Intramolecular energy transfer mechanism between ligands in ternary rare earth complexes with aromatic carboxylic acids and 1,10-phenanthroline

A series of binary and ternary rare earth (Gd, Eu, Tb) complexes with aromatic acids and 1,10-phenanthroline have been synthesized. The lowest triplet state energies of ligands have been obtained by measuring the phosphorescence spectra of binary gadolinium complexes. By comparing the phosphorescence spectra of binary complexes with those of ternary ones, it is found that there exists another intramolecular energy transfer process from the aromatic acids to 1,10-phenanthroline besides the intramolecular energy transfer process between the aromatic acids and the central rare earth ions. The intramolecular energy transfer efficiencies have been calculated by determining phosphorescence lifetimes of binary and ternary gadolinium complexes. The luminescence properties of corresponding europium and terbium complexes are in agreement with the prediction based on energy transfer mechanism. (C) 1998 Elsevier Science S.A. All rights reserved.

The synthesis, characterization and photophysical properties of binary and ternary rare earth complexes with N-phenylanthranilic acid and l,l0-phenanthroline

Some novel binary and ternary complexes of rare earth(Gd, Eu,Tb) with N-Phenylanthranilic acid and 1,10-Phenanthroline were synthesized by homogenous precipitation and their compositions were characterized by,elemental analysis, IR spectra and UV-Vis spectra, The triplet state energies of N-Phenylanthranilic acid was determined to be 24 330 cm(-1) with the phosphorescence spectra of its gadolinium complexes and the energy match between the ligand and the central rare earth ions was studied. The photophysical properties such as luminescence properties and intramolecular energy transfer match between rare earth ions and ligands and between ligands were discussed. The result indicates that terbium complexes with N-Phenylanthranilic acid and 1,10-Phenanthroline have excellent luminescence properties.

Synthesis, characterization, and photophysical properties of rare earth complexes of N-phenyl-2-aminobenzoic acid and 1,10-phenanthroline

Some novel binary and ternary complexes of rare earth ions (Gd, Eu, Tb) with N-phenyl-2-aminobenzoic acid and 1,10-phenanthroline were synthesized by homogenous precipitation and characterized by elemental analysis, IR spectra, UV/Vis spectra, and thermal analysis. The phosphorescence spectra and lifetimes of gadolinium complexes were measured, and the triplet state energies of N-phenyl-2-aminobenzoic acid and 1,10-phenanthroline as well as the energy transfer efficiencies between N-phenyl-2-aminobenzoic acid and 1,10-phenanthroline were determined. The photophysical properties such as luminescence and intramolecular energy transfer between the rare earth center ions and the ligands and between ligands are discussed.

Synthesis and solvent enhanced relaxation property of water-soluble endohedral metallofullerenols

Gadolinium fullerenols, as novel and potential contrast agents for magnetic resonance imaging, were synthesized, which showed excellent efficiency in enhancing water proton relaxation with a relaxivity of 47.0+/-1.0 mM(-1).s(-1).

Synthesis, luminescence properties and energy transfer of binary and ternary rare earth complexes with aromatic acids and 1,10-phenanthroline

A series of binary and ternary rare earth (Gd, Eu, Tb) complexes with ortho hydroxyl benzoic acid, pam aminobenzoic acid, nicotinic acid and 1,10-phenanthroline were synthesized. Phosphorescence spectra and lifetimes of Gd complexes were measured and the lowest triplet state energies of gadolinium binary complexes end the intramolecular energy transfer efficiencies were determined. The luminescence properties and energy transfer process of Eu3+ and Tb3+ complexes were discussed.

The synthesis, luminescence and energy transfer of the binary and ternary complexes of rare earth with aminobenzoic acids and 1,10-phenanthroline

Thirteen kinds of binary and ternary complexes of rare earth (Gd, Eu,Tb) with ortho (para) aminobenzoic acid and 1.10--phenanthroline were synthesized and characterized. The phosphorescence spectra and lifetimes of gadolinium complexes were measured and the lowest triplet state energies of ligands and the energy transfer efficiencies between ligands were determined. The luminescence properties and intramolecular energy transfer of these complexes were studied in details.

H-1 NMR Titration Studies of Two Novel DTPA Derivatives

Polyaminopolycarboxylate gadolinium (III) complexes have been studied intensively in recent years because of their potential uses as contrast agents for magnetic resonance imaging (MHI)([1]). The research interests are mainly focussed on Gd3+ complexes of DTPA, DOTA and their various derivatives. Four kinds of Gd3+ complexes can be used presently in clinical MRI, which are GD(DTPA)([2]), Gd(DOTA)([3]), Gd(DTPA-BMA)([4]) and Gd(HP-DO3A)([5]). Here report two new DTPA bis (amide) derivatives-diethylenetriaminepentaacetic acid-N, N ''-bis (dimethylamide) (DTPA-BDMA) and -bis (diethylamide) (DTPA-BDEA).

