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A synthetic approach based on microwave-assisted Pd cross-coupling reactions is developed to obtain two series of push-pull donor-π-conjugated nonadentate coordinating ligands constructed on bispyrazolylpyridine and bisindazolylpyridine units. Both families of ligands formed stable complexes with Europium and Terbium in H2O. To provide a basis to synthesize the best and most effective markers for bioassays, a study of the effect of different substituents on their photophysical behavior is presented in an effort to shed light on the nature of the structure-property relationships. Both families showed better emission properties for Tb(III) than for Eu(III). Bispyrazolylpyridine derivatives were revealed as better sensitizing ligands despite the promising higher absorptivity and red-shifted excitation wavelengths of their counterpart, bisindazolilpyridine. This straightforward synthetic access to 4-substituted pyridines allows easy optimization of the emission properties of lanthanides. In the case of 4-phenylethynyl substituted bispyrazolylpyridine, the emission properties of Eu(III) and Tb(III) complexes were similar, indicating that they can act as a promising long-lived luminescent dual probe in multiplex analysis.

Switchable lanthanide luminescence is a novel proximity-based binary probe technology wherein two oligonucleotide probes are labelled either with lanthanide ion carrier chelate or light-absorbing antenna ligand. A highly luminescent complex is formed when the two label moieties are brought in close contact by adjacent hybridization of the labelled probes to a target sequence. Herein we report how hybridization distance between the labelled probes and single nucleotide mismatches in the target sequence affect to the luminescence intensity of the complex formed from the label moieties. The highest luminescence intensity was observed when the probes were hybridized to full matched target at a distance of 4–10 nucleotides, a fact that indicates the lanthanide complex requires a certain space to be formed. At optimal hybridization distance between the labelled probes the maximal discrimination efficiency between a full matched and a single mismatched target was 1400-fold. Furthermore, computer-based modelling of the luminescent complex formation was in good agreement with the experimental results.

The structure of Tb 3+ complexes derived from pyrazole-pyridine tripod was investigated using the semiempirical Sparkle model. Four most probable structures were predicted and their excited electronic states were calculated using the intermediate neglect of the differential overlap/spectroscopic (INDO/S) method. The singlet-excited state frequencies and oscillator strengths were used to predict the absorption spectra which were compared to the experimental one. The results suggest that the terbium tripod complex presents the Tb[podand] · 4H 2 O structure where the podand ligand was coordinated to Tb 3+ ion by six oxygen atoms from the carboxylate groups. This finding agrees with the feeble luminescence experimentally measured for this chelate.

Using molecular shape for the functional control of multicomponent systems is one of the challenges in the field of supramolecular chemistry. The well-known emission in the visible region of certain lanthanide (III) salts has found a new dimension by the controlled assembly of supramolecular architectures to enshroud and excite the metal. The emission properties of these systems find applications as luminescent probes in sensing schemes, interaction with bio- molecules, or light conversion systems. Complexes of Tb(III) and Eu(III) can in some cases be highly luminescent and typically exhibit emission lifetimes in the millisecond range. These long lifetimes provide a facile means to detect biomolecules labeled with lanthanide from the short-lived background emission of biosystems. The strongly ionic nature of the bonding in solid lanthanide complexes results in coordination geometries that reveal a balance between electrostatic and steric demands. The inclusion of lanthanide guests into macrocycles, cryptands, cavi- tands and spherands had the purpose of shielding the metals from solvent molecules whose OH, NH or CH groups are able to heavily quench lanthanide luminescence (intensity and lifetime) by deactivation of their emissive levels by vi- bronic coupling. The literature on the various chemical systems, based on nitrogen heteroaromatic rings, used to sensitize lanthanides will be thoroughly reviewed including those molecules synthesized by the authors which displayed high quantum yield of lan- thanide emission.

An expeditious synthesis of new cryptands derived from N,C-pyrazolylpyridine and their full characterization is reported. Emission lifetimes of the europium and terbium cryptates were in the range of milliseconds and terbium quantum yield was high.

Pillared γ-zirconim phosphate at low level with a diphosphonic acid resulting from the addition of pentaethyleneglycol to diethyl vinyl phosphonate was prepared and used as a porous matrix to inter...

