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In this work, [Eu(tta)3(4-picNO)2] and [Eu(dbm)3(4-picNO)] complexes were incorporated on different concentrations (x = 1, 3, 5, 10 and 15%) in PMMA polymeric matrix (4-picNO: 4-Methylpyridine N-oxide) by the solvent casting method, yielding transparent and highly luminescent polymeric films. These materials were analyzed by X-ray diffraction, scanning electron microscopy and by energy dispersive, ultraviolet–visible spectroscopy, luminescence and vacuum ultraviolet–ultraviolet spectroscopies. The luminescence spectra of doped PMMA films are in agreement with an efficient intramolecular diketonate (tta) ligand-to-europium energy transfer. Furthermore, the values of experimental intensity parameters (Ω2,4) for luminescent polymeric materials were quite similar to those ones for isolated complexes, indicating that there is a homogeneous dispersion of Eu3+ complexes in the polymeric matrix, preserving their chemical and structural features. These behavior were also observed from the CIE diagram that show great similarity between the (x,y) coordinates for the doped PMMA samples compared to the isolated β-diketonate complexes with a reddish color tuning. The photostability investigation of the doped PMMA polymeric films and Eu3+ complexes has been also reported.

In the last few years, many synthetic methods have been developed using magnetic nanomaterial-based catalysts with considerable advantages for the efficiency, selectivity and applicability of green procedures. In this work, lanthanide–EDTA complexes covalently bonded on Fe3O4@SiO2 magnetic nanoparticles (Fe3O4@SiO2-xN-EDTA–Ln3+, with x = 1, 2, or 3 N spacer groups, and Ln3+ = La3+, Ce3+, Sm3+, Eu3+, Gd3+, Tb3+, Er3+ or Yb3+) were prepared and investigated as a heterogeneous catalyst for the synthesis of N-acylhydrazones. The target molecules were obtained in good to excellent yields, exclusively as E-diastereomers after short reaction times under mild conditions and low concentration of the easily recyclable catalyst.

This paper reports on the preparation, characterization, and photoluminescence properties of novel hybrid materials, in which the EDTA-Ln-L complexes (where L: H2 O, acac, bzac, dbm, and tta ligands, and Ln: Eu, Gd, and Tb) were covalently linked to the precursor medium molecular weight chitosan surface (CS) matrices or on the chitosan surfaces previously crosslinked with epichlorohydrin (CSech). The emission spectra of these materials were characterized by intraconfigurational-4fN transitions centred on the Eu3+ and Tb3+ ions. Some broad bands from the polymeric matrix were also observed in the emission spectra, however the relative intensities of the intraconfigurational bands increased significantly for systems containing diketonate ligands when the antenna effect became more efficient. The values of the radiative rates (Arad ) were higher for crosslinked hybrid systems with epichlorohydrin, while nonradiative rates (Anrad ) presented the opposite behaviour. These data contributed to an increase in the values of emission quantum efficiency (η) for crosslinked materials. The effect of the modification process and antenna ligand on the values of intensities, intensity parameters Ω2 e Ω4 of the Eu3+ complexes were also investigated. The results showed that the crosslinked biopolymer surfaces have great potential for applications in molecular devices light converters.

MWO4 host matrices (M: Sr, Ba) doped with different Tm3+ concentrations (0.02, 0.04, 0.06, 0.08 and 0.10 mol%) have been successfully prepared by the coprecipitation method at room temperature. The as-prepared nanophosphors were characterized by infrared spectroscopy showing intense absorption bands in the range of 700-1000 cm-1 attributed to the symmetrical and asymmetrical stretching vibrations (ν) of the tetrahedral [WO4]2- group. The X-ray diffraction (XRD) measurements reveal the tetragonal scheelite phase with the I41/a (No. 88) space group. The emission spectra of the MWO4:Tm3+ materials are dominated by the highest intensity narrow band of the intraconfigurational 1D2 → 3F4 transitions in the blue region (ca. 456 nm) arising from the Tm3+ ions. Additional low-intensity emission bands originated from the 1G4 → 3H6 (ca. 475 nm), 1G4 → 3F4 (660 nm) and 3H4 → 3H6 (700 nm) transitions are also observed. These optical results indicate that the materials can be used as an alternative to blue-emitting markers.

Two novel luminescent europium tris ( β -diketonate) complexes [Eu(dbm) 3 ·PX] and [Eu(acac) 3 ·PX] (dbm: dibenzoylmethane, acac: acetylacetonate and PX: piroxicam) were successfully synthesized. These coordination compounds were characterized by infrared vibrational spectroscopy (IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and luminescence spectroscopy. The thermal behavior of the complexes was investigated by thermogravimetric analysis (TG) and differential thermogravimetric analysis (DTG) techniques. The optical results have shown that these complexes present a clear intra and inter-molecular energy transfer and corroborates the sensitivity of their emission efficiency to the excitation wavelength, multiphonon non-radiative decays and temperature dependence. These new complexes may act as efficient light converting molecular devices, suggesting that they can be used for controllable photonic applications.

JOYSpectra is a free-of-charge web platform to perform online calculations of spectroscopic properties of lanthanide-based compounds and materials. It has several features and functionalities to provide a detailed analysis of the intensity parameters. For instance, their dependence on the chemical environment of the lanthanide ion (Ln3+) such as structure and nature of ligating atoms, can be performed automatically and consider covalency and thermal effects. The program can also calculate the intramolecular energy transfer rates from excited donor states up to 310 transitions involving 12 Ln3+ ions. The web platform was designed to be user-friendly for experimentalists and theoreticians interested in calculations and analyses of the photophysical behavior of lanthanides. Its use requires only the structure of the compound and the choices of a few calculation options. To show its easiness and usefulness, a detailed step-by-step calculation and analysis are performed for the [Ln(tta)3(H2O)2] (Ln: Eu and Tb) complexes to explain and quantify their distinct luminescence properties.

In this work the synthesis, characterization and photoluminescent and electroluminescent behavior of the [Eu(DBM)₃(PTSO)₂] complex have been investigated. The emission spectrum of this Eu³⁺–β– diketonate complex show characteristics narrow bands arising from the ⁵D₀→⁷Fȷ (J = 0–4) transitions, which are split according to the selection rule for Cs, Cn or Cnv site symmetries. Triple and doublelayer organic light-emitting diodes (OLEDs) using NPB as hole transporting layer, Alq₃ as electron transporting layer and [Eu(DBM)₃(PTSO)₂] complex as emitting and electron transporting layer were grown and characterized. We found the presence of two concurrent mechanisms for the electroluminescent behavior: (1) the electroluminescence (EL) from the exciton-ligand-Eu³+ ion energy transfer, responsible for the EL narrow bands; and (2) the molecular electrophosphorescence with an initial energy transfer exciton-ligand and posterior intersystem crossing from the excited singlet S₁ to the triplet T state followed by molecular phosphorescence (T→S₀). The electroluminescent behavior of [Eu(DBM)₃(PTSO)₂] complex suggest that this complex is promising to applied at Light Conversion Molecular Devices (LCMDs) such as in OLED devices.

