Synthesis,characterization, DNA-binding,and antioxidant activities of four copper(II) complexes containing N-(3-hydroxybenzyl)-amino amide ligands

Four new substituted amino acid ligands, N-(3-hydroxybenzyl)-glycine acid (HL₁), N-(3-hydroxybenzyl)-alanine acid (HL₂), N-(3-hydroxybenzyl)-phenylalanine acid (HL₃), and N-(3-hydroxybenzyl)-leucine acid (HL₄), were synthesized and characterized on the basis of ¹H NMR, IR, ESI-MS, and elemental analyses. The crystal structures of their copper(II) complexes [Cu(L₁)₂]·2H₂O (1), [Cu(L₂)₂(H₂O)] (2), [Cu(L₃)₂(CH₃OH)] (3), and [Cu(L₄)₂(H₂O)]·H₂O (4) were determined by X-ray diffraction analysis. The ligands coordinate with copper(II) through secondary amine and carboxylate in all complexes. In 2, 3, and 4, additional water or methanol coordinates, completing a distorted tetragonal pyramidal coordination geometry around copper. Fluorescence titration spectra, electronic absorption titration spectra, and EB displacement indicate that all the complexes bind to CT-DNA. Intrinsic binding constants of the copper(II) complexes with CT-DNA are 1.32?×?10^6?M^?1, 4.32?×?10^5?M^?1, 5.00?×?10^5?M^?1, and 5.70?×?10^4?M^?1 for 1, 2, 3, and 4, respectively. Antioxidant activities of the compounds have been investigated by spectrophotometric measurements. The results show that the Cu(II) complexes have similar superoxide dismutase activity to that of native Cu, Zn-SOD.     

Synthesis and Characterization of Dendrimeric Bridged Salen/Saloph Complexes and Investigation of Their Magnetic and Thermal Behaviors

Eight new multinuclear Fe^III and Cr^III complexes involving the tetradentate Schiff bases N,N′‐bis(salicylidene)ethylenediamine (salenH₂) or N,N′‐bis(salicylidene)benzene‐1,2‐diamine (salophH₂) and the two new ligands 4,4′,4″,4′′′,4′′′′,4′′′″‐[1,3,5‐triazine‐2,4,6‐triyltris(nitrilomethylidyne‐4,1‐phenyleneoxy‐1,3,5‐triazine‐6,2,4‐triyldiimino)]hexakis[benzoic acid] ( 4 ) or 5,5′,5″,5′′′,5′′′′,5′′′″‐[1,3,5‐triazine‐2,4,6‐triyltris(nitrilomethylidyne‐4,1‐phenyleneoxy‐1,3,5‐triazine‐6,2,4‐triyldiimino)]hexakis[benzene‐1,3‐dicarboxylic acid] ( 5 ) were synthesized (Schemes 1 and 2) and characterized by means of ¹H‐NMR and FT‐IR spectroscopy, elemental analysis, LC/MS analysis, AAS (atomic‐absorption spectrum) analysis, thermal analyses, and magnetic‐susceptibility measurements. The complexes can also be characterized as low‐spin distorted‐octahedral Fe^III and Cr^III complexes bridged by carboxylato moieties.     

Synthesis,characterization, and catalytic oxidation of styrene,cyclohexene, allylbenzene,and cis-cyclooctene by recyclable polymer-grafted Schiff base complexes of vanadium(IV)

Schiff base-functionalized chloromethylated polystyrenes, PS-[Ae-Eol] (I), PS-[Hy-Eda] (II) and PS-[HyP-Eda] (III), were synthesized by reacting 2-(2-aminoethoxy)ethanol (Ae-Eol), N-(2-hydroxyethyl)ethylenediamine (Hy-Eda), and N-(2-hydroxpropyl)ethylenediamine (HyP-Eda) with oxidized chloromethylated polystyrene. Oxidized chloromethylated polystyrene (PS-CHO) was prepared by oxidation of chloromethylated polystyrene (PS) with sodium bicarbonate in DMSO. By reacting DMSO solution of [VO(acac)₂] with polymer-anchored Schiff base ligands I, II, and III, vanadium(IV) complexes PS-[V^IVO(Ae-Eol)] (1), PS-[V^IVO(Hy-Eda)] (2), and PS-[V^IVO(HyP-Eda)] (3) were prepared. Structure and bonding of I, II, and III as well as corresponding vanadium complexes 1, 2, and 3 were confirmed by FT-IR, UV–vis spectroscopy, SEM, EDX, AAS, TGA, EPR, etc. Polymer-anchored vanadium(IV) complexes 1, 2, and 3 show, efficient catalysis toward oxidation of styrene, cyclohexene, allylbenzene, and cis-cyclooctene in the presence of hydrogen peroxide. Optimized reaction conditions for the oxidation of these alkenes was achieved by changing various reaction parameters (like amount of catalyst, amount of oxidizing agent, volume of solvent, etc.). Polymer-grafted 1, 2, and 3 can be reused multiple times without depletion of their activity.     

