Erbium Complexes Research Articles

X-ray analysis, molecular modeling and NIR-luminescence of erbium(III) 2,4-octanedionate complexes with N,N-donors

X-ray diffraction and semiempirical methods have been used to investigate the structures of novel erbium(III) [Er(od)3(N,N-donor)] complexes, where od=2,4-octanedionate and N,N-donor=2,2′-bipyridine (bipy), bathophenanthroline (bath) or 5-nitro-1,10-phenanthroline (5NO2phen). Structural characteristics for these ternary complexes were also obtained by FTIR spectra. Subsequently, the visible and near-infrared luminescence properties of the compounds have been studied. Upon ligand excitation, the complexes show strong near-infrared luminescence at 1530nm due to antenna effect. These erbium(III) complexes can potentially be applied to polymeric erbium-doped optical amplifiers, planar waveguides or infrared OLEDs.

Preparation, Structure, DNA-Binding Properties, and Antioxidant Activities of a Homodinuclear Erbium(III) Complex with a Pentadentate Schiff Base Ligand

An erbium (III) complex of a pentadentate Schiff base ligand [(NO3)Er(μ-L)2Er(NO3)].2H2O [H2L=bis( N-salicylidene)-3-oxapentane-1,5-diamine] has been synthesised, characterised and its structure confirmed by X-ray crystallography. H2L and the Er(III) complex both bind to DNA via a groove binding mode, and the Er(III) complex binds to DNA more strongly than H2L. The complex shows strong scavenging effects for hydroxyl radicals (OH·) and superoxide radicals (O2-).

Experimental and theoretical approach of photophysical properties of lanthanum(III) and erbium(III) complexes of tris(methoxymethyl)-5-oxine podant

With the aim of evaluating the coordination behavior of a novel polydentate tripodal ligand, 5-[[3-[(8-hydroxy-5-quinolyl)methoxy]-2-[(8-hydroxy-5-quinolyl)methoxymethyl]-2-methyl propoxy]methyl]quinolin-8-ol (TMOM5OX), towards La(III) and Er(III) metal ions, the detailed investigations of photophysical properties by theoritical and experimental (potentiometric, UV–visible and fluorescence spectrophotometry) methods were carried out. TMOM5OX has been found to form protonated complex [Ln(H4L)]4+ (Ln=La or Er) below pH 3.8, which consecutively deprotonates through one-proton processes with rise of pH. The formation constants (logβ) of neutral complexes have been determined to be 36.42 (LaL) and 35.76, 37.62 (for ErL and ErL2, respectively) and the pLn (pLn=−log[Ln3+]) values of 24.6 and 27.1 for La(III) and Er(III) ions, respectively, calculated at pH 7.4, indicating TMOM5OX is a good lanthanide synthetic chelator. The absorption spectroscopy of these complexes show marked spectral variations due to characteristic lanthanide transitions, which support the use of TMOM5OX as a sensitive optical pH based sensor to detect Ln(III) metal ions in biological systems. In addition, these complexes have also been shown to exhibit strong green fluorescence allowing simultaneous sensing within the visible region under physiological pH in competitive medium for both La(III) and Er(III) ions. The intense fluorescence from these compounds were revealed to intermittently get quenched under acidic and basic conditions due to the photoinduced intramolecular electron transfer from excited 8-hydroxyquinoline (8-HQ) moiety to metal ion, just an opposite process. This renders these compounds the OFF–ON–OFF type of pH-dependent fluorescent sensors. The complexes coordination geometries were optimized using the sparkle/PM6 model and the theoretical spectrophotometric studies were carried out in order to validate the experimental findings, based on ZINDO/S methodology at configuration interaction with single excitations (CIS) level. These results clearly attest for the efficacy of the theoretical models employed in all calculations and create new interesting possibilities for the design in-silico of novel and highly efficient lanthanide–organic frameworks.