The triply-doped xTb 3+ /xEu 3+ /xDy 3+ CaWO 4 (x: 0.5, 1.0, 2.0, 3.0, 4.0 and 5.0 mol%) nanomaterials were prepared at room temperature by a coprecipitation method. The luminescence materials were characterized by X-ray powder diffraction (XPD), thermal analysis (TG), infrared absorption spectroscopy (FTIR) and UV excited photoluminescence. The prepared powder phosphors are single-phase scheelite structure with porous morphology and particle sizes around 11 nm. The materials display white color from cool to the warm white, under UV excitation, as a result of the intraconfigurational 4f transitions from trivalent rare earth ions. The non-radiative energy transfer processes from the O→W and O→Eu LMCT as well as the 4f 8 →4f 7 5d 1 states to the intraconfigurational 4f excited levels of rare earth ions and simultaneous emissions from the 4 F 9/2 (Dy 3+ )→ 5 D 4 (Tb 3+ )→ 5 D 1 , 5 D 0 (Eu 3+ ) emitter levels are reported. Furthermore, CIE parameters and the color correlated temperature (CCT) are discussed in order to characterize the color emission. Based on the results, these luminescence materials may be potential candidates for white light emitting diodes and solid-state lighting.

A new magnetic nanoparticle supported-catalyst was developed for the Knoevenagel condensation between malononitrile and several aldehydes. The Fe3O4@SiO2-3N (where 3N = N1-(3-trimethoxysilylpropyl)diethylenetriamine) catalyst was characterized by XRD, infrared spectroscopy, and thermogravimetric analysis. The reactions provide excellent yields in a shorter reaction time in relation to others reported in the literature. The catalyst was easily recovered and reused until six times without significant loss of its catalytic capacity.

The odd-even effect in luminescent [Eu2 (L)3 (H2 O)x ]⋅y(H2 O) complexes with aliphatic dicarboxylate ligands (L: OXA, MAL, SUC, GLU, ADP, PIM, SUB, AZL, SEB, UND, and DOD, where x=2-6 and y=0-4), prepared by the precipitation method, was observed for the first time in lanthanide compounds. The final dehydration temperatures of the Eu3+ complexes show a zigzag pattern as a function of the carbon chain length of the dicarboxylate ligands, leading to the so-called odd-even effect. The FTIR data confirm the ligand-metal coordination via the mixed mode of bridge-chelate coordination, except for the Eu3+ -oxalate complex. XRD results indicate that the highly crystalline materials belong to the monoclinic system. The odd-even effect on the 4 f-4 f luminescence intensity parameters (Ω2 and Ω4 ) is explained by using an extension of the dynamic coupling mechanism, herein named the ghost-atom model. In this method, the long-range polarizabilities ( α * ) were simulated by a ghost atom located at the middle of each ligand chain. The values of α * were estimated using the localized molecular orbital approach. The emission intrinsic quantum yield ( Q L n L n ) of the Eu3+ complexes also presented an the odd-even effect, successfully explained in terms of the zigzag behavior shown by the Ω2 and Ω4 intensity parameters. Luminescence quenching due to water molecules in the first coordination sphere is also discussed and rationalized.

In this study, a novel type of tris(2-acyl-1,3-indandione)-aluminum(III) coordination compounds of the general formula [Al(acind)3]H2O, where 2-acyl-1,3-indandione (acind), 2-acetyl-1,3-indandione (aind), 2-benzoyl-1,3-indandione (bind), and 4-methyl-2-benzoyl-1,3-indandione (mbind), were synthesized and characterized by elemental analysis (CHN), Fourier transform infrared (FTIR) and nuclear magnetic resonance (1H NMR) spectroscopies, thermal analysis (TG/DTG and DTA), and optical absorption spectroscopy in the UV-Vis region. These compounds present remarkably high green luminescence in powder and in thin-film forms. However, when these compounds are applied in glass/ITO/β-NPB/spiro-2CBP/[Al(acind)3]/Al and glass/ITO/β-NPB/[Al(acind)3]/LiF/Al electroluminescent devices, where spiro-2CBP is 2,7-bis(carbazol-9-yl)-9,9-spirobifluorene and β-NPB is N,N’-bis(naphthalen-2-yl)-N,N’-bis(phenyl)-benzidine, the emission color tuned from green to red, reflecting a change from the direct charge recombination in the emitting layer of the [Al(acind)3] complexes to an exciplex-based emission in which [Al(acind)3] complexes and spiro 2-CBP acted as acceptor and donor, respectively. These results suggest that [Al(acind)3] complexes have potential applications as molecular light converter materials for fabricating new electroluminescent devices.

Three new β-diketone–Ln-EDTA (β-diketone = TTA, BTFA, ACAC; Ln=Eu3+ and Tb3+) water-soluble complexes were prepared, and their photophysical properties were investigated in aqueous solutions and compared with the Eu–EDTA complex. A very strong red and green luminescence was observed by the addition of ligands to the aqueous solutions of the Eu–EDTA and Tb–EDTA complexes, respectively, due to the formation of water-soluble β-diketone–Ln–EDTA complexes. To confirm the formation and stoichiometry of the new β-diketone–Ln–EDTA complex, the Judd–Ofelt intensity parameters Ω2 for Eu3+ complexes and the band width at half height (Δλ) for Tb3+ complexes were used. The dependence of these parameters on the addition of the β-diketone strongly suggests that only one β-diketonate ligand is in the first coordination sphere of the β-diketone–Ln–EDTA complexes. These new Eu3+ and Tb3+ systems may act as red and green optical markers for bioassay or bioimaging.

A critical review on the mechanisms and behavior of 4f intraconfigurational transitions in controllable chemical environments related to nonradiative intramolecular energy transfer processes in lanthanide chelates is presented. The term “modeling” is here used in the sense of manipulating and controlling the photophysical properties of these compounds, allowing obtaining distinguished and specific luminescent behavior. In this chapter an effort is made to show that a theoretical model, jointly used with experimental available data, is able to provide this modeling process in a comprehensive and useful way. The model allows estimating quantitatively intramolecular energy transfer rates by several mechanisms. Selection rules and the spectral overlap factor (energy mismatch conditions, for which an analytical expression is available) may be used to define relevant energy transfer pathways, and the solution (analytically or numerically) of appropriate systems of rate equations is crucial to deduce dominant pathways. Emission quantum yields, then, can be estimated and rationalized. In these rate equations all possible transition channels (radiative and non-radiative) must be included; some of them may be taken into account through the level decaying lifetime. Attempts to standardize notation is made, and some misinterpretations, perspectives and challenges on this subject are discussed.

