Sm Complexes Research Articles

Synthesis and fluorescence properties of Sm-2-oxo-quinoline-3-carbaldehyde-isonicotinyl hydrazone decorated with 1,10-phenanthroline

A novel ligand called 2-oxo-quinoline-3-carbaldehyde-isonicotinyl hydrazone (L) was designed and synthesized, and its Sm(III) complex was successfully prepared and characterized by X-ray diffraction. According to investigation, the Sm(III) complex didn’t exhibit characteristic fluorescence due to the mismatching energy between L and Sm(III) ion. However, when the complex was reacted with 1,10-phenanthrolin (Phen) as a secondary ligand, a novel ternary Sm(III) complex was synthesized, which showed efficient luminescence activity through an energy-transfer pathway. These results indicated that 1,10-phenanthrolin was an excellent sensitizer to Sm(III) ion.

Neutral "Cp-Free" Silyl-Lanthanide(II) Complexes: Synthesis, Structure, and Bonding Analysis.

Complexes featuring lanthanide silicon bonds represent a research area still in its infancy. Herein, we report a series of Cp-free lanthanide (+II) complexes bearing σ-bonded silyl ligands. By reactions of LnI2 (Ln = Yb, Eu, Sm) either with a 1,4-oligosilanyl dianion [K-Si(SiMe3)2SiMe2SiMe2Si(SiMe3)2-K)] (1) or with 2 (Me3Si)3SiK (3) the corresponding neutral metallacyclopentasilanes ({Me2Si(Me3Si)2Si}2)Ln·(THF)4 (Ln = Yb (2a), Eu (2b), Sm (2c)), or the disilylated complexes ({Me3Si}3Si)2Ln·(THF)3 (Ln = Yb (4a), Eu (4b), Sm (4c)), were selectively obtained. Complexes 2b, 2c, 4b, and 4c represent the first examples of structurally characterized Cp-free Eu and Sm complexes with silyl ligands. In both series, a linear correlation was observed between the Ln–Si bond lengths and the covalent radii of the corresponding lanthanide metals. Density functional theory calculations were also carried out for complexes 2a–c and 4a–c to elucidate the bonding situation between the Ln(+II) centers and Si.

Direct evidence of energy transfer from a singlet ligand level to lanthanide ions in their diketonate complexes

We have compared the fluorescence intensity of 2-naphthoyltrifluoroacetonate (NTA) in nanoparticles from Gd(NTA)3phen complexes with the fluorescence intensities of this compound in nanoparticles from similar complexes of Pr, Nd, Sm, Eu, Tb, Dy, Er, Ho, and Tm, which absorb in the NTA fluorescence range. We have proven that there is energy transfer from the S1 level of NTA ligands to Ln(III) ions, which occurs with rates ktr ∼ 1011–1012 s−1. We have also studied the competition between two processes: energy transfer from Ln(NTA)3phen to Ln(III) ions and energy transfer to Nile blue molecules incorporated into nanoparticles from complexes of these ions. It has been shown that, in nanoparticles from complexes of Nd(III), Tb(III), Dy(III), and Tm(III) ions, which are incapable of sensitizing the fluorescence of Nile blue, the values of ktr2 for the energy transfer from NTA to Ln(III) ions, which were obtained from the data on the change in the intensity of the sensitized fluorescence of Nile blue, completely coincide with the values of ktr1 determined from the fluorescence quenching of NTA in these nanoparticles. We have found that, in nanoparticles from Pr, Sm, Eu, Er, and Ho complexes, the efficiency of the sensitized fluorescence of Nile blue is higher than that predicted from the fluorescence quenching of NTA by these ions in their complexes, which indicates that all these ions participate as mediators in the energy transfer from ligands to the dye.

Photovoltaic properties of Zn, Al, La, Sm, and Yb complexes with o-iminobenzoquinone ligands

The o-iminobenzoquinone complexes of lanthanum, samarium, and ytterbium, Ln(L)3 (L = 3,5-ditert- butyl-1,2-quinone-1-(2-oxy-3,5-di-tert-butylphenyl)imine) are synthesized. In order to study the photovoltaic properties of the obtained complexes and previously synthesized similar complexes of zinc and aluminum M(L)2 prototypes of photovoltaic cells are prepared on their basis. An examination of the fabricated devices has revealed that nanolayers of all the compounds, except for ytterbium complex, exhibited photovoltaic properties. The best results of energy conversion are achieved for single-layer cells containing zinc complex as a photoactive material (Open-circuit voltage U OC = 1.01 V, short-circuit current J SC = 5.2 nA/cm2).

