Luminescence of Ln3+ lanthanide complexes in polymer matrices

The photoluminescence properties of Tb³⁺ and Eu³⁺ complexes with polymer ligands containing various kinds of complexing groups??namely, carboxyl (5?C20 mol %), pyridylquinoline (5 mol %), or pyridylnaphthyl (5 and 10 mol %) groups??in solution and block are considered. The chemical structure of a neutral comonomer (methyl methacrylate; styrene; isopropyl-, phenyl-, or benzylmethacrylamide; and N-vinylamides) in polymer ligands is varied. The intensity of photoluminescence is dependent not only on the chemical nature of a complexing group but also the chemical nature of a neutral comonomer and a spacer. Variation in the nature of a comonomer and a ligand makes it possible to prepare complexes in which a high luminescence of a low-molecular-mass complex is preserved and advantages inherent in a polymer complex are acquired. The effect of the nature of the polymer matrix (photoactive and photoinert) on the efficiency of electronic-excitation energy transfer is ascertained. The data on the photoluminescence of metal-polymer complexes that are based on polymer ligands containing vinylcarbozole units and that possess hole conductivity make it possible to regard them as materials for electroluminescence. The intensity of photoluminescence of these complexes is related to the competition of oppositely directed photophysical processes in a macromolecule: formation of excimers and migration of electronic excitation energy. An analysis of the published data and of the results of the authors shows that detailed studies of these polymer systems in solution and in matrices are needed to gain insight into the relationship between photo- and electroluminescence properties of metal-polymer complexes, because the matrix plays different roles in photoluminescence and electroluminescence (inner filter or conduction); as a consequence, the emission spectra may differ appreciably. It is shown that the efficiency of electroluminescence may be improved if the transfer of energy from the lanthanide ligand in a complex to the conducting matrix is decreased.     

Polymetallic lanthanide complexes with PAMAM-naphthalimide dendritic ligands: luminescent lanthanide complexes formed in solution

Generation 3 PAMAM dendrimers functionalized with 2,3-naphthalimide chromophoric groups on the end branches were synthesized, and the formation of Eu3+ polymetallic complexes was investigated. The luminescence properties of these complexes upon binding were fully characterized. On addition of Eu3+ to the dendrimer solution, lanthanide luminescence appears. The formation of a luminescent species corresponding to a dendrimer:lanthanide ratio of 1:8 was determined by luminescence batch titration and indicated by the maximum of Eu3+ emission. This indicates an overall average coordination number of 7.5 around each lanthanide metal cation. This is the first report of such characterization in the literature. Luminescence lifetimes indicate that the metal cation is well protected from nonradiative deactivation by the dendritic structure. Despite the limited efficiency of the sensitization of Eu3+, the absolute quantum yield being 0.0006, the good protection of the eight lanthanide cations bound in the dendrimer structure and the high absorptivity leads to the red emission from Eu3+ that is easily observed in solution under irradiation with 354 nm UV light.     

Photophysical properties and tunable colour changes of silica single layers doped with lanthanide(III) complexes

Highly stable Eu(III) and Tb(III) complexes, emitting in the red and green visible regions, respectively, have been anchored onto a single SiO(2) transparent layer, yielding ca. 40 nm thick films; this allows high loading of tailored proportions of the red and green emitters within the films and results in highly uniform and easily colour-tunable luminescent layers.     

Carbon-silica composite matrices for preparing heterogeneous biocatalysts with glucose isomerase activity

Comparative studies have been carried out on the preparation of carbon-silica composite matrices for heterogeneous biocatalysts with glucose isomerase activity. Carbon nanotubes and nanofibers have been included inside SiO₂ xerogel. The enzymatic activity and operating stability of the biocatalysts have been investigated. Bacterial cells of a recombinant glucose isomerase producer strain have been used as the enzymatically active component of the biocatalysts. The steady-state activity of the biocatalysts subjected to “dry” cross linking with a glutaraldehyde solution (0.1–1%) is 1.5 times higher than the activity of the biocatalysts containing no nanocarbon. The initial and steady-state glucose-isomerase activities of the biocatalysts at 70°C are ∼520–540 and ∼150–160 μmol min⁻¹ g⁻¹, respectively. The half-inactivation time of the biocatalysts under continuous monosaccharide (glucose, fructose) isomerization conditions is up to ∼1500 h.     