The fabrication of bifunctional nanocomposites, co-assembling photonic (RE3+) and magnetic (Fe3O4) features into single entity nanostructures is reported through a facile method, using Fe3O4 as core nanoparticles, which were coated with SiO2 shell and further grafted with Eu3+ and Tb3+ complexes. The sophisticated structural features and morphologies of the core-shell Fe3O4@SiO2-(TTA-RE-L) nanomaterials were studied by Small-angle X-ray Scattering. The core mean size 〈 D SAXS 〉 , shell thickness Δ R , cluster size ξ and fractal dimension DF were determined by fitting the experimental SAXS data, corroborating through Transmission Electron Microscopy images. The DC magnetic properties at temperatures of 2 and 300 K were explored in support to the structural conclusions from SAXS and TEM analyses. The magnetic contributions of the RE3+ ions to the magnetizations of the Eu3+ and Tb3+ nanocomposites were discussed. The photoluminescence properties of the Eu3+ and Tb3+ nanocomposites based on the emission spectral data and luminescence decay curves were studied. The experimental intensity parameters (Ωλ), lifetimes (τ), emission quantum efficiencies (η) as well as radiative (Arad) and non-radiative (Anrad) decay rates were calculated and discussed, in addition, the structural conclusions from the values of the 4f-4f intensity parameters in the case of the Eu3+ ion. These novel Eu3+ and Tb3+ nanocomposites may act as red and green emitting layers for magnetic and light converting molecular devices.

Three organic–inorganic hybrid materials based on silica gel functionalized with (3-aminopropyl)trimethoxysilane (APTS), [3-(2-aminoetilamino)-propil]-trimetoxissilano (DAPTS) and 3-[2-(2-aminoetilamino)etilamino] propiltrimetoxysilane (TAPTS) and subsequently modified with EDTA derivative were prepared by nonhomogeneous route and were then characterized. The resulting materials named SilXN-EDTA (X=1 for APTS, 2 for DAPTS and 3 for TAPTS) were used to obtain new lanthanide Ln3+-β-diketonate (Ln3+=Eu3+, Gd3+ and Tb3+) complexes covalently linked to the functionalized silica gel surfaces (named SilXN-EDTALn-dik, dik=tta, dbm, bzac and acac). The photophysical properties of the new luminescent materials were investigated and compared with those with similar system presenting water molecules coordinated to the lanthanide ions, SilXN-EDTALn-H2O. The SilXN-EDTAEu-dik and SilXN-EDTATb-dik systems displayed characteristic red and green luminescence when excited by UV radiation. Furthermore, the quantitative results showed that the emission quantum efficiency (η), experimental intensity parameters Ω2 and Ω4, and Einstein's emission coefficient (A0J) of the SilXN-EDTAEu-dik materials were largely dependent on the ligands. Based on the luminescence data, the most efficient intramolecular energy transfer processes were found to the SilXN-EDTAEu-dik (dik: tta and dbm) and SilXN-EDTATb-acac materials, which exhibited more pure emission colors. These materials are promising red and green phosphors, respectively.

In this work, the coordination compounds presenting the formulas [Eu(acac)(NO3)2 (phen)2]⋅H2O (Eu1) and [Eu(bzac)(NO3)2(phen)2]⋅H2O (Eu2), acac: acetylacetonate, bzac: benzoylacetonate and, phen: 1,10-phenantroline, were successfully synthesized and some spectroscopic properties were investigated by theoretical and experimental methods. These compounds were characterized via elemental analysis, FTIR spectroscopy and thermogravimetric analysis (TGA). The X-ray diffraction data revealed that the compound Eu1 crystallizes in the monoclinic space group P2/n. Spectroscopic data showed that ligand-to-metal charge transfer states (LMCT) in the [Eu(β-dik)(NO3)2(phen)2]⋅H2O complexes (β-dik: acac or bzac) are redshift as compared with [Eu(β-dik)3(phen)] complexes. These data showed that LMCT states play the most important role on the luminescence quenching in the complexes Eu1 and Eu2, which only exhibit high luminescence intensities at low temperatures. Furthermore, the role of changes in the chemical environment on the intensity parameters Ωλ (λ = 2 and 4) have been investigated from the theoretical point of view for the complexes Eu1 to Eu2, and from these to tris β–dik complexes. Interestingly, the theoretical intensity parameters ratio Ω2/Ω4 calculated are in a good agreement with those experimental ones.

Eighteen new Eu3+ complexes and their Gd3+ analogues with 1,3-diketonate as main ligands and N-(pyridine-2-yl)amides or N-(pyrimidine-2-yl)amides as ancillary ligands were synthesized. The replacement of water molecules by those amides in the Eu3+ complexes increase the intrinsic quantum yields of luminescence, making them comparable or even more efficient than Eu3+ complexes with standard ancillary ligands such as 2,2′-bipyridine. The luminescence spectra of Gd3+ complexes in comparison with the Eu3+ ones show that efficient ligand-to-metal intramolecular energy transfer processes take place. In most cases the experimental Judd-Ofelt intensity parameters (Ω2 and Ω4) for the Eu3+ complexes show variations as a function of the temperature (77 and 300 K) that overall apparently does not follow clearly any trend. For this reason, geometric variations (on the azimuthal angle φ and ancillary ligands distances) were carried out in the coordination polyhedron for simulating thermally induced structural changes. It has been observed that, in this way, the Ω2 and Ω4 can be satisfactorily reproduced by in silico experiments. It was concluded that, at low-temperature, the ancillary ligands become closer to the Eu3+ ion and the angular variations affect more Ω2 than Ω4, in agreement to the theoretical calculations. The use of N-(pyridine-2-yl)amides or N-(pyrimidine-2-yl)amides as ancillary ligands in Eu3+ 1,3-diketonates looks to be a good strategy for obtaining highly luminescent complexes.

Trivalent rare-earth (RE3+) phenolate complexes have been receiving growing attention owing to their remarkable structural, luminescent, and magnetic properties. The RE3+ ions play an important role in the synthetic mechanisms acting as template, leading to a large number of homodinuclear and heterodinuclear coordination compounds presenting macrocyclic and macroacyclic phenolate ligands. The photoluminescent behavior of these kinds of complexes has been attributed to an efficient intramolecular energy transfer from the ligands to the RE3+ ions. The RE phenolate complexes have opened new possibilities for practical applications such as in RE3+ separation, in tunable photonic devices, in fluoroimmunoassays, and as paramagnetic contrast agents in magnetic resonance imaging. Keywords: the chemistry of metal phenolate complexes; structural properties of rare-earth phenolate complexes; RE3+ compounds containing acyclic and cyclic phenolate ligands; rare-earth–hydroxyquinolinate, -hydroxypyridine, -hydroxylpicolinate, -hydroxynicotinate cryptate, and -oxazolylphenol complexes; RE3+ luminescence properties

This paper presents a new green protocol for Knoevenagel condensations of aldehydes and compounds with an active methylene group in a binary mixture of ethanol/water (3:7, v/v). This medium favored the uncatalyzed Knoevenagel reactions and easy workup products can be obtained by precipitation in this medium and showed good isolated yields (55-100%) in short reaction times (1-60 min).

