Luminescent and triboluminescent properties of europium(III) hexafluoroacetylacetonate and trifluoroacetate complexes with triphenylphosphine oxide

Crystalline and strongly luminescent complexes of europium hexafluoroacetylacetonate and trifluoroacetate with triphenylphosphine oxide of Eu(HFAA)₃ · 2TPPO and [Eu(TFA)₃ · 2TPPO(H₂O)]₂ composition are synthesized that demonstrating triboluminescent properties. It is established that the measured photoluminescence and triboluminescence spectra of these noncentrosymmetric complex compounds are identical, due to the characteristic f-f-luminescence of the europium(III) ion.     

Europium and terbium Schiff base peptide complexes as potential antimicrobial agents against <Emphasis Type="Italic">Salmonella typhimurium</Emphasis> and <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis>

Eu(III) and Tb(III) Schiff base complexes are applicable in various fields such as sensing, assays, screening protocols in vitro, and imaging studies in vitro or in vivo. Fluorescent europium and terbium complexes and their interaction with cell penetrating peptide (KKKRKC) can represent an excellent key for understanding pathway of peptide transportation though cell membrane and the application of Schiff base complexes as potential antibacterial drugs. The Schiff base–metal complexes and its conjugates with peptide were tested for their antibacterial activity against Pseudomonas aeruginosa and Salmonella typhimurium. Schiff base–metal complexes conjugated with peptide show minor toxicity in normal human PNT1A cells and high antibacterial activity against P. aeruginosa and S. typhimurium, where IC50 down to 125.9 and/or 36.1 µM were found for P. aeruginosa and S. typhimurium, respectively. Our results strongly suggest that Schiff base–metal complexes conjugated with peptide have great potential to be developed into highly effective antibacterial drug.     

Photochemical properties of mixed-ligand complexes europium carboxylates

The photochemical behavior of mixed-ligand complexes of europium carboxylates with nitrogen-and phosphorus-containing neutral ligands of island and dimer types, Eu(L)₃ · xD · nH₂O and [Eu(L)₃ · xD]₂ · nH₂O (L is the trifluoroacetate, toluate, or cinnamate anion), was studied. During UV irradiation of the complexes of europium carboxylates with 1,10-phenanthroline and 2,2′-dipyridyl, a luminescence buildup was observed. EPR measurements demonstrated that the observed buildup of luminescence from europium occurs in parallel with the increase of the concentration of radical anions formed from neutral ligands.     

Luminescent properties of europium(III) and terbium(III) complexes with para- and ortho-ethoxybenzoic acids

The luminescent properties of europium(III) and terbium(III) complexes with para- and ortho-ethoxybenzoic acids are studied. The excitation energies of the triplet states of ligands are determined, a hypothesis is made about the efficient luminescence of europium(III) and terbium(III) complexes, the geometry of the coordination polyhedron of a europium complex is established, and the luminescence quantum yields of the complexes in solution are determined.     

Synthesis,characterization, spectroscopic and catalytic oxidation studies of Fe(III), Ni(II), Co(III), V(IV) and U(VI) Schiff base complexes with N,O donor ligands derived from 2,3-diaminopyridine

Fifteen new complexes of transition metals were designed using three Schiff base ligands and aldol condensation of 2,3-diaminopyridine with 5-R-2-hydroxybenzaldehyde (R = F, Cl, Br) in the 1:2 molar ratio. The tetradentate ligands N,N′-bis(5-R-2-hydroxybenzaldehyde) pyridine were acquired with the common formula H₂[(5-R-sal)₂py] and characterized by IR, UV–Vis spectra, ¹H-NMR and elemental analysis. These ligands produce 1:1 complexes M[(5-R-sal)₂py] with Fe(III), Ni(II), Co(III), V(IV) and U(VI) metal ions. The electronic property and nature of complexes were identified by IR, UV–Vis spectra, elemental analysis, X-ray crystallography and cyclic voltammetric methods. The catalytic activity of complexes for epoxidation of styrene with UHP as primary oxidant at minimal temperature (10 °C) has been planned. The spectral data of the ligands and their complexes are deliberate in connection with the structural changes which happen due to complex preparation. The electrochemical outcome has good conformability with what suggested for electronic interaction among metal center and ligand by the UV–Vis and IR measurements.     