New Sm(III) complexes as electronic-excitation donors of the Seta-632 squaraine dye

We have found optimal formation conditions of new Sm(III) chelate complexes with derivatives of oxoquinolinecarboxylic acid (L 1 and L 2) and determined their spectral-luminescent characteristics (the luminescence and luminescence excitation wavelength maxima and the luminescence lifetimes). We have revealed that the Seta-632 squaraine dye (a fluorescent label of proteins and other biological molecules) quenches the luminescence of complexes Sm(III)-L 1 and Sm(III)-L 2. The quenching of chelate complexes is caused by the Forster resonant electronic-excitation energy transfer (FRET) from the donor (Sm(III)-L 1 or Sm(III)-L 2) to the acceptor (Seta-632). In this case, the luminescence intensity of the Seta-632 dye in the presence of Sm(III)-L 1 and Sm(III)-L 2 increases by factors of 64 and 27, respectively. The values of the Forster radii (R 0(Sm-L1) = 38 A, R 0(Sm-L2) = 35 A) and the overlap integrals of the luminescence spectra of the two energy donors with the absorption spectrum of the acceptor (J Sm-L1 = 1.22 × 1012 M−1 cm−1 nm4 and J Sm-L2 = 1.06 × 1012 M−1 cm−1 nm4), which have been calculated from the luminescence quantum intensity of the donors and from the absorption spectrum of the acceptor and its molar absorption coefficient, have made it possible to characterize the Seta-632 dye as an efficient quencher of the luminescence of Sm(III) ions. We are the first to propose Sm(III)-L 1 and Sm(III)-L 2 chelate complexes as FRET donors.

Highly luminescent Sm(III) complexes with intraligand charge-transfer sensitization and the effect of solvent polarity on their luminescent properties.

Samarium complexes with the highest quantum yields to date have been synthesized, and their luminescence properties were studied in 12 solvents. Sensitization via a nontriplet intraligand charge-transfer pathway was also successfully demonstrated in solution states with good quantum yields.

Synthesis, spectral properties, DNA binding interactions and DNA cleavage studies of lanthanide (III) complexes of 2-acetylpyridine acetoylhydrazone: the X-ray crystal structure of 10-coordinate Ce (III) and Sm (III) complexes

The lanthanide (III) complexes of general formula of [Ln(APAH)2(NO3)(H2O)2]·2NO3·nH2O (where Ln = La, Ce, Pr, Nd, Sm, and APAH = 2-acetylpyridine acetylhydrazone) have been synthesized and characterized by elemental analysis, molar conductance, spectroscopic (UV, IR), electro-chemical, thermal studies and single crystal X-ray diffraction studies. The coordination mode of the ligands and the geometry of [Ce(APAH)2(NO3)(H2O)2]·2NO3·H2O and [Sm(APAH)2(NO3)(H2O)2]·2NO3·2H2O confirmed by single crystal X-ray studies. The crystals are triclinic with P1bar crystallographic symmetry. The central metal is deca-coordinate in both the Ce and Sm complexes. The coordination polyhedron around the cerium atom can be described as a distorted bicapped square antiprism. The results explain that the central lantanide (III) ions in each complex are coordinated through pyridine nitrogen, azomethine nitrogen atom and amide carbonyl oxygen donor atoms. The hydrazone acts as neutral tridentate ligand. The binding properties of these complexes with calf-thymus DNA have been investigated using absorption spectrophotometry. The changes in absorption spectra complexes upon addition of DNA suggest strong π-stacking interaction between the complexes and DNA base pairs. The complexes show nuclease activity via oxidative path way.

New insights into structure and luminescence of Eu(III) and Sm(III) complexes of the 3,4,3-LI(1,2-HOPO) ligand.

We report the preparation and new insight into photophysical properties of luminescent hydroxypyridonate complexes [MIIIL]− (M = Eu or Sm) of the versatile 3,4,3-LI(1,2-HOPO) ligand (L). We report the crystal structure of this ligand with EuIII as well as insights into the coordination behavior and geometry in solution by using magnetic circular dichroism. In addition TD-DFT calculations were used to examine the excited states of the two different chromophores present in the 3,4,3-LI(1,2-HOPO) ligand. We find that the EuIII and SmIII complexes of this ligand undergo a transformation after in situ preparation to yield complexes with higher quantum yield (QY) over time. It is proposed that the lower QY in the in situ complexes is not only due to water quenching but could also be due to a lower degree of f-orbital overlap (in a kinetic isomer) as indicated by magnetic circular dichroism measurements.