Enrichment of lanthanides in aragonite

Using the constant addition technique, the coprecipitation of lanthanum, gadolinium, and lutetium with aragonite in seawater was experimentally investigated at 25 degrees C. Their concentrations in aragonite overgrowths were determined by inductive coupled plasma mass spectrometer. All these lanthanides were strongly enriched in aragonite overgrowths. The amount of lanthanum, gadolinium, and lutetium incorporated into aragonite accounted for 57%-99%, 50%-89%, and 40%-91% of their initial total amount, respectively. With the increase of aragonite precipitation rate, more lanthanides were incorporated into aragonite while their relative fraction in aragonite overgrowths decreased consistently. It indicated that the coprecipitation of lanthanides with aragonite was controlled by the kinetics of aragonite precipitation.

LA Size in Former Elite Athletes

A recent meta-analysis by Iskandar et al. (1) nicely showed that endurance athletes have larger left atrial (LA) diameters compared with control subjects. Yet only 9 of 54 studies included in their analysis reported LA volume values corrected for body surface area (BSA). In fact, few studies have determined LA volume in young athletes, and, to the best of our knowledge, no study has reported this variable in older athletes. This is an important question given the growing debate about the potential deleterious effects of long-term strenuous endurance exercise on the human heart, notably the higher risk of atrial fibrillation (AF), a condition for which both atrial dilation and the normal aging process are thought to be potential causative mechanisms (2). Thus, we aimed to assess the long-term consequences of endurance exercise on LA volume in athletes who were highly competitive at younger ages and are still active. To this end, we compared BSA-corrected LA volumes determined with late gadolinium enhancement magnetic resonance imaging (LGE-MRI) in former elite endurance athletes and sedentary control subjects.

Radiosensitising Nanoparticles as Novel Cancer Therapeutics — Pipe Dream or Realistic Prospect?

The field of high atomic number nanoparticle radiosensitising agents is reviewed. After a brief discussion of the new mode of physicochemical action implied by irradiation of high atomic number nanoparticles embedded in biological systems, a series of exemplars are discussed. Silver-, gadolinium- and gold-based nanoparticles are discussed in order of increasing atomic number with functionalisation strategies being outlined. In vitro and in vivo evidence for radio-enhancement and the mechanisms attributed to the increased biological effect are discussed.

Optimising element choice for nanoparticle radiosensitisers

There is considerable interest in the use of heavy atom nanoparticles as theranostic contrast agents due to their high radiation cross-section compared to soft tissue. However, published studies have primarily focused on applications of gold nanoparticles. This study applies Monte Carlo radiation transport modelling using Geant4 to evaluate the macro- and micro-scale radiation dose enhancement following X-ray irradiation with both imaging and therapeutic energies on nanoparticles consisting of stable elements heavier than silicon. An approach based on the Local Effect Model was also used to assess potential biological impacts. While macroscopic dose enhancement is well predicted by simple absorption cross-sections, nanoscale dose deposition has a much more complex dependency on atomic number, with local maxima around germanium (Z = 32) and gadolinium (Z = 64), driven by variations in secondary Auger electron spectra, which translate into significant variations in biological effectiveness. These differences may provide a valuable tool for predicting and elucidating fundamental mechanisms of these agents as they move towards clinical application.

Síntese e estudos estruturais de novos materiais luminescentes

A presente dissertação teve como objectivo a síntese, caracterização e estudo das propriedades luminescentes de complexos livres e/ou imobilizados no material mesoporoso MCM-41. Na primeira parte estudaram-se complexos do tipo, Eu(NTA)3L2, onde NTA corresponte ao β-dicetonato 1-(2-naftoil)-3,3,3-trifluoro-acetonato, e L2 aos ligandos bidentados de azoto derivados do pirazolilpiridina e L aos ligandos monodentados (etil-4-piridilacetato, água, piridina e metilfenilsulfóxido). Alguns destes ligandos foram imobilizados e/ou impregnados no MCM-41, tendo-se posteriormente complexado o fragmento Eu(NTA)3. Na segunda parte estudou-se o efeito do contra-ião no complexo C[Eu(NTA)4], usando os catiões (C): tetrabutilamónio [NBu4]+, 1-butil-3-metilimidazolilo [C4mim]+ e 1-butil-3-metilpiridínio [C4mpy]+. O anião [Eu(NTA)4]- foi imobilizado no MCM-41 derivatizado com grupos 1-propil-3-metilimidazolilo. Todos os complexos preparados foram caracterizados pelas técnicas de análise elementar, termogravimetria, espectroscopias vibracionais (Infravermelho e Raman) e de ressonância magnética nuclear, e os materiais preparados foram adicionalmente analisados por difracção de raios-X de pós e ressonância magnética nuclear de estado sólido. Foram também estudadas as propriedades fotoluminescentes dos compostos, e para facilitar a análise dos resultados, nalguns casos foram preparados e caracterizados os compostos análogos de gadolínio.