Synthesis,characterization and photophysical properties of homoleptic platinum(II) complexes with 2,2′-biimidazole-based ligands

Eight pairs of cis–trans isomeric homoleptic platinum(II) complexes based on N-alkyl- or aryl-substituted 2,2′-biimidazole ligands were synthesized, and their photophysical properties were investigated. The cis and trans isomers readily interconvert at slightly elevated temperature, implying that the activation barrier for this process is low. Single crystal X-ray diffraction analysis revealed that the complexes have an ideal square-planar geometry. Their UV–Vis spectra showed lower energy absorption bands in the range of 345–378 nm, which are assigned to the typical MLCT mixed with LC transitions. In frozen glass solution at 77 K and also in the powder state, these complexes exhibit green emission ranging from 440 to 540 nm with photoluminescence quantum yields of 3.3–24.4%. The emitting excited state is dominated by ³ππ* character with some contributions from ³MLCT according to the excitation spectra.     

Crystal structure of a new binuclear complex bis(2,4,6,8-tetramethyl-2,4,6,8-tetraazabicyclo(3.3.0)octane-3,7-dione-o,o′)-tetraaqua-hexakis(nitrato-o,o′)-dieuropium(III)

A centrosymmetric binuclear complex of europium(III) nitrate with bicyclic bisurea (2,4,6,8-tetramethyl-2,4,6,8-tetraazabicyclo(3.3.0)octane-3,7-dione, or mebicar, Mk) [Eu(C₈H₁₄N₄O₂)(H₂O)₂(NO₃)₃]₂ (I) is synthesized and its atomic structure (CIF file CCDC No. 1451437) is determined. The crystals of I are triclinic: space group \(P\overline 1 \), a = 9.8343(4) Å, b = 10.2544(4) Å, c = 10.9411(4) Å, α = 74.366(3)°, β = 67.734(4)°, γ = 67.673(4)°, V = 934.32(7) ų, ρ(calc.) = 2.03398 g/cm³, Z = 1. The europium atom is coordinated by two oxygen atoms of two Mk molecules connected by a symmetry operation, three bidentate nitrate anions, and two water molecules. The coordination polyhedron of the europium atom is a 10-vertex polyhedron, the Eu…Eu distance is 9.7433(6) Å.     

Multicomponent reactions in the synthesis of dihydropyrimidine-containing podands having tuberculostatic activity

Dihydropyrimidinethione podands, as well as podands containing 2-thienyl substituents have been synthesized via the multicomponent Biginelli reaction. Tuberculostatic activity of the novel podands was shown to depend on the polyether unit length. In particular, activity of dihydropyrimidinethione podands against laboratory strains of Mycobacterium tuberculosis, H₃₇Rv, M. avium, M. terrae, and the clinical strain of multi-drug resistant M. tuberculosis (MDR), increases with a shortening of the polyether unit length.     

Synthesis of a novel chelating ligand from pentane-2,4-dione and 3-aminopropyl[tris(trimethylsilyloxy)]silane. europium(III) and erbium(III) imino enolates

Acetylacetone reacts with 3-aminopropyl[tris(trimethylsilyloxy)]silane to give a mixture of the isomers 4-[3′-tris(trimethylsilyloxy)silylpropyl]iminopent-2-en-2-ol (90%) and 4-[3′-tris(trimethylsilyloxy)silylpropyl]aminopent-3-en-2-one (10%). According to ¹H and ¹³C NMR data, both isomers exist in the cis-and trans-forms. Anhydrous europium(III) and erbium(III) tris{4-[3′-tris(trimethylsilyloxy)silylpropyl]iminopent-2-en-2-olates} were obtained from the mixture of the isomers and the corresponding propan-2-olates Eu(OPr _i )₃ and Er(OPr _i )₃. The resulting complexes are transparent air-stable liquids that are distillable in vacuo and well soluble in photopolymerizable polyorganosiloxane caoutchoucs and urethane acrylate oligomers. The volatility parameters of the europium(III) complex were studied.     

