Luminescent lanthanide ions hosted in a fluorescent polylysin dendrimer. Antenna-like sensitization of visible and near-infrared emission

Terpyridyl-Imidazole Based Ligand Coordinated to Ln(Hexafluoroacetyl acetonate)3 Core: Synthesis, Structural Characterization, Luminescence Properties, and Thermosensing Behaviors in Solution and PMMA Film

A new array of ternary lanthanide complexes of the form [Ln(hfa)3(tpy-HImzphen)] have been synthesized and thoroughly characterized wherein Ln = LaIII (1), EuIII (2), SmIII (3), and TbIII (4); hfa = hexafluoroacetylacetonate; and tpy-HImzphen = 2-(4-[2,2':6',2″]terpyridin-4'-yl-phenyl)-1H-phenanthro[9,10-d]imidazole. Incorporation of tpy-HImzphen onto the Ln-hfa moiety induced a bathochromic shift of the absorption window of the complexes into the visible region. Extensive investigations of the luminescence characteristics have been conducted both at RT and at 77 K to understand the deactivation pathways of the complexes. Both steady-state and time-resolved emission spectral behaviors indicate four distinctive behaviors upon incorporation of tpy-HImzphen onto the lanthanide core, viz., a huge red-shift of the ligand-centered peak for LaIII; almost complete energy transfer for EuIII; very little energy transfer for SmIII, while reverse energy transfer in the case of TbIII. In addition, the EuIII-complex exhibits its excellence in luminescence thermometry in the solution state as well as in poly(methyl methacrylate) (PMMA) thin films. The thermosensitive luminescence response in solution was further utilized to mimic set-reset flip-flop logic operation. A plausible energy transfer scheme has been devised to explain dissimilar luminescence behaviors in the complexes. The role of LMCT was also considered for the observed thermosensing property of the Eu(III) complex.

Finely manipulating room temperature phosphorescence by dynamic lanthanide coordination toward multi-level information security

Room temperature phosphorescence materials have garnered significant attention due to their unique optical properties and promising applications. However, it remains a great challenge to finely manipulate phosphorescent properties to achieve desirable phosphorescent performance on demand. Here, we show a feasible strategy to finely manipulate organic phosphorescent performance by introducing dynamic lanthanide coordination. The organic phosphors of terpyridine phenylboronic acids possessing excellent coordination ability are covalently embedded into a polyvinyl alcohol matrix, leading to ultralong organic room temperature phosphorescence with a lifetime of up to 0.629 s. Notably, such phosphorescent performance, including intensity and lifetime, can be well controlled by varying the lanthanide dopant. Relying on the excellent modulable performance of these lanthanide-manipulated phosphorescence films, multi-level information encryption including attacker-misleading and spatial-time-resolved applications is successfully demonstrated with greatly improved security level. This work opens an avenue for finely manipulating phosphorescent properties to meet versatile uses in optical applications.

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.

Functional Copolymers Married with Lanthanide(III) Ions: A Win-Win Pathway to Fabricate Rare Earth Fluorescent Materials with Multiple Applications

Lanthanide(III)-based luminescent materials have attracted great research interests due to their unique optical, electronic, and chemical characteristics. Up to now, how to extend these materials into large, broad application fields is still a great challenging task. In this contribution, we are intended to present a simple but facile strategy to enhance the luminescence from lanthanide ions and impart lanthanide(III)-based luminescent materials with more applicable properties, leading to meet the requirements from different purposes, such as being used as highly emissive powders, hydrogels, films, and sensitive probes under external stimuli. Herein, a water soluble, blue color emissive, temperature sensitive, and film-processable copolymer (Poly-ligand) was designed and synthesized. Upon complexing with Eu³⁺ and Tb³⁺ ions, the red color-emitting Poly-ligand-Eu and green color-emitting Poly-ligand-Tb were produced. After finely tuning the ratios between them, a standard white color emitting Poly-ligand-Eu₁:Tb₄ (CIE = 0.33 and 0.33) was obtained. Furthermore, the resulted materials not only possessed the emissive luminescent property but also inherited functions from the copolymer of Poly-ligand. Thus, these lanthanide(III)-based materials were used for fingerprint imaging, luminescent soft matters formation, colorful organic light-emitting diode device fabrication, and acid/alkali vapors detection.

