Different crystal structure and photophysical properties of lanthanide complexes with 5-bromonicotinic acid

Five novel lanthanide (Eu³⁺ (1), Tb³⁺ (2), Sm³⁺ (3), Dy³⁺ (4) and Gd³⁺ (5)) complexes with 5-Bromonicotinic acid (5-Brnic) were synthesized and two of them (Tb³⁺, Sm³⁺) were characterized by X-ray diffraction. The results reveal that {[Tb(5-Brnic)₃(H₂O)₃]·H₂O}_n (2) and [Sm(5-Brnic)₃(H₂O)₂·H₂O]₂ (3) exhibit different coordination geometries and crystal structures. Complex 2 has a one-dimensional chain-like polymeric structure through the bridged 5-Brnic anions which links up two neighboring terbium ions, while Complex 3 forms a dimeric molecular structure. The lowest triplet state energy of 5-Brnic was determined to be 24 330 cm⁻¹ corresponded to the 0-0 transition in the phosphorescence spectrum of its gadolinium complex at 411 nm. The strong luminescent emission intensities of these complexes indicated that the triplet state energy of 5-Brnic is suitable for the sensitization of luminescence of Eu³⁺, Tb³⁺, Sm³⁺ and Dy³⁺, especially for that of Tb³⁺ and Dy³⁺.     

Hydrothermal syntheses,and crystal structures of new lanthanide coordination polymers with nitrilotriacetic acid

Hydrothermal reactions of Nd(ClO₄)₃·6H₂O, Gd(ClO₄)₃·6H₂O and Er₂O₃ with H₃NTA (nitrilotriacetic acid) afford three new lanthanide coordination polymers, {[Nd(NTA)(H₂O)]· 2H₂O} _n (1), {[Gd(NTA)(H₂O)]·2H₂O} _n (2) and {[Er(NTA)(H₂O)]·H₂O} _n (3), characterized by elemental analysis and IR spectroscopy. X-ray single crystal structural analyses showed that 1 and 2 are an isomorphous 2D-layered framework containing the nine-coordinated Nd(III) (or Gd(III)), and woven into a 3D suprastructure by interlayer hydrogen bonding while 3 is a 3D structure with eight-coordinate Er(III).     

Preparation,crystal structure and thermal stability of porous lanthanide complexes with 5-methyl isophthalic acid

Three lanthanide complexes 1–3 with 5-methyl isophthalic acid (5-CH₃-H₂bdc) were prepared under hydrothermal conditions, two have formula Eu₂(5-CH₃-bdc)₃(EtOH) (2) and [Er(5-CH₃-bdc)_1.5] · (H₂O) (3) and were characterized by X-ray single crystal diffraction. In 2, there are two europium(III) ions in seven-coordinate pentagonal bipyramid and eight-coordinate bicapped trigonal prism geometries. Complex 2 is a 3-D porous structure with 1-D channels (potential solvent area = 453 ų, 15.7%). One crystallographic independent erbium(III) ion exists and lies in a pentagonal bipyramidal geometry in 3, in which one-dimensional channels are rectangular (potential solvent area = 470 ų, 16.4%). TG-DTG experiments show that these complexes have stability to 750–880°C decomposing to corresponding Ln₂O₃.     

Two binuclear lanthanide complexes with 4-quinoline carboxylic acid: crystal structures and luminescent properties

Two isomorphic lanthanide complexes [Eu₂(L)₆(H₂O)₄] · 2H₂O (1) and [Tb₂(L)₆(H₂O)₄] · 2H₂O (2), (HL = 4-quinoline carboxylic acid) have been synthesized and structurally characterized by single-crystal X-ray diffraction. Both complexes are binuclear and each metal center adopts nine-coordination with nine oxygens from two H₂O molecules and carboxylates of three ligands; L exhibits three different coordination modes. Luminescent properties of 1 and 2 at room temperature indicate that the triplet-state level of this ligand matches better with the lowest excited state level of Eu(III) than with Tb(III).     

