Lanthanide complexes with the Schiff base containing sterically hindered phenol: Synthesis,structure, and luminescence properties

The syntheses of the 2,6-di-tert-butyl-4-(2-hydroxybenzylideneamino)phenolate (L) complexes of Gd (I), Nd (II), Er (III), Yb (IV), Tm (V), Sm (VI), and Tb (VII) are described. The structures of the Gd and Er complexes are determined by X-ray diffraction analysis (CIF files CCDC nos. 1558820 (I) and 1558819 (III)). All synthesized compounds exhibit ligand-centered photoluminescence in a range of 405–485 nm. In addition, the luminescence spectra of solid samples of the neodymium and ytterbium complexes contain narrow bands of f–f transitions characteristic of Nd³⁺ and Yb³⁺ ions.     

Synthesis,structure, and optical properties of lanthanum(III), cerium(III), praseodymium(III), and nickel(II) heterometallic complexes with glycine

New cluster complexes of lanthanides(III) and nickel(II) [Ln{Ni(Gly)₂}₆]³⁺[Ln(NO₃)₆]^3– have been synthesized, where Ln = La (I), Ce (II), and Pr (III); and Gly is glycinate. The structures of compounds I–III are determined by X-ray diffraction. The icosahedral cavity in the complex cation, where the lanthanide ion resides, has a fixed size independent of the nature of the central Ln(III) ion. In the complex anion, on the contrary, the Ln–O distances naturally decrease from La(III) to Pr(III). The optical properties of cationanion complexes I–III are studied. Based on the assignment in the electronic absorption spectra of the complexes, it is shown that the absorption bands are caused by d–d electronic transitions.     

A New Highly Selective Neodymium(III) Polyvinylchloride Membrane Electrode Based on 4-Hydroxypyrrolidine-2-Carboxylic Acid as an Active Material

The present paper describes the fabrication of a new polyvinylchloride (PVC) membrane electrode for the determination of Nd(III) ion based on 4-hydroxypyrrolidine-2-carboxylic acid (LHP) as an active material along with sodium tetraphenyl borate (NaTPB) as an anionic additive and acetophenone (AP) as solvent mediator. The optimum composition (%, w/w) of the best performing membrane contained 66 AP, 30 PVC, 2 NaTPB and 3 LHP. The basic analytical parameters of this electrode such as slope characteristics, detection limit, response time, selectivity and pH effect were assessed. The electrode displayed a Nernstian response in terms of slope (20.5 ± 0.4 mV per decade) and response time (~8 ± 1 s) over a wide neodymium ion concentration range of 10^–6 to 10^–2 M with a detection limit of 7.5 × 10^?7 M. The potentiometric response of the electrode was constant in the pH range of 3.2?8.9. According to the selectivity coefficients determined by the matched potential method, the interference of many common alkaline, alkaline earth, transition, heavy metals and specially lanthanide ions in determination of Nd(III) ion was very low. The proposed electrode has been successfully used as an indicator electrode in the potentiometric titration of Nd(III) ion with EDTA and applied for determination of Nd(III) ion in mixtures of different ions.     

Hydrothermal Synthesis,Crystal Structures,and Fluorescence Properties of Ni(II)–Ln(III) Complexes (Ln = Sm,Pr, Eu)

Three novel 3d–4f heterometal complexes [Ln(NiL)₃(Btca)(NO₃)] · xH₂O (Ln = Sm(III) (I), Pr(III) (II), Eu(III) (III) (H₂L = 2,3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tetraazacyclo-pentadeca-7,13-dien, H₂Btca = benzotriazole-5-carboxylic acid) were solvothermally synthesized and characterized by singlecrystal X-ray diffraction (CIF files CCDC nos. 1555557 (I), 1555555 (II), 1555556 (III)). They crystallized in the monoclinic space group P2₁/n for I (x = 1.5) and C2/c for (II) and (III) (x = 1), respectively. In these complexes, the central Ln(III) and external nickel ions are bridged by macrocyclic oxamide groups. The metal center of Ln(III) resides in a distorted bicapped square antiprism surrounding with six oxygen atoms of three oxamide groups, two oxygen atoms of Btca^2– ion and two oxygen atoms of NO₃^-. Furthermore, there are C–H···O and/or C–H···N hydrogen bond interactions among nitrate, benzotriazole-5-carboxylate, macrocyclic oxamide and water to form three-dimensional superamolecular architecture. The fluorescence properties of the compounds I and II are also discussed.     