Semiempirical Quantum Chemistry Model for the Lanthanides: RM1 (Recife Model 1) Parameters for Dysprosium, Holmium and Erbium

Complexes of dysprosium, holmium, and erbium find many applications as single-molecule magnets, as contrast agents for magnetic resonance imaging, as anti-cancer agents, in optical telecommunications, etc. Therefore, the development of tools that can be proven helpful to complex design is presently an active area of research. In this article, we advance a major improvement to the semiempirical description of lanthanide complexes: the Recife Model 1, RM1, model for the lanthanides, parameterized for the trications of Dy, Ho, and Er. By representing such lanthanide in the RM1 calculation as a three-electron atom with a set of 5 d, 6 s, and 6 p semiempirical orbitals, the accuracy of the previous sparkle models, mainly concentrated on lanthanide-oxygen and lanthanide-nitrogen distances, is extended to other types of bonds in the trication complexes’ coordination polyhedra, such as lanthanide-carbon, lanthanide-chlorine, etc. This is even more important as, for example, lanthanide-carbon atom distances in the coordination polyhedra of the complexes comprise about 30% of all distances for all complexes of Dy, Ho, and Er considered. Our results indicate that the average unsigned mean error for the lanthanide-carbon distances dropped from an average of 0.30 Å, for the sparkle models, to 0.04 Å for the RM1 model for the lanthanides; for a total of 509 such distances for the set of all Dy, Ho, and Er complexes considered. A similar behavior took place for the other distances as well, such as lanthanide-chlorine, lanthanide-bromine, lanthanide, phosphorus and lanthanide-sulfur. Thus, the RM1 model for the lanthanides, being advanced in this article, broadens the range of application of semiempirical models to lanthanide complexes by including comprehensively many other types of bonds not adequately described by the previous models.

Active layer solution-processed NIR-OLEDs based on ternary erbium(III) complexes with 1,1,1-trifluoro-2,4-pentanedione and different N,N-donors.

Using a fluorinated 1,1,1-trifluoro-2,4-pentanedione (Htfac) ligand and either 2,2'-bipyridine (bipy), bathophenanthroline (bath) or 5-nitro-1,10-phenanthroline (5NO2phen) as an ancillary ligand, three new ternary erbium(iii) octacoordinated complexes have been synthesized. The single crystal structures of the new complexes (namely [Er(tfac)3(bipy)], [Er(tfac)3(bath)] and [Er(tfac)3(5NO2phen)]) have been determined and their properties have been investigated by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy and thermodynamic analysis. After ligand-mediated excitation of these complexes in the UV, they all show the characteristic near-infrared (NIR) luminescence of the corresponding Er(3+) ion at 1532 nm. The same emission in the C-band transmission window can also be obtained from the solution-processed organic light-emitting diodes (OLEDs) with structure: glass/ITO/PEDOT:PSS/[Er(tfac)3(N,N-donor)]/Ca/Al. In spite of the fact that the photoluminescence intensity of [Er(tfac)3(5NO2phen)] is stronger than those of [Er(tfac)3(bipy)] and [Er(tfac)3(bath)], the best electroluminescence results correspond to the OLED based on the [Er(tfac)3(bath)] complex, as a consequence of the superior electron transport capabilities of bathophenanthroline.

Effect of the capping ligand on luminescent erbium(iii) β-diketonate single-ion magnets

Erbium complexes featuring β-diketonate ligand 2,4-hexanedione (Hh) and N,N-donor-ligands 2,2'-bipyridine (bipy), 5-nitro-1,10-phenanthroline (5NO2phen) and bathophenanthroline (bath) have been synthesized. The structures of the ternary complexes [Er(h)3(bipy)], [Er(h)3(5NO2phen)] and [Er(h)3(bath)] have been determined by single crystal X-ray diffraction. Excitation of the complexes in the ultraviolet region (337 nm) led to near infrared (NIR) luminescence at 1532 nm characteristic of the trivalent erbium ion in the three compounds, with an improved antenna effect in the 5-nitro-1,10-phenanthroline complex. The AC susceptibility studies conducted at frequencies ranging from 33 to 9995 Hz and at temperatures in the 1.7 to 10 K range revealed that the application of a static magnetic field induces a slow magnetic relaxation in all three compounds. The complex with the bulkier capping ligand (bathophenanthroline) exhibits the highest energy barrier U/k(B) = 23 K.