Photoluminescent properties of novel Y(III), Sm(III), Eu(III), Gd(III) and Tb(III) complexes with 2-(1H-1,2,4-Triazol-3-yl)pyridine

2-(1H-1,2,4-Triazol-3-yl)pyridine was investigated as suitable ligand for the preparation of new Y(III), Sm(III), Eu(III), Gd(III) and Tb(III) complexes. Elemental analysis, mass spectrometry, thermal analysis, FT-IR and P-XRD methods were used to investigate their structural configuration. All the prepared complexes are highly luminescent, having an impressive visual emission under UV excitation. Fluorescence spectroscopy revealed in case of Sm(III), Eu(III) and Tb(III) complexes intense metal centered specific narrow band emissions from the f–f transitions within 4f orbitals, while in case of Gd(III) and Y(III) complexes intense wide band emissions were recorded most probable due the heavy atom effect over the excited intraligand states. The excitation peaks are conveniently located in UV-A region for all prepared complexes apart from Sm(III) complex where the excitation peak is located within the violet region of the spectrum. The remarkable luminescent properties might recommend these complexes for applications in optical devices, as photonic conversion media.

A family of fourteen soluble stable macrocyclic [NiII3LnIII] heterometallic 3d–4f complexes

Fourteen macrocyclic NiII3LnIII (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu) complexes were made, and checked for Single-Molecule Magnet behaviour; two acyclic analogues were structurally characterised.

Phosphonium-based tetrakis dibenzoylmethane Eu(iii) and Sm(iii) complexes: synthesis, crystal structure and photoluminescence properties in a weakly coordinating phosphonium ionic liquid

Luminescent anionic β-diketonate complexes of formula [P8,8,8,1][Ln(dbm)4], (Ln = Eu3+ and Sm3+, [P8,8,8,1] = trioctylmethylphosphonium and dbm = 1,3-diphenylpropane-1,3-dione) were synthesized, characterized and their photoluminescence properties studied.

Unique lanthanide frameworks with 63 topology based on 1,5-naphthalenedisulfonate and 1H-imidazo[4,5-f][1,10]-phenanthroline: syntheses, crystal structure, photoluminescence, and white light emission

Lanthanide complexes with a 63 net topology were synthesized. White light emissions were realized by the Sm(iii) complex and Ln(iii)-doped Eu(iii) complexes.

Triply phenoxo bridged Eu(iii) and Sm(iii) complexes with 2,6-diformyl-4-methylphenol-di(benzoylhydrazone): structure, spectra and biological study in human cell lines

Two dinuclear lanthanide(iii) complexes, [M2(HL)3] (M = Sm(iii) (1), Eu(iii) (2); H3L, 2,6-diformyl-4-methylphenol-di(benzoylhydrazone)) were generated with good yield and characterised systematically.

The first near-linear bis(amide) f-block complex: a blueprint for a high temperature single molecule magnet.

We report the first near-linear bis(amide) 4f-block compound and show that this novel structure, if implemented with dysprosium(III), would have unprecedented single molecule magnet (SMM) properties with an energy barrier, Ueff, for reorientation of magnetization of 1800 cm(-1).

RM1 modeling of neodymium, promethium, and samarium coordination compounds

The RM1 model is parameterized for the prediction of geometries of Nd(iii), Sm(iii), and Pm(iii) complexes.

Structural, spectroscopic, and theoretical comparison of traditional vs recently discovered Ln(2+) ions in the [K(2.2.2-cryptand)][(C5H4SiMe3)3Ln] complexes: the variable nature of Dy(2+) and Nd(2+).

The Ln(3+) and Ln(2+) complexes, Cp'3Ln, 1, (Cp' = C5H4SiMe3) and [K(2.2.2-cryptand)][Cp'3Ln], 2, respectively, have been synthesized for the six lanthanides traditionally known in +2 oxidation states, i.e., Ln = Eu, Yb, Sm, Tm, Dy, and Nd, to allow direct structural and spectroscopic comparison with the recently discovered Ln(2+) ions of Ln = Pr, Gd, Tb, Ho, Y, Er, and Lu in 2. 2-La and 2-Ce were also prepared to allow the first comparison of all the lanthanides in the same coordination environment in both +2 and +3 oxidation states. 2-La and 2-Ce show the same unusual structural feature of the recently discovered +2 complexes, that the Ln-(Cp' ring centroid) distances are only about 0.03 Å longer than in the +3 analogs, 1. The Eu, Yb, Sm, Tm, Dy, and Nd complexes were expected to show much larger differences, but this was observed for only four of these traditional six lanthanides. 2-Dy and 2-Nd are like the new nine ions in this tris(cyclopentadienyl) coordination geometry. A DFT-based model explains the results and shows that a 4f (n)5d(1) electron configuration is appropriate not only for the nine recently discovered Ln(2+) ions in 2 but also for Dy(2+) and Nd(2+), which traditionally have 4f (n+1) electron configurations like Eu(2+), Yb(2+), Sm(2+), and Tm(2+). These results indicate that the ground state of a lanthanide ion in a molecule can be changed by the ligand set, a previously unknown option with these metals due to the limited radial extension of the 4f orbitals.

