•Ln3+ complexes with organic ligands have unique optical features.•Incorporating of Ln3+ complexes into polymers matrices can improve their stability.•Synthesis methods of Ln3+ complex-containing ...polymers are summarized in this review.•The critical strategies to prepare self-healing polymers will be discussed in detail.•Various emerging applications of luminescent polymers are summarized in this review.
Lanthanide (Ln3+) complexes with organic ligands have recently gained extensive attention due to their unique optical features such as high color purity, narrow and intense emission bands and long excited state lifetimes, showing diverse applications in tunable lasers, optical amplifiers, biomedical diagnosis, high density information storage and so on. However, some inherent shortcomings, such as poor stability (photo-, thermal- and mechanical), low processability and the tendency to aggregate significantly, limit their full exploitation in practical applications. Incorporating of Ln3+ complexes into polymers matrices are effective means to improve their properties and broaden their applications. In recent decades, significant progress has been made in Ln3+ complexes-containing polymers, varying from structural evolution of ligand molecules and polymers to application expansion of luminescent functional polymers. This review will systematically summarize the key points in the synthesis methods (including both physical doping and chemical cross-linking) of Ln3+ complexes-containing polymers. The critical strategies to prepare self-healing luminescent polymers will be discussed in detail. We then review the emerging applications of Ln3+ complexes-containing polymers ranging from light-conversion films, organic light-emitting diodes, bio-imaging to temperature sensing applications. At the end of this review, we will provide an outlook on the opportunities and challenges of Ln3+ complexes-containing polymers.
The lanthanide Schiff base complexes: La(H2L)2(NO3)2NO3 (1), Sm(H2L)2(NO3)2NO3 (2), Eu(H2L)2(NO3)2NO3 (3), Gd(H2L)2(NO3)2NO3 (4), Tb(H2L)2(NO3)2NO3 (5) and Dy(H2L)2(NO3)2NO3 (6) were prepared by ...reactions between Ln(NO3)3.xH2O {where Ln, x: La, 6; Sm, 6; Eu, 5; Gd, 6: Tb, 5; Dy, 6} and salicylaldehyde picolinoylhydrazone (H2L) Schiff base ligand. These complexes were characterized by 1H and 13C NMR, UV–vis, and IR spectroscopy, elemental analysis, molar conductance and thermogravimetric analysis. The two H2L units are coordinated to the central lanthanide ion as tridentate ONO ligand through their carbonyl and phenolic oxygen atoms, and azomethine nitrogen atoms. Two nitrate groups acting as bidentate ligands are coordinated to Ln(III) ion which results in a coordination number of eight for Ln(III). The luminescence study on the free H2L and its corresponding complexes revealed that all complexes exhibit ligand-centered emission. Coordination of H2L to Ln(III) ions and as a result the LMCT explains the blue shift observed in the ligand-centered emission band in the complexes. The MIC values showed that 1–6 complexes exhibit moderate antibacterial activity against treated gram negative bacteria (S., Kp. and Ec.) and are inactive against treated gram positive bacteria (Sa., M. and Ef.). In contrast, H2L ligand is inactive against all treated bacteria. H2L and 1–6 complexes exhibit good antifungal activity against C. albicans fungal as compared to that of reference drug. The DPPH scavenging activity of H2L enhances on complex formation and complex 5 possess the highest activity. The catalytic activities of complexes 1–6 were investigated toward the oxidation of aniline and substituted anilines using hydrogen peroxide as the oxidant at room temperature. Complex 6 provided the highest conversion with the highest selectivity towards azoxybenzene, 79.9%. The oxidative reaction of aromatic aniline incorporated with 4-(4-chlorophenoxy) on the para position proceeded with the formation of azoxybenzene with excellent yield, 91%.
Six new salicylaldehyde-2-picolinoylhydrazone lanthanide complexes have been synthesized and characterized. Complexes applicability as antioxidants, antimicrobials and catalysts for oxidation of aniline has been investigated. The luminescence properties investigation of free H2L and its corresponding complexes revealed that all complexes exhibit ligand-centered emission. Display omitted
•Six lanthanide Schiff base complexes were obtained.•The luminescence spectrum of the complexes 1–6 were studied.•The antimicrobial activity of complexes 1–6 against several microbial were studied.•The oxidation of aniline and substituted anilines by 1–6 were investigated.
