Structure effect of nucleotides in terbium(III)—nucleotide fluorescent reaction New evidence for the binding sites of terbium(III) on nucleotides

Upon addition of Tb³⁺ to 16 nucleotides and homopolynucleotides, all of them showed a characteristic green emission from Tb³⁺, but with much different intensity, upon excitation in the aromatic region of bases. The result suggested that nucleotides with at least one carbonyl group in nucleotide bases are better enhancers to the fluorescence of Tb³⁺. The complexes of ATP, GDP and GTP with Tb³⁺ are synthesized as two types of models. Guanine type nucleotides with one carbonyl group in the bases are the best enhancers, while adenine type nucleotides with no carbonyl group in the bases are poorest enhancers to the fluorescence of Tb³⁺. Comparing the IR spectra of ATP, GTP, GDP and their Tb³⁺ complexes suggested that C-6 carbonyl group in GTP and GDP may be involved in complex formation, which may be responsible for the effective energy transfer. This is further supported by comparing the UV spectra of ATP, Poly(A), GTP, and Poly(G) with their Tb³⁺ complexes in water solution.     

The first sideways-bonded peroxo complex for a tetraaminecobalt(III) species

Cobalt(II) salts react with H2O2 in the presence of 2 equiv of tetramethylethylenediamine (tmen) to produce a stable sideways bonded mononuclear peroxo complex [Co(tmen)2O2]ClO4 which has been characterized chemically and by a single crystal X-ray determination. This is the first such tetraaminecobalt(III) complex, indeed, the first for any tetraaminemetal ion complex. The mononuclear peroxo complex can also be synthesized by O2 2- anation of cis-[Co(tmen)2(OH2)2]3+. This reaction is reversed in acid, and this offers the potential to develop Co(III) catalyzed oxidation reactions.     

Single-molecule magnetic behavior in a neutral terbium(III) complex of a picolinate-based nitronyl nitroxide free radical

The terdentate anionic picolinate-based nitronyl nitroxide (picNN) free radical forms neutral and robust homoleptic complexes with rare earth-metal ions. The nonacoordinated Tb(3+) complex Tb(picNN)(3)·6H(2)O is a single-molecule magnet with an activation energy barrier Δ = 22.8 ± 0.5 K and preexponential factor τ(0) = (5.5 ± 1.1) × 10(-9) s. It shows magnetic hysteresis below 1 K.     

Nonradiative intramolecular deactivation of Tb3+ fluorescence in a vapor phase terbium(III) complex

For the first time, fluorescence lifetime studies are reported for a trivalent rare-earth gas: specifically, for the ⁵D₄ state of Tb³⁺ in the vapor phase chelate 2,2,6,6-tetramethyl-3,5-heptanedione. Measurements of the fluorescence decay as a function of temperature and pressure demonstrate that intermolecular collisional deactivation is unimportant and that nonradiative deactivation by intramolecular processes dominates the fluorescence lifetime at temperatures of 230–300°C. The rate for the latter processes is well described by an Arrhenius equation and suggests that the Tb³⁺ relaxation occurs via transfer to low-lying excited states of the chelate.     

Synthesis, X-ray crystallographic characterization, and electronic structure studies of a di-azide iron(III) complex: implications for the azide adducts of iron(III) superoxide dismutase

We have synthesized and characterized, using X-ray crystallographic, spectroscopic, and computational techniques, a six-coordinate diazide Fe (3+) complex, LFe(N 3) 2 (where L is the tetradentate ligand 7-diisopropyl-1,4,7-triazacyclononane-1-acetic acid), that serves as a model of the azide adducts of Fe (3+) superoxide dismutase (Fe (3+)SOD). While previous spectroscopic studies revealed that two distinct azide-bound Fe (3+)SOD species can be obtained at cryogenic temperatures depending on protein and azide concentrations, the number of azide ligands coordinated to the Fe (3+) ion in each species has been the subject of some controversy. In the case of LFe(N 3) 2, the electronic absorption and magnetic circular dichroism spectra are dominated by two broad features centered at 21 500 cm (-1) (approximately 4000 M (-1) cm (-1)) and approximately 30 300 cm (-1) (approximately 7400 M (-1) cm (-1)) attributed to N3 (-) --> Fe (3+) charge transfer (CT) transitions. A normal coordinate analysis of resonance Raman (RR) data obtained for LFe(N 3) 2 indicates that the vibrational features at 363 and 403 cm (-1) correspond to the Fe-N 3 stretching modes (nu Fe-N3) associated with the two different azide ligands and yields Fe-N 3 force constants of 1.170 and 1.275 mdyne/A, respectively. RR excitation profile data obtained with laser excitation between 16,000 and 22,000 cm (-1) reveal that the nu Fe-N3 modes at 363 and 403 cm (-1) are preferentially enhanced upon excitation in resonance with the N 3 (-) --> Fe (3+) CT transitions at lower and higher energies, respectively. Consistent with this result, density functional theory electronic structure calculations predict a larger stabilization of the molecular orbitals of the more strongly bound azide due to increased sigma-symmetry orbital overlap with the Fe 3d orbitals, thus yielding higher N 3 (-) --> Fe (3+) CT transition energies. Comparison of our data obtained for LFe(N 3) 2 with those reported previously for the two azide adducts of Fe (3+)SOD provides compelling evidence that a single azide is coordinated to the Fe (3+) center in each protein species.     