Effect of Fluorination on the Radiative Properties of Er3+ Organic Complexes: An Opto-Structural Correlation Study

It is expected that fluorinated organic erbium(III) complexes, of interest for optical applications at λ = 1.5 μm, have improved performance with respect to hydrogenated counterparts. However, the intrinsic radiative properties (including the absorption/emission line strengths) of organic Er3+ complexes have not been systematically studied and compared up to date. This has precluded the observation of opto-structural correlations as well as a proper characterization of the infrared f-f transitions and thus a lack of meaningful figures for the optical efficiency of these materials at the 1.5 μm emission. We have performed a complete opto-structural correlation study of the oscillator strengths of the f-f transitions of hydrogenated and fluorinated organic erbium(III) complexes, including a Judd-Ofelt analysis. The Judd-Ofelt analysis on the crystals has allowed the study of the interdependence of the chemical nature, structure, and spectroscopic behavior. We observe clear trends that can help the design an...

A new near-IR luminescent erbium(III) complex with potential application in OLED devices

We report the synthesis and X-ray structural characterization of the new Er3+ ternary complex [Er(hd)3(bipy)] (where Hhd is 3,5-heptanedione and bipy is 2,2′-bipyridine) as well as its absorption/luminescent properties. X-ray analysis of the novel complex reveals its triclinic centrosymmetric structure with two symmetry independent complexes in the unit cell. Each lanthanide ion is surrounded by 6 oxygen atoms and 2 nitrogen atoms in a square antiprismatic geometry. The solid-state electronic absorption spectra and the luminescence spectrum show long-wavelength 4f–4f transitions which provide a potential use of the compound as a NIR emitting material in organic light-emitting devices (OLEDs).

Synthesis, spectroscopic, thermal and quantum chemical studies on trivalent erbium NO chelating sulfamonomethoxine–cyclophosph(V)azane complex

Novel hexachlorocyclophosph(V)azane of sulfamonomethoxine (L), was prepared and their coordinating behavior toward the lanthanide ion erbium (III) was studied. The structures of the isolated products were proposed based on elemental analyses, IR, UV–VIS, 1H NMR, 31P NMR, SEM, TEM, XRD, mass spectra, effective magnetic susceptibility measurements and thermogravimetric analysis (TGA). The coordination polyhedra of the eight donor atoms around the two erbium (III) ions are best described as distorted dodecahedral. Computational studies were carried out at the DFT-B3LYP/6-31G(d) level of theory on the structural and spectroscopic properties of L and its binuclear erbium (III) complex. Different tautomers of the ligand were optimized at the ab initio DFT level. Keto-form structure is about 30.5kcal/mol more stable than the enol form (taking zpe correction into account). Simulated IR frequencies were scaled and compared with that experimentally measured. TD-DFT method was used to compute the UV–VIS spectra in gas phase and DMF.

Lanthanides as NMR Probes of Fast Molecular Dynamics at High Magnetic Fields and Temperature Sensors: Conformational Interconversion of Erbium Ethylenediaminetetraacetate Complexes

