Dy2 cluster complexes

Two new Zn₂Dy₂ complexes were constructed from Zn (II) salen‐type Schiff base complex fragment and 2,6‐pyridinedimethanol (H₂pdm) or its Br‐substituted analogue (4‐bromopyridine‐2,6‐diyl)dimethanol (H₂Brpdm); their molecular formulas are [Zn₂Dy₂(L)₂(pdm)₂(MeOH)₂](ClO₄)₂ [ 1 , H₂L = N, N′‐ bis(3‐methoxysalicylidene)‐1,3‐diaminopropane] and [Zn₂Dy₂(L)₂(Brpdm)₂(MeOH)₂](ClO₄)₂ [ 2 ], the Dy (III) ions of which have a NO₇ triangular dodecahedral coordination sphere. The two complexes show not only ferromagnetic interaction but also field‐induced single‐molecule magnet (SMM) behavior, which are rare Dy (III)‐containing cluster complexes with the NO₇ triangular dodecahedral coordination sphere that can show good magnetic relaxation. The energy barrier value of complex 2 is higher than those of complex 1 and the Dy (III) complexes with the DyNO₇ triangular dodecahedral coordination configuration reported in the literature.     

Dimeric hexakis(4‐methyl­benzoato)­bis(1,10‐phenanthroline)didyspros­ium(III)

The title compound, [Dy₂(C₈H₇O₂)₆(C₁₂H₈N₂)₂], forms binuclear complexes, viz. di‐μ‐4‐methyl­benzoato‐κ⁴O:O′‐bis[bis(4‐methyl­benzoato‐κ²O,O′)(1,10‐phenanthroline‐κ²N,N′)dyspros­ium(III)] tetra‐μ‐4‐methyl­benzoato‐κ⁸O:O′‐bis[(4‐methyl­benzoato‐κ²O,O′)(1,10‐phenanthroline‐κ²N,N′)dyspros­ium(III)]. There are two independent binuclear com­plexes in the asymmetric unit, both of which are centrosymmetric. In one, the Dy^III ions are linked by two bridging 4‐­methyl­benzoate groups, while in the other, the Dy^III ions are linked by four bridging 4‐methyl­benzoate groups. The remaining 4‐methyl­benzoate groups and 1,10‐phenanthroline units coordinate to just one metal ion in bidentate modes.     

Three Phenoxo‐Bridged Dinuclear Lanthanide Complexes: Syntheses,Crystal Structures,and Magnetic Properties

Three dinuclear lanthanide complexes [Ln₂(H₂L)₂(NO₃)₄] [Ln = Dy ( 1 ), Tb ( 2 ), and Gd ( 3 )] [H₃L = 2‐hydroxyimino‐N′‐[(2‐hydroxy‐3‐methoxyphenyl)methylidene]‐propanohydrazone] were solvothermally synthesized by varying differently anisotropic rare earth ions. Single‐crystal structural analyses demonstrate that all the three complexes are crystallographically isostructural with two centrosymmetric Ln^III ions aggregated by a pair of monodeprotonated H₂L^– anions. Weak intramolecular antiferromagnetic interactions with different strength were mediated by a pair of phenoxo bridges due to superexchange and/or single‐ion anisotropy. Additionally, the Dy^III‐based entity shows the strongest anisotropy exhibits field‐induced single‐molecule magnetic behavior with two thermally activated relaxation processes. In contrast, 3 with isotropic Gd^III ion has a significant cryogenic magnetocaloric effect with the maximum entropy change of 25.7 J · kg^–1 · K^–1 at 2.0 K and 70.0 kOe.     

