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.     

Carbazole-based Schiff base: A sensitive fluorescent ‘turn-on’ chemosensor for recognition of Al(III) ions in aqueous-alcohol media

Carbazole-based Schiff base chemosensor was synthesized in one-pot synthesis using 2-hydroxy-1-naphtaldehyde for fluorescent sensing of Al³⁺ ions. Characterization of the ligand (L) was revealed through spectroscopic and physicochemical techniques. The fluorescence emission responses of L to various metal ions and anions were investigated. The chelation was studied by UV–vis, ¹H NMR, LC-MS/MS, fluorescence titration and Job’s plot analysis. Bathochromic shift resulted from charge transfer from L to electrophilic Al³⁺ ion was observed in the chelation of L with Al³⁺. The potentiality of L to be a distinguished probe to detect Al³⁺ ions was due to a chelation enhanced fluorescence (CHEF) effect, concomitant with noticeable fluorescent enhancement. A significant fluorescence enhancement at 533 nm was observed in ethanol–water (1:1, v/v) solution upon addition of Al³⁺ along with a distinct color change from yellow to white. Non-fluorescent ligand exposed highly sensitive turn-on fluorescent sensor behavior for selectively sensing Al³⁺ ions via 1:1 (ligand:metal) stoichiometry. The ligand’s specificity in the existence of other tested metal ions and anions indicated no observation in color change. The ligand-Al³⁺ complex formation was reversible upon addition of chelating agent EDTA. The ligand interacted with Al³⁺ ions with an association constant of K_a = 5 × 10⁴ M^?1. The limit of detection (LOD) was found to be 2.59 × 10^-7 M. The synthesized Schiff base could efficiently detect Al³⁺ ions as a fluorescent sensor.     

Hexanuclear Co4Dy2, Zn4Dy2, and Co4Y2 Complexes with Defect Tetracubane Cores: Syntheses,Structures, and Magnetic Properties

A hexanuclear heterometallic cluster of composition [Dy₂Co₄(L)₄(NO₃)₂(OH)₄(C₂H₅OH)₂] ⋅ 2 C₂H₅OH ( 1 ) was synthesized by employing a Schiff base 2-(((2-hydroxy-3-methoxybenzyl) imino)methyl)-4-methoxyphenol (H₂L) as ligand and utilizing Dy(NO₃)₃ ⋅ 6H₂O and Co(NO₃)₂ ⋅ 6H₂O as metal ion sources. X-ray single-crystal diffraction analysis indicated that complex 1 contains a defect tetracubane core and possesses central symmetric structure, with two Dy^III ions being in the central body position of the molecule and four Co^II ions being arranged at the outer sites. Magnetic studies reveal that complex 1 behaves as single-molecule magnet (SMM) with energy barrier of 27.50 K. To investigate the individual contribution of Dy^III and Co^II ions to the SMM behavior, another two complexes of formulae [Dy₂Zn₄(L)₄(NO₃)₂(OH)₄] ⋅ 4CH₃OH ( 2 ) and [Y₂Co₄(L)₄(NO₃)₂(OH)₄(C₂H₅OH)₂] ⋅ 2 C₂H₅OH ( 3 ) were prepared. Complexes 1 and 3 are isomorphous. The coordination geometries of Dy^III ions in 1 and 2 are different. The Dy^III ions are eight-coordinated in 2 and nine-coordinated in 1 . Complex 2 exhibits SMM behavior with energy barrier of 69.67 K, but complex 3 does not display SMM property. These results reveal that the SMM behaviors of 1 and 2 are mainly originated from Dy^III ions. It might be the higher symmetry of Dy^III ions in 2 that results in the higher energy barrier.     

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.     

