Lidia M. Vallarino

Increasing the luminescence of lanthanide complexes

This review compares the chemical and physical properties of lanthanide ion complexes and of other narrow‐emitting species that can be used as labels for cytometry. A series of luminescent lanthanide ion macrocyclic complexes, Quantum Dyes®, which do not release or exchange their central lanthanide ion, do accept energy transfer from ligands, and are capable of covalent binding to macromolecules, including proteins and nucleic acids, is described and their properties are discussed.

X-ray crystal structures and nuclear magnetic resonance spectra of macrocyclic complexes of neodymium(III) and europium(III)

Abstract The compounds of formula [M(CH3COO)2LI]Cl·4H2O, in which M is neo-dymium(III) or europium(III) and LI is a six-nitrogen-donor macrocyclic ligand (C22H26N6), have been investigated by single crystal X-ray diffraction, thermogravimetric analysis and nuclear magnetic resonance spectroscopy. The two compounds are isostructural and crystallize in the triclinic system, space group P 1 . The complex cations present in the crystal lattice consist of a 10-coordinate metal centre linked to the six nitrogen-donor atoms of the macrocyclic ligand and to two bidentate chelating acetates, situated on opposite sides of the macrocycle and staggered by approximately 90°; an ionic chloride balances the residual metal charge. The paramagnetic-shifted NMR spectra of the complexes were measured in various solvents, and confirm that the metal-macrocycle moieties remain undissociated. Also, the spectra depend on the counterions, showing that, on average, at least one of the labile acetate ligands is bound to the metal ion even in aqueous solution.

Synthesis, characterization, and x-ray crystal structure of tris-isothiocyanato complexes of the yttrium(III) and europium(III) ions with a six-nitrogen-donor macrocyclic ligand

Abstract Tris-isothiocyanato complexes of the general formula [M(NCS)3L] have been synthesized and characterized, in which M is yttrium(III) or europium(III) and L is an 18-member macrocyclic ligand with a six-nitrogen-donor cavity (LI = C22H26N6, LII = C18H18N6). X-ray analysis of the yttrium(III) and europium(III) complexes of ligand LI showed the coexistence in the same crystal of two kinds of nine-coordinate molecules with different macrocycle conformations. The two complexes were isostructural and crystallized in the monoclinic Cc space group, with cell parameters a = 33.244(3), b = 11.976(2), c = 14.164(2) A, β = 92.72(5)° for europium and a = 33.226(3), b = 11.986(2), c = 14.102(2) A, β = 92.84(5)° for yttrium. The structure of the europium(III) complex, refined by block matrix least-squares, gave the final values R = 0.0236 and Rw = 0.0244; the structure of the yttrium(III) complex, refined by full matrix, resulted in R = 0.042 and Rw = 0.039.

Time-gated flow cytometry : an ultra-high selectivity method to recover ultra-rare-event μ-targets in high-background biosamples

A fundamental problem for rare-event cell analysis is auto-fluorescence from nontarget particles and cells. Time-gated flow cytometry is based on the temporal-domain discrimination of long-lifetime (>1 micros) luminescence-stained cells and can render invisible all nontarget cell and particles. We aim to further evaluate the technique, focusing on detection of ultra-rare-event 5-microm calibration beads in environmental water dirt samples. Europium-labeled 5-microm calibration beads with improved luminescence homogeneity and reduced aggregation were evaluated using the prototype UV LED excited time-gated luminescence (TGL) flow cytometer (FCM). A BD FACSAria flow cytometer was used to sort accurately a very low number of beads (<100 events), which were then spiked into concentrated samples of environmental water. The use of europium-labeled beads permitted the demonstration of specific detection rates of 100%+/-30% and 91%+/-3% with 10 and 100 target beads, respectively, that were mixed with over one million nontarget autofluorescent background particles. Under the same conditions, a conventional FCM was unable to recover rare-event fluorescein isothiocyanate (FITC) calibration beads. Preliminary results on Giardia detection are also reported. We have demonstrated the scientific value of lanthanide-complex biolabels in flow cytometry. This approach may augment the current method that uses multifluorescence-channel flow cytometry gating.

NMR, luminescence, and X-ray crystallographic studies of the interaction of uncharged N-donor ligands with europium(III) in the macrocyclic complex [Eu(CH3COO)2(C22H26N6)]Cl·4(H2O)

Abstract The interaction of unchanged N-donor ligands with the complex [Eu(CH3COO)2L]Cl·4(H2O), where L is the macrocyclic ligand C22H26N6, was investigated in solution by NMR spectroscopy and luminescence titration. Both experiments indicated little or no interaction of the N-donor ligands with the metal centre of the macrocyclic complex. Attempts to isolate a 1,10-phenanthroline complex of the europium macrocycle produced instead {[Eu(CH3COO)L]2(μ-CO3)}(OH)2·7H2O, which incorporated atmospheric carbon dioxide. The X-ray crystal structure showed a bis-chelating carbonato group linking two europium macrocycles, each of which was folded in a butterfly configuration towards the external bidentate chelating acetates. Ionic hydroxides and clathrated water molecules completed the structure.