In this work, synthesis, characterization and photophysical properties of trivalent rare earth complexes with a nonsteroidal anti-inflammatory drug [the indomethacinate (indo), presenting formulas RE(indo)3(H2O)x (x = 3, for Eu3+ and Gd+3, and x = 4 for Tb+3), RE(indo)3(bipy) and RE(indo)3(phen) (bipy: 2,2'-bipyridine, and phen: 1,10-phenanthroline)] were investigated. Based on photoluminescent results, the intramolecular energy transfer process from T1 triplet states of indo, phen and bipy ligands to the 5D0 emitting level of the Eu3+ ion in the coordination compounds is discussed. Accordingly, it is proposed two possible intramolecular energy transfer mechanisms between indomethacinate ligand and rare earth ions, which involve the participation of excited electronic states of the heterocyclic ligands as intermediate ones.

Vermiculite clays were leached with nitric acid and functionalized with (3-chloropropyl)trimethoxysilane. The resulting materials were modified with the methylimidazolium (MID) group to yield cationic surfaces. These materials were characterized by infrared spectroscopy, elemental analyses, and specific surface area. Tetrakis(β-diketonate)europate(III) complexes, [EuL4]– [L = dibenzoylmethane (DBM) and thenoyltrifluoroacetone (TTA)], were immobilized on the vermiculite surface containing the imidazolium cation to yield hybrid surfaces named Vx-MID-EuL4 (x = 0, 1, and 2), in which x represents the acid nitric concentration in mol L–1 that is used in the leaching process. The highest luminescence intensities of the intraconfigurational-4f 5D07FJ transitions (for which J = 0, 1, 2, 3, and 4) arising from [EuL4]– complexes were presented by the hybrid materials containing the amount of imidazolium cation, which depend on the leaching process. The excitation and emission spectra suggested an efficient intramolecular energy-transfer process from ligand-to-Eu3+ ion in the supported materials. The photoluminescent properties of the hybrid materials were investigated based on the emission quantum efficiency (η), experimental intensity parameters Ω2 and Ω4, and Einstein's emission coefficient (A0J). The values of these parameters for the V2-MID-EuL4 surface are close to those assigned to the [EuL4]– isolated complexes, which indicates that hybrid vermiculite materials are promising red phosphors.

In this work it is reported the photoluminescence sensitization effect of the bis(dibenzo-18-crown-6)diaquatris(thenoyltrifluoroacetonate)europium(III) compound, [Eu(tta) 3 (DB18C6) 2 (H 2 O) 2 ], doped into a blend of poly(methylmethacrylate) (PMMA) and polyethylene glycol (PEG) in film form. The TGA results indicate that the Eu 3+ -complex precursor is immobilized in the polymer matrix by the interaction between the Eu 3+ complex and the oxygen atoms of the PMMA polymer. The thermal behavior of these luminescent systems is similar to that of the undoped polymer. The emission spectra of the Eu 3+ -complex in the PMMA/PEG blends recorded at room temperature exhibit the characteristic bands arising from the 5 D 0 → 7 F J ( J = 0–4) intraconfigurational transitions. The emission quantum efficiency of the Eu 3+ ion doped films increased significantly, indicating an effective interaction between the Eu 3+ -complex and the polymer matrix, and both the substitution of water molecules in the first coordination sphere and an efficient luminescence co-sensitization of the Eu 3+ luminescent centers.

Mechanoluminescence (ML) involves all luminescence phenomena induced by mechanical action on solids. In this case, a wide varieties of mechanical stimuli, such as compressing, stretching, static loading (pressure-step), pressure pulse, cleaving, rubbing, and grinding, might induce the excitation of solids, yielding luminescence phenomena. The present chapter discusses on mechanoluminescent properties of transition metal and lanthanide coordination compounds. The principal aim of this chapter is to describe the recent facts about the mechanisms of mechanoluminescence and their correlation with structural properties. It will be also presented a concise overview on the latest progress made on the current variety of ML coordination compounds or materials based on transition and lanthanide metals. The recent studies in this area may lead to the development of ML materials for smart optical sensors for real-time damage detections, monitoring civil and military structures, luminescent probes for biological applications, and lightning systems.

Bifunctional optical magnetic materials with a high europium content have been prepared. Chelating groups were introduced on the Fe3O4 surface with organosilanes containing ethylenediaminetetraacetic acid (EDTA) derivatives, which were previously prepared via a reaction between EDTA-dianhydride and aminoalkoxysilane agents: 3-(trimethoxysilyl)propylamine (1N), N-[3(trimethoxysilyl)propyl]ethylenediamine (2N) and N(1)-(3-trimethoxysilylpropyl)diethylenetriamine) (3N). The first coordination sphere of Ln-EDTA complexes present on the modified surfaces of Fe3O4 particles was completed by addition of β-diketonate ligands (tta: thenoyltrifluoroacetone, dbm: dibenzoylmethane, bzac: benzoylacetone and acac: acetylacetone) in order to improve their luminescence properties. The materials were characterized by powder X-ray diffraction (XRD), vibrating sample magnetometry (VSM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and wavelength dispersive X-ray fluorescence (WDXRF) and Fourier-transform infrared (FT-IR) spectroscopy as well as by zeta potential measurements and luminescence spectroscopy. The hybrid materials exhibited intense red emission, which can be assigned to the 4f-4f transitions of the Eu(3+) ion, indicating an efficient intramolecular ligand-to-metal energy transfer. The experimental intensity parameters (Ω2 and Ω4), lifetimes (τ), as well as radiative (Arad) and non-radiative (Anrad) decay rates of the Eu(3+) ion were determined and discussed. The strategies used to obtain these materials may contribute to the development of several bifunctional systems for practical applications.

The complex BiCl3·L (L = 1,10-phenanthroline) was synthesized and characterized by elemental analysis and infrared spectroscopy (IR). Infrared spectroscopy data suggested that the nitrogen atom of the aromatic ring is bonded to the bismuth atom. The kinetic study of thermal degradation was determined by non-isothermal thermogravimetry. Two methods based on integral equation of Coats-Redfern, were necessary for determining the kinetic trip: the fitting method, known as the checking model and an iso-conversional method. The latter gives the activation energy for each degree of conversion and the first, the kinetic model gives activation energy and the pre-exponential factor for thermal decomposition processes that occur through a single simple mechanism. The kinetic parameters, E a and log A for the heating rates of 5, 10, and 15 min K−1, were determined considering the decomposition model denoted by F0/R1 in the range of degree of conversion between 0.065 and 0.71.

