Sensitization of Ho III and Sm III luminescence by efficient energy transfer from antenna ligands: Magnetic, visible and NIR photoluminescence properties of Gd III , Ho III and Sm III coordination polymers

Red-emitting β-diketonate Eu(III) Complexes With Substituted 1,10-phenanthroline Derivatives: Optoelectronic and Spectroscopic Analysis

A series of europium diketonate complexes with 1-phenyl-1,3-butanedione (PBD) and 1,10-phenanthroline derivatives were synthesized and explored spectroscopically. Photophysical characteristics of synthesized complexes have been investigated experimentally as well as theoretically. Photoluminescence emission spectra of complexes do not contain any peak of ligand revealing efficient transferal of energy from ligand to Eu³⁺ ion. Presence of peak at 611 nm corresponding to ⁵D₀ → ⁷F₂ transition is responsible for red emanation of ternary europium complexes. Photophysical parameters viz., Judd-Ofelt, quantum efficiency, radiative and non radiative decay rates were also estimated theoretically from LUMPAC software. Geometry optimization of complexes was done via Avogadro software. All synthesized trivalent complexes exhibit red emission which was further sustained by the position of chromaticity coordinates in CIE triangle. These red emanating materials could be utilized in designing electroluminescent display devices.

Magnetic and Luminescence Properties of 8-Coordinate Holmium(III) Complexes Containing 4,4,4-Trifluoro-1-Phenyl- and 1-(Naphthalen-2-yl)-1,3-Butanedionates

A new series of mononuclear Ho³⁺ complexes derived from the β-diketonate anions: 4,4,4-trifluoro-1-phenyl-1,3-butanedioneate (btfa⁻) and 4,4,4-trifuoro-1-(naphthalen-2-yl)-1,3-butanedionate (ntfa⁻) have been synthesized, [Ho(btfa)₃(H₂O)₂] (1a), [Ho(ntfa)₃(MeOH)₂] (1b), (1), [Ho(btfa)₃(phen)] (2), [Ho(btfa)₃(bipy)] (3), [Ho(btfa)₃(di-^tbubipy)] (4), [Ho(ntfa)₃(Me₂bipy)] (5), and [Ho(ntfa)₃(bipy)] (6), where phen is 1,10-phenantroline, bipy is 2,2′-bipyridyl, di-^tbubipy is 4,4′-di-tert-butyl-2,2′-bipyridyl, and Me₂bipy is 4,4′-dimethyl-2,2′-bipyridyl. These compounds have been characterized by elemental microanalysis and infrared spectroscopy as well as single-crystal X-ray difraction for 2–6. The central Ho³⁺ ions in these compounds display coordination number 8. The luminescence-emission properties of the pyridyl adducts 2–6 display a strong characteristic band in the visible region at 661 nm and a series of bands in the NIR region (excitation wavelengths (λ_ex) of 367 nm for 2–4 and 380 nm for 5 and 6). The magnetic properties of the complexes revealed magnetically uncoupled Ho³⁺ compounds with no field-induced, single-molecule magnet (SMMs).

Variable Luminescence and Chromaticity of Homoleptic Frameworks of the Lanthanides together with Pyridylpyrazolates

Homoleptic, 3D coordination polymers of the formula ³³ _∞ [Ln(3-PyPz)₃ ] and ³ _∞ [Ln(4-PyPz)₃ ], (3-PyPz)^- =3-(3-pyridyl)pyrazolate anion, (4-PyPz)^- =3-(4-pyridyl)pyrazolate anion, both C₈ H₆ N₃ ^- , Ln=Sm, Eu, Gd, Tb, Dy, were obtained as highly luminescent frameworks by reaction of the lanthanide metals (Ln) with the aromatic heterocyclic amine ligands 3-PyPzH and 4-PyPzH. The compounds form two isotypic series of 3D coordination polymers and exhibit fair thermal stability up to 360 °C. The luminescence properties of all ten compounds were determined in the solid state, with an antenna effect through ligand-metal energy transfer leading to high efficiency of the luminescence displayed by good quantum yields of up to 74 %. The emission is mainly based on ion-specific lanthanide-dependent intra 4 f-4 f transitions for Tb³⁺ : green, Dy³⁺ : yellow, Sm³⁺ : orange-red, Eu³⁺ : red. For the Gd³⁺ -containing compounds, the yellow emission of ligand triplet-based phosphorescence is observed at room temperature and 77 K. Co doping of the Gd-containing frameworks with Eu³⁺ and Tb³⁺ allow further shifting of the chromaticity towards white light emission.