First MnIII complexes with tetradentate (N2O2) Schiff bases and tricyanomethanide: synthesis,crystal structure,and magnetic properties

The first Mn^III complexes with Schiff bases and tricyanomethanide-anion were synthesized: [Mn(salen)C(CN)₃(H₂O)] (1), [Mn(5-Brsalen)C(CN)₃(H₂O)] (2), [Mn(salpn)C(CN)₃(H₂O)] (3), [Mn(3-MeOsalen)C(CN)₃(H₂O)] (4), [Mn(5-Brsalen)(MeOH)(H₂O)][C(CN)₃] (5), and [Mn(3-MeOsalpn)(H₂O)₂][C(CN)₃] (6), where SalenH₂ is N,N′-bis(salicylidene)ethylenediamine, 5-BrsalenH₂ is N,N′-bis(5-bromosalicylidene)ethylenediamine, SalpnH₂ is N,N′-bis-(salicylidene)-1,3-diaminopropane, 3-MeOsalenH₂ is N,N′-bis(3-methoxysalicylidene)-ethylenediamine, 3-MeOsalpnH₂ — N,N′-bis(3-methoxysalicylidene)-1,3-diaminopropane. The tricyanomethanide anion in complexes 1–4 acts as a the terminal ligand, whereas in complexes 5 and 6 tricyanomethanide is not coordinated by Mn^III and acts as an out-of-sphere counterion. The structures of complexes 1–4 are characterized by the formation of dimers due to hydrogen bonds between the water molecules and oxygen atoms of the Schiff bases. The Mn...Mn distances inside the dimers are 4.69–5.41 Å. Complex 6 has a zigzag chain structure consisting of the [Mn(3-MeOsalpn)(H₂O)₂]⁺ cations bound by double bridging aqua ligands. The study of the magnetic properties of complexes 1, 3, 4, and 6 showed the existence of antiferromagnetic interactions between the Mn^III ions through the system of hydrogen bonds.     

Antiradical activity of morpholine- and piperazine-functionalized triphenylantimony(V) catecholates

The antiradical activity of the functionalized triphenylantimony(V) catecholates Ph₃Sb[4-O(CH₂CH₂)₂N-3,6-DBCat] (I), Ph₃Sb[4,5-Piperaz-3,6-DBCat] (II), and Ph₃Sb[4-PhN(CH₂CH₂)₂N-3,6-DBCat] (III) (where [4-O(CH₂CH₂)₂N-3,6-DBCat]^2?, [4,5-Piperaz-3,6-DBCat]^2?, and [4-PhN(CH₂CH₂)₂N-3,6-DBCat]^2? are the dianionic ligands 3,6-di-tert-butyl-4-(morpholin-1-yl)-, 3,6-di-tert-butyl-4,5-(piperazine-1,4-diyl)-, and 3,6-di-tert-butyl-4-(4-phenylpiperazin-1-yl)catecholates, respectively) was studied in reactions with the diphenylpicrylhydrazyl radical during autooxidation of unsaturated fatty (oleic and linoleic) acids with lipid peroxidation of Russian sturgeon (Acipenser gueldenstaedti B.) sperm and human blood erythrocytes in vitro as examples. The EC₅₀ and n _DPPH values obtained indicate the high antiradical activity of complexes II and III in the reactions with the stable radical. On the whole, complexes I–III inhibit the lipid peroxidation in both model (oxidation of unsaturated fatty acids) and in vitro experiments. The inhibiting effects of the complexes are comparable with and even, in some cases, higher than those of the known antioxidant ionol.     