Coordinate Structures of PrIII, GdIII, TmIII, and YbIII Complexes with Nitrilotriacetic Acids

The crystal and molecular structures of the [Pr^III(nta)(H₂O)₂]·H₂O (nta = nitrilotriacetic acids), K₃[Gd^III(nta)₂(H₂O)]·6H₂O, and K₃[Yb^III(nta)₂]·5H₂O complexes have been determined by single-crystal X-ray structure analyses. In [Pr^III(nta)(H₂O)₂]·H₂O, the Pr^IIINO₈ part forms a nine-coordinate pseudo-monocapped square antiprismatic structure in which one N and three O atoms are from one nta ligand in the same molecule, three O atoms from another nta ligand in the neighboring molecule and two O atoms from two coordinate water molecules. In K₃[Gd^III(nta)₂(H₂O)]·6H₂O, the [Gd^III(nta)₂(H₂O)^3- complex anion has a nine-coordinate pseudo-monocapped square antiprismatic structure in which each nta acts as a tetradentate ligand with one N atom of the amino group and three O atoms of the carboxylic groups. In K₃[Yb^III(nta)₂]·5H₂O, each nta also acts as a tetradentate ligand with one N atom of amino group and three O atoms of the carboxylic groups, but the [Yb^III(nta)₂ ^3- complex anion has an eight-coordinate structure with a distorted square antiprismatic prism. All the results including those for [Tm^III(nta)(H₂O)₂]·2H₂O confirm the inferences on the coordinate structures and coordination numbers of rare earth metal complexes with the nta ligand.     

Synthesis,Structure, and Fluorescent Properties of Lanthanide Complexes Based on 8‐Hydroxyquinoline‐7‐carboxylic Acid

The lanthanide complex [Eu₃(8‐HQCA)₃(COOH)(OH)₂(H₂O)₃]_n · nH₂O (8‐HQCA = 8‐hydroxyquinoline‐7‐carboxylic acid) was synthesized and characterized. Single‐crystal X‐ray diffraction shows that the trinuclear structures are linked by ligands to form 2D layers. The results of DFT calculation shows that energy can be transferred effectively from the ligand to Eu^III ions. A series of heteronuclear complexes {[(Eu_1–xY_x)₃(8‐HQCA)₃(COOH) (OH)₂(H₂O)₃]_n · nH₂O (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8)} were synthesized and their luminescent properties were studied. The results showed that the doping of Y^III ions could change the fluorescent intensity of the Eu^III complex, but could not change their positions.     

Synthesis,Characterization, and Reactivity of Cobalt(III)–Oxygen Complexes Bearing a Macrocyclic N‐Tetramethylated Cyclam Ligand

Mononuclear metal–dioxygen species are key intermediates that are frequently observed in the catalytic cycles of dioxygen activation by metalloenzymes and their biomimetic compounds. In this work, a side‐on cobalt(III)–peroxo complex bearing a macrocyclic N‐tetramethylated cyclam (TMC) ligand, [Co^III(15‐TMC)(O₂)]⁺, was synthesized and characterized with various spectroscopic methods. Upon protonation, this cobalt(III)–peroxo complex was cleanly converted into an end‐on cobalt(III)–hydroperoxo complex, [Co^III(15‐TMC)(OOH)]²⁺. The cobalt(III)–hydroperoxo complex was further converted to [Co^III(15‐TMC‐CH₂‐O)]²⁺ by hydroxylation of a methyl group of the 15‐TMC ligand. Kinetic studies and ¹⁸O‐labeling experiments proposed that the aliphatic hydroxylation occurred via a Co^IV–oxo (or Co^III–oxyl) species, which was formed by O? O bond homolysis of the cobalt(III)–hydroperoxo complex. In conclusion, we have shown the synthesis, structural and spectroscopic characterization, and reactivities of mononuclear cobalt complexes with peroxo, hydroperoxo, and oxo ligands.     

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].     