Luminescent lanthanide complexes with liquid crystalline properties

Lewis-base adducts of tris(β -diketonato)lanthanide(III) complexes were prepared, where the β -diketone is para -alkoxy-substituted 1,3-diphenyl-1,3-propanedione. These compounds are the first examples of liquid crystalline lanthanide complexes in which the mesomorphism is introduced via a β -diketonate ligand. Depending on the type of the Lewis base, the metallomesogens exhibit a monotropic smectic A or a monotropic highly ordered smectic phase. Intense photoluminescence was observed for the europium(III) complexes at room temperature.     

Luminescent lanthanide complexes with analyte-triggered antenna formation

A new strategy for accessing analyte-responsive luminescent probes is presented. The lanthanide luminescence of Eu and Tb centers is switched on by the analyte-triggered formation of a sensitizing antenna from a nonsensitizing caged precursor. As the cage can be freely varied, an array of probes for different analytes (Pd(0/2+), H(2)O(2), F(-), β-galactosidase) can be created from the same core structure. The probe design affords nanomolar to micromolar detection limits, provides the capability to detect two analytes in parallel, and can be utilized to monitor enzymatic activity in live cells.     

Novel Z-selective head-to-head dimerization of terminal alkynes catalyzed by lanthanide half-metallocene complexes

Various terminal alkynes have been cleanly dimerized into the corresponding head-to-head (Z)-enynes by use of the half-metallocene lutetium alkyl complexes Me2Si(C5Me4)(NAr)Lu(CH2SiMe3)(THF) (Ar = Ph, C6H3Me2-2,6, C6H2Me3-2,4,6) as catalysts. Aromatic C-Cl, C-Br, and C-I bonds, which are known to be extremely susceptible to reductive cleavage by transition metals, survived in the present reactions. The corresponding dimeric alkynide species [Me2Si(C5Me4)(NAr)Lu(mu-CCR)]2 are thought to be the true catalysts, some of which have been isolated and structurally characterized. These alkynide species were thermally stable and soluble at the reaction temperatures (80-110 degrees C), but they precipitated upon cooling to room temperature after completion of the reaction. Therefore, this catalyst system works homogeneously but can be separated and reused, thus constituting the first example of a recyclable catalyst system for the dimerization of terminal alkynes and also the first example of (Z)-selective head-to-head dimerization of aromatic terminal alkynes.     

Luminescent lanthanide complexes with liquid crystalline properties

Lewis-base adducts of tris( β-diketonato)lanthanide(III) complexes were prepared, where the β-diketone is para -alkoxy-substituted 1,3-diphenyl-1,3-propanedione. These compounds are the first examples of liquid crystalline lanthanide complexes in which the mesomorphism is introduced via a β-diketonate ligand. Depending on the type of the Lewis base, the metallomesogens exhibit a monotropic smectic A or a monotropic highly ordered smectic phase. Intense photoluminescence was observed for the europium(III) complexes at room temperature.     

Novel microporous lanthanide silicates with tobermorite-like structure

The synthesis and structural characterization of microporous lanthanide silicates (Na(1.08)K(0.5)Ln(1.14)Si(3)O(8.5).1.78H(2)O, Ln = Eu, Tb, Sm, Ce) are reported. The structure of these solids is closely related with the structure of hydrated calcium silicate minerals known as tobermorites and was solved by powder X-ray diffraction ab initio (direct) methods and further characterized by chemical analysis, thermogravimetry, scanning electron microscopy, (23)Na and (29)Si MAS NMR and luminescence spectroscopy. These materials combine microporosity with interesting photoluminescence properties, and their structural flexibility allows fine-tuning of luminescence properties, by introducing a second type of lanthanide ion in the framework. Thus, they may find applications in new types of sensors.     