Complexes of α-, β-, and γ-cyclodextrins with nitrophenols: A theoretical study of the structure and energy

Detailed quantum mechanical calculations of the interaction of cyclodextrin (α-, β-, and γ-CD) with 4-nitrophenol (I), 4-nitro-2,6-dimethylphenol (II), 4-nitro-3,5-dimethylphenol (III), and their anions (IVVI) with the formation of intercalation complexes are carried out for the first time. The calculations of the compounds are performed within the density functional theory by the hybrid Becke–Lee–Yang–Parr (B3LYP) method with LanL2DZ basis sets. For the α-CD+III and α-CD+VI complexes it is shown that a nitrophenol molecule of III and a nitrophenolate anion of VI are not contained in the α-CD torus, which agrees with the experimental equilibrium constants. It is found that the calculated equilibrium constants of the formation of guest–host complexes with phenolate anions are much larger than those of neutral molecules. The most stable CD complexes with nitrophenols and their anions should be expected for γ-CD. The β-CD complexes when the guest enters into the host cavity are formed only with compounds I, V, and VI.     

Four Mixed 3d-4f 12-Metallacrown-4 Complexes: Syntheses,Structures and Magnetic Properties

The incorporation of Ln^III ions into the 12-metallacrown-4 topology affords the formation of four mixed 3d-4f pentanuclear complexes of compositions [NH(C₂H₅)₃]{[Ln(OAc)₄] [12-MC _Mn ^III _(N)shi-4]}·xH₂O (Ln = Sm (1), Gd (2), Tb (3), Dy (4); x = 0.5 for 1 and 3, x = 0.25 for 2, x = 0 for 4; H₃shi = salicylhydroxamic acid). Compounds 1–4 were obtained from the reactions of H₃shi with Mn(CH₃COO)₂·4H₂O and Ln(NO₃)₃·6H₂O, in the presence of N(C₂H₅)₃. They all contain a crown-like [Mn₄Ln(μ-NO)₄]¹¹⁺ core with four Mn^III atoms being at the rim of the crown and an Ln^III ion occupying the dome of the crown. The peripheral ligation about the core is provided by four η¹:η¹:µ acetate groups. The identity of the Ln^III ions slightly affects the 12-metallacrown-4 frameworks, as demonstrated by the gradual decrease of the distances between the Ln^III ions and the centres of the Mn₄ planes (1.85 Å for 1, 1.81 Å for 2, 1.80 Å for 3, and 1.77 Å for 4). Variable-temperature dc magnetic susceptibility studies were carried out on polycrystalline samples of 1–4. Antiferromagnetic interactions are determined for complexes 1–4.     

Sorption selective membranes based on polydimethylsildimethylene- and polydimethylsiltrimethylenedimethylsiloxane

Using cationic and anionic polymerization of 1,1,3,3-tetramethyl-2-oxa-1,3-disilacyclopentane (I) and 1,1,3,3-tetramethyl-2-oxa-1,3-disilacyclohexane (II), α,ω-dihydroxypolydimethylsildimethyleneand α,ω-dihydroxypolydimethylsiltrimethylenedimethylsiloxanes (III and IV, respectively) were synthesized. The polymer materials for the flat membranes MI and MII with stable mechanical properties were produced via crosslinking condensation of tetraethoxysilane and the terminal hydroxyl groups of III and IV. Methane and butane were applied to demonstrate the gas transport properties of these membranes. It was shown that compared to PDMS, the synthesized MI and MII have a higher butane/methane ideal selectivity at high permeability coefficients (7800 and 6600 Barrer, respectively). An increase in butane/methane selectivity is achieved due to the high coefficients of butane solubility in the membrane materials.     