(1)H NMR measurements are reported for D2O solutions of paramagnetic complex [Er(H2O)(EDTA(4-))](-) (I) for temperature interval 273-319 K. Diamagnetic complex [Lu(H2O)(EDTA(4-))](-) (II) was used as an NMR reference compound. The spectra obtained have been analyzed using a band-shape analysis technique in the framework of dynamic NMR (DNMR) taking into account the temperature dependence of lanthanide-induced shifts. Intramolecular dynamics in I was assigned to the interconversion of Δ-λE-δδδδ and Δ-δE-δδδδ conformers with estimated activation free energy ΔG(‡)(298 K) = 50 ± 4 kJ/mol. The methodology of paramagnetic 4f-element probe applications on the example of Er(3+) for the study of free-energy changes in chemical exchange processes, as well as the advantages of this method in comparison with DNMR studies of diamagnetic substances, is discussed. In accordance with the literature reviewed, the fulfilled experimental study is the first example of intramolecular dynamics determination for erbium complexes. An additional advantage of the investigation is in the approach proposed which extends the range of measurement of the NMR rate constants for paramagnetic 4f-element complexes compared to diamagnetic ones. Coordination compounds investigated represent a new type of thermometric NMR sensors and lanthanide paramagnetic probes for in situ temperature control in solutions.

Synthesis and Characterization of Paramagnetic Lanthanide Benzyl Complexes

The organometallic chemistry of paramagnetic lanthanides (Ln, from Ce to Yb) is far less developed compared to that of their diamagnetic counterparts (Sc, Y, La, and Lu). Lack of available starting materials and characterization methods are the major obstacles. Herein we report the synthesis and characterization of trisbenzyl complexes of neodymium, gadolinium, holmium, and erbium. In addition, we introduce a direct procedure for the synthesis of lanthanide benzyl and iodide complexes supported by a ferrocene diamide ligand starting from the corresponding oxides. All newly synthesized compounds were characterized by X-ray crystallography, 1H NMR spectroscopy (except for gadolinium compounds, which were NMR silent), and elemental analysis.

Fast uptake, water-soluble, mitochondria-specific erbium complex for a dual function molecular probe – imaging and photodynamic therapy

A water-soluble, mitochondria-permeable erbium(III) complex has been designed as a responsive bi-functional probe. This may be used to induce the mild formation of singlet oxygen (ΦΔ = 0.10) and causes local damage in cellulo when exposed to UV and near-infrared laser excitation.

Novel erbium(iii) complexes with 2,6-dimethyl-3,5-heptanedione and different N,N-donor ligands for ormosil and PMMA matrices doping

Three novel complexes, [Er(dmh)3(bipy)], [Er(dmh)3bath] and [Er(dmh)3(5NO2phen)], with 2,6-dimethyl-3,5-heptanedione (Hdmh) as the main sensitizer and either 2,2′-bipyridine (bipy), bathophenanthroline (bath) or 5-nitro-1,10-phenanthroline (5NO2phen) as synergistic ligands were synthesized. Upon excitation at the maximum absorption of the ligands, the complexes show the characteristic near-infrared (NIR) luminescence of the Er3+ ions, due to efficient energy transfer from the ligands to the central Er3+ ion via the antenna effect. Single crystals were grown and their structures were determined showing different Er–N distances. The compound with shorter Er–N distances, [Er(dmh)3(5NO2phen)], was found to be the best light harvester and the best for transferring the energy to the lanthanide among the three studied compounds. Finally, the novel complexes have been assessed for their application in sol–gel and polymer-based waveguides and optical amplifiers through their inclusion into ormosil and polymethylmethacrylate matrices. The dispersion was successful in the bipy and 5NO2phen cases, with the properties of the hybrid materials mimicking those of the pure complexes.

Dehydrogenation of secondary amines: synthesis, and characterization of rare-earth metal complexes incorporating imino- or amido-functionalized pyrrolyl ligands