Mixed-ligand lanthanide complexes with acylpyrazolones and phosphorus-containing ligands

The reactions of lanthanum acetylacetonate with various phosphorus-containing pesticides, toxic gases, and products of their hydrolysis are modeled by quantum-chemical methods. In the most cases, the enthalpy of substitution for water by organophosphorus compounds is negative. The complexes are studied in solutions using ethyl (diethoxyphosphoryl) acetate as a model compound. The mixed-ligand lanthanide complexes with acylpyrazolones and ethyl (diethoxyphosphoryl) acetate are synthesized. The crystal structure is determined for the samarium complex.     

Stability constants of lanthanide complexes with salicylhydroxamic acid

The stability constants of La, Pr, Nd, Sm, Eu, Gd, Dy, Er, Yb and Y complexes of salicylhydroxamic acid have been determined potentiometrically in 3:1 v v acetone-water medium at 25 +/- 0.5 degrees and at an ionic strength of 0.1 with respect to sodium perchlorate. The stability constants are comparable with those of other lanthanide complexes with oxygen-donating ligands such as benzoylacetone and benzoylphenylhydroxylamine.     

Far-infrared spectra of lanthanide complexes with 8-hydroxyquinoline

Summary Vibrational spectra of lanthanide oxines have been measured in the far-infrared region. In addition, the similar yttrium complex was investigated for further experimental evidence for the proposed band assignments. The most important metal-oxygen and metal-nitrogen bond vibrations have been attributed to absorptions between 390–350 cm^–1 and 210–170 cm^–1, respectively.

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Ferne IR-Spektren von Lanthanidenkomplexen mit 8-Hydroxychinolin

Zusammenfassung Es wurden die Vibrationsspektren von Lanthanid-Oxinen im fernen IR-Bereich gemessen. Zusätzlich wurde der analoge Yttrium-Komplex untersucht, um die Bandenzuordnungen experimentell zu stützen. Die wichtigsten Metall-Sauerstoff- und Metall-Stickstoff-Bindungsschwingungen wurden den Absorptionen zwischen 390–350 cm^–1 und 210–170 cm^–1 zugeordnet.

     

First lanthanide dipolar complexes for second-order nonlinear optics

New push-pull NLO-phores based on lanthanide complexes (Ln = La, Gd, Dy, Yb) featuring an annelated dibutylaminophenyl functionalised terpyridyl ligand have been synthesised and shown to exhibit large first-order hyperpolarizability.     

Novel one-dimensional lanthanide acrylic acid complexes: an alternative chain constructed by hydrogen bonding

Novel one-dimensional (1D) chains of three lanthanide complexes La(L¹)₃(CH₃OH)]·CH₃OH (L¹=(E)-3-(2-hydroxyl-phenyl)-acrylic acid) 1, La(L²)₃(H₂O)₂]·2.75H₂O (L²=(E)-3-(3-hydroxyl-phenyl)-acrylic acid) 2, and La(L³)₃(CH₃OH)₂(H₂O)]·CH₃OH (L³=(E)-3-(4-hydroxyl-phenyl)-acrylic acid) 3 are reported. The crystal structure data are as follows for 1: C₂₉H₂₉LaO₁₁, monoclinic, P2₁/n, a=15.4289(12) Å, b=7.9585(6) Å, c=23.041(2) Å, β=99.657(2)°, Z=4, R₁=0.0637, wR₂=0.0919; for 2: C₂₇H_30.50LaO_13.75, triclinic, P−1, a=8.4719(17) Å, b=13.719(3) Å, c=14.570(3) Å, α=62.19(3)°, β=99.657(2)°, γ=78.22(3)°, Z=2, R₁=0.0384, wR₂=0.0820; and for 3: C₃₀H₃₅LaO₁₃, monoclinic, P2(1)/c, a=9.5667(6) Å, b=24.3911(15) Å, c=14.0448(9) Å, β=109.245(2)°, Z=4, R₁=0.0374, wR₂=0.0630. All the three structure data were collected using graphite monochromated molybdenum Kα radiation and refined using full-matrix least-squares techniques on F². These structures show that four kinds of the carboxylato bridge modes are included in these chains to link the La(III) ions. It is the first time that it has been found that the intra-chain hydrogen bonding can construct an alternative chain even, when the coordination bridge mode is the same along the chain (complex 2). There are 2D and 3D hydrogen bonding in the crystal lattices of complexes 1-3.     