Assessment of terbium (III) as a luminescent probe for the detection of tuberculosis biomarkers

A detection method for nicotinic acid, a specific metabolite marker of Mycobacterium tuberculosis present in cultures and patients' breath, is studied in complex solutions containing other metabolites and in biological media such as urine, saliva and breath condensate. The method is based on the analysis of the luminescence increase of Tb³⁺ complexes in the presence of nicotinic acid due to the energy transfer from the excited ligand to the lanthanide ion. It is shown that other potential markers found in M. tuberculosis culture supernatant, such as methyl phenylacetate, p-methyl anisate, methyl nicotinate and 2-methoxy biphenyl, can interfere with nicotinic acid via a competitive absorption of the excitation photons. A new strategy to circumvent these interferences is proposed with an upstream trapping of volatile markers preceding the detection of nicotinic acid in the liquid phase via the luminescence of Tb³⁺ complexes. The cost of the method is evaluated and compared with the Xpert MTB/RIF test endorsed by the World Health Organization.     

The first lanthanide(III) monoporphyrin complex liquid crystal

Hydroxy [5,10,15,20-tetra[P-decyloxy- ^m -methyloxy)phenyl]porphyrin Yb(III) exhibits a discotic hexagonal columnar phase, it is the first example of a monoporphyrin rare earth complex liquid crystal.     

The first lanthanide(III) monoporphyrin complex liquid crystal

Hydroxy [5,10,15,20-tetra[ p -decyloxy- m -methyloxy)phenyl]porphyrin Yb(III) exhibits a discotic hexagonal columnar phase, it is the first example of a monoporphyrin rare earth complex liquid crystal.     

A dinuclear lanthanide complex for the recognition of bis(carboxylates): formation of terbium(III) luminescent self-assembly ternary complexes in aqueous solution

The synthesis and photophysical properties of a coordinatively unsaturated cationic dinuclear terbium complex, 2.Tb(2), that can detect the presence of mono- or bis(carboxylates) in buffered aqueous solution at physiological pH is described. Full ligand synthesis and structural characterization of 2.Na(2) are also described. Spectroscopic measurements determined that each Tb(III) metal center has two metal-bound water molecules (q = 2). The recognition or sensing of N,N-dimethylaminocarboxylic acid, 4, and the bis(carboxylate) terephthalic acid, 5, which can also function as sensitizing antennae, was found to occur through the binding of these carboxylates to the metal center via the displacement of the metal bound water molecules. This gave rise to the formation of luminescent ternary complexes in solution in 2:1 or 1:1 (ion:2.Tb(2)) stoichiometry, respectively. Aliphatic bis(carboxylates) also bind to 2.Tb(2) where the selectivity for the ion recognition and stoichiometry was dictated by the structure of the anion, being most selective for pimelic acid, 6. Binding of either l- or d-tartaric acid gave rise to the formation ternary complex formation, with 2:1 stoichiometry, where the ion recognition resulted in quenching of the lanthanide emission.     

Polyaryl ether dendrimer with a 4-phenylacetyl-5-pyrazolone-based terbium(III) complex as core: synthesis and photophysical properties

A series of novel dendritic beta-diketone ligands, 1-phenyl-3-[G-n]-4-phenylacetyl-5-pyrazolone (n = 0-3, G stands for polyaryl ether), were synthesized by introducing Fréchet-type dendritic branches. The corresponding Tb3+-cored dendritic complexes were characterized by X-ray crystallography, elemental analysis, ESI mass spectra, and FT-IR spectra. These dendritic complexes, prepared from aqueous solution, exhibit high stability. Interestingly, the study of photophysical properties shows that the luminescence quantum yields of the dendritic Tb-complexes increase from 0.1 to 2.26% with an increase of the dendritic generation from 0 to 3. Importantly, an "energy-reservoir effect" was observed in the dendritic system using the method based on the resonance energy transfer from these complexes to rhodamine 6G. With the increase of the dendritic generation, the metal-centered luminescence quantum yield was almost the same, and the energy transfer (phi(transfer)) from the ligand to Tb(3+) increased. Further measurements of the triplet state and oxygen quenching of these dendritic complexes verify that this enhancement of the energy transfer (phi(transfer)) is attributed to both an "antenna effect" and a "shell effect".     