Several new ionophores derived from crown ethers and iminodiacetic subunits attached to 3-aroylcoumarins have been synthesized and fully characterized. The alkaline-earth complexes of these new ligands were studied from their UV–visible and fluorescence data. Some systems displayed strong bathochromic shifts upon complexation with Mg 2+ that may make them useful signaling devices of this cation. The corresponding Eu 3+ and Tb 3+ chelates were easily formed and their photophysical properties were measured. In all the cases, lanthanide emission lifetimes were in the range of milliseconds albeit quantum yields were low. Possible energy-transfer mechanisms are discussed. © 2002 Elsevier Science B.V. All rights reserved.

[structure: see text] New macrocyclic chelates based on bis-pyrazolylpyridine and diethylenetriaminepentaacetic acid are synthesized, and the remarkable luminescence properties of their lanthanide chelates are reported.

We have devised efficient reaction pathways to attach aminopolycarboxylate subunits to the 3-aroylcoumarin chromophore. Two series of compounds were thus prepared in which the chelating arms were directly bonded to the coumarin ring (series A) or to the 3-aroyl moiety (series B). The corresponding Eu(III) and Tb(III) chelates were easily formed and their photophysical properties measured. In all the cases, lanthanide emission lifetimes were in the range of ms. Unfortunately, quantum yields were relatively low. Measurement of T1 states gave too low range of values to sensitize Tb(III). In fact, the metal emission of Tb(III) chelates of series A was not observed. However, series B was able to sensitize both metals. The absorption/energy-transfer/emission mechanisms are discussed.

The synthesis of macrobicyclic cryptands 1 , 2 from an 18-membered diazatetralactam and 6,6′-bis(bromomethyl)-2,2′-bipyridine or 2,6-bis(3-bromomethyl-1-pyrazolyl)pyridine has been investigated using various metal carbonates. The analysis of the distribution products by gel permeation chromatography showed that macrocyclization process was markedly conditioned by cation template effects. Optimum yields were obtained for Li + and Na + in the preparation of 1 and 2 , respectively. The cryptate structure of the corresponding complexes of Ln(III) (Ln=Eu, Tb, Gd) is discussed on the basis of spectroscopic and photophysical data.

Substituted 3-aroylcoumarins incorporated in a polyethylenoxy cryptand (2.2.2) by the 3-aroyl group were synthesized with the purpose of developing new markers to be used in time-resolved fluorimetric bioaffinity assays based on the unique luminescence properties of Eu(III) and Tb(III) ions. Some spectral properties and luminescence intensities of the complexes were measured in acetonitrile and MeOH. The mechanism of metal sensitization depended on lanthanide and will be discussed in detail. Copyright © 2000 John Wiley & Sons, Ltd.

The synthesis by means of ‘click’ chemistry of a new ligand bearing the bis-triazolylpyridine motif and pendant phosphonate groups is described. The topotactic phosphate/phosphonate exchange of the ligand into gamma-zirconium phosphate led to an organic–inorganic-layered material which revealed an excellent matrix to achieve the efficient sensitization of emitting lanthanides.

The synthesis of four new podands with three arms containing the N,C-pyrazolyl-pyridine chromophore is described with the aim of using the resulting tripods as ligands to sensitize lanthanide luminescence.

A new, relatively simple tetra-acid ligand derived from acetophenone was synthesized and its luminescence properties when forming Eu(III) and Tb(III) chelates were evaluated in aqueous and methanol solutions. The titled compound displayed excellent quantum yields of triplet sensitization of lanthanide luminescence (0.20–0.25 for Eu 3+ and 0.95–1.00 for Tb 3+ ). Results suggested that the metal and the cromophore should be in close contact and that the iminodiacetic arms isolate very well the metal from the surrounding OH oscillators which normally quench lanthanide luminescence.

The luminescence properties of 41 different Eu(III) and Tb(III) chelates that were synthesized with the purpose of developing new markers for chemical and biochemical applications were measured in aqueous solution and their suitability for labels in time-resolved immunoassays were evaluated. In spite of the influence of numerous factors on the luminescence quantum yields, a clear correlation was obtained between the energies of the lowest triplet state levels of the ligands and lanthanide (III) luminescence quantum yields of the respective chelates. Simultaneously Eu(III) and Tb(III) ions were observed to accept energy by their several different 5Dj, resonance levels depending on the energy of the lowest triplet state level of the ligand, and the Tb(III) luminescence quantum yields were observed to decrease due to the energy back transfer from excited Tb(III)∗ to the ligand when the energy difference between the 5D4 level of Tb(III) and the lowest triplet state energy level of the ligand is less than 1850 cm−1.