Two Lanthanide(III) Complexes based on the Schiff Base N,N′‐Bis(salicylidene)‐1,5‐diamino‐3‐oxapentane: Synthesis,Characterization, DNA‐binding Properties,and Antioxidation

The Schiff base N,N′‐bis(salicylidene)‐1,5‐diamino‐3‐oxapentane (H₂L) and its lanthanide(III) complexes, PrL(NO₃)(DMF)(H₂O) ( 1 ) and Ho₂L₂(NO₃)₂ · 2H₂O ( 2 ), were synthesized and characterized by physicochemical and spectroscopic methods. Single crystal X‐ray structure analysis revealed that complex 1 is a discrete mononuclear species. The Pr^III ion is nine‐coordinate, forming a distorted capped square antiprismatic arrangement. Complex 2 is a centrosymmetric dinuclear neutral entity in which the Ho^III ion is eight‐coordinate with distorted square antiprismatic arrangement. The DNA‐binding properties of H₂L and its Ln^III complexes were investigated by spectrophotometric methods and viscosity measurements. The results suggest that the ligand H₂L and its Ln^III complexes both connect to DNA in a groove binding mode; the complexes bind more strongly to DNA than the ligand. Moreover, the antioxidant activities of the Ln^III complexes were in vitro determined by superoxide and hydroxyl radical scavenging methods, which indicate that complexes 1 and 2 have OH ^· and O₂^{– ·} radical scavenging activity.     

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

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

Synthesis of new 14- and 16-membered macrocycles and their transition metal complexes

Summary Benzoylacetic acid (1 mol) interacts with ethylenediamine or with propanediamine (2 mol) to yield new N₄ macrocycles 1,5,8,12-tetraazacyclotetradeca-2,4,9,11-tetraphenyl-3, 10-dicarboxylic-4,11-diacetic acid- 1,8-diene (L¹) and 1,5,9,13-tetraazacyclohexadeca-2,4,10,12-tetraphenyl-3, 11-dicarboxylic-4,12-diacetic acid-1,9-diene (L²), respectively. These macrocycles have been successfully complexed with Cr^III, Fe^III, Mn^II, Co^II, Ni^II, Cu^II and Zn^II. The complexes of the divalent metal ions are non-electrolytes, while those of Fe^III and Cr^III are 1:1 electrolytes in DMSO. On the basis of ligand field spectra and magnetic moments an octahedral geometry has been proposed for all the complexes.     

Synthesis,crystal structures,and catalytic properties of phenoxo-bridged dinuclear manganese(III) complexes with bis-Schiff bases

Two structurally similar centrosymmetric phenoxo-bridged dinuclear manganese(III) complexes, [Mn₂(L¹)₂(N₃)₂] (1) and [Mn₂(L²)₂(NCS)₂] (2), were prepared from the tetradentate bis-Schiff base ligands, N,N’-bis(salicylidene)propane-1,2-diamine (H₂L¹) and N,N’-bis(salicylidene)ethane-1,2-diamine (H₂L²), respectively, in the presence of pseudohalides. The complexes have been characterized by FTIR, elemental analyses, and molar conductivity. Structures of the complexes have been confirmed by single-crystal X-ray determination. The bis-Schiff base ligands coordinate with Mn through their phenolate oxygen and imino nitrogen. Each Mn is an octahedral. The complexes showed that they exhibit high activity in catalytic olefin oxidation.     

Some Tribenzyl Tin(IV) Complexes with Thiohydrazides and Thiodiamines. Synthesis,characterization and thermal studies

Tribenzyl tin(IV) chloride complexes of morpholine N-thiohydrazide (L¹), aniline-N-thiohydrazide (L²),N-(morpholine-N-thio)-1,3-propanediamine (L³) and (aniline-N-thio)-1,3-propanediamine (L⁴) of the type (C₆H₅CH₂)₃Sn(L)Cl (where L=L¹, L², L³ and L⁴) have been synthesised in dioxane and in H₂O and acetone mixture. These were characterized by C,H,N-analysis, UV, IR and ¹HNMR spectral studies. In both the complexes ligands act as bidentate, coordinating through sulphur and terminal nitrogen. The complexes are 1:1 metal ligand complexes. Various thermodynamic parameters have been calculated for the decomposition steps using TG/DTA curves in air as well as nitrogen atmosphere. This revised version was published online in July 2006 with corrections to the Cover Date.     

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

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

Three one-dimensional chains with bulky backbone carboxylate ligands: Syntheses,crystal structures,and luminescent properties