Surface supramolecular organization of a terbium(III) double-decker complex on graphite and its single molecule magnet behavior

The two-dimensional self-assembly of a terbium(III) double-decker phthalocyanine on highly oriented pyrolitic graphite (HOPG) was studied by atomic force microscopy (AFM), and it was shown that it forms highly regular rectangular two-dimensional nanocrystals on the surface, that are aligned with the graphite symmetry axes, in which the molecules are organized in a rectangular lattice as shown by scanning tunneling microscopy. Molecular dynamics simulations were run in order to model the behavior of a collection of the double-decker complexes on HOPG. The results were in excellent agreement with the experiment, showing that-after diffusion on the graphite surface-the molecules self-assemble into nanoscopic islands which align preferentially along the three main graphite axes. These low dimension assemblies of independent magnetic centers are only one molecule thick (as shown by AFM) and are therefore very interesting nanoscopic magnetic objects, in which all of the molecules are in interaction with the graphite substrate and might therefore be affected by it. The magnetic properties of these self-assembled bar-shaped islands on HOPG were studied by X-ray magnetic circular dichroism, confirming that the compounds maintain their properties as single-molecule magnets when they are in close interaction with the graphite surface.     

Infinite terbium(III) chains formed from a tetra-phosphorylated resorcinarene cavitand

Reaction of [Tb(III)(DMSO)(8)](CF(3)SO(3))(3) with a resorcinarene cavitand substituted by four -CH(2)P(O)Ph(2) pendant arms afforded an infinite 1D inorganic polymer, in which the consecutive resorcinarene units are linked through two terbium strands, this connection involves pairs of phosphoryl groups occupying adjacent positions of the resorcinarene units.     

Europium(III) and terbium(III) chelates of quinolonecarboxylic acid derivatives as labels for immunofluorimetric assay

Luminescence properties of Tb(III) and Eu(III) complexes of quinolonecarboxylic acid derivatives were studied. Optimal conditions of luminescence were determined, and the influence of surfactants and diethylenetriaminepentaacetic acid on the luminescence properties of the complexes was studied. It was demonstrated that species-specific immunoglobulins labeled with terbium ions can be determined with the detection limit of the lanthanide label 5 x 10^-14 M.     

Efficient green OLEDs achieved by a terbium(III) complex with photoluminescent quantum yield close to 100%

Science China Chemistry - Electroluminescence of f-f transition lanthanide complex is a traditional topic for display over decades. Here we report highly efficient organic light-emitting diodes...     

Structure and properties of terbium(III) dipivaloylmethanate and its adducts with Bipy and Phen

The complex of terbium(III) with dipivaloylmethane (2,2,6,6-tetramethylheptane-3,5-dione = Htmhd) [Tb(tmhd)₃]₂ (1) and two its adducts with bipyridyl (Bipy) and phenanthroline (Tb(tmhd)₃·Bipy (2) and Tb(tmhd)₃·Phen (3)) are synthesized and analyzed by single crystal X-ray diffraction. The crystals of [Tb(tmhd)₃]₂ (1) belong to the monoclinic crystal system: P2₁/n space group, a = 12.2238(2) Å, b = 27.6369(5) Å, c = 21.8740(4) Å, β = 105.146(1)°, V = 7133.0(2)ų, Z = 4; the crystals of Tb(tmhd)₃·Bipy (2) and Tb(tmhd)₃·Phen (3) belong to the triclinic crystal system with unit cell parameters: (2) \(P\bar 1\) space group, a = 11.0554(6) Å, b = 12.2761(7) Å, c = 17.7096(8) Å, α = 77.457(2)°, β = 85.557(2)°, γ = 69.659(2)°, V = 2199.8(2) ų, Z = 2; (3) \(P\bar 1\) space group, a = 10.8814(3) Å, b = 12.2852(4) Å, c = 18.3590(6) Å, α = 80.463(1)°, β = 87.587(1)°, γ = 68.640(1)°, V = 2253.6(1) ų, Z = 2. The structures of the complexes are molecular and involve isolated [Tb₂(tmhd)₆] (1), Tb(tmhd)₃·Bipy (2), and Tb(tmhd)₃·Phen (3) molecules. The thermal properties of the obtained terbium complexes are studied by TG-DTA.