Rational Electrostatic Design of Easy‐Axis Magnetic Anisotropy in a ZnII–DyIII–ZnII Single‐Molecule Magnet with a High Energy Barrier

Two novel trinuclear complexes [ZnCl(μ‐L)Ln(μ‐L)ClZn][ZnCl₃(CH₃OH)]?3 CH₃OH (Ln^III=Dy ( 1 ) and Er ( 2 )) have been prepared from the compartmental ligand N,N′‐dimethyl‐N,N′‐bis(2‐hydroxy‐3‐formyl‐5‐bromo‐benzyl)ethylenediamine (H₂L). X‐ray studies reveal that Ln^III ions are coordinated by two [ZnCl(L)]^? units through the phenoxo and aldehyde groups, giving rise to a LnO₈ coordination sphere with square‐antiprism geometry and strong easy‐axis anisotropy of the ground state. Ab initio CASSCF+RASSI calculations carried out on 1 confirm that the ground state is an almost pure M_J=±15/2 Kramers doublet with a marked axial anisotropy, the magnetic moment is roughly collinear with the shortest Dy?O distances. This orientation of the local magnetic moment of the Dy^III ion in 1 is adopted to reduce the electronic repulsion between the oblate electron shape of the M_J=±15/2 Kramers doublet and the phenoxo‐oxygen donor atoms involved in the shortest Dy?O bonds. CASSCF+RASSI calculations also show that the ground and first excited states of the Dy^III ion are separated by 129 cm^?1. As expected for this large energy gap, compound 1 exhibits, in a zero direct‐current field, thermally activated slow relaxation of the magnetization with a large U_eff=140 K. The isostructural Zn–Er–Zn species does not present significant SMM behavior as expected for the prolate electron‐density distribution of the Er^III ion leading to an easy‐plane anisotropy of the ground doublet state.     

Two C3‐Symmetric Dy3III Complexes with Triple Di‐μ‐methoxo‐μ‐phenoxo Bridges,Magnetic Ground State,and Single‐Molecule Magnetic Behavior

Two series of isostructural C₃‐symmetric Ln₃ complexes Ln₃ ? [BPh₄] and Ln₃ ? 0.33[Ln(NO₃)₆] (in which Ln^III=Gd and Dy) have been prepared from an amino‐bis(phenol) ligand. X‐ray studies reveal that Ln^III ions are connected by one μ₂‐phenoxo and two μ₃‐methoxo bridges, thus leading to a hexagonal bipyramidal Ln₃O₅ bridging core in which Ln^III ions exhibit a biaugmented trigonal‐prismatic geometry. Magnetic susceptibility studies and ab initio complete active space self‐consistent field (CASSCF) calculations indicate that the magnetic coupling between the Dy^III ions, which possess a high axial anisotropy in the ground state, is very weakly antiferromagnetic and mainly dipolar in nature. To reduce the electronic repulsion from the coordinating oxygen atom with the shortest Dy?O distance, the local magnetic moments are oriented almost perpendicular to the Dy₃ plane, thus leading to a paramagnetic ground state. CASSCF plus restricted active space state interaction (RASSI) calculations also show that the ground and first excited state of the Dy^III ions are separated by approximately 150 and 177 cm^?1, for Dy₃ ? [BPh₄] and Dy₃ ? 0.33[Dy(NO₃)₆], respectively. As expected for these large energy gaps, Dy₃ ? [BPh₄] and Dy₃ ? 0.33[Dy(NO₃)₆] exhibit, under zero direct‐current (dc) field, thermally activated slow relaxation of the magnetization, which overlap with a quantum tunneling relaxation process. Under an applied H_dc field of 1000 Oe, Dy₃ ? [BPh₄] exhibits two thermally activated processes with U_eff values of 34.7 and 19.5 cm^?1, whereas Dy₃ ? 0.33[Dy(NO₃)₆] shows only one activated process with U_eff=19.5 cm^?1.     