Synthesis and crystal structure of two praseodymium 2-iodobenzoic acid complexes

Two new complexes, {[Pr(2-IBA)₃?·?2,2′-bipy]₂·[Pr(2-IBA)₃?·?2,2′-bipy]₂?·?0.5C₂H₅OH?·?H₂O} (1) and [Pr(2-IBA)₃?·?phen]₂ (2) (2-IBA?=?2-iodobenzoate; 2,2′-bipy?=?2,2′-bipyridine; phen?=?1,10-phenanthroline) were synthesized, and their crystal structures were determined by X-ray diffraction. Complex 1 consists of two binuclear molecules [Pr(2-IBA)₃?·?2,2′-bipy]₂ (a) and [Pr(2-IBA)₃?·?2,2′-bipy]₂ (b), half uncoordinated ethanol and one uncoordinated water. In the two molecules (a) and (b), the coordination environment of central ions is similar. The Pr1³⁺ ion in molecule (a) and Pr2³⁺ ion in molecule (b) are nine-coordinate with seven oxygen atoms from five 2-IBA ligands and two nitrogen atoms from one 2,2′-bipy molecule. The crystal structure of complex 2 is similar to that of binuclear [Pr(2-IBA)₃?·?2,2′-bipy]₂ in complex 1.     

Hydrothermal syntheses,crystal structures and luminescence properties of two lanthanide dinuclear complexes with hexafluoroglutarate

Two complexes [Ln₂(hfga)₂(phen)₄(H₂O)₆] · hfga · 2H₂O (H₂hfga = hexafluoroglutaric acid, phen = 1, 10-phenanthroline, Ln=Tb, 1; Eu, 2) were synthesized under hydrothermal conditions and their structures determined by X-ray crystallography. The complexes consist of dinuclear units with an inversion center. Each Ln(III) is nine-coordinate with two carboxylate oxygens from two hfga ligands, three oxygens from water and four nitrogens from two phen molecules. Two carboxylate groups of one hfga adopt monodentate coordination to Ln(III) as a long bidentate bridge linking two Ln(III) ions to form a dimer. Ln(III) ··· Ln(III) distances of 9.027(3) Å for 1 and 9.043(3) Å for 2 were observed. Both complexes emit strong fluorescence and show characteristic emission of Tb(III) and Eu(III) ions, respectively.     

Supramolecular networks constructed from mono- and bi-nuclear lanthanide complexes with 1,2-phenylenedioxydiacetic acid

[Tb₂(1,2-pdoa)₃ · 6H₂O] · H₂O (1) and [La(1,2-pdoa)(1,2-H₂pdoa)(OH) · H₂O] · 5H₂O (2) (1,2-H₂pdoa = 1,2-phenylenedioxydiacetic acid) have been synthesized and structurally characterized by single crystal X-ray diffraction. Complex 1 is a binuclear molecule in which one 1,2-pdoa ligand is a tetradentate bridge linking two Tb³⁺ ions, the other two 1,2-pdoa ligands bond Tb1³⁺ and Tb1A³⁺ via tetradentate chelating coordination. Tb³⁺ is nine-coordinate by six oxygens of 1,2-pdoa and three waters. Complex 2 is mono-nuclear with La³⁺ ten-coordinate by eight oxygens of two 1,2-pdoa, one hydroxide and one water. 1,2-Pdoa is tetradentate chelating with La³⁺ ion. The packing diagrams of 1 and 2 show supramolecular networks via H-bonds. The fluorescence spectrum of 1 shows characteristic emission of Tb³⁺ with ⁵D₄ → ⁷F_j (j = 6–3) transitions.     

Hydrothermal synthesis and crystal structure of two new lanthanide coordination polymers with 1,2-phenylenediacetate

Two new compounds {[Ln₂(1,2-pda)₃(H₂O)₂]·?2H₂O} _n (1,2-H₂pda?=?1,2-phenylenediacetic acid, Ln?=?Tb, 1; Ho, 2) were prepared by hydrothermal reaction and characterized by X-ray crystallography. The Ln³⁺ is nine-coordinate by eight oxygen atoms of six 1,2-pda ligands and one oxygen of water. Ln³⁺ ions are bridged by 1,2-pda ligands via bridging/chelating-bridging pentadentate and chelating-bridging/chelating-bridging hexadentate coordination to form 3-D framework structures. Complex 1 emits strong green fluorescence corresponding to ⁵D₄???⁷F_j (j?=?6–3) transitions of the Tb³⁺.     

