X-ray structure and temperature dependent luminescent properties of two bimetallic europium complexes

The structural, luminescent and temperature dependent luminescent properties of two homodinuclear europium complexes bridged by 2,2′-bipyrimidine (bpm) are reported. β-Diketonate ligands 4,4,4-trifluoro-1-(2-furyl)-1,3-butanedione (tfa) and 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (tta) are used as capping ligands resulting in complexes of the form [Eu(tfa)₃]₂bpm (1) and [Eu(tta)₃]₂bpm (2). All Eu^III ions are eight coordinate with six O atoms from the β-diketones and two N atoms from the polyazine bridging ligand. Excitation of the β-diketonate ligands tfa or tta at ca. 340 nm in toluene solutions results in the characteristic Eu^III emission in the visible region of the spectrum. The emission intensity and lifetime associated with the Eu^III centers decrease as the temperature of the solution is increased. Lifetime measurements are fit to a monoexponential while the temperature dependent lifetime data is fit to an Arrhenius-type equation. Evaluation of the data in comparison to data obtained from the monometallic Eu^III analogs reveal very similar photoluminescent properties. This suggests little electronic communication between Eu^III ions via the polyazine bpm bridging ligand.     

Optical properties of a tetradentate bis(beta-diketonate) europium(III) complex

Eu₂(BPOPB)₃H₂O, an europium complex chelated with bis(β-diketone), was synthesized. Its properties have been investigated by absorption spectrum, emission spectrum and luminescence lifetime measurement. The complex displays strong red luminescence upon irradiation at the ligand band around 355 nm, which indicates that the bis-β-diketonate ligand BPOPB is an efficient sensitizer. The Judd–Ofelt parameters obtained from the emission spectrum of Eu₂(BPOPB)₃H₂O have been used to calculate the total spontaneous emission probabilities (A), the radiative lifetime (τ_rad), the fluorescence branching ratio (β) and the stimulated emission cross-sections (σ). The luminescence lifetimes are determined to be 402 and 169 μs for Eu₂(BPOPB)₃H₂O and Eu(DBM)₃(H₂O)₂, respectively. The relationship between the structures of rare-earth complexes and luminescence lifetimes was analyzed. The radiative properties reveal that Eu₂(BPOPB)₃H₂O is potential to be an efficient luminescent material.     

由(E)-β-碘代烯基砜和末端炔合成多取代的1,3-烯炔

通过(E)-b-碘代烯基砜与末端炔的Sonogashira偶联反应,以中等到良好的产率合成了磺酰基取代的1,3-烯炔。在NiCl2(PPh3)2催化下,产物与格氏试剂发生脱磺酰基偶联反应,磺酰基被进一步转化为不同的取代基。     

Synthesis,crystal structure,and luminescence of a quaternary binuclear europium complex [Eu2(phth)2(Hphth)2(phen)2(H2O)4]

A quaternary binuclear europium complex [Eu₂(phth)₂(Hphth)₂(phen)₂(H₂O)₄] (H₂phth?=?phthalic acid, phen?=?1,10-phenanthroline) has been synthesized. The structure was determined by X-ray crystallography which reveals that it is binuclear with each europium nine-coordinate. Intermolecular hydrogen bonds link the complex units to form a 3D supermolecular network. Its properties have been studied by means of luminescence spectrum and thermal analysis. Fluorescence spectra show that the complex exhibits strong red emission.     

Hydrothermal synthesis of a luminescent Europium(III) sulfate with three-dimensional chiral framework structure

The crystal structure and luminescent property of hydrothermally grown crystals of [NaEu(H₂O)(SO₄)₂] (1) are reported. The crystal structure is composed of three kinds of right-handed helical chains, {EuOSO₄}, {NaOSO₄} and {EuONa}, which are connected together to form a three-dimensional framework structure via corner-shared polyhedra. The sharp peaks in the emission spectrum of 1 are assigned and analyzed. Crystal data: Trigonal, P3₁21, with , and z=3.     