Thermal behaviour of hydrated lanthanide complexes with heptanedioic acid

The multi-step dehydration and decomposition of trivalent lanthanum and lanthanide heptanediate polyhydrates were investigated by means of thermal analysis completed with infrared study. Further more, X-ray diffraction data for investigated heptanediate complexes of general stoichiometry Ln₂(C₇H₁₀O₄)₃.nH₂O (wheren=16 in the case of La, Ce, Pr, Nd and Sm pimelates,n=8 for Eu, Gd, Tb, Dy, Er and Tm pimelates,n=12 for Ho, Yb and Lu pimelates) were also reported.

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Zusammenfassung Mittels TG, DTG, DTA wurde in Verbindung mit IR-Methoden der mehrstufige Dehydratations- und der Zersetzungsvorgang der Polyhydrate der PimelinsÄuresalze von dreiwertigem Lanthan und dreiwertigen Lanthanoiden untersucht. Röntgendiffraktionsdaten der untersuchten Heptandiat-Komplexe mit der allgemeinen Formel Ln₂(C₇H₁₀O₄)₃ nH₂O (mitn=16 für Ln=La, Ce, Pr, Nd und Sm,n=8 für Ln=Eu, Gd, Tb, Dy, Er und Tm sowien=12 für Ln=Ho, Yb und Lu) werden ebenfalls gegeben.

     

Diisopropyl-N,N-diethylcarbamylphosphonate complexes with lanthanide nitrates and chlorides

Solid adducts of lanthanide nitrates and chlorides with diisopropyl-N,N-diethylcarbamylphosphonate were prepared and studied. The La, Ce, Pr, Nd, Sm, Gd, and Tb nitrate adducts were isolated and shown to have the structure

The Dy, Er, Ho, and Yb nitrate adducts were difficult to isolate and were found to have no single, discrete structure. The chloride adducts of La, Pr, Sm, and Tb were isolated and assigned the structure

     

Highly luminescent bis-diketone lanthanide complexes with triple-stranded dinuclear structure

A new bis-β-diketone, 3,3'-bis(4,4,4-trifluoro-1,3-dioxobutyl)biphenyl (BTB), has been designed and prepared for the synthesis of a series of dinuclear lanthanide complexes [Ln(2)(BTB)(3)(C(2)H(5)OH)(2)(H(2)O)(2)] [Ln = Eu (1), Gd (2)], [Ln(2)(BTB)(3)(DME)(2)] [Ln = Nd (3), Yb (4); DME = ethylene glycol dimethyl ether] and [Eu(2)(BTB)(3)(L)(2)] [L = 2,2-bipydine (5); 1,10-phenanthroline (6); 4,7-diphenyl-1,10-phenanthroline (7)]. Complexes 1-7 have been characterized by various spectroscopic techniques and their photophysical properties are investigated. X-ray crystallographical analysis reveals that complexes 1, 3 and 4 adopt triple-stranded dinuclear structures which are formed by three bis-bidentate ligands with two lanthanide ions. The complexes 1 and 3-7 display strong visible red or NIR luminescence upon irradiation at ligand band around 372 nm, depending on the choice of the lanthanide. The solid-state photoluminescence quantum yields and the lifetimes of Eu(3+) complexes are determined and described.     

Infrared spectra of lanthanide complexes with eriochrome cyanine r

An infrared spectroscopic study of the composition of these complexes in the solid state is described. Evaluation of the spectra made it possible to distinguish changes in the character of the lanthanide—ligand bonds in the series La — Lu, and to study the “double-double” effect.