The synthesis, structural investigation, and photophysical properties of the complex [Tb(TTA)2(NO3)(TPPO)2] are reported. Unlike the analog tris-diketonate complex [Tb(TTA)3(TPPO)2], the new complex presents abnormally high luminescence intensity centered on the terbium ion. Our results clearly suggest a higher energy transfer efficiency from the TTA antenna ligand to the Tb(III) ion in the bis-diketonate complex compared with that in the tris-diketonate complex. A mechanism involving the increasing of triplet state energy when one TTA ligand is replaced by the NO3− group in the first coordination sphere is suggested and experimentally investigated to explain the anomalous luminescence properties of the new complex [Tb(TTA)2(NO3)(TPPO)2].

Red, blue and green emitting rare earth compounds (RE3+=Eu3+, Gd3+ and Tb3+) containing the benzenetricarboxylate ligands (BTC) [hemimellitic (EMA), trimellitic (TLA) and trimesic (TMA)] were synthesized and characterized by elemental analysis, complexometric titration, X-ray diffraction patterns, thermogravimetric analysis and infrared spectroscopy. The complexes presented the following formula: [RE(EMA)(H2O)2], [RE(TLA)(H2O)4] and [RE(TMA)(H2O)6], except for Tb-TMA compound, which was obtained only as anhydrous. Phosphorescence data of Gd3+-(BTC) complexes showed that the triplet states (T) of the BTC3− anions have energy higher than the main emitting states of the Eu3+ (5D0) and Tb3+ (5D4), indicating that BTC ligands can act as intramolecular energy donors for these metal ions. The high values of experimental intensity parameters (Ω2) of Eu3+-(BTC) complexes indicate that the europium ion is in a highly polarizable chemical environment. Based on the luminescence spectra, the energy transfer from the T state of BTC ligands to the excited 5D0 and 5D4 levels of the Eu3+ and Tb3+ ions is discussed. The emission quantum efficiencies (η) of the 5D0 emitting level of the Eu3+ ion have been also determined. In the case of the Tb3+ ion, the photoluminescence data show the high emission intensity of the characteristic transitions 5D4→7FJ (J=0–6), indicating that the BTC ligands are good sensitizers. The RE3+-(BTC) complexes act as efficient light conversion molecular devices (LCMDs) and can be used as tricolor luminescent materials.

Fabrication and electroluminescent properties of devices containing europium complexes of general formula [Eu(ACIND) 3 (TPPO) 2 ], where ACIND, 2-acyl-1,3-indandionate ligands; and TPPO, triphenylphosphine oxide, as emitter layers are discussed. The double-layer devices based on these complexes present the following configurations: device 1 : ITO/TPD/[Eu(AIND) 3 (TPPO) 2 ]/Al; device 2 : ITO/TPD/[Eu(ISOVIND) 3 (TPPO) 2 ]/Al and device 3 : ITO/TPD/[Eu(BIND) 3 (TPPO) 2 ]/Al, where AIND, 2-acetyl-1,3-indandionate; ISOVIND, 2-isovaleryl-1,3-indandionate; and BIND, 2-benzoyl-1,3-indandionate, respectively. These devices exhibited photo and electroluminescent emissions. An important characteristic presented by devices is that their electroluminescent (EL) spectra, in the region of 5 D 0 → 7 F J ( J = 0, 1, 2, 3 and 4) transitions of Eu 3+ ion, show profiles that are different from photoluminescent (PL) ones. In addition to narrow bands arising from intraconfigurational-4f 6 transitions, devices 1 and 2 also exhibited a broad band with maximum at around 500 nm which is assigned to electrophosphorescence from the indandionate ligands. On the other hand, EL spectra of device 3 present only narrow bands from 5 D 0 → 7 F J transitions. [Eu(ACIND) 3 (TPPO) 2 ] complexes are promising candidates to prepare efficient organic light-emitting devices (OLEDs) when compared with those containing Eu 3+ -complexes of aliphatic β-diketonate anions.

MgAl 2 O 4 :Eu, Dy nanoparticles were prepared by citrate sol–gel method and thermally treated at 600, 700, 800 and 900 °C. The trivalent europium ion is partially reduced to the divalent state at 700 and 800 °C. Infrared spectra of the phosphors showed bands around 700 and 520 cm −1 corresponding to the AlO 6 groups. X-ray diffraction patterns present sharp reflections of samples heated from 700 to 900 °C indicating the MgAl 2 O 4 spinel phase. Grain size in the range 20–30 nm were observed by measurement of transmission electron microscopy (TEM). The emission spectra of the phosphors show a broadened band at 480 nm assigned to the 4f 6 5d → 4f 7 ( 8 S 7/2 ) transition of Eu 2+ ion overlapped to the 4 F 9/2 → 6 H 15/2 transition of the Dy 3+ ion. Besides, the 4 F 9/2 → 6 H 13/2 transition (579 nm) of Dy 3+ ion is overlapped with the 5 D 0 → 7 F 0 (578 nm) and 5 D 0 → 7 F 1 (595 nm) transitions from the Eu 3+ ion. Excitation spectra of the sample heated at 900 °C monitoring the excitation at 615 nm of 5 D 0 → 7 F 2 transition of Eu 3+ ion exhibit a broad band assigned to the O → Eu 3+ ligand-to-metal charge-transfer states (LMCT) around 280 nm. The samples present green persistent luminescence after exposure to UV radiation. The chromaticity coordinates were obtained from the luminescence emission spectrum.

This work reports the energy transfer mechanism process of [Eu(TTA)2(NO3)(TPPO)2] (bis-TTA complex) and [Eu(TTA)3(TPPO)2] (tris-TTA complex) based on experimental and theoretical spectroscopic properties, where TTA=2-thienoyltrifluoroacetone and TPPO=triphenylphosphine oxide. These complexes were synthesized and characterized by elemental analyses, infrared spectroscopy and thermogravimetric analysis. The theoretical complexes geometry data by using Sparkle model for the calculation of lanthanide complexes (SMLC) is in agreement with the crystalline structure determined by single-crystal X-ray diffraction analysis. The emission spectra for [Gd(TTA)3(TPPO)2] and [Gd(TTA)2(NO3)(TPPO)2] complexes are associated to T→S0 transitions centered on coordinated TTA ligands. Experimental luminescent properties of the bis-TTA complex have been quantified through emission intensity parameters Ωλ (λ=2 and 4), spontaneous emission rates (Arad), luminescence lifetime (τ), emission quantum efficiency (η) and emission quantum yield (q), which were compared with those for tris-TTA complex. The experimental data showed that the intensity parameter value for bis-TTA complex is twice smaller than the one for tris-TTA complex, indicating the less polarizable chemical environment in the system containing nitrate ion. A good agreement between the theoretical and experimental quantum yields for both Eu(III) complexes was obtained. The triboluminescence (TL) of the [Eu(TTA)2(NO3)(TPPO)2] complexes are discussed in terms of ligand-to-metal energy transfer.