To explore the influence of bulky backbone on complexes, three Co(II) and Zn(II) complexes with phenanthrene-9-carboxylate (L¹), 9H-fluorene-9-carboxylate (L²) or biphenyl-4-carboxylate (L³) together with incorporating auxiliary bridging ligad 4,4′-bipyridine (4Bipy), were synthesized and characterized: [Co(L¹)₂(4Bipy)(H₂O)₂]_∞ (I), [Zn(L²)₂(4Bipy)_0.5(4Bipy)_0.5]_∞ (II), and [Zn₃(L³)₄(4Bipy)_0.5(4Bipy)_0.5(4Bipy)_0.5(OH)₂]_∞ (III). X-ray single-crystal diffraction analyses show that complexes I–III both assume one-dimensional (1D) structures by incorporating the bridging 4Bipy (CIF file CCDC nos. 942729 (I), 942727 (II), and 942733 III). In I, mononuclear six-coordinated Co²⁺ ions are linked into a 1D linear chain by 4Bipy. While in II, mononuclear four-coordinated Zn²⁺ ions are linked into a 1D zigzag chain by 4Bipy. But in III, because of the existence of OH^?, hexanuclear Zn(II) can be regarded as a node, then bridge adjacent hexanuclear Zn(II) nodes by almost parallelled three 4Bipy ligands into a 1D linear chain. Finally the 1D chains of I–III are further assembled into an overall three-dimensional (3D) framework via intermolecular H-bonding, π…π stacking, and/or C-H…π supramolecular interactions, respectively. The results indicate that, besides different metal ions Co²⁺ and Zn²⁺ or OH^? anions, the steric hindrance of backbone ligands play an important role in the formation of I–III. Moreover, the luminescent properties of corresponding ligands and their complexes were briefly investigated.     

Mixed-ligand platinum(IV) complexes with amino acids and cytosine

Complex formation in platinum(IV)-cytosine-amino acid (glycine, α-alanine, lysine, or histidine) systems is studied using pH titration. Stability constants for 1:1:1 stoichiometry of complexes are determined. The stability of the mixed-ligand complexes varies in the following order: Lys < Ala < Gly < His. Reactions of aqueous solutions yields the following complexes: Pt(Cyt)(Gly^?)Cl₃ · 3H₂O (I), pt(Cyt)(Ala^?)Cl₃ · 3H₂O (II), Pt(Cyt)(Hist)Cl₄ · 2H₂O (III), and Pt(Cyt)(Lys)Cl₄ · 2H₂O (IV). ¹³C NMR, IR, and XPS spectra show that glycine and alanine are complexed via amino and carboxy groups, lysine via its α-amino group exclusively, and histidine via its amino group and heterocyclic N3 atom. Cytosine in these complexes is bidentate (it is complexed via C=O oxygen and N3 heterocyclic atoms).     

Cobalt(III) complexes with biguanide derivatives: Synthesis,structures, and antiviral activity

Three Co(III) complexes with biguanide derivatives [Co(NH₂C(=NH)NHC(=NH)NR¹R²)₃]Cl₃ (R¹R² = Me₂ (I), Et₂ (II), and H^sBu (III)) were obtained and characterized by elemental analysis, IR spectroscopy, and electronic absorption spectroscopy. Structure III was confirmed by X-ray diffraction (CIF file CCDC no. 1401783). Complexes I–III and [M(SC(NH₂)₂)₄]Cl₂ (M = Pd, Pt, and [Co(En)₃]Cl₃) were tested for in vitro antiviral activity against the A/California/07/09 (H1N1pdm09) influenza virus. The best results were achieved with complex III and both thiourea complexes.     

Synthesis and structural characterization of nitrite-coordinating CoII and CoIII complexes as models for the reaction center of Co-substituted nitrite reductase

Co^II and Co^III complexes containing nitrite and tridentate aromatic amine compounds [bis(6-methyl-2-pyridylmethyl)amine (Me₂bpa) and bis(2-pyridylmethyl)amine (bpa)] have been prepared as models of the catalytic center in Co-substituted nitrite reductase: [Co^II(Me₂bpa)(NO₂)Cl]₂ · acetone (2), Co^II(Me₂bpa)(NO₂)₂ (3), Co^II(bpa)(NO₂)Cl (4), Co^II(bpa)(NO₂)₂ (5), Co^III(Me₂bpa)(NO₂)(CO₃) (6), and Co^III(bpa)(NO₂)₃ (7). The X-ray crystal structure analyses of these Co^II and Co^III complexes indicated that the geometries of the cobalt centers are distorted octahedral and the Me₂bpa and bpa with three nitrogen donors exhibit mer- (2, 3, and 7) and fac-form (4 and 6). The coordination mode of nitrite depends on the cobalt oxidation state, to Co^II through the oxygen (nitrito coordination, O- and O,O-coordination) and to Co^III through nitrogen (nitro coordination, N-coordination mode). These findings are consistent with the results of their IR spectra, except that another oxygen of the O-coordinated nitrito group in 3 might interact weakly with Co^II according to its IR spectrum. Reductions of the nitrite in 2, 3, 4, and 5 to nitrogen monoxide were not accelerated in the presence of proton, perhaps due to the nitrito coordination in these Co^II complexes.     