Trinuclear [CoIII2–LnIII] (Ln=Tb,Dy) Single‐Ion Magnets with Mixed 6‐Chloro‐2‐Hydroxypyridine and Schiff Base Ligands

The Schiff base ligand N1,N3‐bis(3‐methoxysalicylidene)diethylenetriamine (H₂valdien) and the co‐ligand 6‐chloro‐2‐hydroxypyridine (Hchp) were used to construct two 3d–4f heterometallic single‐ion magnets [Co₂Dy(valdien)₂(OCH₃)₂(chp)₂] ? ClO₄ ? 5 H₂O ( 1 ) and [Co₂Tb(valdien)₂(OCH₃)₂(chp)₂] ? ClO₄ ? 2 H₂O ? CH₃OH ( 2 ). The two trinuclear [Co^III₂Ln^III] complexes behave as a mononuclear Ln^III magnetic system because of the presence of two diamagnetic cobalt(III) ions. Complex 1 has a molecular symmetry center, and it crystallizes in the C2/c space group, whereas complex 2 shows a lower molecular symmetry and crystallizes in the P2₁/c space group. Magnetic investigations indicated that both complexes are field‐induced single‐ion magnets, and the Co^III₂–Dy^III complex possesses a larger energy barrier [74.1(4.2) K] than the Co^III₂–Tb^III complex [32.3(2.6) K].     

One‐dimensional Salen‐type Chain‐like Lanthanide(III) Coordination Polymers: Syntheses,Crystal Structures,and Fluorescence Properties

Four salen‐type lanthanide(III) coordination polymers [LnH₂L(NO₃)₃(MeOH)_x]_n [Ln = La ( 1 ), Ce ( 2 ), Sm ( 3 ), Gd ( 4 )] were prepared by reaction of Ln(NO₃)₃ · 6H₂O with H₂L [H₂L = N,N′‐bis(salicylidene)‐1,2‐cyclohexanediamine]. Single‐crystal X‐ray diffraction analysis revealed that H₂L effectively functions as a bridging ligand forming a series of 1D chain‐like polymers. The solid‐state fluorescence spectra of polymers 1 and 2 emit single ligand‐centered green fluorescence, whereas 3 exhibits typical red fluorescence of Sm^III ions. The lowest triplet level of ligand H₂L was calculated on the basis of the phosphorescence spectrum of Gd^III complex 4 . The energy transfer mechanisms in the lanthanide polymers were described and discussed.     

161Dy Time‐Domain Synchrotron Mössbauer Spectroscopy for Investigating Single‐Molecule Magnets Incorporating Dy Ions

Time‐domain synchrotron Mössbauer spectroscopy (SMS) based on the Mössbauer effect of ¹⁶¹Dy has been used to investigate the magnetic properties of a Dy^III‐based single‐molecule magnet (SMM). The magnetic hyperfine field of [Dy(Cy₃PO)₂(H₂O)₅]Br₃?2 (Cy₃PO)?2 H₂O?2 EtOH is with B₀=582.3(5) T significantly larger than that of the free‐ion Dy^III with a ⁶H_15/2 ground state. This difference is attributed to the influence of the coordinating ligands on the Fermi contact interaction between the s and 4f electrons of the Dy^III ion. This study demonstrates that ¹⁶¹Dy SMS is an effective local probe of the influence of the coordinating ligands on the magnetic structure of Dy‐containing compounds.     

Controlled Synthesis of Heterotrimetallic Single‐Chain Magnets from Anisotropic High‐Spin 3 d–4 f Nodes and Paramagnetic Spacers