Synthesis, structures, luminescent and magnetic properties of four coordination polymers with the flexible 1,3-phenylenediacetate ligands

Four coordination polymers, [Zn(pda)(bpy)(H₂O)]_n·nH₂O (1), [Cd(pda)(prz)(H₂O)]_n (2), [Co₃(μ₃-OH)₂(pda)₂(pyz)]_n·2nH₂O (3) and [Pr₂(pda)₃(H₂O)₂]_n (4) (H₂pda=1,3-phenylendiacetic acid, bpy=4,4′-bipyridine, prz=piperazine and pyz=pyrazine) have been hydrothermally synthesized and characterized. Complex 1 is a 1D wheel-like chain structure, which is further extended into a 3D metal-organic supramolecular framework by H-bonds and π-π stacking interactions. Complex 2 is a 1D ladder-like chain structure, which is also further extended into a 3D metal-organic supramolecular framework by H-bonds. Complex 3 possess a 2D sheet structure with infrequent two pairs of double-helix chains. Complex 4 features a 3D structure. Both 1 and 2 display strong blue fluorescent emission at room temperature. Magnetic susceptibility measurements of complexes 3 and 4 exhibit antiferromagnetic interactions between the nearest metal ions, with C=9.99 and 3.43 cm³ mol⁻¹ K, and θ=−23.9 and −46.3 K, respectively.     

Synthesis and peptide-binding properties of a luminescent pyrimidine zinc(II) complex

The synthesis and peptide-binding properties of a Zn(II)nitrilotriacetate complex substituted with pyrimidine hydrazine amides are reported. The metal complex provides millimolar binding affinity in aqueous buffer to peptides bearing N-terminal His. The pyrimidine heterocycles intermolecularly interact with the bound peptide and quench the emission of nearby Trp residues by energy transfer.     

3(1,3-Heterazolidin-3-yl-methyl)-1,3-oxazolidines and their reduction with borane–THF

Preparation of bis-heterazolidines bonded by a CH₂, CH₂–S–CH₂ or CH₂SCH₂SCH₂ groups through their nitrogen atoms is reported: 3-(1,3-oxazolidin-3-ylmethyl)-1,3-oxazolidine 1, 3-(4,4-dimethyl-1,3-oxazolidin-3-ylmethyl)-1,3-oxazolidine 2, 3-(1,3-diazolidin-3-ylmethyl)-1,3-diazolidine 3, 3-(1,3-thiazolidin-3-ylmethyl)-1,3-thiazolidine 4, 3-(1,3-thiazolidin-3-ylmethylsulfanylmethyl)-1,3-thiazolidine 5 and 3-(1,3-oxazolidin-3-ylmethylsulfanylmethyl-sulfanylmethyl)-1,3-oxazolidine 6. The solid state structures of 4 and 5 were determined by X-ray diffraction analyses. BH₃–THF reduction reactions of compounds 1–6 were investigated. N→BH₃ mono- and di-adducts of 1–6 were prepared and their structures calculated (ab initio 3-21G*).     

Tetranuclear Zn(II) complexes with compartmental and dicyanamido ligands: synthesis,structure, and luminescent properties

New tetranuclear compounds have been obtained by reacting binuclear complexes, [Zn₂L ⁿ (μ-OH)(H₂O)₂](ClO₄)₂, with sodium dicyanamide (HL ⁿ are end-off bicompartmental ligands resulting from condensation between 2,6-diformyl-p-cresol with N,N-dimethyl-ethylenediamine or 2-aminomethyl-pyridine). The complexes, [{L¹(μ-OH)Zn₂}(μ _1,5-dca)₂{Zn₂(μ-OH)L¹}](ClO₄)₂ (1) and [{Zn₂L²(μ ₃-OH)(dca)}₂](ClO₄)₂?·?2H₂O (2), have been characterized by single-crystal X-ray diffraction. The angular nature of the bridging dicyanamido induces the “M” shape of the tetranuclear cationic unit in 1. The tetranuclear cation, because of its particular shape, acts as a receptor toward one perchlorate ion, which is hydrogen bonded to the hydroxo groups. This tetranuclear unit in 2 has a defective heterocubane structure. The luminescence properties of the new tetranuclear complexes have been investigated.     

Synthesis,structure and luminescent properties of a new two-dimensional (4,4) network cadmium coordination polymer with dicyanamide and benzimidazole ligands

The new cadmium coordination polymer [Cd(bim)₂(dca)₂]_n (1), (bim?=?benzimidazole, dca?= dicyanamide) was synthesized and characterized by IR, thermogravimetric analysis and luminescent properties. The coordination geometry of cadmium atom is distorted octahedral, coordinated equatorially by four nitrogen atoms from four dicyanamide ligands, and axially by two nitrogen atoms from two benzoimidazoles. Each dca ligand links two cadmium(II) atoms and 1 forms a two-dimensional (4,4) network.     