Synthesis,Structure, and Magnetic Properties of a Twist Linear Tetranuclear Co<Stack><Subscript>2</Subscript><Superscript>III</Superscript></Stack>Ln<Stack><Subscript>2</Subscript><Superscript>III</Superscript></Stack> Complexes

A series of twist linear tetranuclear 3d–4f Co ₂ ^III Ln ₂ ^III [Ln = Gd (1), Tb (2), Dy (3), Ho (4), Er (5)] complexes have been prepared under solvothermal conditions and structurally characterized with Schiff-base ligand 2-(((2-hydroxy-3-methoxyphenyl)methylene)amino)-2-(hydroxymethyl)-1,3-propanediol (H₄L). The two central Co ions are linked by two alkoxyl oxygen atoms, and one Ln ion lying above and the other below the Co–Co dimer, form a twist linear array. The magnetic susceptibility studies reveal antiferromagnetic or ferromagnetic behaviour, whilst dynamic magnetic studies indicate no slow magnetic relaxation for these complexes.     

Copper(II) and cobalt(II) complexes with a chiral 5-pyrazolone derivative obtained from the terpene (+)-3-carene: Synthesis and properties

The complexes [CuLCl₂] (I), [CoLCl₂] (II), and CuLBr₂ (III) (where L is the derivative of optically active 5-pyrazolone prepared from the terpene (+)-3-carene) were obtained and characterized. According to X-ray diffraction data, crystal structures I and II (orthorhombic crystal system) are built from mononuclear acentric molecules. In the resulting complexes, the Cu²⁺ or Co²⁺ ion coordinates two N atoms of the chelating bidentate ligand L and two Cl atoms, thus making a distorted tetrahedron. Intermolecular contacts and the hydrogen bonds Cl(1)…H-O(1) give rise to columns parallel to axis y. For complexes I and III, μ_eff = 1.83 and 1.81 μB, respectively; these values correspond to the electronic configuration d ⁹ . For complex II, μ_eff = 4.42 μB, which suggests the tetrahedral structure of the coordination entity CoCl₂N₂. Complexes I and III were studied by EPR spectroscopy.     

Crystal structures and enhanced luminescence of Zn(II) and Cd(II) complexes containing conjugated organic ligands

By self-assembly of delocalized organic ligands (L¹ and L²) with Cd(SCN)₂, ZnI₂ and Zn(NCS)₂, three luminescent complexes ZnI₂(L¹)₂ (I), [Cd(L¹)₂(μ_1,3-SCN)₂] _n (II) and Zn(NCS)₂(L²)₂ (III) were obtained (L¹ = 2-{5,5-dimethyl-3-[2-(pyridine-4-yl)ethenyl]cyclohex-2-enylidene}propanedinitrile and L² = 2-{5,5-dimethyl-3-[2-(pyridine-3-yl)ethenyl]cyclohex-2-enylidene}propanedinitrile). The structures of the complexes were determined by single crystal X-ray diffraction analysis (CIF files CCDC nos. 1406116 (I), 1406115 (II), and 1400360 (III)). In complex I, Zn(II) is coordinated by two functional organic ligands and two I^– ions, to form a I₂N₂ distorted tetrahedral geometry. In 1D coordination polymer II, the Cd(II) centers show six-coordinated geometries, two organic ligands and four SCN^– ions involve in coordination with each Cd(II) center. The thiocyanate groups show μ_1,3-SCN bridging coordination modes and the adjacent Cd(II) ions are bridged by double μ_1,3-SCN ions to form an infinite chain. In complex III, Zn(II) is coordinated by two functional organic ligands and two NCS^– groups, to form a N₄ distorted tetrahedral geometry. Compared with the free ligands, the complexes show superior luminescent property with red-shift and enhancement of fluorescence intensity.     

Cation-induced aggregation of sandwich lutetium(III) and Yb(III) complexes with tetra(15-crown-5)-substituted phthalocyanine as probed by <Superscript>1</Superscript>H NMR

The cation-induced aggregation of sandwich crown-substituted complexes [Ln(R₄Pc)₂] (Ln = Lu (I) and Yb (II), R₄Pc^2? is the 4,5,4′,5′,4″,5″,4?,5?-tetrakis(1,4,7,10,13-pentaoxatridecamethylene)phthalocyaninate ion) and Ln₂(R₄Pc)₃(Ln = Lu (III) and Yb (IV) in a CDCl₃-DMSO-d ₆ solution has been studied by ¹H NMR. The data obtained are consistent with the conclusions concerning the composition of supramolecular aggregates drawn from spectrophotometric titration data. The molecules of double-decker complexes I and II form supramolecular oligomers, whereas triple-decker complexes III and IV form supramolecular dimers, which is presumably due to the stronger distortion of the planes of the outer decks of the triple-decker complexes as compared to their double-decker analogues.     