A Series of Lanthanide-Based Metal-Organic Frameworks Derived from Furan-2,5-dicarboxylate and Glutarate: Structure-Corroborated Density Functional Theory Study, Magnetocaloric Effect, Slow Relaxation of Magnetization, and Luminescent Properties

Herein, through a dual-ligand strategy, we report eight isorecticular lanthanide(III) furan-2,5-dicarboxylic acid metal-organic frameworks (Ln-MOFs) with the general formula {[Ln(2,5-FDA)_0.5(Glu)(H₂O)₂]· xH₂O} _n [Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5), Ho (6), Er (7), and Yb (8); 2,5-FDA^2- = furan-2,5-dicarboxylate and Glu^2- = glutarate; x = 0.5 for 1, 2, and 4 and x = 0 for 3 and 5-8], synthesized under solvothermal conditions by using an N, N'-dimethylformamide/H₂O mixed solvent system. Crystallographic data reveal that all eight Ln-MOFs 1-8 crystallize in the orthorhombic Pnma space group. All of the MOFs are isostructural as well as isomorphous with distorted monocapped square-antiprismatic geometry around the Ln1 metal center. In Ln-MOFs 1-8, the 2,5-FDA^2- and Glu^2- ligands exhibit μ₂-κ⁴,η¹:η¹:η¹:η¹ and μ₃-κ⁵,η²:η¹:η¹:η¹ coordination modes, respectively. Topologically, assembled Ln-MOFs 1-8 consist of the 2D cem topological type. The designed Ln-MOFs 1-8 are further explored for structure-corroborated density functional theory study. Meanwhile, room temperature photoluminescence properties of Ln-MOFs 2 and 4 and magnetic properties of Ln-MOFs 3 and 5 have been explored in detail. A highly intense, ligand-sensitized, Ln³⁺ f-f photoluminescence emission is exhibited by Ln-MOFs 2 [Eu³⁺ (red emission)] and 4 [Tb³⁺ (green emission)]. Magnetic studies suggest weak antiferro- and ferromagnetic interactions between adjacent Gd^III ions in Ln-MOF 3, thereby displaying a large magnetocaloric effect. The magnetic data measured at T = 2 K and Δ H = 30 kOe depict that the -Δ S_m value per unit mass reaches 32.1 J kg^-1 K^-1, which is larger than most of the Gd^III-based complexes reported. The alternating-current susceptibility measurements on Ln-MOF 5 revealed that out-of-phase signals are frequency- and temperature-dependent under both 0 and 2 kOe direct-current fields, thereby suggesting a typical slow magnetic relaxation behavior with two relaxation processes. This is further supported by the Cole-Cole plots at 2.4-6 K.

2,5-Furandicarboxylic acid as a linker for lanthanide coordination polymers: the role of heteroaromatic π–π stacking and hydrogen bonding

Heteroaromatic carboxylate ligands are very intriguing components of coordination assemblies such as coordination polymers (CPs) due to their inherently multitopic structures.

Aggregation of [LnIII12] clusters by the dianion of 3-formylsalicylic acid. Synthesis, crystal structures, magnetic and luminescence properties

Three different lanthanides (Eu^III, Gd^III, Dy^III) have been used to generate [Ln₁₂] clusters with specific optical and magnetic properties.

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.

Luminescence and white-light emitting luminescent sensor of tetrafluoroterephthalate-lanthanide metal–organic frameworks

H₂TFBDC lanthanide complexes emitting white light was synthesized and a luminescent sensor for the detection of benzaldehyde has been produced.