Lanthanide clusters of phenanthroline containing a pyridine-pyrazole based ligand: magnetism and cell imaging

In this contribution, we report the synthesis, characterization and luminescence-magnetic properties of Ln-clusters (Ln = Gd3+, Eu3+ and Tb3+) using a new pyridine-pyrazole functionalized ligand fitted with a chromophoric phenanthroline backbone. The unorthodox N-rich ligand forms isostructural trinuclear lanthanide complexes with a topology that closely resembles two interdigitating hairpins. The clusters crystallize in chiral space groups and also exhibit chirality for bulk samples, which were further confirmed using solid state CD spectra. Magnetic studies on the complexes reveal their interesting features while the Gd cluster shows a significant cryogenic magnetic cooling behaviour with a moderately high magnetic entropy change of -23.42 J kg-1 K-1 at 7 T and 2 K. On the other hand, Eu and Tb complexes exhibit interesting fluorescence properties. The compounds were subsequently used as fluorescent probes for the imaging of human breast adenocarcinoma (MCF7) cells. Live cell confocal microscopy images show that the complexes penetrate beyond the usual cytoplasm region and can be useful in imaging the nucleus region of MCF7 cells.

Synthesis, structure, photophysical properties, and energy transfer mechanism of an erbium–mercury compound

A hydrothermal reaction leads to the formation of a novel erbium–mercury compound [Er(IA)3(H3O)(H2O)] n(0.5 nHg2I6) (1) (HIA = isonicotinic acid). The compound has been characterized by single-crystal X-ray diffraction. It is characteristic of a one-dimensional chain-like structure and a two-dimensional supramolecular layer. A solid-state photoluminescence experiment reveals that this compound displays upconversion green photoluminescence. The photoluminescence emission peaks can be attributed to the 4 G11/2 → 4 I15/2, 4 F7/2 → 4 I15/2, and 2 H11/2 → 4 I15/2 of the Er3+ ions. The energy transfer mechanism is consistent with the energy-level diagrams of the erbium ions and isonicotinic acid ligand. This compound possesses Commission Internationale de I'Éclairage chromaticity coordinates of 0.1755 and 0.5213. A solid-state diffuse reflectance measurement reveals that this compound features a narrow optical band gap of 1.97 eV.

Photophysical properties and energy transfer mechanism of a praseodymium compound with a two-dimensional layer

A hydrothermal reaction results in the formation of a novel [Pr2(2,5-PA)2(2,5-HPA)2(H2O)4] n·2 nH2O complex (2,5-H2PA = 2,5-pyridinedicarboxylic acid). The complex is structurally characterized by single-crystal X-ray diffraction and crystallizes in the space group P21 of the monoclinic system with two formula units in one cell. This praseodymium complex is characterized by a two-dimensional layered structure. A solid-state photoluminescence experiment reveals that the praseodymium complex shows an emission in the red region. The complex has Commission Internationale de I’Éclairage chromaticity coordinates of 0.5495 and 0.4492. The photoluminescence emission bands could be assigned to the characteristic emission of the 4 f electron intrashell transition of the 3 P0 → 3 H5, 1 D2 → 3 H4, 3 P0 → 3 H6, 3 P0 → 3 F2, and 3 P1 → 3 F3 of the Pr3+ ions. The energy transfer mechanism is explained by the energy level diagrams of the praseodymium ions and the 2,5-H2PA ligand. A solid-state diffuse reflectance measurement shows that the complex possesses a wide optical band gap of 3.48 eV.