Syntheses and luminescence of three lanthanide complexes constructed by flexible carboxylate ligand

Three new complexes, namely {[Ln(L)₃(2,2′-Bipy)] _n · H₂O} (Ln = Pr (I), Sm (II), and Nd (III)) (HL = 3-(2-hydroxyphenyl)propanoic acid), have been synthesized and structurally characterized. The structural determinations indicated (CIF files CCDC nos. 1472729 (I), 1472730 (II), 1472734 (III)) that I–III have similar dinuclear structures, which can be further linked into 2D sheet via the hydrogen bond interactions. Furthermore, the luminescent properties of I–III show the strong emissive power and feature.     

Synthesis,characterization and X-ray crystal structure of novel nickel Schiff base complexes and investigation of their catalytic activity in the electrocatalytic reduction of alkyl and aryl halides

Novel potentially bidentate NO Schiff base ligands, HL ¹ and HL ² derived from condensation reaction of 2′-methoxyphenyl-2-ethylamine with salicylaldehyde (HL ¹ ) and with 2-hydroxy-4-methoxybenzaldehyde (HL ² ), and their nickel complexes were synthesized and characterized by usual spectroscopic techniques such as FT-IR, UV–Vis, ¹H NMR, ¹³C NMR and elemental analysis. It was revealed that the bidentate Schiff base ligands coordinate with Ni(II) ions yielding mononuclear complexes with 1:2 (metal/ligand) stoichiometry. This result has been determined by using X-ray crystallographic technique of HL ² and the nickel complex derived from HL ¹ (Ni(II)-2L ¹ ). So, the structural studies showed that the two Ni(II) complexes adopt a square-planar geometry around the central metal ion. Cyclic voltammetry studies were investigated in 0.1 M TBAP in DMF solution and indicate that the nickel complexes show one reduction wave related to Ni(II)/Ni(I) redox couple. The electrocatalytical properties of these complexes were also studied in the same electrolyte medium. Their electrocatalytic performances have been tested toward the electroreduction reaction of bromocyclopentane and iodobenzene, showing a promoted activity in the case of the Ni(II)-2L ² complex.     

Three metal complexes based on tetrazolyl ligands: Hydrothermal syntheses,crystal structures,and fluorescence properties

Three new complexes based on 1-tetrazole-4-imidazole-benzene (Tibz), namely, [Cd(Tibz)₂(H₂O)₂] _n (I), [Mn(Tibz)₂(H₂O)₄] · 2H₂O (II) and [Co(Tibz)₂(H₂O)₄] · 2H₂O (III) have been synthesized through hydrothermal method and structurally characterized by element analyses, IR spectroscopy and single-crystal X-ray diffraction analyses (CIF files CCDC nos. 1443867 (I), 1443868 (II), 1443869 (III)). Single-crystal X-ray diffraction reveals that complex I is a 1D double-chain architecture, II and III are both mononuclear complexes. The results of single-crystal X-ray diffraction analyses indicate that the hydrogen bond and π··· π stacking exist in the complexes, which make great contribution to the stabilities of complexes I–III. The fluorescent properties of these complexes have also been studied in the solid state at room temperature.     

Novel peripherally tetra substituted metal-free,cobalt(II), copper(II) and manganese(III) phthalocyanines bearing polyethoxy chain attached by 2,6-diphenylphenol groups: synthesis,characterization and their electrochemical studies

Metal free (6), cobalt(II) (7), copper(II) (8) and manganese(III) (9) phthalocyanines, which are tetra substituted at the peripheral positions with 2-[2-(1,1′:3′,1′′-terphenyl-2′-yloxy)ethoxy]ethoxy groups, were synthesized and characterized by IR, ¹H-NMR,¹³C-NMR, UV–Vis and mass spectroscopy. Electrochemistry of the phthalocyanines were studied with voltammetric measurements by using cyclic voltammetry and square wave voltammetry techniques in DCM/TBAP electrolyte on a Pt working electrode. Electrochemical measurements exhibit that incorporation of redox active metal ions, Co^II and Mn^III, into the phthalocyanine core extends the redox capabilities of the Pc ring including the metal-based reduction couples of the metal. While Mn^IIIClPc showed only metal based reduction reactions, Co^IIPc showed metal based and ligand based reduction reactions as expected. Cyclic and square wave voltammetric studies showed that phthalocyanines have reversible/quasireversible/irreversible redox processes, which are the main requirement for the technological usage of these compounds.     