Photochromic RAFT reagent helps construct superior photoswitchable fluorescent polymer nanoparticles for rewritable fluorescence patterning and intracellular dual-color imaging

Photoswitchable fluorescent polymeric nanoparticles with photochromic RAFT chain transfer reagent were synthesized for rewritable fluorescence patterning and intracellular dual color imaging.

Single-component Eu3+–Tb3+–Gd3+-grafted polymer with ultra-high color rendering index white-light emission

Color-tuning to white-light (CIE coordinates of x = 0.322, y = 0.331; CCT of 5979 K; ultra-high CRI of 94) with a highly luminous efficiency (17.8%) was achieved for single-component Eu³⁺−Tb³⁺−Gd³⁺-grafted polymer Poly(MMA-co-2-co-3-co-4).

Bismuth Complexes in Phenylazomethine Dendrimers: Controllable Luminescence and Emission in the Solid State

Dendritic phosphors were obtained by the stepwise integration of BiCl₃ in phenylazomethine dendrimers. The bismuth-coordinated phenylazomethines displayed photoluminescence at 500-800 nm, and the intensity could be tuned by changing the stoichiometry of BiCl₃ and the dendrimer. This phosphor did not show serious luminescence quenching even though the local concentration of BiCl₃ in the dendrimer was as high as 20 M, and luminescence was also observed in the solid state. The absorption and emission properties could be reversibly switched by addition of a Lewis base or under electrochemical redox control, which induced the reversible complexation of BiCl₃ in the dendrimer.

Insight into the roles of structures and energy levels of mono- and bis-β-diketones on sensitizing Nd(iii) NIR-luminescence

Three neodymium complexes Nd(TTA)3(DMSO)2 (1, TTA = 2-thenoyltrifluoroacetone), Nd2(BDT)3(DMSO)6 (2, BDT = bis(4,4,4-trifluoro-1,3-dioxobutyl)thiophene) and Nd2(BTT)3(DMSO)4 (3, BTT = bis(4,4,4-trifluoro-1,3-dioxobutyl)(2,2'-bithiophene)) constructed from three thiophene-based β-diketonate ligands, were prepared for the purpose of building the relationships between the structures, energy levels of the complexes and NIR luminescence properties of Nd(iii) ions. X-ray crystallographical analysis reveals that complex 1 is a mononuclear structure, the central Nd(iii) ion is coordinated by eight oxygen atoms from three mono-β-diketones (TTA) and two DMSO, whereas, complexes 2 and 3 adopt triple-stranded dinuclear structures, in which the two Nd(iii) ions are wrapped by three bis-β-diketones, the central Nd(iii) ions are nine and eight coordinated by oxygen atoms from ligands and the coordinated DMSO molecules. The photophysical properties related to the electronic transition are characterized by the absorbance spectra, the excitation spectra, the phosphorescence spectra, the emission spectra, the emission quantum yields, and the emission lifetimes. The luminescence quantum yields experiment reveals that the dinuclear complexes (0.49% and 0.33% for 2 and 3) show higher luminescence efficiencies compared to the mononuclear complex 1 (0.22%). This enhancement is mainly attributed to their binuclear structures, which effectively represses the nonradiative transition caused by high-energy oscillators in ligands and/or solvents. On the other hand, the energy level matching also plays an important role in this enhancement.

Synthesis and properties of peptide dendrimers containing fluorescent and branched amino acids

In this report, we describe dendritic peptides possessing central fluorescent amino acids with adjacent branched amino acids. These fluorescent-peptide dendrimers were prepared using (9-fluorenyl)methoxycarbonyl (Fmoc)-based solid-phase peptide synthesis and Fmoc-derivative fluorescent and branched amino acids. The branched amino acids featured multiple carboxylic acids in their side chains, making the fluorescent-peptide dendrimers highly water-soluble compared with the analogous peptides containing the fluorescent amino acids only. The branched amino acid units also improved the fluorescence intensity of the dendrimers. Based on high-pressure liquid chromatography and fluorescence spectroscopy results, we determined that the fluorescent groups were located in the core and that the carboxylic acids were located on the surface of the dendrimers. Fluorescence resonance energy transfer was achieved among the three proximal fluorescent groups in one of the fabricated fluorescent-peptide dendrimers.