Synthesis and crystal structures of lanthanide complexes with foliage growth regulator: phenoxyalkanoic acid

Reactions of Ln(ClO₄)₃?·?6H₂O (Ln=La(III), Eu(III), Nd(III)), 1,10-phenanthroline (phen) and phenoxyacetic acid (PA) or 2,4-dichlorophenoxyacetic acid (2,4-D) yield [La(PA)₂ (phen)₂]₂(ClO₄)₂ (1), [Eu(2,4-D)₂(phen)₂]₂(ClO₄)₂ (2) and [Nd(2,4-D)₃(C₂H₅OH)] _n (3). Compounds 1–3 are characterized by elemental analyses, IR, UV–Vis, ESI-MS spectra and TGA. 1 is also characterized by ¹H and ¹³C NMR. Single crystal X-ray diffraction analyses reveal that 1 and 2 are binuclear, and 3 has a one-dimensional polymeric structure. The La(III), Eu(III) and Nd(III) are nine-coordinate with a distorted tricapped trigonal-prism geometry.     

Preparation of three terbium complexes with p-aminobenzoic acid and investigation of crystal structure influence on luminescence property

Three new rare earth p-aminobenzoic acid complexes, [Tb₂L₆(H₂O)₂]_n (1), [Tb₂L₆(H₂O)₄]·2H₂O (2) and [Tb(phen)₂L₂(H₂O)₂](phen)L·4H₂O (3) (HL: p-aminobenzoic acid; phen: 1, 10-phenanthroline), with different structural forms are reported in this paper. Complex 1 is a polymolecule with a two-dimensional plane structure. Compound 2 is a binuclear molecule, and 3 appears to be a mononuclear complex. The fluorescence intensity, the fluorescence life-time and emission quantum yield of 2, which has two coordination water molecules, is better than those of 1, which has only one coordination water molecule. This is an unusual phenomenon for general fluorescent rare earth complexes. The fluorescence performance of 3 is the most unsatisfactory among the three complexes. Their crystal structures show that the coordination mode of the ligand is an important factor influencing the luminescence properties of a fluorescent rare earth complex.     

Syntheses and crystal structures of four lanthanide complexes based on two tri-protonated hexacarboxylic acids of 1,2,3,4,5,6-cyclohexane-hexacarboxylic acid and mellitic acid

Four lanthanide complexes with two tri-protonated hexacarboxylic acids [1,2,3,4,5,6-cyclohexane-hexacarboxylic acid (H₆chhc) and mellitic acid (H₆Mel)], [Pr(H₃chhc)(DMF)₃(H₂O)]·H₂O (1), Nd(H₃chhc)(DMF)₃ (2), [Er(H₂O)₈]·(H₃Mel)·9(H₂O) (3), and [Yb(H₂O)₈]·(H₃Mel)·8.5(H₂O) (4), have been synthesized in solution at room temperature and characterized by elemental analysis, IR spectrum, and single-crystal X-ray diffraction. The crystal structures of 1 and 2 are made up of a (4⁴, 6²) 2-D network extended infinitely parallel to the (1?0?0) plane. The H₃chhc^3? anions assume a cis-e,a,e,a,e,a-conformation with the central ring in chair-shaped configuration. In 3 and 4, the H₃Mel^3? as counter ions are interconnected by hydrogen bonds to form 2-D organic supramolecular layers. The coordination modes and abilities of H₆chhc and mellitic acid are discussed and compared. The luminescences of 1–4 have been investigated.     

Synthesis, structure and reactivity of samarium complexes supported by Schiff-base ligands

Three tris(salicyladiminato) samarium complexes were synthesized by the reaction of anhydrous SmCl₃ with the sodium salts of the Schiff-bases in THF in 3:1 molar ratio. X-ray diffraction studies revealed that the coordination geometry around samarium atom could be best described as a distorted pentagonal bipyramidal for complexes 1 and 2 and as a distorted tricapped trigonal prism for complex 3. It was found that the coordination environment around samarium atom has significant effect on the catalytic activity of homoleptic Schiff-base complexes of lanthanide. The increasing order of the catalytic activity for the ring-opening polymerization of ε-caprolactone, as well as guanylation of aniline with N,N-diisopropylcarbodiimide is 3 < 2 < 1.     