Crystal structure of copper sulfate and thiocyanate complexes with 5-bromo-and 5-nitrosalicylaldehyde thiosemicarbazones

The crystal structures of (5-bromosalicylidenethiosemicarbazido)aquacopper(II) sulfato(5-bromosalicylidenethiosemicarbazido)aquacuprate(II) tetrahydrate (I), (5-nitrosalicylidenethiosemicarbazido)dimethylsulfoxide(methanol)copper(II) sulfate (II), and catena(μ-thiocyanato)(5-nitrosalicylidenethiosemicarbazido)copper(II) (III) were determined. In structure I, the independent part of the unit cell contains four water molecules of crystallization and the cation-anion complex [Cu(H₂O)(L)][Cu(H₂O)(L)(SO₄)] containing two nonequivalent copper complexes (A and B). In these, the metal atom coordinates monodeprotonated 5-bromosalicylaldehyde thiosemicarbazone (HL) and water molecules, and in anion B also a sulfate ion. In complex ions A and B, sulfur, azomethine nitrogen, and phenolic oxygen of the salicylidene thiosemicarbazone fragment, and also water molecule form a distorted planar square around the metal atom. The axial vertex of the pyramid in anion B is occupied by the oxygen atom of the monodentate sulfate anion. In structure II, the independent part of the unit cell contains the (5-nitrosalicylidenethiosemicarbazido)dimethylsulfoxide(methanol)copper(II) complex cation and the sulfate anion. The coordination polyhedron of the central atom is a slightly distorted tetragonal pyramid whose base is formed by sulfur, azomethine nitrogen, phenolic oxygen of thiosemicarbazone, and dimethyl sulfoxide oxygen. The axial position is occupied by the methanol oxygen atom. In structure III, the copper atom coordinates 5-nitrosalicylaldehyde thiosemicarbazone and the thiocyanate ion, which combines complexes into infinite polymer chains along the [010] direction. The copper coordination polyhedron in III is a slightly distorted tetragonal pyramid whose base is formed by sulfur, azomethine nitrogen, phenolic oxygen of thiosemicarbazone, and nitrogen of thiocyanate ion, the axial vertex is occupied by sulfur of thiocyanate ion of the neighboring complex.     

μ<Subscript>2</Subscript>-Oxobis[(aroxo)tris(<Emphasis Type="Italic">para</Emphasis>-tolyl)antimony]: Synthesis and Structure

µ₂-Oxobis[(2,4,6-tribromophenoxo)tris(para-tolyl)antimony] (I), µ₂-oxobis[(2,3,4,5,6-pentachlorophenoxo) tris(para-tolyl)antimony] (II), and µ₂-oxobis(2,4-dinitrophenoxo)tris(para-tolyl)antimony] (III) have been synthesized with high yields by the reaction of tris(para-tolyl)antimony with 2,4,6-tribromo-, 2,3,4,5,6-pentachloro-, and 2,4-dinitrophenol, respectively, in ether in the presence of tert-butylhydroperoxide. The Sb atoms in complexes I, II, and III have a distorted trigonal bipyramidal coordination with the aroxyl ligands and the bridging oxygen atom in axial positions. The central Sb–O–Sb moiety in molecules of complexes I–III has an angular structure.     

Europium and Ytterbium Complexes with the Redox Active Acenaphthene-1,2-Diimine Ligand