Pure white-light and colour-tuning of Eu3+–Gd3+-containing metallopolymer

The first example of Eu³⁺–Gd³⁺-containing metallopolymer Poly(2-co-NVK-co-4) was constructed to exhibit tunable photoluminescence and even direct white-light emission.

Spectroscopic studies of lanthanide complexes of varying nuclearity based on a compartmentalised ligand

Spectroscopic studies of lanthanide-based coordination compounds of varying nuclearity with a compartmental ligand which show NIR luminescence.

Self-assembly of Terbium(III)-based metal-organic complexes with two-photon absorbing active

Hybrid complexes based on D-π-A type dyes p-aminostyryl-pyridinum and Terbium(III) complex anion (1, 2) have been synthesized by ionic exchange reaction. Meanwhile two different alkyl-substituted amino groups were used as electron donors in organic dyes cations. The synthesized complexes were characterized by element analysis. In addition, the structural features of them were systematic studied by single crystal X-ray diffraction analysis. Their linear properties have been systematically investigated by absorption spectra and fluorescence, the results show that the energy transfer takes place from the trans-4-[4'-(N,N-diethylamino)styryl]-N-methyl pyridinium (2') cation to Tb(III). In addition, complex 2 exhibit a large two-photon absorption coefficient β: 0.044cm/GW at 710nm.

Hybrid lanthanide complexes based on a novel β-diketone functionalized polyhedral oligomeric silsesquioxane (POSS) and their nanocomposites with PMMA via in situ polymerization

β-diketone-functionalized POSS dendrimer acted as a ligand to coordinate with lanthanide ions (Eu³⁺ and Tb³⁺) to form hybrid luminescent materials.

Extended potential-gradient architecture of a phenylazomethine dendrimer

A dendritic nanoshell based on rigid phenylazomethine units was synthesized up to fifth generation around a zinc porphyrin core. Due to the finely organized sparse architecture, accessibility to the core can be discriminated by the size of the molecules and ionic species. By using this function, the lifetime of the photochemically produced radical ion pair can be extended over 200 times longer along with a good quantum yield.

Enhanced photoluminescence by tyrosine-containing bolaamphiphile self-assembly

Photoluminescent spherical nanostructures were prepared through the self-assembly of a tyrosine-containing bolaamphiphilic molecule, and their antenna effect was examined. The photoluminescent spherical nanostructures were simply prepared by self-assembly of bolaamphiphile molecules in an aqueous solution in which water-soluble photosensitizers and lanthanide ions were dissolved. The photosensitizers and lanthanide cations were incorporated with the phenol group and the carboxyl end of the tyrosine moiety, respectively. Through fluorescence microscopy and photoluminescence spectroscopy analyses, the various combinations of two lanthanide ions (Eu and Tb) and four photosensitizers were screened for synergetic photoluminescence with bolaamphiphile self-assembly. The bolaamphiphile assembly enhanced the photoluminescence intensity by a factor of around 2 when it was associated with Tb and salicylic acid. This enhancement is driven by the phosphorescence enhancement of the photosensitizer induced by the π-π interactions with the phenol group in tyrosine. These results indicate that the tyrosine-containing bolaamphiphile is a promising molecule that can easily produce a soft nanoscaled host matrix with an antenna effect for photoluminescence.

Dendrimers as Nd3+ ligands: effect of generation on the efficiency of the sensitized lanthanide emission

We have designed two novel dendrimers with cyclam cores with appended poly(amido amine) (PAMAM) dendrons, decorated at the periphery with four and eight dansyl chromophores, respectively. The photophysical properties of the dendrimers and their Nd(3+) complexes have been investigated. The energy-transfer efficiency to the lanthanide ions from these dendrimers has been studied as a function of the generation. It has been observed that an increase in the dendrimer generation as well as the number of amide units enhances the energy transfer to the lanthanide ion.