Synthesis,crystal structure,and luminescence properties of a novel europium(III) complex

A novel europium(III) complex, [Eu(C₇H₅O₂)₂(C₇H₆O₂)₂(C₁₂H₈N₂)₂Cl], was synthesized and characterized by elemental analysis and single-crystal X-ray determination. It crystallizes in the monoclinic system, space group Cc with a = 17.2814(16), b = 17.9421(17), c = 14.9971(14) Å, β = 101.6510(10)°, Z = 4, ρ _c = 1.508 g/cm³, μ = 1.496 mm^?1, the final R = 0.0516 and wR = 0.1267 for 6435 observed reflections with I > 2σ(I). Structural analysis shows that the Eu(III) atom is nine-coordinated by one chlorine atom, four N atoms of two 1,10-phenanthroline (Phen) ligands, and four O atoms from four carboxybenzene ligands, to form a distorted tricapped trigonal prism. The luminescence spectrum of the complex indicates that the intensity of the emission wavelength at 612 nm is strongest among all emission wavelengths and the second phen ligand shows an enhancement effect on the luminescence of the complex.     

Complexation of radionuclide <Superscript>152+154</Superscript>Eu(III) with alumina-bound fulvic acid studied by batch and time-resolved laser fluorescence spectroscopy

To contribute to the understanding of Eu(III) interaction preperties on hydrous alumina particles in the absence and presence of fulvic acid (FA), the complexation properties of Eu(III) with hydrous alumina, FA and FA-alumina hybrids are studied by batch and time-resolved laser fluorescence spectroscopy (TRLFS) techniques. The continuous increase in the fluorescence lifetime of Eu-alumina and Eu-FA with increasing pH indicates that the complexation is accompanied by decreasing number of hydration water in the first coordination sphere of Eu(III). Eu(III) is adsorbed onto alumina particles as outer-sphere surface complexes of ≡(Al?O)?Eu· (OH)· 7H₂O and ≡(Al?O)?Eu· 6H₂O at low pH values, and as inner-sphere surface complexes as ≡(Al?O)₂?Eu⁺· 4H₂O at high pH. In FA solution, Eu(III) forms complexes with FA as (COO)₂Eu⁺(H₂O) _x and the hydration water number in the first coordination sphere decreases with pH increasing. The formation of ≡COO?Eu?(O?Al≡)· 4H₂O is observed on FA-alumina hybrids, suggesting the formation of strong inner-sphere surface complexes in the presence of FA. The surface complexes are also characterized by their emission spectra [the ratio of emission intensities of ⁵ D ₀→⁷ F ₁ (λ=594 nm) and ⁵ D ₀→⁷ F ₂ (λ=619 nm) transitions] and their fluorescence lifetime. The findings is important to understand the contribution of FA in the complexation properties of Eu(III) on FA-alumina hybrids that the clarification of the environmental behavior of humic substances is necessary to understand fully the behavior of Eu(III), or its analogue trivalent lanthanide and actinide ions in natural environment.     