The dehydrogenation of pyrrolyl-functionalized secondary amines initiated by rare-earth metal amides was systematically studied. Reactions of the rare-earth metal amides [(Me(3)Si)(2)N](3)RE(μ-Cl)Li(THF)(3) with pyrrolyl-functionalized secondary amines 2-(t)BuNHCH(2)-5-R-C(4)H(2)NH (R = H (1), R = (t)Bu (2)) led to dehydrogenation of the secondary amines with isolation of imino-functionalized pyrrolyl rare-earth metal complexes [2-(t)BuN=CH-5-R-C(4)H(2)N](2)REN(SiMe(3))(2) (R = H, RE = Y (3a), Dy (3b), Yb (3c), Eu (3d); R = (t)Bu, RE = Y (4a), Dy (4b), Er (4c)). The mixed ligands erbium complex [2-(t)BuNCH(2)-5-(t)Bu-C(4)H(2)N]Er[2-(t)BuN=CH-5-(t)BuC(4)H(2)N](2)ClLi(2)(THF) (4c') was isolated in a short reaction time for the synthesis of complex 4c. Reaction of the deuterated pyrrolyl-functionalized secondary amine 2-((t)BuNHCHD)C(4)H(3)NH with yttrium amide [(Me(3)Si)(2)N](3)Y(μ-Cl)Li(THF)(3) further proved that pyrrolyl-amino ligands were transferred to pyrrolyl-imino ligands. Treatment of 2-((t)BuNHCH(2))C(4)H(3)NH (1) with excess (Me(3)Si)(2)NLi gave the only pyrrole deprotonated product {[η(5):η(2):η(1)-2-((t)BuNHCH(2))C(4)H(3)N]Li(2)N(SiMe(3))(2)}(2) (5), indicating that LiN(SiMe(3))(2) could not dehydrogenate the secondary amines to imines and rare-earth metal ions had a decisive effect on the dehydrogenation. The reaction of the rare-earth metal amides [(Me(3)Si)(2)N](3)RE(μ-Cl)Li(THF)(3) with 1 equiv. of more bulky pyrrolyl-functionalized secondary amine 2-[(2,6-(i)Pr(2)C(6)H(3))NHCH(2)](C(4)H(3)NH) (6) in toluene afforded the only amine and pyrrole deprotonated dinuclear rare-earth metal amido complexes {(μ-η(5):η(1)):η(1)-2-[(2,6-(i)Pr(2)C(6)H(3))NCH(2)]C(4)H(3)N]LnN(SiMe(3))(2)}(2) (RE = Nd (7a), Sm (7b), Er (7c)), no dehydrogenation of secondary amine to imine products were observed. On the basis of experimental results, a plausible mechanism for the dehydrogenation of secondary amines to imines was proposed.

Quenching effect of C-H bond in long lived NIR luminescent erbium complexes

AbstractErbium excited state deactivation is studied for two fluorinated complexes based on N-(P,P-ditetrafluorophosphinoyl-P,P-ditetrafluorophenyl phosphinimidates and N-(P,P-dipentafluoro phosphinoyl)-P,P-dipentafluorophenyl phosphinimidates ligands. We show that the substitution of a fluorine atom in para-position by an hydrogen atom on each phenyl ring of the perfluorinated organic ligand results in a decrease in near infrared luminescence lifetimes from 800 µs to 70 µs when measured under vacuum on sublimated powder samples. These experiments show that the introduction of C-H bonds, although outside the first coordination sphere of the erbium ion, can still induce a one order of magnitude decrease in its excited state lifetime. The found lifetime however is still longer than most reported partially fluorinated complexes, which opens the way for new functionalized complexes.

Encapsulation of Erbium(III) and Thulium(III) Nanocomplexes Containing 18- and 20-Membered Dioxa Tetraaza Macryclic Ligands Within the Framework of Zeolite

AbstractZeolite framework stabilized erbium(III) and thulium(III) complex nanoparticles was prepared for the first time by using a two step procedure: the ion exchange of Ln3+ (Ln: Er and Tm) with the extra framework Na+ ions in zeolite-Y, the template synthesis of 2,6-diformyl-4-methylphenol with different diamines. Analysis of the data indicated that the Ln(III) complexes has been encapsulated within the nanocavity of zeolite Y and exhibit different property from those of the free complexes, which can arise from distortions caused by steric effects due to the presence of sodium cations, or from interactions with the zeolite matrix.