Cationic Iridium(III) Complex Containing both Triarylboron and Carbazole Moieties as a Ratiometric Fluoride Probe That Utilizes a Switchable Triplet–Singlet Emission

A novel cationic Ir^III complex [Ir(Bpq)₂(CzbpyCz)]PF₆ (Bpq=2‐[4‐(dimesitylboryl)phenyl]quinoline, CzbpyCz = 5,5′‐bis(9‐hexyl‐9H‐carbazol‐3‐yl)‐2,2′‐bipyridine) containing both triarylboron and carbazole moieties was synthesized. The excited‐state properties of [Ir(Bpq)₂(CzbpyCz)]PF₆ were investigated through UV/Vis absorption and photoluminescence spectroscopy and molecular‐orbital calculations. This complex displayed highly efficient orange‐red phosphorescent emission with an emission peak of 583 nm and quantum efficiency of Φ=0.30 in dichloromethane at room temperature. The binding of fluoride ions to [Ir(Bpq)₂(CzbpyCz)]PF₆ can quench the phosphorescent emission from the Ir^III complex and enhance the fluorescent emission from the N^N ligand, which corresponds to a visual change in the emission from orange‐red to blue. Thus, both colorimetric and ratiometric fluoride sensing can be realized. Interestingly, an unusual intense absorption band in the visible region was observed. And the detection of F^? ions can also be carried out with visible light as the excitation wavelength. More importantly, the linear response of the probe absorbance change at λ=351 nm versus the concentration of F^? ions allows efficient and accurate quantification of F^? ions in the range 0–50 μM .     

Fluorimetric Detection of Phosphates in Water Using a Disassembly Approach: A Comparison of FeIII-, ZnII-, MnII- and MnIII-salen Complexes

Details of the reaction sequence used for the fluorimetric detection of phosphates by disassembly of transition metal Schiff base complexes were investigated for [Fe^III(salen)(H₂O)]⁺, [Zn^II(salen)], [Mn^II(salen)(H₂O)₂], and [Mn^III(salen)(H₂O)]⁺. The reactivity of these compounds towards phosphorus oxoanions of differing charge, number of donor atoms and steric hindrance was detected by UV/Vis and fluorescence spectroscopy in both aprotic organic and aqueous media. Selectivity of [Fe^III(salen)(H₂O)]⁺ towards pyrophosphate over all other tested phosphorus-containing analytes was strongly supported. [Zn^II(salen)] showed a faster reactivity but was much less selective. In contrast, [Mn^III(salen)(H₂O)]⁺ proved to be more stable than the iron complex but generally showed little reactivity towards phosphorus oxoanions. The influence of the charge of the central atom was investigated using the Mn^II analogue [Mn^II(salen)(H₂O)₂]. As expected, the reduced charge resulted in a reactivity comparable to the Zn^II complex in organic solution but lead to hydrolysis of the complex in water. Finally, the reaction products of [Fe^III(salen)(H₂O)]⁺ with phosphates were characterized by IR spectroscopy and mass spectrometry, providing further insights into the reaction mechanism of the disassembly process.     

Synthesis of LnII-in-Cryptand Complexes by Chemical Reduction of LnIII-in-Cryptand Precursors: Isolation of a NdII-in-Cryptand Complex

Lanthanide triflates have been used to incorporate Nd^III and Sm^III ions into the 2.2.2-cryptand ligand (crypt) to explore their reductive chemistry. The Ln(OTf)₃ complexes (Ln=Nd, Sm; OTf=SO₃CF₃) react with crypt in THF to form the THF-soluble complexes [Ln^III(crypt)(OTf)₂][OTf] with two triflates bound to the metal encapsulated in the crypt. Reduction of these Ln^III-in-crypt complexes using KC₈ in THF forms the neutral Ln^II-in-crypt triflate complexes [Ln^II(crypt)(OTf)₂]. DFT calculations on [Nd^II(crypt)]²⁺], the first Nd^II cryptand complex, assign a 4f⁴ electron configuration to this ion.     

