Marian Elbanowski

The lanthanides as luminescent probes in investigations of biochemical systems

A review of the luminescence properties of lanthanides, their role as structural and analytical probes and the application of lanthanide complexes in fluoroimmunological and nucleic acid hybridization assays is presented.

Energy transfer in solution of lanthanide complexes

The lanthanides with their well-defined energy levels provide an excellent basis to study different Ln(III)-specific energy transfer processes in a variety of chemical environments. The studies concerning intramolecular and intermolecular energy transfer processes with participation of Ln(III) ions and a variety of ligand groups in solution are reviewed. Phenomena of energy transfer from ligands to Ln(III) ions, resulting consequently in a great enhancement of the Ln(III) ion luminescence (ligand sensitized luminescence), as well as from Ln(III) to other species and between Ln(III) ions are presented.

Chemiluminescence of systems containing lanthanide ions

A review of the chemiluminescent reactions in the systems containing lanthanide ions as emitters and different chemical compounds is presented. The systems in which lanthanide ions enhance the chemiluminescence intensity, thanks to the energy transfer processes, as well as the systems in which redox reactions involving lanthanide ions cause chemiluminescence and the systems showing electrogenerated luminescence and lyoluminescence are discussed.

Luminescence studies of Eu(III) mixed ligand complexes

Abstract A series of europium(III) mixed ligand complexes, Ln/L/X based on pyridine carboxylic acid N-oxides, L, plus 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen), X, have been studied. The complexes were characterized using Eu luminescence (conventional and laser-induced) spectroscopy. A number of N-oxide ligand designs, including mono- and dicarboxylic acids and their derivatives (aryl-substituted), having various steric groups, have been tested with the main goal of optimizing the luminescence properties under various experimental conditions. Potentiometric titration of acid N-oxides have been carried out in aqueous solution in order to determine their p K a and the pH values, important for complexation conditions. Based on the Eu(III) luminescence lifetime measurements, hydration numbers of the Eu(III) complexes have been obtained, which evidenced the formation of binary EuL and EuL 2 complexes and mixed ligand EuL 2 X complexes. The results suggest that in ternary complex formation the steric requirement of the secondary ligand play an important role. The results of these studies lead us to achieve a better understanding of the factors, as aryl substituted groups (e.g. Br, NO 2 , NH 2 , CH 3 , OCH 3 ) and a kind of solvent, influencing the luminescence intensity and lifetime of the Eu(III) complexes studied.

Improvement of emission intensity in luminescent materials based on the antenna effect

Abstract Ternary Eu(III) complexes with macrobicyclic and acyclic ligands+co-ligands were encapsulated in silica or methylated silicate xerogels. Additionally, deuterated reagent and solvent were used in the sol–gel procedure. This preparation method with moderate thermal treatment reduced the concentration of OH groups in the materials and simultaneously improved their photophysical properties, i.e. increased luminescence intensity and prolonged luminescence lifetime. The best results were obtained for the Eu(III) complex with a cryptand of the [biqO2·2·2]+1,10-phenanthroline type (where biqO2=3,3′-biisoquinoline-2,2′-dioxide) immobilized in methyl-modified silicate xerogel. The effective luminescence properties of this sample make it a promising candidate for use as a luminescent material.

Fluorescence of lanthanide(III) complexes in aqueous solutions the influence ofpH and solution composition

The fluorescence of lanthanide ions and of their complexes withEDTA,NTA andAA in aqueous solutions was investigated. It has been shown that the fluorescence band intensities of Sm(III), Eu(III), Gd(III), Tb(III) and Dy(III) complexes depend on thepH and the complexing agent concentration. Fluorescence measurements were used to characterise the lanthanide complexes formed and an attempt was made to interpret the results theoretically.ZusammenfassungDie Fluoreszenz von wäßrigen Lösungen der Ionen und Komplexe einiger Lanthaniden mit Ethylendiamintetraessigsäure, Nitrilotriessigsäure und Essigsäure wurde untersucht. Der Einfluß vonpH und Konzentration der Komplexbildner auf die Intensität der Fluoreszenzbanden von Sm(III), Eu(III), Gd(III), Tb(III) und Dy(III) wurde bewiesen. Die Fluoreszenzmessungen wurden für die Charakterisierung von Lösungen der Lanthanidenkomplexe genützt und ein Versuch der theoretischen Interpretation der beobachteten Änderungen im Spektrum wurde unternommen.