Ruthenium complexes with lumazine derivatives: structural,electrochemical, computational and radical scavenging studies

In this research study, the formation and characterization of new ruthenium(II) and (III) complexes encompassing multidentate ligands derived from 6-acetyl-1,3,7-trimethyllumazine (almz) are reported. The 1:1 molar coordination reactions of trans-[RuCl₂(PPh₃)₃] with N-1-[1,3,7-trimethyllumazine]benzohydride (bzlmz) and 6-(N-methyloxime)-1,3,7-trimethyllumazine (ohlmz) formed a diamagnetic ruthenium(II) complex, cis-[RuCl₂(bzlmz)(PPh₃)] (1), and paramagnetic complex, cis-[Ru^IIICl₂(olmz)(PPh₃)] (2) [Holmz = 6-(N-hydroxy-N′-methylamino)-1,3,7-trimethyllumazine], respectively. These ruthenium complexes were characterized via physico-chemical and spectroscopic methods. Structural elucidations of the metal complexes were confirmed using single crystal X-ray analysis. The redox properties of the metal complexes were investigated via cyclic voltammetry. Electron spin resonance spectroscopy confirmed the presence of a paramagnetic metal centre in 2. The radical scavenging activities of the metal complexes were explored towards the DPPH and NO radicals. Quantum calculations at the density functional theory level provided insight into the interpretation of the IR and UV–Vis experimental spectra of 1.     

On the relationship between the luminescence of heterometallic terbium-copper-podand complexes and the ligand structure

The formation conditions and luminescence of heterometallic Tb-Cu complexes with structurally similar podands containing different numbers of oxymethylene fragments were studied (n = 2?7). The component ratio in mono- and different-metal complexes were 1: 1 and 1: 1: 1, respectively. The possibility of complex formation for the carbonyl and enol forms was estimated by molecular mechanics. The results were in good agreement with experimental data. The most pronounced enhancement of luminescence intensity of Tb(III) ions in heterometallic Tb-Cu complexes was observed for podands containing two and three oxymethylene fragments (L1 and L2, respectively) and the probability of complex formation with these podands is higher than with the podands containing four to seven oxymethylene fragments (L3–L5).     

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.     

Density functional theory insight into Eu(III) and Am(III) complexes with two 2,6-dicarboxypyridine diamide-type ligands

Extraction complexes of Eu(III) and Am(III) with two 2,6-dicarboxypyridine diamide-type ligands L–A and L–B (Fig. 1) are studied by density functional theory (DFT). At both B3LYP/6-31G(d)/RECP and MP2/6-31G(d)/RECP levels of theory, the geometrical optimizations of the structures of the complexes can achieve the same accuracy and obtain the same geometrical configuration. At the B3LYP/6-311G(d,p)/RECP level of theory Eu³⁺ and Am³⁺ prefer to form [ML]³⁺ complexes under the solvation conditions, and the Am(III) complexes with L–A are more stable than the corresponding Eu(III) complexes. In the system with the ligand L–B, both [ML]³⁺ and [ML(NO₃)₃] species are very unstable.     

Synthesis,characterization, thermal,antimicrobial and antioxidant studies of some transition metal dithiocarbamates

Metal dithiocarbamate complexes of Co(II) [1], Cu(II) [2], Mn(II) [3], Cr(III) [4], and Pd(II) [5] have been synthesized using sodium N-ethyl-N-phenyldithiocarbamate (NaL). The complexes were characterized by elemental analyses, FTIR and UV–vis spectroscopic techniques, magnetic moment, molar conductance and thermal analyses (TGA and DSC). The infrared spectra indicated the coordination of dithiocarbamate through the two sulphur atoms in a symmetrical bidentate fashion. The thermal behavior of these complexes showed that the hydrated complexes lost water molecules in the first step, followed by decomposition of the ligand molecules in the final steps. Mass loss considerations at these final decomposition steps indicate conversion of the complexes to sulphides. The antimicrobial potentials of the complexes were evaluated against some selected bacteria strains (Escherichia coli, Pseudomonas aureginosa, Salmonella typhi and Staphylococcus aureus) and fungi organisms (Aspergillus flavus and Fasiparium oxysporium). The compounds showed a broad spectrum of fungicidal and bactericidal activities which exceeds that of the control drugs at a 100 μg/mL concentration. The antioxidant properties of the ligand and its Cu(II) complex were evaluated in vitro using DPPH assay, and the complex was found to exhibit better radical scavenging ability than the free ligand.     