By using the node‐and‐spacer approach in suitable solvents, four new heterotrimetallic 1D chain‐like compounds (that is, containing 3d–3d′–4f metal ions), {[Ni(L)Ln(NO₃)₂(H₂O)Fe(Tp*)(CN)₃] ? 2 CH₃CN ? CH₃OH}_n (H₂L=N,N′‐bis(3‐methoxysalicylidene)‐1,3‐diaminopropane, Tp*=hydridotris(3,5‐dimethylpyrazol‐1‐yl)borate; Ln=Gd ( 1 ), Dy ( 2 ), Tb ( 3 ), Nd ( 4 )), have been synthesized and structurally characterized. All of these compounds are made up of a neutral cyanide‐ and phenolate‐bridged heterotrimetallic chain, with a {? Fe? C?N? Ni(? O? Ln)? N?C? }_n repeat unit. Within these chains, each [(Tp*)Fe(CN)₃]^? entity binds to the Ni^II ion of the [Ni(L)Ln(NO₃)₂(H₂O)]⁺ motif through two of its three cyanide groups in a cis mode, whereas each [Ni(L)Ln(NO₃)₂(H₂O)]⁺ unit is linked to two [(Tp*)Fe(CN)₃]^? ions through the Ni^II ion in a trans mode. In the [Ni(L)Ln(NO₃)₂(H₂O)]⁺ unit, the Ni^II and Ln^III ions are bridged to one other through two phenolic oxygen atoms of the ligand (L). Compounds 1 – 4 are rare examples of 1D cyanide‐ and phenolate‐bridged 3d–3d′–4f helical chain compounds. As expected, strong ferromagnetic interactions are observed between neighboring Fe^III and Ni^II ions through a cyanide bridge and between neighboring Ni^II and Ln^III (except for Nd^III) ions through two phenolate bridges. Further magnetic studies show that all of these compounds exhibit single‐chain magnetic behavior. Compound 2 exhibits the highest effective energy barrier (58.2 K) for the reversal of magnetization in 3d/4d/5d–4f heterotrimetallic single‐chain magnets.     

Five Rare μ4‐O‐Centered Ln6 Clusters with Single‐Molecule Magnet Behavior for Dy6

Five hexanuclear lanthanide clusters of composition [Ln₆(μ₄‐O)₂(HCOO)₂L₄(HL′)₂(dmf)₂] [Ln=Dy ( 1 ), Er ( 2 ), Ho ( 3 ), Tb ( 4 ), Gd ( 5 ); H₂L=2‐{[2‐(hydroxymethyl)phenylimino]methyl}‐6‐methoxyphenol; H₃L′=3‐{[2‐(hydroxymethyl)phenylimino]methyl}benzene‐1,2‐diol; H₃L′ was derived in situ from the H₂L ligand] were prepared under solvothermal conditions. The [Ln₆] cores of 1 – 5 possess an unprecedented motif, namely, two tetrahedron Ln₄ units sharing an edge and two vertices. The six Ln^III ions of 1 – 5 are connected through two μ₄‐O anions. Magnetic susceptibility studies reveal that complex 1 exhibits frequency dependence of the alternating current susceptibility typical of single‐molecule magnets. Complex 1 possesses a relatively large energy barrier of 85 K among all of the reported Dy₆ single‐molecule magnets.     

Copolymerization of carbon dioxide with cyclohexene oxide catalyzed by bimetallic dysprosium complexes containing hydrazine‐functionalized Schiff‐base derivatives

A series of dinuclear Dy^III acetate complexes containing three different hydrazine‐functionalized Schiff‐base ligands ( hmb , hmi, and hb ) have been synthesized by one‐pot reaction with Dy(OAc)₃·4H₂O as the metal precursor. [Dy₂( hmb )₂(OAc)₄]·MeCN ( 1 ·MeCN) and [Dy₂( hmi )₂(OAc)₂(MeOH)₂]·H₂O ( 2 ·H₂O) with keto and enol forms of the corresponding ligands, respectively, were shown the similar core structures but different ratio of Dy^III to OAc^–. Moreover, the different coordination environments of complex [Dy₂( hb )₂(μ‐OAc)₂(OAc)₂(H₂O)₂]·DMF·H₂O ( 3 ·DMF·H₂O) also offered an opportunity to understand the relationship between structural model and catalytic properties. Bimetallic dysprosium complexes 1 – 3 were demonstrated to be active catalysts for copolymerization of carbon dioxide (CO₂) and cyclohexene oxide (CHO) without cocatalysts. To the best of our knowledge, well‐defined catalyst 2 appears to be the first example of an air‐stable bimetallic dysprosium complex that is effective for CO₂/CHO copolymerization and the formation of the perfectly alternating poly(cyclohexenecarbonate) with a high molecular weight. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 321–328     