Quenching of the triplet state of benzophenone by lanthanide 1,3-diketonate chelates in solutions

The phosphorescence of benzophenone in benzene and acetonitrile was quenched by several lanthanide (Sm, Eu, Gd, Tb and Dy) acetylacetonate chelates. The results ofStern-Volmer analysis including the quenching of benzophenone triplet and sensitization of lanthanide emission indicate that the quenching process occurs by the energy transfer mechanism via the excited triplet state of the ligand.ZusammenfassungDie Phosphoreszene von Benzophenon in Benzophenon in Benzen und Acetonitril wurde durch 1,3-Diketonat-Chelatverbindungen von einigen Lanthaniden (Sm, Eu, Gd, Tb und Dy) gelöscht. Die Resultate derStern-Volmer-Analyse einschließlich der Auslöschung des Benzophenon-Tripletts und die Sensibilisierung der Lanthanid-Emission zeigen, daß der Löschprozeß mittels Energieübertragungsmechanismus via angeregtem Triplettzustand des Liganden stattfindet.

SPECTRAL CHARACTERISTICS AND MECHANISM OF CHEMILUMINESCENCE FROM TRYPTOPHAN SOLUTIONS INDUCED BY UV-IRRADIATION

The spectral distribution of the chemiluminescence, fluorescence and phosphorescence of tryptophan aqueous solutions irradiated with high and low pressure mercury lamps has been measured. The blue emission bands in the region of 380–520 nm observed both in the chemi‐ and photoluminescence, as well as an absorbance increase at 230 and 330 nm, indicate oxidative degradation of tryptophan leading to the formation of derivatives of N‐formylkynurenine, xanthurenic and anthranilic acids. Red emission bands at 630 and 705 nm in the spectrum of the chemiluminescence, an enhancement of light intensity by D2O and its decrease by NaN3 and DABCO suggest a partial contribution of O2(1Δg) to the photooxidation and chemiluminescence of tryptophan. The enthalpy of the exergonic reactions, leading to the formation of luminescing products, was calculated to average ‐270 kJ‐mol.

The antenna effect of Eu(III) cryptate entrapped in xerogel matrices

Abstract The europium(III) complex with [biq.2.2] cryptand, where biq is 3,3′-biisoquino-line-2,2′-dioxide and complexes with additional secondary ligands such as 1,10-phenanthroline (phen) or triphenylphosphine oxide (TPPO) were entrapped by the sol-gel method in silica or silicate xerogel organically modified with methyl groups. The photophysical properties of such materials were studied. The luminescence behaviour of the complexes in the rigid matrix was studied by means of emission, excitation spectra and lifetime measurements. The results indicated that the Eu(III)-[biq.2.2] complex in the methylated silicate xerogel displayed a distinctly higher emission intensity and longer lifetime than in the silica matrix, whereas in the case of the complexes with the secondary ligands these changes were not so pronounced. It was also observed for the silica xerogel with Eu(III) complex that the emission intensity increased up to 110 °C with temperature.

Spectroscopic study of lanthanide(III) complexes with chosen aminoacids and hydroxyacids in solution

Abstract Luminescence spectra and lifetime of Eu(III) and Tb(III) ions in complexes with glycine (AAA), glycolic acid (GA), aspartic acid (ASP) and malic acid (MA) were studied. The effect of the amino–NH2 and hydroxyl–OH groups on the intensity and lifetime of the lanthanides luminescence were examined. Hydration number for Eu(III) in the systems studied indicated the involvement of carboxyl and hydroxyl groups as well as donor nitrogen atoms in the coordination. The phenomenon of Gd(III) ion emission quenching was analyzed and quantitatively described by determination of the quenching constant KSV.