In vitro antimicrobial and antioxidant evaluation of rare earth metal Schiff base complexes derived from threonine

Six novel Ln(III) Schiff base complexes were synthesized using rare earth metals with threonine and 5‐bromosalicylaldehyde, namely Pr(III), Sm(III), Gd(III), Tb(III), Er(III) and Yb(III) Schiff bases. These complexes were characterized using elemental analysis, molar conductivity, Fourier transform infrared and UV–visible spectroscopies, and thermogravimetry–differential thermal analysis. The general formula of the complexes is [Ln(L)(NO3)2(H2O)].NO3 (L = Schiff base ligand). The spectroscopic data reveal that the Schiff base ligand behaves as a tridentate ligand with ONO donor atoms sequencing towards the central metal ion. An investigation of fluorescence properties of the Sm(III), Er(III) and Tb(III) complexes shows that the Ln(III) ions can be sensitized efficiently by the ligand to some extent. Antimicrobial activity testing indicates that all six complexes exhibit antibacterial and antifungal ability against microbes with broad antimicrobial spectra. In addition, the antioxidant properties of the complexes were also screened. Copyright © 2014 John Wiley & Sons, Ltd.

Synthesis, characterization and luminescent properties of lanthanide complexes with a novel multipodal ligand

Solid complexes of lanthanide nitrates with an novel multipodal ligand, 1,2,4,5-tetramethyl-3,6-bis{N,N-bis[((2′-furfurylaminoformyl)phenoxyl)ethyl]-aminomethyl}-benzene (L) have been synthesized and characterized by elemental analysis, infrared spectra and molar conductivity measurements. At the same time, the luminescent properties of the Sm(III), Eu(III), Tb(III) and Dy(III) nitrate complexes in solid state were investigated. Under the excitation of UV light, these complexes exhibited characteristic emission of central metal ions. The lowest triplet state energy level of the ligand indicates that the triplet state energy level (T1) of the ligand matches better the resonance level of Tb(III) than other lanthanide ions.

PMLABe Diol Synthesized by Ring-Opening Polymerization of Racemic Benzyl β-Malolactonate Initiated by Rare-Earth Trisborohydride Complexes: An Experimental and DFT Study

Polymer diols are a class of polymeric building blocks of high interest for the synthesis of complex macromolecular edifices. Rare-earth borohydride complexes are known as efficient initiators for the ring-opening polymerization (ROP) of cyclic esters, directly affording α,ω-dihydroxy-telechelic polyesters. Here, were report the direct synthesis of poly(benzyl β-malolactonate) (PMLABe) diols, from the ROP of racemic (benzyl β-malolactonate) (rac-MLABe), a valuable and renewable monomer, initiated by the homoleptic [Ln(BH4 )3 (thf)3 ] (Ln=La, Nd, and Sm) complexes. These initiators enabled the controlled ROP of this β-lactone, affording well-defined syndiotactic-enriched (Pr ≈0.83) PMLABes (Mn up to 21 300 g mol(-1) , ÐM ≈1.5) as evidenced by size exclusion chromatography, (1) H and (13) C NMR spectroscopy, and MALDI-ToF mass spectrometry analyses. The first and second insertions of rac-MLABe, as assessed by DFT calculations, revealed more favorable stationary front-side than migratory back-side insertions, the thermodynamically and kinetically competitive ROP on two distinct arms with that on a one arm-only, and the thermodynamically slightly favored formation of syndiotactic-enriched PMLABes.

Local Structure of Pr, Nd, and Sm Complex Oxides and Their X-ray Absorption Near Edge Structure Spectra

Pr, Nd, and Sm L1-edge and L3-edge X-ray absorption near edge structure (XANES) spectra of their complex oxides were measured to investigate the relationship between the characteristic feature of the spectra and the local structure around the Pr, Nd, and Sm atoms. The pre-edge peak area of the L1-edge and the full width at half-maximum (fwhm) of the white line of the L3-edge XANES spectra are extracted by curve fitting analyses with one Gaussian and one cubic spline function as a background or with one arctangent and one pseudo-Voigt function, respectively. As a result, a clear correlation between the pre-edge peak area and the fwhm is found with another correlation with abstract physical parameters defined by bond angles formed with Pr, Nd, or Sm and two adjacent oxygen atoms, which represent an indicator of disorder of local configuration of the target element. This finding will open a way to estimate an average local structure of lanthanide elements by means of XANES spectroscopy.