Synthesis of LnII‐in‐Cryptand Complexes by Chemical Reduction of LnIII‐in‐Cryptand Precursors: Isolation of a NdII‐in‐Cryptand Complex

Lanthanide triflates have been used to incorporate Nd^III and Sm^III ions into the 2.2.2‐cryptand ligand (crypt) to explore their reductive chemistry. The Ln(OTf)₃ complexes (Ln=Nd, Sm; OTf=SO₃CF₃) react with crypt in THF to form the THF‐soluble complexes [Ln^III(crypt)(OTf)₂][OTf] with two triflates bound to the metal encapsulated in the crypt. Reduction of these Ln^III‐in‐crypt complexes using KC₈ in THF forms the neutral Ln^II‐in‐crypt triflate complexes [Ln^II(crypt)(OTf)₂]. DFT calculations on [Nd^II(crypt)]²⁺], the first Nd^II cryptand complex, assign a 4f⁴ electron configuration to this ion.     

Sensitized near-infrared emission of Yb from an Ir–Yb bimetallic complex

A new cyclometalated ligand 1,3-dimethyl-5-phenyl-1H-[1,2,4]-triazole (pdt) was designed and synthesized. And the corresponding Ir^III complex Ir(pdt)₂(phen5f) (phen5f stands for 4,4,5,5,5-pentafluoro-1-(1′,10′-phenanthrolin-2′-yl)-pentane-1,3-dionate) was obtained. According to the measurement of the lowest triplet state energy level of Ir(pdt)₂(phen5f), it is suitable for sensitizing NIR (near-infrared) lanthanide ions instead of Eu^III. The bimetallic complex [(pdt)₂Ir(μ-phen5f)YbCl₂ · 2CH₃CH₂OH · H₂O]Cl was synthesized by the approach of “complexes as ligands”. Data showed that the emission quenching was observed in the solid state when the Ir^III–Yb^III complex was compared with the Ir^III complex, which implied that energy transfer might occur from Ir^III complex-ligand to Yb^III ion. Upon irradiation of the MLCT (metal-to-ligand charge transfer) absorption of Ir(pdt)₂(phen5f), the characteristic emission of Yb^III was obtained with the peak around 978 nm.     

Mechanistic Insight into the NN Bond‐Cleavage of Azo‐Compounds that was Induced by an Al?Al‐bonded Compound [L2−AlII?AlIIL2−]

An α‐diimine‐stabilized Al? Al‐bonded compound [L^2?Al^II? Al^IIL^2?] (L=[{(2,6‐iPr₂C₆H₃)NC(Me)}₂]; 1 ) consists of dianionic α‐diimine ligands and sub‐valent Al²⁺ ions and thus could potentially behave as a multielectron reductant. The reactions of compound 1 with azo‐compounds afforded phenylimido‐bridged products [L^?Al^III(μ₂‐NPh)(μ₂‐NAr)Al^IIIL^?] ( 2 – 4 ). During the reaction, the dianionic ligands and Al²⁺ ions were oxidized into monoanions and Al³⁺, respectively, whilst the [NAr]^2? imides were produced by the four‐electron reductive cleavage of the N?N double bond. Upon further reduction by Na, the monoanionic ligands in compound 2 were reduced to the dianion to give [(L^2?)₂Al^III₂(μ₂‐NPh)₂Na₂(thf)₄] ( 5 ). Interestingly, when asymmetric azo‐compounds were used, the asymmetric adducts were isolated as the only products (compounds 3 and 4 ). DFT calculations indicated that the reaction was quite feasible in the singlet electronic state, but the final product with the triplet‐state monoanionic ligands could result from an exothermic singlet‐to‐triplet conversion during the reaction process.     

An antiferromagnetic {Mn8} ring supported by planar multidentate ligands

Complexation of the planar multidentate ligand 3,5-bis-(2-hydroxyphenyl)pyrazole (H 3 L) with manganese chloride leads to the formation of the polynuclear complex [Mn Ⅲ 8 L 4 O 4 (MeO) 4 (MeOH) 8 ] (1). 1 has an octanuclear macrocyclic core in which the MnⅢ ions are bridged by four L molecules to form a ring type structure. Antiferromagnetic interactions were shown to be operative between metal centers.     