Al 2 O 3 :Eu 3+ (1%) samples were prepared by combustion, ceramic, and Pechini methods annealed from 400 to 1400 °C. XRD patterns indicate that samples heated up to 1000 °C present disordered character of activated alumina (γ-Al 2 O 3 ). However, α-Al 2 O 3 phase showed high crystallinity and thermostability at 1200–1400 °C. The sample characterizations were also carried out by means of infrared spectroscopy (IR), scanning electron microscopy (SEM) and specific surface areas analysis (BET method). Excitation spectra of Al 2 O 3 :Eu 3+ samples present broaden bands attributed to defects of Al 2 O 3 matrices and to LMCT state of O → Eu 3+ , however, the narrow bands are assigned to 7 F 0 → 5 D J , 5 H J and 5 L J transitions of Eu 3+ ion. Emission spectra of samples calcined up to 1000 °C show broaden bands for 5 D 0 → 7 F J transitions of Eu 3+ ion suggesting that the rare earth ion is in different symmetry sites showed by inhomogeneous line broadening of bands, confirming the predominance of the γ-alumina phase. For all samples heated from 1200 to 1400 °C the spectra exhibit narrow 5 D 0 → 7 F J transitions of Eu 3+ ion indicating the conversion of γ to α-Al 2 O 3 phases, a high intensity narrow peak around 695 nm assigned to R lines of Cr 3+ ion is shown. Al 2 O 3 :Eu 3+ heated up to 1100 °C presents an increase in the Ω 2 intensity parameter with the increase of temperatures enhancing the covalent character of metal–donor interaction. The disordered structural systems present the highest values of emission quantum efficiencies ( η ). CIE coordinates of Al 2 O 3 :Eu 3+ are also discussed.

Novel unexpected coordination polymer [Tb(PHTHGLY)(CBGLY)(H2O)2](H2O)3 complex containing simultaneously N-phthaloylglycinate and N-(2-carboxybenzoyl)glycinate ligands has been prepared and characterized by single crystal X-ray structure, thermogravimetric analysis and infrared spectroscopy. The X-ray crystal diffraction indicates that the Tb3+-complex crystallizes in a triclinic crystal system and space group P 1 ¯ , forming a 1D polymer where carboxylate groups bridge the Tb3+ ions. The photoluminescence data revel that the ligands act as efficient “antennas” sensitizing the luminescence of the Tb3+ ion showing a strong green emission color arising from intraconfigurational 5D4 → 7FJ transitions (J = 0–6).

Eu2+ ion doped into SrB4O7 matrix was prepared by combustion method heated at 900 °C in air, using urea (U) or glycine (G) as fuels in different ratios (U100, A10, A25, G10, G25, G75, and G100). In some compositions, ammonium acetate (AA) was used to reduce the exothermicity of combustion reaction. X-ray diffraction and luminescence spectroscopy were used to characterize the material. The high intense emission band at 367 nm is assigned to 4f65d → 4f7(8S7/2) transition arisen from divalent europium ion. It is observed that the interconfigurational transition is dependent on the molar ratio of glycine:urea fuels. Glycine fuel favors Eu2+ formation in SrB4O7 host lattice prepared by combustion method.

[RE(TLA)·(H2O)n:Eu3+] (RE3+: Y, Gd and Lu; TLA: trimellitic acid) precursor complexes were synthesized by an one step aqueous co-precipitation method. After annealing for 1 h, RE2O3:Eu3+ nanophosphors were formed through the benzenetricarboxylate low temperature thermolysis method (500-1000 oC). The compounds were characterized by using different techniques [elemental analysis (CHN), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG/DTG), X-ray powder diffraction (XPD) and scanning electron microscope (SEM)]. The XPD data indicated that the Y2O3:Eu3+ materials have crystallite size range from 11 to 62 nm. The SEM and transmission electron microscopy (TEM) images show that the annealed materials keep morphological similarities with the precursor complexes. The photoluminescence properties were studied based on the excitation and emission spectra, and luminescence decay lifetimes of the 5D0 emitting level of the Eu3+ ion. The experimental intensity parameters (Ωλ), lifetimes (τ), as well as radiative (Arad) and non-radiative (Anrad) decay rates were calculated and discussed. The RE2O3:Eu3+ phosphors (RE: Y3+ and Lu3+) annealed at 500 to 1000 oC have emission quantum efficiency (intrinsic quantum yield) values from 60 to 82%, indicating that this material can be potentially used for optical markers applications.

Two new bis(dipivaloylmethanate)nitrato-bis(triphenylphosphine oxide)lanthanide(III) complexes [Eu(dpm)2(NO3)(tppo)2] (1) and [Tb(dpm)2(NO3)(tppo)2] have been prepared in monomeric form. The structural behavior of these coordination compounds is significantly different from those of [Eu2(dpm)6] and [Tb2(dpm)6] dimeric complexes. The photoluminescent properties of the monomeric and dimeric complexes are dependent on the energy positions of the low-lying ligand-to-metal charge-transfer (LMCT) state, which may be correlated with the chelating and chelate bridging coordination modes of the dpm ligand, respectively. The monomeric complex presents higher luminescence intensity than the dimeric complex due to the higher energy of the LMCT state in this system. Although the excited energy levels of the EuIII ion in complex 1 undergo efficient depopulation by LMCT, the same is not observed for the 5D0 emitting level, which presents values of the emitting lifetime that are almost temperature independent. The triboluminescence phenomenon of the [Ln(dpm)2(NO3)(tppo)2] complex is also discussed.

Europium complexes presenting general formulas [Eu(ACIND)3(H2O)2] and [Eu(ACIND)3(TPPO)2] have been synthesized and characterized. In these formulas ACIND is stands for the ligands 2-acetyl-1,3-indandionate (AIND), 2-isovaleryl-1,3-indandionate (ISOVIND) or 2-benzyl-1,3-indandionate (BIND). The [Eu(ISOVIND)3(H2O)(EtOH)] complex was also prepared and its structure determined by single crystal X-ray analysis, showing that this complex crystallize in a monoclinic space group P21/n with the water molecules bridging through the hydrogen bond. The Eu(III) ion is eight-coordinate in a bicapped trigonal prismatic geometry defined by the oxygen donor atoms with a site of symmetry close to C2ν. Isovaleryl groups in the ISOVIND molecules in the structure are disordered over two positions of the europium complex. Carbon atoms in ethanol molecule are disordered by the thermal vibration. Photoluminescence properties of these complexes in solid state were investigated both experimentally and theoretically, suggesting an efficient ligand-to-metal intramolecular energy transfer process.