Designing of luminescent GdPO4:Eu@LaPO4@SiO2 core/shell nanorods: Synthesis,structural and luminescence properties

GdPO₄:Eu³⁺ (core) and GdPO₄:Eu@LaPO₄ (core/shell) nanorods (NRs) were successfully prepared by urea based co-precipitation process at ambient conditions which was followed by coating with amorphous silica shell via the sol-gel chemical route. The role of surface coating on the crystal structure, crystallinity, morphology, solubility, surface chemistry and luminescence properties were well investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, Fourier Transform Infrared (FTIR), UV-Vis, and photoluminescence spectroscopy. XRD pattern revealed highly purified, well-crystalline, single phase-hexagonal-rhabdophane structure of GdPO₄ crystal. The TEM micrographs exhibited highly crystalline and narrow size distributed rod-shaped GdPO₄:Eu³⁺ nanostructures with average width 14–16 nm and typical length 190–220 nm. FTIR spectra revealed characteristic infrared absorption bands of amorphous silica. High absorbance in a visible region of silica modified core/shell/Si NRs in aqueous environment suggests the high solubility along with colloidal stability. The photoluminescence properties were remarkably enhanced after growth of undoped LaPO₄ layers due to the reduction of nonradiative transition rate. The advantages of presented high emission intensity and high solubility of core/shell and core/shell/Si NRs indicated the potential applications in monitoring biological events.     

Synthesis and photophysical properties of novel organic–inorganic hybrid materials covalently linked to a europium complex

A novel sol–gel derived hybrid material (classed as Eu-DBM-Si) covalently grafted with Eu(DBM-OH)₃·2H₂O (where DBM-OH = o-hydroxydibenzoylmethane) was prepared through the primary β-diketone ligand DBM-OH. All the synthesized ligands were characterized by ¹H NMR, elemental analyses and Fourier transform infrared spectra (FTIR). The resultant Eu-DBM-Si material exhibited good transparent and homogenous property. Compared to the Eu-DBM hybrid prepared by physically doped silicon dioxide with Eu(DBM-OH)₃·2H₂O, the Eu-DBM-Si hybrid presented more efficient ligand-to-Eu³⁺ energy transfer and a significant improvement in the measured emission quantum yield. Furthermore, the photophysical properties of these hybrid materials, such as the photoluminescence (PL) spectra, PL intensities, symmetry properties, lifetime decays, and Judd-Ofelt parameters were also investigated in detail.     

The enhancement of luminescent properties of Tb3+ complexes with tetra-1,3-diketone ligands promoted by the tetrathiacalix[4]arene scaffold

This is the first report on the synthesis and characterization of tetra-1,3-diketone derivatives of tetrthia- and calix[4]arenes substituted by acetylacetonyl or dipivaloylmethanyl moieties at the upper rim and bearing hydroxyl groups at the lower rim as ligands for Tb³⁺ complexes. The spatial structure and tautomeric content for the synthesized ligands have been determined by means of X-ray, IR and NMR spectroscopy. Comparison of the sensitizing properties of tetrathiacalix[4]arenes and their calix[4]arene analogues on the Tb³⁺-centered luminescence in DMF solutions has been performed. A substantial enhancement of the luminescent properties of Tb³⁺- complexes with tetra-1,3-diketone ligands promoted by the tetrathiacalix[4]arene scaffold was established.     

Synthesis and structure of 1,3-dialkyl-4-(sulfonylimino)imidazolidin-2-ones

The reactions of 1,3-dialkyl-4,5-dihydroxyimidazolidin-2-ones with alkyl sulfamides have been studied and previously undescribed 1,3-dialkyl-4-(alkylaminosulfonylimino)imidazolidin-2-ones have been obtained. The structure of 1,3-dimethyl-4-(benzenesulfonylimino)imidazolidin-2-one was investigated by X-ray structural analysis. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1159–1166, August, 2007.     

Synthesis and photochromic properties of 1,2-dihetarylethenes with 1,3-dioxole- and 1,3-oxazole-2-thione bridges

Methods for the synthesis of substituted bis(2,5-dimethyl-3-thienyl)ethenes with 1,3-dioxole- and 1,3-oxazole-2-thione fragments as ethene bridges were developed. These compounds exhibit photochromic properties. Dedicated to Academician N. K. Kochetkov on the occasion of his 90th birthday. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1299–1301, May, 2005.     