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•Gadolinium Complex, Terbium Complex and Europium Complex.•Structure of Lanthanide Coordination Polymers.•Photoluminescence: lifetime, Judd-Ofelt intensity parameters, quantum yield ...and LMCT.•Molecular Modeling of structural and luminescent properties, Kinetic Model, DFT.
Three new complexes NaLn(pic)4ּ⋅2.5H2O (Ln = Tb, Eu or Gd; pic = picolinate) were synthesized and characterized by infrared spectroscopy, powder X-ray diffraction and thermogravimetric analyses. The molecular structures of the complexes have been determined by single-crystal X-ray diffraction. The three isostructural lanthanide complexes crystalize in the hexagonal system with space group P6122 to Eu complex and Gd complex and space group P6522 to Tb complex. In each of the complexes, the picolinate ligands are bonded to Ln3+ and Na+ ions by different coordination modes promoting polymeric structures. The photoluminescent properties of complexes were studied and combined with theoretical studies using the density functional theory (DFT: B3LYP, PBE1PBE) and the semiempirical method AM1/Sparkle from the single crystal X-ray diffraction structures to assign a suitable model for describing the system. The B3LYP DFT functional was considered the most adequate for providing structural properties of the compounds and for describing luminescence properties. The excited triplet states (T1) and excited singlet states (S1) of the ligand were determined theoretically using Time-dependent DFT calculations (TD-DFT: B3LYP, CAM-B3LYP and LC-wPBE) and INDO/S-CIS, with the best agreement with experimental values obtained from the LC-wPBE DFT functional. The photoluminescent spectra of the complexes and their lifetime measurements were determined indicating that the Eu complex and Tb complex display different intramolecular energy transfer mechanisms with higher efficiency to ligand-to-terbium energy transfer. In addition, the experimental and theorical Judd-Ofelt intensity parameters and quantum yields of the complexes were also determined and discussed besides to a proposed 9-state diagram to describe the luminescence properties of the Eu complex. The low value of emission quantum efficiency of 5D0 emitting level of Eu(III) ion was explained by the presence of the ligand-to-metal charge transfer state (LMCT) evidenced experimentally and theoretically. A good agreement was obtained between the proposed kinetic model and experimental results showing the consistency of the set of rate equations assumed and the intramolecular pathways proposed.
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•Systematic study of four series of lanthanide coordination complexes.•Systematic analysis of the effect of the lanthanide contraction.•Emphasises the importance of the solvent in ...obtaining crystalline complexes.•Emphasises the complex equilibria in the solution chemistry of the lanthanide complexes.
We report herein on remote control over a reversible phase transition of robust luminescent hybrid hydrogels as enabled by the rational selection and incorporation of photoswitches. Azobenzene units ...functionalized with a guanidinium group were utilized as the photoswitches and incorporated through a host–guest inclusion method involving α‐cyclodextrins functionalized with 2,6‐pyridinedicarboxylic acid (PDA) groups. While the guanidinium functional groups bind to the negatively charged Laponite matrix surface to connect organic and inorganic components, the PDA groups enable simultaneous coordination with different lanthanide metal ions, thus rendering the hydrogel broadly luminescent. Owing to its conformation‐dependent binding behavior with α‐cyclodextrin, the isomerization of azobenzene induced association or dissociation of the inclusion complexes and thus lead to a reversible photocontrolled sol↔gel phase transition of the luminescent hybrid hydrogels.
Remote control over a reversible sol↔gel phase transition of a robust luminescent hybrid hydrogel (see picture) was enabled by the incorporation of photoswitchable host–guest inclusion compounds into the hydrogel system. Guanidinium groups on the azobenzene guest units bind to a Laponite matrix, and pyridinedicarboxylic acid groups on the α‐cyclodextrin host units coordinate to lanthanide ions, thus rendering the hydrogel broadly luminescent.