The oxidation of [(Dpp-Bian)Eu(Dme)₂] (I) (Dpp-Bian is the 1,2-bis[(2,6-diisopropylphenyl) imino]acenaphthene dianion, Dme = 1,2-dimethoxyethane), prepared in situ, with 0.5 mol equiv. of iodine in Thf gives europium(II) dimer, [(Dpp-Bian)Eu(μ-I)(Thf)₂]₂ (II) (Thf = tetrahydrofuran), with the Dpp-Bian ligand as radical anion. The exchange reaction of II with potassium dithiocarbamate affords europium( II) dimer, [(Dpp-Bian)Eu[SC(S)NMe₂](Thf)]₂ (III), which also contains the Dpp-Bian radical anion. However, the oxidation of the ytterbium complex [(Dpp-Bian)Yb(Dme)₂] (IV) with 0.5 mol equiv. of [Me₂NC(S)S]₂ gives the monomeric product [(Dpp-Bian)Yb[SC(S)NMe₂](Dme)] (V), in which Dpp-Bian is still the dianion and the ytterbium atom is oxidized to the trivalent state. The reaction of II with potassium thiocyanate gives europium(II) isothiocyanate complex with the radical anion diimine ligand [(Dpp-Bian)Eu(NCS)(Dme)₂] (VI). The molecular structures of complexes II, III, V, and VI were determined by X-ray diffraction (CIF files CCDC 1576687–1576690, respectively).     

Tris(5-bromo-2-methoxyphenyl)bismuth dicarboxylates [(C<Subscript>6</Subscript>H<Subscript>3</Subscript>(Br-5)(MeO-2)]<Subscript>3</Subscript>Bi[OC(O)CHal<Subscript>3</Subscript>]<Subscript>2</Subscript> (Hal = F,Cl): synthesis and structure

Tris(5-bromo-2-methoxyphenyl)bismuth dicarboxylates [(C₆H₃(Br-5)(MeO-2)]₃Bi[OC(O)CHal₃]₂, Hal = F (II) and Cl (III), have been synthesized by the reaction between tris(5-bromo-2-methoxyphenyl)bismuth (I) and trifluoroacetic acid and thrichloroacetic acid, respectively, in the presence of hydrogen peroxide in ether. According to X-ray diffraction data, a crystal of complex I contains two types of crystallographically independent molecules (a and b) both with a trigonal pyramid configuration. The bismuth atoms in complexes II and III have a distorted trigonal bipyramidal coordination with carboxylate substituents in axial positions. Axial OBiO angles are 166.3(3)° (II) and 171.6(2)° (III); equatorial CBiC angles are 118.0(3)°–123.1(3)° (II) and 113.6(3)°–127.4(3)° (III). Bi–C bond lengths are 2.189(7)–2.200(8) Å (II) and 2.190(8)–2.219(7) Å (III), and Bi–О distances are 2.280(6), 2.459(16) Å (II) and 2.264(5), 2.266(5) Å (III). Intramolecular contacts between the central atom and the oxygen atoms of carbonyl groups (Bi···O 3.028(9), 3.162(9) Å (II); 3.117(9), 3.202(9) Å (III)) are observed at maximum equatorial angles. The oxygen atoms of methoxy groups are coordinated to the bismuth atom. The Bi···O distances in complexes II and III (3.028(16), 3.157(16), 3.162(16) and 3.17(16), 3.143(16), 3.202(16) Å, respectively) are slightly longer than in complex I (3.007(9)–3.136(4) Å).     

Mono- and heteroligand iron(II) complexes with tris(3,5-dimethylpyrazol-1-yl)methane

Coordination compounds of iron(II) thiocyanate with tris(3,5-dimethylpyrazol-1-yl)methane (HC(3,5-Me₂Pz)₃), [Fe(HC(3,5-Me₂Pz)₃)₂](NCS)₂] (I) and [Fe(HC(3,5-Me₂Pz)₃)(Рhz)(NCS)₂] · H₂O (II), where Рhz is phthalazine, are synthesized. The complexes are studied by X-ray diffraction analysis, diffuse reflectance and IR spectroscopy, and static magnetic susceptibility measurements. The single crystals are obtained, and the molecular and crystal structures of complex II and compounds [Fe(HC(3,5-Me₂Pz)₃)(3,5-Me₂Pz)(NCS)₂] · С₂H₅OH (III), where 3,5-Me₂Pz is 3,5-dimethylpyrazole, and [Fe(HC(3,5-Me₂Pz)₃)₂][Fe(HC(3,5-Me₂Pz)₃)(NCS)₃]₂ (IV) are determined (CIF files CCDC 1415452 (II), 1415453 (III), and 1415454 (IV)). The study of the temperature dependence μ_eff(Т) in a range of 2–300 K shows exchange interactions of the antiferromagnetic character between the iron(II) ions in complexes I and II.