Syntheses and structural analyses of nine-coordinate protonated (Py)2[GdIII(HNta)(Nta)(H2O)] · 5H2O and eight-coordinate (NH4)3[HoIII(Nta)2] complexes

The syntheses and structural determination of Gd(III) and Ho(III) complexes with nitrilotriacetic acids (Nta) were reported in this paper. Their structures and compositions were determined and characterized by single-crystal X-ray structure analyses, elemental analyses, and IR spectra. The first protonated Nta complex was found. Structural analyses indicate that the structure greatly changes, while an alternative Nta ligand was protonated in the ((Py)₂[Gd^III(HNta)(Nta)(H₂O)] · 5H₂O complex and the(NH₄)₃[Ho^III(Nta)₂] complex crystallized as a centrosymmetric structure. By contrast, it is further confirmed that the coordination number and coordinate structure of all trivalent rare-earth metal complexes with aminopolycarboxylic acids mainly depend on the ionic radii and electronic configuration of the central metal ions and their countercations.     

Radiative decay channel assessment to understand the sensing mechanism of a fluorescent turn-on Al3+ chemosensor

The turn-on luminescent chemosensor [2-Hydroxy-1-naphthaldehyde-(2-pyridyl) hydrazone] (L), selective to Al³⁺ ions, was studied by means of density functional theory (DFT) and time-dependent-DFT quantum mechanics calculations. The UV-Vis absorption and the radiative channel from the adiabatic S₁ excited state were assessed in order to elucidate the selective sensing mechanism of L to Al³⁺ ions. We found that twisted intramolecular charge transfer (TICT) and photoelectron transfer (PET), which alter the emissive state, are responsible for the luminescence quenching in L. After coordination with Al³⁺, the TICT is blocked, and PET is no longer possible. So, the emission of the coordination complex is activated, and a fluorescence effect enhanced by chelation is observed. For compounds with Zn²⁺ and Cd²⁺, the luminescence quenching is caused by PET, while for Ni²⁺, ligand to metal charge transfer is the prominent mechanism. To go into more detail, the metal-ligand interaction was analyzed via the Morokuma-Ziegler energy decomposition scheme and the natural orbital of chemical valence.     

Heterotrimetallic Coordination Polymers: {CuIILnIIIFeIII} Chains and {NiIILnIIIFeIII} Layers: Synthesis,Crystal Structures,and Magnetic Properties

The use of the [Fe^III(AA)(CN)₄]^? complex anion as metalloligand towards the preformed [Cu^II(valpn)Ln^III]³⁺ or [Ni^II(valpn)Ln^III]³⁺ heterometallic complex cations (AA=2,2′‐bipyridine (bipy) and 1,10‐phenathroline (phen); H₂valpn=1,3‐propanediyl‐bis(2‐iminomethylene‐6‐methoxyphenol)) allowed the preparation of two families of heterotrimetallic complexes: three isostructural 1D coordination polymers of general formula {[Cu^II(valpn)Ln^III(H₂O)₃(μ‐NC)₂Fe^III(phen)(CN)₂ {(μ‐NC)Fe^III(phen)(CN)₃}]NO₃ ? 7 H₂O}_n (Ln=Gd ( 1 ), Tb ( 2 ), and Dy ( 3 )) and the trinuclear complex [Cu^II(valpn)La^III(OH₂)₃(O₂NO)(μ‐NC)Fe^III(phen)(CN)₃] ? NO₃ ? H₂O ? CH₃CN ( 4 ) were obtained with the [Cu^II(valpn)Ln^III]³⁺ assembling unit, whereas three isostructural heterotrimetallic 2D networks, {[Ni^II(valpn)Ln^III(ONO₂)₂(H₂O)(μ‐NC)₃Fe^III(bipy)(CN)] ? 2 H₂O ? 2 CH₃CN}_n (Ln=Gd ( 5 ), Tb ( 6 ), and Dy ( 7 )) resulted with the related [Ni^II(valpn)Ln^III]³⁺ precursor. The crystal structure of compound 4 consists of discrete heterotrimetallic complex cations, [Cu^II(valpn)La^III(OH₂)₃(O₂NO)(μ‐NC)Fe^III(phen)(CN)₃]⁺, nitrate counterions, and non‐coordinate water and acetonitrile molecules. The heteroleptic {Fe^III(bipy)(CN)₄} moiety in 5 – 7 acts as a tris‐monodentate ligand towards three {Ni^II(valpn)Ln^III} binuclear nodes leading to heterotrimetallic 2D networks. The ferromagnetic interaction through the diphenoxo bridge in the Cu^II?Ln^III ( 1 – 3 ) and Ni^II?Ln^III ( 5 – 7 ) units, as well as through the single cyanide bridge between the Fe^III and either Ni^II ( 5 – 7 ) or Cu^II ( 4 ) account for the overall ferromagnetic behavior observed in 1 – 7 . DFT‐type calculations were performed to substantiate the magnetic interactions in 1 , 4 , and 5 . Interestingly, compound 6 exhibits slow relaxation of the magnetization with maxima of the out‐of‐phase ac signals below 4.0 K in the lack of a dc field, the values of the pre‐exponential factor (τ_o) and energy barrier (E_a) through the Arrhenius equation being 2.0×10^?12 s and 29.1 cm^?1, respectively. In the case of 7 , the ferromagnetic interactions through the double phenoxo (Ni^II–Dy^III) and single cyanide (Fe^III–Ni^II) pathways are masked by the depopulation of the Stark levels of the Dy^III ion, this feature most likely accounting for the continuous decrease of χ_M T upon cooling observed for this last compound.     