FDU-1 is a highly ordered, large-pore silica with a cage-like mesoporous cubic structure. FDU-1 was synthesized from tetraethyl orthosilicate (TEOS) in the presence of poly(ethylene oxide)–poly(butylene oxide)–poly(ethylene oxide) triblock copolymer (PEO–PBO–PEO) template in strongly acid media, using a microwave oven as heating source. Rare earth complexes were encapsulated in ordered mesoporous silica in order to improve their thermal stability, necessary for applications. Eu(dbm) 3 · TPPO (dbm = dibenzoylmethane and TPPO = triphenylphosphine oxide) and Eu(pic) 3 · 2Leu · 5H 2 O (pic = picrate and Leu = l -leucine) were encapsulated into FDU-1 silica and modified FDU-1 silica by 3-aminopropyltriethoxysilane (APTES). Thermogravimetry/derivative thermogravimetry (TG/DTG) showed that the decomposition temperature increased after encapsulation of the complex. Small angle X-ray diffraction (SAXRD) results showed that the mesoporous silica remains ordered after the encapsulation of the europium complexes. Rutherford back-scattering spectrometry (RBS) revealed a much higher Eu encapsulation for the dibenzoylmethane complex compared to picrate and, with a weight percent similar to the nominal concentration of Eu set at the synthesis process. All infrared spectra are similar and present the profile of amorphous silica. The complexes in FDU-1 silica still present luminescence.

This work reports the preparation of system containing RE2+ ions (RE=Sm and Eu)-doped in SrB4O7 matrix by ceramic, Pechini and combustion methods. These compounds were prepared by reduction of RE3+ to RE2+ in air, which exhibit some different features according to the preparation method. Photoluminescent properties of these systems were investigated based on the emission and excitation spectral data. The emission spectra of SrB4O7:Eu2+ system prepared by combustion and Pechini methods are characterized by a broad band assigned to interconfigurational 4f65d→4f7 transition, while SrB4O7:Sm2+ compound exhibit narrow emission bands arising from intraconfigurational-4f6 also shows 4G5/2→6HJ′ transitions ( J ′ = 5 2 , 7 2 , 9 2 and 11 2 ) arising from Sm3+ ion, transitions. SrB4O7:RE system prepared by combustion method presents emission bands from RE3+ ions as intense as that arising from RE2+, suggesting that the preparation route is not efficient for the reduction RE3+→RE2+ process. Emission quantum efficiency and radiative emission rates of Sm2+ ion are determined and discussed.

The design of bifunctional magnetic luminescent nanomaterials containing Fe3O4 functionalized with rare earth ion complexes of calixarene and β-diketonate ligands is reported. Their preparation is accessible through a facile one-pot method. These novel Fe3O4@calix-Eu(TTA) (TTA = thenoyltrifluoroacetonate) and Fe3O4@calix-Tb(ACAC) (ACAC = acetylacetonate) magnetic luminescent nanomaterials show interesting superparamagnetic and photonic properties. The magnetic properties (M-H and ZFC/FC measurements) at temperatures of 5 and 300 K were explored to investigate the extent of coating and the crystallinity effect on the saturation magnetization values and blocking temperatures. Even though magnetite is a strong luminescence quencher, the coating of the Fe3O4 nanoparticles with synthetically functionalized rare earth complexes has overcome this difficulty. The intramolecular energy transfer from the T1 excited triplet states of TTA and ACAC ligands to the emitting levels of Eu(3+) and Tb(3+) in the nanomaterials and emission efficiencies are presented and discussed, as well as the structural conclusions from the values of the 4f-4f intensity parameters in the case of the Eu(3+) ion. These novel nanomaterials may act as the emitting layer for the red and green light for magnetic light-converting molecular devices (MLCMDs).

Rare earth complexes with the formulae Sm(TPAC)3·3H2O, Eu2(TPAC)6·5.25H2O and RE(TPAC)3·3.5H2O (where RE=Gd and Tb), and TPAC=2-thiopheneacetate) have been synthesized and characterized by complexometric titration, elemental analyses, infrared spectroscopy, and X-ray crystallography. Infrared data suggested the presence of both bridging and chelating TPAC anions. The crystal structure of the [Eu2(TPAC)6·(H2O)3]·2.25H2O complex in the solid state, determined by X-ray diffraction, revealed that it crystallizes in the orthorhombic crystal system (space group Aba2), with two crystallographically independent Eu3+ centers (Eu1 and Eu2). These europium centers are held together by one bidentate bridging and two tridentate bridging carboxylate groups. The existence of two Eu3+ centers was also supported by the emission spectrum. The luminescence properties of the RE–TPAC complexes were investigated by measuring the excitation and emission spectra, and the intramolecular ligand-to-rare earth energy transfer mechanisms were discussed. The emission spectra of the Eu3+ and Tb3+ ions displayed only narrow bands arising from 5D0→7F0 and 5D0→7F0–4 transitions, respectively, indicating an efficient luminescence sensitization of these ions by the TPAC ‘antenna’. On the other hand, the emission spectrum of the Sm3+-complex displayed a broad band from the phosphorescence of the TPAC ligand which overlapped the 4f5-intraconfigurational transitions. The theoretical intensity parameters Ωλ (λ=2 and 4), maximum splitting of the 7F1 state (ΔE) and the ratio between the 5D0→7F0 and 5D0→7F2 transition intensities (R02) were calculated based on the X-ray crystalline structure for the Eu3+-complex, and a comparison with experimental data were made. The emission quantum efficiency (η) of the D 5 emitting level of the Eu3+ ion was also determined.

In this work, we reported the preparation and the characterization of triple-layer electroluminescent organic devices using different blends of the samarium and europium β-diketonate complexes [SmxEuy(TTA)3(TPPO)2] (x=0.7, 0.9; y=0.3, 0.1) as emitting layer. The organic light-emitting diode (OLED) devices contained 1-(3-methylphenyl)-1,2,3,4-tetrahydroquinoline-6-carboxyaldehyde-1,1′-diphenylhydrazone (MTCD) as hole-transporting layer and tris(8-hydroxyquinoline) aluminum (Alq3) as electron transporting layer. The electroluminescence (EL) spectra present emission narrow bands characteristic of the Sm3+ and Eu3+ ions overlapped with a broad band attributed to the molecular electrophosphorescence (EP) from the triplet–singlet (T1→S0) transition from the TTA ligand. The intensity ratio of the peaks is determined by the bias voltage applied to the OLED and this fact, together with the ligand electrophosphorescence, allows fabrication of a voltage-tunable color light source.