Ultrafiltration membranes based on interpolyelectrolyte complexes: Adsorption and mass-exchange properties

Ultrafiltration membranes based on interpolyelectrolyte complexes of a sulfonated aromatic copolyamide, an acrylonitrile–N,N-dimethyl-N,N-diallylammonium chloride copolymer, and poly-N,N-dimethyl-N,N-diallylammonium chloride were prepared. The adsorption (in batch experiments and under conditions of ultrafiltration of myoglobin, lysozyme, and bovine serum albumin solutions) and mass-exchange properties of the membranes were studied. Correlation between the procedure for performing the interpolymer reaction, the composition of the complexes formed, and the characteristics of the membranes prepared was found. The protein/membrane interaction in the system studied is mainly due to Coulomb forces. The effect of the protein adsorption on the separation and transport properties of the membranes was considered. The general level of the mass-exchange properties of the membranes based on the interpolyelectrolyte complexes is higher compared to the samples containing ionic groups of like charge.     

Thermal behavior of europium tris(hexafluoroacetylacetonate) Eu(hfa)<Subscript>3</Subscript> and the mixed-ligand 4-cyanopyridine-<Emphasis Type="Italic">N</Emphasis>-oxide complex [Eu(hfa)<Subscript>3</Subscript>(cpo)]

The thermal behavior and thermodynamic properties of europium tris(hexafluoroacetylacetonate) Eu(hfa)₃ and the mixed-ligand 4-cyanopyridine-N-oxide complex [Eu(hfa)₃(cpo)] were investigated by thermal analysis and Knudsen effusion mass spectrometry. The compounds sublime congruently. The composition of the gas phase over the compounds and the partial pressures of the components were determined. The enthalpies of sublimation, polymerization, and dissociation of these compounds were derived from experimental data.     

Crystal structure and triboluminescence of tetraethylammonium tetrakis(thenoyltrifluoroacetonato)europium

An atomic structure of complex Et₄N[Eu(ТТA)₄] (TTA is the thenoyltrifluoroacetonate anion, Et₄N⁺ is the tetraethylammonium cation) possessing strong luminescence and triboluminescence was determined by X-ray crystallography. The crystal system of centrosymmetric crystals is monoclinic: a = 10.2495(1) Å, b = 20.2162(3) Å, c = 23.5788(3) Å, β = 102.551(1)°, space group P2₁/c, Z = 4, d _calc = 1.625 g cm^–3. The crystals of the compound have an isle structure, which comprises individual complex anions [Eu(TTA)₄]^– and tetraethylammonium cations Et₄N⁺. The structural aspects of a possible model for the formation of triboluminescent properties were considered, the role of cleavage planes and disordering was discussed.     

Synthesis of silver(I) and palladium(II) <Emphasis Type="Italic">N</Emphasis>-heterocyclic carbene complexes and their use as catalysts for the direct C5 arylation of heteroaromatic compounds

Silver(I) N-heterocyclic carbene complexes were synthesized in good yields by the reactions of 1,3-dialkylperhydrobenzimidazolium salts with silver(I) oxide in dichloromethane. The silver complexes were used as carbene-transfer agents to synthesize palladium(II) N-heterocyclic carbene complexes. All of the complexes were characterized by physicochemical and spectroscopic methods. The new palladium complexes were tested as catalysts in the direct C5 arylation of 2-n-butylfuran, 2-n-butylthiophene and 2-n-propylthiazole with aryl bromides at 130 °C in N,N-dimethylacetamide. The arylation reactions proceeded selectively at the C5 position of the heteroaromatic compounds, and the corresponding coupling products were obtained in moderate to good yields by using 0.5 mol% of the palladium complex.