Syntheses,Structures, and Properties of Two New Tri‐spin Lanthanide‐Nitronyl Nitroxide (LnIII = GdIII and HoIII) Complexes

Abstract. Two radical–Ln^III–radical complexes, [Ln(hfac)₃(NITPh‐Ph)₂] [Ln = Gd ( 1 ) and Ho ( 2 ), hfac = hexafluoroacetylacetonate; and NITPh‐Ph = 4′‐biphenyl‐4, 4, 5, 5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide] were synthesized and characterized by X‐ray diffraction, elemental analysis, magnetic measurements, as well as IR and UV/Vis spectroscopy. X‐ray crystal structure analysis revealed that the structures of both complexes are isomorphous, the central Ln^III ions are coordinated by six oxygen atoms from three hfac ligand molecules and two oxygen atoms from nitronyl radicals. The temperature dependencies of the magnetic susceptibilities were studied. They showed that in the Gd^III complex, ferromagnetic interactions between Gd^III and the radicals and antiferromagnetic interactions between the radicals coexist in this system (with J_Rad–Gd = 0.1 cm^–1, J_Rad–Rad = –0.309 cm^–1).     

Hydrothermal Syntheses,Crystal Structures,and Luminescent Properties of Three Organic‐Lanthanide Complexes with 3‐Hydroxycinnamic Acid

Three new homodinuclear lanthanide(III) complexes [Ln₂(L)₆(2,2′‐bipy)₂] [Ln = Tb^III ( 1 ), Sm^III ( 2 ), Eu^III ( 3 ); HL = 3‐hydroxycinnamic acid (3‐HCA); 2,2′‐bipy = 2,2′‐bipyridine] were synthesized and characterized by IR spectroscopy, elemental analyses, and X‐ray diffraction techniques. Complexes 1 – 3 crystallize in triclinic system, space group P$\bar{1}$ . In all complexes the lanthanide ions are nine‐coordinate by two nitrogen atoms from the 2,2′‐bipy ligand and seven oxygen atoms from one chelating L ligands and four bridging L ligands, forming distorted tricapped trigonal prismatic arrangements. The lanthanide(III) ions are intramolecularly bridged by eight carboxylate oxygen atoms forming dimeric complexes with Ln ··· Ln distances of 3.92747(15), 3.9664(6), and 3.9415(4) Å for complexes 1 – 3 , respectively. The luminescent properties in the solid state of HL ligand and Eu^III complex are also discussed.