Synthesis,crystal structure and properties of three ternary dysprosium 2-halogenated benzoic acid complexes

Three ternary dysprosium complexes [Dy(2-ClBA)₃?·?phen]₂ (1), [Dy(2-ClBA)₃?·?2,2′-bipy]₂ (2), and [Dy(2-BrBA)₃?·?phen]₂ (3) (where 2-ClBAH?=?2-ClC₆H₄COOH, 2-BrBAH?= 2-BrC₆H₄COOH, phen?=?1,10-phenanthroline, and 2,2′-bipy?=?2,2′-bipyridine) have been synthesized and characterized by X-ray single crystal diffraction. Complex 1 consists of two independent binuclear molecules, [Dy(2-ClBA)₃?·?phen]₂ (a) and [Dy(2-ClBA)₃?·?phen]₂ (b), in which the coordination environment is similar. Each Dy³⁺ is nine coordinate with two nitrogens from phen and seven oxygens from five 2-ClBA groups. 2-ClBA groups coordinate to Dy³⁺ in three ways, bidentate chelating, bidentate-bridging and terdentate-bridging. Complexes 2 and 3 consist of one binuclear molecule. The crystal structure of 2 is similar to that of binuclear molecule (a) or (b) of complex 1. In 3, each Dy³⁺ ion is eight-coordinate by two nitrogens from phen and six oxygens from five 2-BrBA groups. 2-BrBA groups coordinate to the Dy³⁺ ion in two ways, bidentate chelating and bidentate-bridging. The complexes were studied by UV, DTA-TG, and fluorescence spectrometry.     

Preparation and characterization of d tungsten compounds with amino acid derivatized diimine ligands and preparation of dipeptide derivatives using peptide coupling agents

Attempts to prepare dipeptide compounds from organometallic N-substituted amino acids are reported. Condensation of pyridine-2-carboxaldehyde, α-amino acids (H-l-Ala-OH or H-l-Asp-OH) and W(CO)₄(pip)₂ leads to formation of W(CO)₄(pyca-Et) (1) (pyca refers to the α-diimine fragment, C₅H₄NCHN) following decarboxylation of one or two equivalents of CO₂. This decarboxylation does not occur for β-alanine or GABA (γ-aminobutyric acid). Coupling of [Hpip][W(CO)₄(pyca-β-Ala-O)] (2) or [Hpip][W(CO)₄(pyca-GABA-O)] (3) to amino acid esters, H-l-Ala-OEt, or H-l-Val-OMe, using the standard 1,3-dicyclohexylcarbodiimide (DCC), 1-hydroxybenzotriazole (HOBt) procedure produced four new dipeptide compounds, 4-7. The reactions proceed in good yield and compounds were characterized spectroscopically. The dipeptide complex, W(CO)₄(pyca-Ala-Ala-OMe) (8), was prepared by reaction of W(CO)₄(pip)₂ with H-l-Ala-l-Ala-OMe and pyridine-2-carboxaldehyde. In addition the molecular structure of W(CO)₄(pyca-β-Ala-Val-OMe) (5) is reported.     

Synthesis, crystal structure, and chirality of divalent lanthanide reagents containing tri- and tetraglyme

Six new divalent lanthanide complexes using triglyme (trigly) and tetraglyme (tetgly) as achiral ligands have been prepared, using a facile synthetic method, in search for enantioselective solid-state reagents. The crystal structures of cis-[SmI₂(trigly)thf] (1), trans-[YbI₂(trigly)thf] (2), trans-[SmI₂(trigly)dme] (3), trans-[YbI₂(tetgly)] (4), trans-[EuI₂(tetgly)thf] (5), and [Sm(tetgly)₂][SmI₃(tetgly)]I (6) have been determined. All complexes, except 5, are chiral. The 10-coordinate cation in 6 displays a helical chirality since the two tetraglyme ligands are wrapped around the samarium ion. Since trans-[YbI₂(tetgly)] (4), which has a chiral arrangement of terminal methyl groups, crystallizes as a conglomerate, preferential crystallization and consequent enantioselective reduction of acetophenone was attempted, but resulted in racemic products, possibly on account of racemic twinning in 4.     

Synthesis and characterization of two 3-D polymeric lanthanide complexes constructed from 1,2,4,5-benzenetetracarboxylic acid