Syntheses,Structures, and Magnetism of Trinuclear Zn2Ln Complexes with 2,6‐Dipicolinoylbis(N,N‐diethylthiourea)

The bifunctional ligand 2,6‐dipicolinoylbis(N,N‐diethylthiourea) (H₂L) readily reacts with mixtures of Zn(CH₃COO)₂ and LnCl₃ in MeOH at ambient temperature with formation of trinuclear heterobimetallic complexes [Zn₂Ln(L)₂(OAc)₃] ( 1a – 1f ) (Ln = Ce, Nd, Sm, Gd, Dy, Er). The X‐ray single‐crystal diffraction and structural studies of the complexes revealed their isostructural nature, in which two doubly‐charged ligands {L^2–} bind two Zn²⁺ ions with the terminal acylthiourea sites and one Ln³⁺ ion with the central 2,6‐pyridinedicarboxamide site. In the complexes, the coordination numbers of Ln^III and Zn^II ions are 9 and 5, respectively. Magnetic properties of the complexes were studied by temperature‐dependent dc magnetic measurements. The observed μ_eff values at room temperature are all closed to the calculated values. Fitting χ_M and M data of [Zn₂Gd(L)₂(OAc)₃] ( 1d ) shows a g_iso value of 1.94.     

Role of Dicarboxylate Linkers in MnIII‐Salicylaldoximate Based Extended Structures: Synthesis,Structures, and Magnetic Behavior

Four new oxo‐centered Mn^III‐salicylaldoximate triangle‐based extended complexes [Mn^III₆O₂(salox)₆(EtOH)₄(phda)]_n?(saloxH₂)_n?(2H₂O)_n ( 1 ), [Mn^III₆O₂(salox)₆(MeOH)₅(5‐I‐isoph)]_n?(3 MeOH)_n ( 2 ), [Mn^III₆O₂(salox)₆(MeOH)₄(H₂O) (5‐N₃‐isoph)]_n?(4 MeOH)_n ( 3 ) and [Mn^III₃NaO(salox)₃(MeOH)₄(5‐NO₂‐isoph)]_n?(MeOH)_n (H₂O)_n ( 4 ) [salox=salicylaldoximate, phda=1,3‐phenylenediacetate, isoph=isophthalate] have been synthesized under similar reaction conditions. Single crystal X‐ray structures show that in 1 , only one type of Mn₆ cluster is arranged in 1 D, whereas in 2 and 3 there are two types of clusters, differing in the way the triangle units are joined and assembled. In complex 4 , however, the basic building structure is heteronuclear and based on Mn₃ units extended in 2 D. Susceptibility measurements (dc and ac) over a wide range of temperatures and fields show that the complexes 1 , 2 , and 3 behave as single molecule magnets (SMMs) with S=4 ground state, while 4 is dominantly antiferromagnetic with a ground spin state S=2. Density functional theory calculations have been performed on model complexes to provide a qualitative theoretical interpretation for their overall magnetic behavior.     

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?.     

N,N′‐Bis(Salicylidene)‐1,2‐Cyclohexanediamine Lanthanide(III) Coordination Polymers: Syntheses,Crystal Structures,and Luminescence Properties

The salen‐type ligand H₂L [H₂L = N,N′‐bis(salicylidene)‐1,2‐cyclohexanediamine] was utilized for the synthesis of two lanthanide(III) coordination polymers [LnH₂L(NO₃)₃MeOH]_n [Ln = Eu ( 1 ) and Ln = Lu ( 2 )]. The single‐crystal X‐ray diffraction analyses of 1 and 2 revealed that they are isomorphous and exhibit one‐dimension neutral structure, in which H₂L effectively functions as a bridging ligand and give rise to a chain‐like polymer. The luminescent properties of polymers in solid state and in solution were investigated and 1 exhibits typical red luminescence of Eu^III ions in solid state and dichloromethane solution and 2 emits the ligand‐centered blue luminescence. The energy transfer mechanisms in these luminescent lanthanide polymers were described through calculation of the lowest triplet level of ligand H₂L.     