The synthesis of three novel pyrazole-containing complexing acids, N,N,N′,N′-{2, 6-bis[3-(aminomethyl)pyrazol-1-yl]-4-methoxypyridine}tetrakis(acetic acid)(1), N,N,N′,N′-{2, 6-bis[3-(aminomethyl)pyrazol-1-yl]pyrazine}-tetrakis(acetic acid) (2), and N,N,N′,N′-{6, 6′-bis[3-(aminomethyl)pyrazol-1-yl]-2, 2′-bipyridine}tetrakis(acetic acid) (3) is described. Ligands 1–3 formed stable complexes with EuIII, TbIII, SmIII, and DyIII in H2O whose relative luminescence yields, triplet-state energies, and emission decay lifetimes were measured. The number of H2O molecules in the first coordination sphere of the lanthanide ion were also determined. Comparison of data from the EuIII and TbIII complexes of 1–3 and those of the parent trisheterocycle N,N,N′,N′-{2, 6-bis[3-(aminomethyl)pyrazol-l-yl]pyridine}tetrakis(acetic acid) showed that the modification of the pyridine ring for pyrazine or 2, 2′-bipyridine strongly modify the luminescence properties of the complexes. MeO Substitution at C(4) of 1 maintain the excellent properties described for the parent compound and give an additional functional group that will serve for attaching the label to biomolecules in bioaffinity applications.

Synthesis of fluoroionophores consisting of 3-benzoylcoumarins fused with crown ethers in two different modes are described. The resulting macrocycles bore emission properties strongly dependent on metal ions and coumarin substitution and may be therefore used as cation dependent fluorescence signaling systems or triplet sensitizers for lanthanide luminescence.

Synthesis of fluoroionophores consisting of 3-benzoylcoumarins fused with crown ethers in two different modes are described. The resulting macrocycles bore emission properties strongly dependent on metal ions and coumarin substitution and may be therefore used as cation dependent fluorescence signaling systems or triplet sensitizers for lanthanide luminescence.

This work presents the analytical procedure developed to quantify Eu and Tb lanthanides by Total-reflection X-Ray Fluorescence (TXRF) by a direct solid method for first time. These rare-earth elements are doping the organic-inorganic hybrid compound γ-ZrP-TerPy which is currently being investigated as a highly efficient luminescent system. The developed procedure allows for the analysis of very low sample quantities, ca. 5 mg, with an adequate expanded uncertainty, around 8%, and detection limits lower than 0.002 wt% for Eu and Tb. The hereby described direct solid procedure has been tested against the usual quantitative analysis by means of the acid digestion of the samples by TXRF and ICP-MS. Discrepancies as large as one order of magnitude were found between the direct and the acid-digestion measurements. The combination of several unanticipated chemical effects, produced in the conventional digestion procedure of this material, explain its strong loss of Eu and Tb. The thorough optimization of the digestion procedures finally confirmed the validity of the easy and simple direct procedure carried out by TXRF in a solid way without sluggish sample digestion. This research shows once again the versatility and confidence of the quantitative direct solid measurements performed by TXRF.

The luminescence of certain lanthanides can be obtained in full if the metals are chelated to a suitable chromophor (antenna effect). This phenomenon may be achieved within the body of a porous solid. There are many examples in the literature regarding this approach. The present paper accounts for our recent findings concerning lanthanide luminescence within zirconium phosphate, a quite versatile laminar inorganic salt. The strategy of building 3D scaffolds from the 2D inorganic salt and 1D organic pillars is detailed. The covalent attachment of conveniently functionalized chromophores to the lanthanide-containing inorganic lamellae renders solid materials that can be used as organic–inorganic phosphors. The creation of supramolecular chirality within these layered solids, something that have been easily achieved by us in previous work, may lead to a new kind of phosphor producing circularly polarized luminescence with high efficiency.