Light emission from organic electroluminescent diodes (OLEDs) in which mixed samarium and europium β-diketonate complexes, [Sm 0.7 Eu 0.3 (TTA) 3 (TPPO) 2 ], was used as the emitting layer is described. The electroluminescence spectra exhibit narrow peaks arising from 4f-intraconfigurational transitions of the Sm 3+ and Eu 3+ ions and a broad emission band attributed to the electrophosphorescence of the TTA ligand. The intensity ratio of the peaks determined by the bias voltage applied to the OLED, together with the ligand electrophosphorescence, allows to obtain a voltage-tunable color light source.

The influence of amide ligands on the photoluminescent behavior of tris(thenoyltrifluoroacetonate)- europium(III) in the solid state is reported. Elemental analysis showed that these compounds have the following formulas [Eu(TTA)3·(ANL)2] and [Eu(TTA)3·PZA], where ANL = acetanilide and PZA = pyrazinamide. The photoluminescence spectra of the complexes recorded in the range 420-720 nm at 77 K show narrow bands arising from the 5D0 → 7F J transitions (where J = 0-4), under excitation at 394 nm. Based on the emission spectra and luminescence decay curves the intensity parameters (Ωλ), lifetime (τ) and emission quantum efficiency (η) were determined. The Ω2 values indicate that the Eu3+ion in these complexes is in a highly polarizable chemical environment. The higher value of η (60%) obtained for the complex with the ANL ligand, in comparison with the complex with the PZA ligand (30%), indicates a more efficient deactivation of the Eu3+ion in the [Eu(TTA)3·PZA] complex.

In this paper we report on a photoluminescent investigation of complexes involving Sm 3+ -β-diketonates with sulfoxides, phosphine oxides and amides ligands. In the synthesis of the coordination compounds we used samarium tris(thenoyltrifluoroacetonate) dihydrated precursor with the following ligands (L): DBSO and PTSO sulfoxides; TPPO phosphine oxide and (PHA) N -phenylacetamide. They have shown high orange luminescence characteristic of the Sm 3+ ion. The emission spectra of the Sm 3+ -complexes present narrow bands arising from the 4 G 5/2 → 6 H J ( J =5/2, 7/2, 9/2, 11/2) transitions with the hypersensitive 4 G 5/2 → 6 H 9/2 transition as a prominent group. It is observed an efficient intramolecular energy transfer from the triplet state (T) of the ligands to the emitting 4 G 5/2 state of the Sm 3+ ion. The experimental intensity parameters ( η Sm and η Eu ) for the Sm and Eu complexes have been determined and compared. The lifetimes ( τ ) of the emitting level 4 G 5/2 of the Sm-complexes are approximately 10 times higher than in the precursor compound [Sm(TTA) 3 ·(H 2 O) 2 ] indicating that radiative processes are operative in all the compounds due to the absence of multiphonon relaxation by coupling with the OH oscillators.

This work reports the synthesis, characterization and spectroscopic studies of Eu(III)-perchlorate complexes with amide ligands derived from N -[ x -methylpyridyl]acetamide where x =3, 4 and 6. The Eu(ClO 4 ) 3 3( x -mpa) complexes were characterized by elemental analyses, molar conductance, TG analyses and vibrational spectroscopy. Raman and infrared data show that the perchlorate ion, (ClO 4 − ), is bonded to Eu(III) as a monodentate ligand and that in these three complexes water molecules are not coordinated to the rare earth ion. The profiles of the emission spectra of the complexes with 3- and 4-mpa ligands are very similar but they differ from the complex containing 6-mpa ligand. This spectroscopic behavior can be rationalized in terms of the Ω λ ( λ =2 and 4) and R 02 experimental intensity parameters. The values of Ω 2 (∼6.5×10 −20 cm 2 ) in these complexes are smaller than in Eu(III)-TTA compounds ( Ω 2 ∼35.0×10 −20 cm 2 ), indicating that in the former case the rare earth ion is in a chemical environment less polarizable. Lifetime and emission quantum efficiency measurements for the emitting level 5 D 0 were carried out and the results are discussed.

This work reports Eu(III) and Tb(III) luminescence titrations in which the lanthanide ions were used as spectroscopic probes for Ca(II) ions to determine the metal binding ability of Ac–NESVKEEGGW–NH 2 and Ac–NESVKEDGGW–NH 2 . These decapeptides correspond to the putative calcium binding region of the plant antifungal proteins SI-α1 from Sorghum bicolor and of Zeathionin from Zea mays , respectively. The luminescence spectra for the Eu(III)–decapeptide system (red emission) with the excitation at the Trp band at 280 nm showed an enhancement of the intensities of the 5 D 0 → 7 F J transitions (where J =0–4) with increments of Eu(III) ion concentration. The photoluminescence titration data of the terbium ion (green emission) in the decapeptide solutions showed intensification of the 5 D 4 → 7 F J transitions ( J =0–6), similar to that observed for the Eu(III) ion. Thus, energy transfer from Ac–NESVKEEGGW–NH 2 and Ac–NESVKEDGGW–NH 2 to the trivalent lanthanide ions revealed that these peptides are capable of binding to these metal ions with association constants of the order of 10 5 M −1 . The amino acid derivative Ac–Trp–OEt also transferred energy to Tb(III) and Eu(III) ions as judged from the quenching of tryptophan luminescence. However, the energy transfers were significantly lower. Taken together the luminescence titration data indicated that Ac–NESVKEEGGW–NH 2 and Ac–NESVKEDGGW–NH 2 bind efficiently to both trivalent lanthanide ions and that these ions may be used as probes to distinguish an anionic peptide from a neutral amino acid derivative.

Novel Ln3+-indandionate complexes of formulas [Ln(aind)3L(H2O)] and [Ln(bind)3L]∙H2O (L: 1,10-phenanthroline (phen) or 4,7-dimethyl-1,10-phenanthroline (dmphen), Ln3+: Eu3+ or Gd3+, aind: 2-acetyl-1,3-indandionate and bind: 2-benzoyl-1,3-indandionate) were synthesized and characterized by elemental analysis, infrared spectroscopy, and thermogravimetric analyses. The characterization data are consistent with the presence of a water lattice molecule in the [Ln(bind)3L]∙H2O compounds. However, the data also suggest that the water acts as a coordinated molecule in the [Ln(aind)3L(H2O)] ones. Theoretical geometries of the Eu3+-complexes have been optimized via the SPARKLE/AM1 Model for lanthanide complexes that are consistent with their luminescence experimental data. The photoluminescence properties of the Eu3+-compounds have been discussed in terms of experimental intensity parameters (Ω2 and Ω4), radiative (Arad), and non-radiative (Anrad) spontaneous emission coefficients. The higher values of emission quantum efficiency (η) of the [Eu(bind)3L]∙H2O compounds reflect the absence of luminescence-quenching water molecule in their first coordination spheres.