2,2′‐Bipyrimidine as Efficient Sensitizer of the Solid‐State Luminescence of Lanthanide and Uranyl Ions from Visible to Near‐Infrared

Treatment of Ln(NO₃)₃?nH₂O with 1 or 2 equiv 2,2′‐bipyrimidine (BPM) in dry THF readily afforded the monometallic complexes [Ln(NO₃)₃(bpm)₂] (Ln=Eu, Gd, Dy, Tm) or [Ln(NO₃)₃(bpm)₂]?THF (Ln=Eu, Tb, Er, Yb) after recrystallization from MeOH or THF, respectively. Reactions with nitrate salts of the larger lanthanide ions (Ln=Ce, Nd, Sm) yielded one of two distinct monometallic complexes, depending on the recrystallization solvent: [Ln(NO₃)₃(bpm)₂]?THF (Ln=Nd, Sm) from THF, or [Ln(NO₃)₃(bpm)(MeOH)₂]?MeOH (Ln=Ce, Nd, Sm) from MeOH. Treatment of UO₂(NO₃)₂?6H₂O with 1 equiv BPM in THF afforded the monoadduct [UO₂(NO₃)₂(bpm)] after recrystallization from MeOH. The complexes were characterized by their crystal structure. Solid‐state luminescence measurements on these monometallic complexes showed that BPM is an efficient sensitizer of the luminescence of both the lanthanide and the uranyl ions emitting visible light, as well as of the Yb^III ion emitting in the near‐IR. For Tb, Dy, Eu, and Yb complexes, energy transfer was quite efficient, resulting in quantum yields of 80.0, 5.1, 70.0, and 0.8 %, respectively. All these complexes in the solid state were stable in air.     

Observation of a Less Stable Conformer of N,N′‐Piperazine‐bis(methylenephosphonate) Ligand in a Six‐coordinated ­Samarium Phosphonate Framework

The three‐dimensional (3D) samarium phosphonate framework [Sm₂(H₂L)₃]_n · 5n(H₂O) ( 1 ) [H₄L = N,N′‐piperazine‐bis(methylenephosphonic acid)] was synthesized by hydrothermal reaction of Sm₂O₃ with N,N′‐piperazine‐bis(methylenephosphonic acid) hydrochloride in the presence of glutaric acid. Single‐crystal X‐ray diffraction analysis reveals that it has a 3D open framework structure with helical channels along the crystallographic c axis. The channels are filled up by discrete pentameric water clusters, which are hydrogen‐bonded to the host. Compound 1 displays two interesting structural features: (a) two of three H₂L^2– ligands adopt the less stable a,e‐cis conformation; (b) both of the Sm^III ions exhibit rather unusual octahedral coordination arrangements. In addition, the photoluminescent property was investigated.     

A Dinuclear Dysprosium Complex as an Air‐Stable and Recyclable Catalyst: Applications in the Deacetylation of Carbohydrate,Aliphatic, and Aromatic Molecules

Two dinuclear Dy^III complexes, [Dy₂(hmb)₂(OTf)₂(H₂O)₄] ? HOTf ? 2 THF ( A? HOTf ? 2 THF) and [Dy₂(hmi)₃(H₂O)₂] ? 2 HOTf ( B? 2 HOTf), have been synthesized by the reaction of Dy(OTf)₃ and the Schiff‐base ligands H₂hmb (N′‐(2‐hydroxy‐3‐methoxybenzylidene)benzohydrazide) or H₂hmi ((2‐hydroxy‐3‐methoxyphenyl)methylene isonicotinohydrazine). Disarmed glycosyl trichloroacetimidates can be activated by complex A in the synthesis of 1,2‐trans‐glycosides with primary and secondary acceptors. This method offers an efficient route to selectively deacetylated monosaccharides and disaccharides in high yields and a green catalyst that can be easily recycled and reused.