Eu@PMMA and Sm@PMMA nanofibers prepared by electrospinning: structure, morphology, luminescence and magnetic properties

Eu³⁺ and Sm³⁺ coordination polymers and a series of Eu@PMMA and Sm@PMMA nanofibers were prepared. Color tunability was achieved with the luminescence changing from reddish orange in the bulk state to near-white light in the nanofiber stage.

Lanthanide complexes based on a conjugated pyridine carboxylate ligand: structures, luminescence and magnetic properties

Three lanthanide compounds have been synthesized, namely, {[Dy₂(bpda)₃(H₂O)₃]₄·2H₂O}(Dy-1), {[Sm(bpda)₂·(H₂O)]·H₂O}_n (Sm-2) and {[Tb₂(bpda)₃(H₂O)₃]₄·2H₂O} (Tb-3) (H₂bpda = 2,2′-bipyridine-6,6′-dicarboxylic acid). Their structures were determined by single crystal X-ray diffraction and characterized by elemental analysis, infrared spectroscopy and thermogravimetric analysis. Dy-1 and Tb-3 are isostructural with a conjugate bimolecular four-nuclear cluster structure constructed with intramolecular hydrogen bonds and they form a 3D supramolecular structure with intermolecular hydrogen bonding. Sm-2 is a one-dimensional chain structure and is further connected by intricate hydrogen bonds into a three-dimensional supramolecular structure. These three compounds exhibit significant characteristic luminescence from the ligand to the central Ln(iii) ion, which is found by solid-state photoluminescence measurement. Sm-2 exhibits a long luminescence lifetime and high fluorescence quantum yield. A slow relaxation phenomenon is observed for the dysprosium compound by measuring the alternating-current susceptibility at low temperature and the underlying mechanism was further confirmed by theoretical calculations.

The structures, fluorescence and magnetic properties of series three lanthanide complexes have been investigated. Dysprosium complex exhibit the single-molecule behavior.

Misconceptions in electronic energy transfer: bridging the gap between chemistry and physics

Many treatments of energy transfer (ET) phenomena in current literature employ incorrect arguments and formulae and are not quantitative enough. This is unfortunate because we witness important breakthroughs from ET experiments in nanoscience. This review aims to clarify basic principles by focusing upon Förster-Dexter electric dipole-electric dipole (ED-ED) ET. The roles of ET in upconversion, downconversion and the antenna effect are described and the clichés and simple formulae to be avoided in ET studies are highlighted with alternative treatments provided.

Spectroscopic investigation and DFT modelling studies of Eu3+ complex with 1-(2,6-dihydroxyphenyl)ethanone

Eu³⁺ complex with 1-(2,6-dihydroxyphenyl)ethanone in the solid state has been synthesized and characterized by elemental analysis, UV-visible, FT-IR and FT-Raman spectroscopies, powder X-ray diffraction, electron emission under femtosecond laser excitation. The stoichiometry and the formula of the studied complex have been proposed. Its physicochemical properties have been analyzed in terms of the structure and DFT calculations performed for the ligand. The luminescence and dynamics of the excited states depopulation have been studied using femtosecond laser excitation. Spectral and energetic transformation of femtosecond light impulses has been studied and possibility of the energy transfer between the ligand and the Eu³⁺ electron levels has been analyzed.

Four Salamo-type 3d–4f hetero-bimetallic [ZnIILnIII] complexes: syntheses, crystal structures, and luminescent and magnetic properties

A series of [Zn^IILn^III] complexes (Ln = Sm, Eu, Tb and Dy) are synthesized by Salamo-type ligand H₂L. Only [Zn^IISm^III] shows the characteristic transitions of Sm³⁺ ion, indicating the effective energy transfer between the ligand and Sm³⁺ ion.