Interaction of neutral and anionic o-donor organic ligands with europium(III) in the macrocyclic complex [Eu(CH3COO)2(C22H26N6)]Cl · 4H2O and crystal structure of [Eu(CH3COO)2(C22H26N6)](CH3COO) · 9H2O

Abstract The interaction of the paramagnetic complex [Eu(CH3COO)2L]Cl·4H2O, where L is the six N-donor macrocyclic ligand C22H26N6, with a series of organic substrates having potential O-donor atoms has been investigated. The 1H NMR resonances of anionic or acidic substrates were greatly shifted in the presence of the europium complex, whereas those of uncharged substrates remained essentially unchanged. The 5D0 → 7F2 emission of the europium complex was considerably enhanced in the presence of certain heteroaromatic carboxylates; new complexes of the formula [Eu(RCOO)2L]Cl·nH2O, where R is C6H5, C4H3O, C4H3S, C4H3NH or C5H4N and n = 2–4, were isolated in the solid state. The crystal and molecular structure of the triacetate, [Eu(CH3COO)2L](CH3COO)·9H2O, was established by single-crystal X-ray crystallography. The structure is ionic, with a 10-coordinate europium(III) linked to the six N-donor atoms of the macrocyclic ligand and to wo bidentate chelating acetates situated on opposite sides of the macrocycle. An ionic acetate and a network of hydrogen-bonded H2O molecules (nine per complex unit) completed the crystal lattice.

Synthesis, characterization and X-ray crystal structure of yttrium (III) macrocyclic complexes with a six-nitrogen-donor cavity

Abstract Two novel six-nitrogen-donor macrocyclic complex cations of yttrium(III) were obtained from the metal-templated Schiff-base condensation of 1,2-diaminoethane with either 2,6-diacetylpyridine or 2,6-diformylpyridine. The complex cations were isolated as salts of coordinating as well as non-coordinating anions. Single crystal X-ray analysis was carried out for the mixed acetate perchlorate salt of composition Y(C22H26N6) (CH3COO)2(H2O)0.5ClO4, which crystallized in the triclinic system, space group P 1 with Z = 2, in a unit cell having a = 13.052(2), b = 11.362(2), c = 11.426(2) A, α = 108.87(4), β = 104.73(4) and γ = 100.26(4)°. The structure was characterized by the presence of two slightly different coordination entities, statistically distributed in the crystal lattice in a 1 : 1 ratio. Both entities contained a yttrium(III) ion linked to the six-nitrogen-donor atoms of the macrocycle, which was slightly folded into a butterfly configuration. A bidentate chelating acetate on the convex side of the macrocycle and either a monodentate acetate or a molecular of water on the opposite side, completed the coordination sphere, resulting in coordination number nine. Ionic acetate and perchlorate balanced the residual charges of the complex cations. The yttrium(III) macrocyclic cations remained undissociated in solution, as shown by the chemical behaviour and NMR spectra.

Influence of the catalyst on the Pd0-mediated reactions of BrZnCH(CH3) COOtBu with vinyl and aryl triflates

Abstract A series of Pd II complexes containing various Group V-donors were reduced with diisobutylaluminum hydride and the products screened as potential catalysts for the coupling of representative vinyl- and aryl-trifluoromethanesulfonate substrates to the Reformatsky reagent BrZnCH(CH 3 )(COO t C 4 H 9 . The desired coupling product was obtained only with “reduced” dichlorobis(1,1-diphenylphosphino)ferrocene as catalyst and 2-naphthyl triflate as the substrate. These results are discussed in terms of the structural features of the reactants and catalyst.

Lanthanide(III) complexes of six-nitrogen-donor macrocyclic ligands with benzyl-type peripheral substituents, and crystal structure of [La(NO3)2(H2O)(C36H38N6)](NO3)(H2O)

Abstract Lanthanide(III) complexes of six-nitrogen-donor macrocyclic ligands carrying a benzyl-type group, CH2C6H4X (X=H, OH, or NH2), at each di-imine side chain were synthesized by the metal-templated, cyclic Schiff-base condensation of 2,6-diacetylpyridine with substituted S- or R,S-1,2-diaminopropanes. The complexes were obtained as mixtures of constitutional isomers and stereoisomers, which were identified by 1H NMR spectra and separated by fractional crystallization. The molecular structure of the 11-coordinate complex [La(NO3)2(H2O)(C36H38N6)](NO3)(H2O) was established by X-ray crystallography.

Interaction of β-diketones with LaIII, EuIII and YIII complexes of the six-nitrogen-donor macrocyclic ligand C22H26N6 and crystal structure of [Eu(CH3COO) ∗(C6H5CO)2CH∗(C22H26N6)](CH3COO) · 6(H2O)

Abstract The interaction of several β-diketones [pentane-2,4-dione, 1,3-diphenylpropane-1,3-dione, 1,1,1-trifluoro-4(2-thienyl)butane-2,4-dione] and their sodium salts with complexes of the type [ML(CH3COO)2]X·n(H2O), where M is LaIII, EuIII or YIII, L is the macrocyclic ligand C22H26N6, X is Cl− or CH3COO− and n is 4–9, was investigated in solution by NMR and luminescence spectroscopy. A number of crystalline ∗ML∗-(β-diketonate) complexes were isolated and characterized; the structure of one member of the series, [EuL(CH3COO)∗(C6H5CO)2CH∗](CH3COO) · 6(H2O), was established by X-ray crystallography. The structure is ionic; the 10-coordinate EuIII is bonded to the six nitrogens of the macrocyclic ligand, two oxygens of a bidentate acetate and two oxygens of the chelating β-diketonate. The coordinated acetate and the β-diketonate are situated on opposite sides of the ∗EuL∗ macrocycle; an uncoordinated acetate provides charge neutrality.