Extension of electrochemically active sites in SOFCs and SOECs

Solid oxide fuel (SOFCs) and electrolyzer (SOECs) cells have been promoted as promising technologies for the stabilization of fuel supply and usage in future green energy systems. SOFCs are devices that produce electricity by the oxidation of hydrogen or hydrocarbon fuels with high efficiency. Conversely, SOECs can offer the reverse reaction, where synthetic fuels can be generated by the input of renewable electricity. Due to this similar but inverse nature of SOFCs and SOECs, these devices have traditionally been constructed from comparable materials. Nonetheless, several limitations have hindered the entry of SOFCs and SOECs into the marketplace. One of the most debilitating is associated with chemical interreactions between cell components that can lead to poor longevities at high working temperatures and/or depleted electrochemcial performance. Normally such interreactions are countered by the introduction of thin, purely ionic conducting, buffer layers between the electrode and electrolyte interface. The objective of this thesis is to assess if possible improvements in electrode kinetics can also be obtained by modifying the transport properties of these buffer layers by the introduction of multivalent cations. The introduction of minor electronic conductivity in the surface of the electrolyte material has previously been shown to radically enhance the electrochemically active area for oxygen exchange, reducing polarization resistance losses. Hence, the current thesis aims to extend this knowledge to tailor a bi-functional buffer layer that can prevent chemical interreaction while also enhancing electrode kinetics.The thesis selects a typical scenario of an yttria stabilized zirconia electrolyte combined with a lanthanide containing oxygen electrode. Gadolinium, terbium and praseodymium doped cerium oxide materials have been investigated as potential buffer layers. The mixed ionic electronic conducting (MIEC) properties of the doped-cerium materials have been analyzed and collated. A detailed analysis is further presented of the impact of the buffer layers on the kinetics of the oxygen electrode in SOFC and SOEC devices. Special focus is made to assess for potential links between the transport properties of the buffer layer and subsequent electrode performance. The work also evaluates the electrochemical performance of different K2NiF4 structure cathodes deposited onto a peak performing Pr doped-cerium buffer layer, the influence of buffer layer thickness and the Pr content of the ceria buffer layer. It is shown that dramatic increases in electrode performance can be obtained by the introduction of MIEC buffer layers, where the best performances are shown to be offered by buffer layers of highest ambipolar conductivity. These buffer layers are also shown to continue to offer the bifunctional role to protect from unwanted chemical interactions at the electrode/electrolyte interface.

Electrospun Contrast Agent-Loaded Fibers for Colon-Targeted MRI

Magnetic resonance imaging is a diagnostic tool used for detecting abnormal organs and tissues, often using Gd(III) complexes as contrast-enhancing agents. In this work, core–shell polymer fibers have been prepared using coaxial electrospinning, with the intent of delivering gadolinium (III) diethylenetriaminepentaacetate hydrate (Gd(DTPA)) selectively to the colon. The fibers comprise a poly(ethylene oxide) (PEO) core loaded with Gd(DTPA), and a Eudragit S100 shell. They are homogeneous, with distinct core–shell phases. The components in the fibers are dispersed in an amorphous fashion. The proton relaxivities of Gd(DTPA) are preserved after electrospinning. To permit easy visualization of the release of the active ingredient from the fibers, analogous materials are prepared loaded with the dye rhodamine B. Very little release is seen in a pH 1.0 buffer, while sustained release is seen at pH 7.4. The fibers thus have the potential to selectively deliver Gd(DTPA) to the colon. Mucoadhesion studies reveal there are strong adhesive forces between porcine colon mucosa and PEO from the core, and the dye-loaded fibers can be successfully used to image the porcine colon wall. The electrospun core–shell fibers prepared in this work can thus be developed as advanced functional materials for effective imaging of colonic abnormalities.

Synthesis and Spectral Characterization of Lanthanide Complexes with Sulfamethoxazole and Their Antibacterial Activity

A series of nonelectrolytic lanthanide(III) complexes, [ ML 2 Cl 3 ] · 2 H 2 O, where M is lanthanum(III), praseodymium(III), neodymium(III), samarium(III), gadolinium(III), terbium(III), dysprosium(III), and yttrium(III), containing sulfamethoxazole ligand (L) are prepared. The structure and bonding of the ligand are studied by elemental analysis, magnetic susceptibility measurements, IR, 1 H NMR, TG / DTA , X-ray diffraction studies, and electronic spectra of the complexes. The stereochemistry around the metal ions is a monocapped trigonal prism in which four of the coordination sites are occupied by two each from two chelating ligands, sulfonyl oxygen, and nitrogen of the amide group and the remaining three positions are occupied by three chlorines. The ligand and the new complexes were tested in vitro to evaluate their activity against the bacteria Escherichia coli and Staphylococcus aureus.