Syntheses and Characterization of Samarium and Erbium Borohydrido Complexes Supported by N‐Aryliminopyrrole Ligand

AbstractReaction of potassium salt of N‐aryliminopyrrole ligand [2‐(2, 6‐iPr2C6H3N=CH)–C4H3NK] (1) with samarium tris‐boro‐hydride [Sm(BH4)3(THF)3] gave a samarium ate complex [η2‐{2‐(2, 6‐iPr2C6H3N=CH)–C4H3N}3Sm(η1‐BH4){K(THF)6] (2); whereas similar treatment with erbium borohydride [Er(BH4)3(THF)3] afforded the mono(iminopyrrolyl) complex [η2‐{2‐(2, 6‐iPr2C6H3N=CH)–C4H3N}Er(η3‐BH4)2(THF)2] (3). In the solid‐state structures, the samarium complex 2 shows a rarely observed η1 and the erbium complex 3 shows a usual η3 coordination mode of the borohydrido ligand.

Simultaneous Patterning of Independent Metal/Metal Oxide Multi-Layer Films Using Two-Tone Photo-Acid Generating Compound Systems.

(1) The photo-induced solubility and positive-tone direct photo-patterning of iron, copper and lanthanides chelated with 4-(2-nitrobenzyloxycarbonyl)catechol (NBOC) or 4-(6-nitroveratryloxycarbonyl)catechol (NVOC) was investigated. Photo-patterning of iron, copper, cerium, samarium, europium, terbium, dysprosium, holmium, erbium and lutetium complexes was accomplished. Continuous films were formed by the pyrolysis of metal complex films at 500 °C. (2) Based on the difference in the photo-reaction excitation wavelength profile of NBOC and NVOC complexes, a short and simple method for simultaneous micro-patterning of two independent films on each side of a transparent glass substrate was developed. Using the developed procedure, indium tin oxide and/or titanium oxide films were formed on each side of a quartz substrate without use of resist or etching.

Preparation and Physical Properties of Erbium-Doped Polymer Patterns by Micromolding in Capillaries for Optical Waveguide Amplifiers

Er3+-doped precursor solutions were first prepared using 2,2,3,3,4,4,5,5-octafluoropentyl acrylate as a fluoromonomer, tetrahydrofurfuryl acrylate as a solubility enhancer, Ebecryl 220 as a cross-linking agent, Darocur 4265 as a radical photoinitiator and erbium(III) trifluoromethane sulfonate as an erbium source with various weight ratios. The crosslinked, patterned and erbium-doped fluoropolymer films were fabricated by micromolding in capillaries on glass substrates for planar optical amplifier applications. The fluoropolymer films acting as host materials for the Er3+ ions had excellent transmission properties (more than 90% over the visible and near-infrared regions), high thermal decomposition temperatures (greater than 300°C) and the ability to support high erbium complex concentrations (up to 10 wt% based on the polymer matrix). These results are sufficient for the films to be used in planar optical amplifier applications.

Dinuclear lanthanide(III) complexes with large-bite Schiff bases derived from 2,6-diformyl-4-chlorophenol and hydrazides: Synthesis, structural characterization and spectroscopic studies

Two Schiff bases (H3L1 and H5L2), derived from 2,6-diformyl-4-chlorophenol and hydrazides, and their complexes with some lanthanides (Y, La, Nd, Sm, Dy and Er) have been synthesized. These compounds have been characterized by means of elemental analysis, UV–Vis spectroscopy, IR spectroscopy, 1H and 13C NMR (for the organic ligands), molar conductance and room temperature magnetic measurements. Single crystal X-ray analysis of the two complexes [La2(H2L1)3(C2H5OH)2]·(Cl)·(NO3)2·((CH3)2CO)2·(H2O)2 (1) and [Er2(H4L2)3]·(SCN)3·(H2O) (8) has revealed the nature of the structures; the lanthanide(III) ions are intramolecularly bridged by three phenolic oxygen atoms, forming a dinuclear complex. The lanthanum atom is ten-coordinated, while the erbium atom is nine-coordinated. The coordination polyhedron of the erbium complex is best described as a tricapped trigonal prism.