Gold(III)pentafluorophenylarylazoimidazole: Synthesis and spectral (H, C, COSY, HMQC NMR) characterisation

Reaction of [Au^III(C₆F₅)₃(tht)] with RaaiR′ in dichloromethane medium leads to [Au^III(C₆F₅)₃ (RaaiR′)] [RaaiR′=p-R-C₆H₄-N=N-C₃H₂-NN-l-R′, (1-3), R = H (a), Me (b), Cl (c) and R′= Me (1), CH₂CH₃ (2), CH₂Ph (3), tht is tetrahydrothiophen]. The nine new complexes are characterised by ES/MS as well as FAB, IR and multinuclear NMR (¹H,¹³C,¹⁹F) spectroscopic studies. In addition to dimensional NMR studies as¹H,¹H COSY and¹H¹³C HMQC permit complete assignment of the complexes in the solution phase.     

Synthesis and spectral characterization of macrocyclic Schiff base by reaction of 2,6-diaminopyridine and 1,4- bis (2-carboxyaldehydephenoxy)butane and its CuII, NiII, PbII, CoIII and LaIII complexes

A new macrocyclic ligand, 1,3,5-triaza-2,4:7,8:15,16-tribenzo-9,15-dioxacycloheptadeca-1,5-diene (L) was synthesized by reaction of 2,6-diaminopyridine with 1,4-bis(2-carboxyaldehydephenoxy)butane. Then, its Cu^II, Ni^II, Pb^II, Co^III and La^III complexes were synthesized by the template effect by reaction of 2,6-diaminopyridine and 1,4-bis (2-carboxyaldehydephenoxy)butane and Cu(NO₃)₂ · 3H₂O, Ni(NO₃)₂ · 6H₂O, Pb(NO₃)₂, Co(NO₃)₂ · 6H₂O, La (NO₃)₃ · 6H₂O, respectively. The ligand and its metal complexes were characterized by elemental analysis, IR, ¹H- and ¹³C-n.m.r., UV-vis spectra, magnetic susceptibility, thermal gravimetric analysis, conductivity measurements and mass spectra. All complexes are diamagnetic and the Cu^II complex is binuclear. The Co^II complex was oxidised to Co^III.     

209Bi NQR study of bismuth(III) complexes

Potassium pentafluorobismuthate(III), nitrate-chloride Bi^III complexes MBiCl₃NO₃ (M=K, (NH₂)₂CNH₂), sulfate-chloride Bi^III complexes MBiCl₂SO₄ (M=K, Rb, NH₄, (NH₂(₂CNH₂), and Bi^III complexonates with the anions of ethylenediaminetetraacetic acid M[Bi(edta)]₂·nH₂O (M=Mg, Ca, Ni, Cd) and nitrilotriacetic acid Bi(nta)·2H₂O, and Bi(nta)·3thio·H₂O (thio is thiourea) were studied by²⁰⁹Bi NQR spectroscopy. A second-order phase transition was observed in K₂BiF₅ at 100 K. The compounds Bi(nta)·2H₂O, (NH₂)₂CNH₂BiCl₃NO₃, and MBiCl₂SO₄ (M=K, NH₄) are piezoelectrics. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2237–2240, November, 1998.     

Crystal structures of some lanthanide(III) complexes with acylhydrazone and their coordination chemistry

Three new lanthanide(III) complexes with N-(2-propionic acid)-salicyloylhydrazone (H₂L, C₁₀H₁₀N₂O₄) ligand [La(HL)₂(NO₃)(H₂O)₂]₃ ·4H₂O(I), [Gd(HL)₃] · 2(C₂H₅)₃ N(II) and [Er(L)(HL)(H₂O)₂] · 2H₂O(III) has been synthesized and characterized by elemental analyses, IR, UV, and molar conductivity. The crystal structures of three complexes have been determined by X-ray single-crystal diffractometer. In complex I, the La³⁺ ion is ten-coordinated by two tridentate ligands, one bidentate nitrate, and two water molecules. In complex II, the Gd³⁺ ion has a coordination number of nine by three tridentate ligands. In complex III, the Er³⁺ ion is eight-coordinated by two tridentate ligands and two water molecules. In all structures, tridentate ligands are coordinated by carboxyl O and acyl O atoms and azomethine N atom to form two stable five-membered rings sharing one side in the keto mode as indicated by the results of crystal structures and infrared spectral analysis.     

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

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