Two new 3-D lanthanide coordination polymers, [CeK(btec)(H₂O)₂] _n (1), [Ho(btec)_0.5(ad)_0.5(H₂O)] _n (2) (H₄btec?=?1,2,4,5-benzenetetracarboxylic acid, H₂ad?=?adipic acid), have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR spectroscopy, and single-crystal X-ray diffraction. Structural analyses reveal that both complexes crystallized in monoclinic space group P2₁/c and possessed 3-D net-structures. In 1, btec adopts two types of coordination modes: µ₁₂–η²:η²:η²:η¹:η²:η²:η²:η¹ bridging mode linking six Ce(III) ions and six K⁺ ions and the other µ₈–η¹:η²:η²:η¹:η¹:η²:η²:η¹ bridging mode connecting four Ce(III) ions and four K⁺ ions. In 2, btec adopts a µ₆-bridging with each carboxylate group of btec ligand in a µ₂–η¹–η² mode, the adipate is µ₄-bridging with each carboxylate µ₂–η¹–η¹-monodentate. The topological analysis shows that 1 can be simplified to a 3-nodal net with the Schläfli symbol {3²,4⁸,5³,6²}₄{3⁴,4¹²,5¹²}{4³⁸,6²⁶,8²} and 2 can be simplified to a 3-nodal network with the Schläfli symbol {4²,8⁴}{4⁶,6⁶,8³}{4⁷,6³}₂. The thermogravimetric analyses and the X-ray powder diffraction of 1 and 2 are discussed.     

Synthesis,characterization, crystal structure,and biological studies of vanadium complexes with glycolic acid

Synthesis, characterization, crystal structure, and biological studies of two complexes with glycolic acid are described. The solid complexes were formulated as K₂[VO(C₂H₂O₃)(C₂H₃O₃)₂] · H₂O (1) and K₂[{VO₂(C₂H₂O₃)}₂] (2) and characterized by X-ray studies, Fourier transform infrared spectroscopy (FTIR), Electron paramagnetic resonance (EPR), and magnetic susceptibility. Conversion of 1 to 2 was studied in aqueous solution by UV–Vis spectroscopy and in the solid state by diffuse reflectance spectroscopy. Complex 2 contains dinuclear [{VO₂(C₂H₂O₃)}₂]^2? anions in which glycolate(2?) is a five-membered chelating ring formed by carboxylate and α-hydroxy groups. The geometry around the vanadium in 2 was interpreted as intermediate between a trigonal bipyramid and a square pyramid. Vanadium(IV) is pentacoordinate in 1 as a distorted square pyramid. Complex 1 contains a vanadyl group (V=O) surrounded by two oxygens from deprotonated carboxylate and hydroxy groups forming a five-membered ring. Two oxygens from different glycolates(1?) are bonded to the (V=O) also. Biological analysis for potential cytotoxic effects of 1 was performed using Human Cervix Adenocarcinoma (HeLa) cells, a human cervix adenocarcinoma-derived cell line. After incubation for 48 h, 1 causes 90 and 95% of HeLa cells death at 20 and 200 μmol L^?1, respectively.     

Synthesis and crystal structure of diorganotin(IV) complexes with pyruvic acid benzoylhydrazone and pyruvic acid salicylhydrazone

Six diorganotin esters of Schiff-base ligands formulated as [R₂SnLY]₂, where L₁ is C₆H₅CON₂C(CH₃)CO₂ with Y?=?CH₃CH₂OH, R?=?mClC₆H₄CH₂ (1), oFC₆H₄CH₂ (2), pFC₆H₄CH₂ (3) and L₂ is 2-HOC₆H₄CON₂C(CH₃)CO₂ with Y?=?CH₃OH, R?=?oFC₆H₄CH₂ (4), pFC₆H₄CH₂ (5), mClC₆H₄CH₂ (6) have been prepared and characterized by elemental analysis, IR, ¹H and ¹¹⁹Sn NMR spectra. The crystal structures of complexes 1 and 4 have been determined by X-ray single crystal diffraction. The structure analyses reveal that the Sn atom in both 1 and 4 is seven-coordinate in distorted pentagonal bipyramid geometries with a planar SnO₄N unit and two apical aryl carbon atoms, thus forming a dimeric molecule, which sits on a crystallographic center of symmetry. Intramolecular or intradimeric hydrogen bonds contribute to the stability and compactness of the crystal structures.     

Crystal structures and luminescence properties of two new terbium complexes with aromatic carboxylic acid

Two new terbium complexes with aromatic carboxylic acids, [(Tb)₂(L₁)₆(H₂O)₄] (1) and [(Tb)₂(L₂)₆(H₂O)₂(DMF)₂] (2) (HL₁: nicotinic acid; HL₂: 4-hydroxybenzoic acid), with different coordination geometries have been synthesized and their crystal structures determined. The luminescence properties of the two complexes, including the phosphorescence lifetime, have been investigated. The effect of a secondary ligand on luminescence of the ternary terbium complex with carboxylic acid and the relationship between luminescence properties and crystal structure, including coordination mode of the carboxyl groups from HL₁ and HL₂ and coordination mode of a secondary ligand, are discussed.