Synthesis,crystal structure and luminescence of three europium complexes with 2-iodobenzoic acid

Three new complexes, [Eu(2-IBA)₃?·?H₂O] _n (1), [Eu(2-IBA)₃?·?2,2′-bpy]₂ (2), and [Eu(2-IBA)₃?·phen]₂ (3) (2-IBA?=?2-iodobenzoato; 2,2′-bpy?=?2,2’-bipyridine; phen?=?1,10-phenanthroline) were synthesized, and their crystal structures determined by X-ray diffraction. In complex 1, Eu³⁺ ions are linked through carboxylate groups via bridging – chelating – bridging coordination modes to form a one-dimensional polymeric chain. The carboxylate groups are tetradentate-bridged. Complex 2 is binuclear with an inversion center, in which europium is nine-coordinated with seven oxygen atoms from five 2-IBA ligands and two nitrogen atoms from one 2,2′-bpy molecule in a distorted monocapped square antiprism. The crystal structure of 3 is similar to that of 2. These complexes emit red light luminescence. The ⁵ D ₀?→?⁷ F _j (j?=?1–4) transition emission of Eu³⁺ ion has been observed.     

链状Eu(BO_2)_3的合成与发光性能研究

采用固相反应合成出链状结构的稀土硼酸盐Eu(BO2)3发光材料。分别利用XRD、TEM、SAED、EDS和PL等测试技术对产物进行了研究,结果表明:链状结构的Eu(BO2)3属于单斜晶系,空间群为I2/a,直径约10～15nm,长度达几个微米,探讨了链状Eu(BO2)3的生长机理。在395nm紫外光激发下,Eu(BO2)3能发出Eu3+的特征红色荧光,发射主峰位于591nm,归属于5D0→7F1磁偶极跃迁。     

Synthesis,structure and luminescent properties of zinc(II) and Hg(II) complexes with substituted 1,10-phenanthroline

Two d¹⁰ group 12 metal complexes, 2-(2-methoxyphenyl)-1,10-phenanthroline zinc dichloride (2a) and 2-(2-methoxyphenyl)-1,10-phenanthroline mercury dichloride (2b) were synthesized and characterized by IR, ¹H and ¹³C NMR as well as elemental analysis. Structure of 2b in the solid state was determined by single-crystal X-ray crystallography, revealing that 2b is four-coordinate in a distorted tetrahedral geometry with the methoxy group uncoordinated. Luminescent properties of 2a and 2b in solution and the solid state were studied.     

Synthesis and photoluminescence properties of BF2 complexes with 1,3-diketone ligands

BF₂ complexes with 1,3-diketone ligands were synthesized, and their optical and electrochemical properties were studied. The colors of the complexes varied depending on the structures of the 1,3-diketone ligands. The absorption and emission maxima of the complexes with 1,3-diaryl-1,3-diketone ligands were considerably red shifted as compared to those of the complexes with 1-aryl-3-trifluoromethyl-1,3-diketone ligands, suggesting an extended π-conjugation of the 1,3-diaryl-1,3-diketone moieties. The molar absorption coefficients and quantum yields of the complexes with 1,3-diaryl-1,3-diketone ligands were larger than those of the complexes with 1-aryl-3-trifluoromethyl-1,3-diketone ligands. Cyclic voltammetry measurements revealed that the reduction potentials of the BF₂ complexes were higher than those of the free ligands. These complexes exhibited various emission colors in the solid states due to the intermolecular interactions.     

Synthesis of 1,3-bis(acetylacetonyloxy)- and 1,3-bis(benzoylacetonyloxy)benzene and their complexation with lanthanide ions

Claisen condensation of 1,3-bis(methoxycarbonylmethoxy)benzene with acetone and acetophenone afforded new chelating ligands consisting of two β-diketonate fragments, viz., 1,3-bis(acetylacetonyloxy)benzene and 1,3-bis(benzoylacetonyloxy)benzene, which are linked to each other through the resorcinol spacer. In the crystal, 1,3-bis(acetylacetonyloxy)benzene, unlike the starting ester, adopts a planar conformation and exists in the enol form. The acidities of these compounds and their complexation with lanthanide ions in aqueous ethanolic solutions were studied by pH-potentiometry. Depending on the concentration conditions and pH, the La³⁺, Gd³⁺, and Lu³⁺ ions form 1 : 1, 1 : 2, or 1 : 3 complexes with bis(β-diketones). The stability of the complexes increases as the atomic number of the lanthanide increases (La³⁺ < Gd³⁺ ≤ Lu³⁺). The complexation constants and selectivity of complexation substantially increase with increasing degree of deprotonation of the ligands, which indicates that both chelate groups of the ligands are simultaneously involved in coordination. The Ph substituents in bis(β-diketone) have a considerable effect on the composition and stability of complexes with lanthanide ions due to additional noncovalent inner-sphere interactions.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 614–622, March, 2005.