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•The ratiometric nanothermometer shows excellent anti-interference in cells.•The nanothermometer exhibits Sr(max) of 1.9% ℃-1, and δT(min) of 0.1℃ in cells.•The relationship between ...temperature and intracellular Ca2+i is elucidated.
Herein, we report a ratiometric nanothermometer to study the correlation of heat/temperature and intracellular calcium transport. Firstly, poly(methyl methacrylate)-based copolymeric nanoparticles (NPs) from nanoprecipitation encapsulates two lanthanide complexes (Eu(DNPD)3Phen and Sm(DBM)3Phen) to enhance fluorescence of lanthanide ions (Ln3+). NPs were thereafter coated with an amphiphilic block copolymer pluronic F-127 to prevent nonspecific interaction between NPs and proteins, which ensures internalization of the nanothermometer into living cells. The back energy transfer (BET) from the excited state of Ln3+ to the triplet energy levels of ligand endows the temperature dependence on ratiometric fluorescence of Eu3+ and Sm3+. This nanothermometer has excellent anti-interference ability, ensuring accurate cell temperature measurement within a range of 29.0–40.0℃. It exhibits a maximum relative thermal sensitivity of 1.9 % ℃-1 at 29.0℃ and a minimum temperature resolution of 0.1℃ at 39.0℃ in live HeLa cells. The nanothermometer was applied for studying temperature or heat induced intracellular Ca2+ transport. It illustrated that free cytoplasmic Ca2+ concentration (Ca2+i) increased only when the cell temperature reached a certain threshold under photothermal stimulation, and the rise of temperature corresponds to the increase of Ca2+i. Furthermore, Ca2+ burst induced Ca2+ transport from cytoplasm to endoplasmic reticulum, which promoted ATP hydrolysis along with the rise of intracellular temperature. 200 s stimulation with FCCP enhanced ca. 1.7℃ of intracellular temperature along with 2.2 folds increment of Ca2+i, as FCCP induces Ca2+ efflux from mitochondria by increasing proton concentration therein. These results indicate that a close relationship between intracellular temperature and Ca2+ transport, which is of great significance for further understanding the role of temperature in signaling pathways and neurotransmitter release events.
A family of two-dimensional salen-type lanthanide complexes was synthesized through a facile solution diffusion method. The two-dimensional lanthanide complexes were characterized by single-crystal ...X-ray diffraction (SCXRD) and X-ray photoelectron spectroscopy (XPS) analytical techniques. The SCXRD and XPS analyses reveal that the obtained two-dimensional structures are rich in uncoordinated imine (−CHN−) groups located on the skeleton of the salen-type organic ligand, which retain strong coordination ability with metal ions. On the basis of this unique feature, a highly dispersed CeO2-supported Ni catalyst (Ni/CeO2-CAS) with highly strong metal–support interaction was first synthesized via a coordination-assisted synthesis (CAS) method, which exhibits a much better catalytic activity in the hydrogenation of nitrobenzene than the traditional Ni/CeO2-IWI catalyst prepared by incipient wetness impregnation (IWI). The origin of the improved catalytic activity of Ni/CeO2-CAS as well as the role of Ni@Ce–H2salen was revealed by using diverse characterizations. On the basis of the comparative characterization results, the superior catalytic performance of Ni/CeO2-CAS to Ni/CeO2-IWI could have resulted from the smaller and highly dispersed Ni nanoparticulates, the intensified Ni–CeO2 interaction, the enhanced NiO reducibility, and the higher concentration of oxygen vacancies, favoring the H2 dissociation and adsorption of the nitrobenzene reactant. The Ni/CeO2-CAS catalyst also exhibits high catalytic performance for reduction of diverse nitroarenes to their corresponding functionalized arylamines. We anticipated that this coordination-assisted strategy may provide a new way for preparing other highly oxide-supported catalysts with potential applications in various catalytic reactions.
•Nine novel lanthanide complexes have been successfully synthesized.•The mechanism of thermal decomposition of nine novel lanthanide complexes were studied.•The luminescent properties for complexes ...of Sm, Eu,Tb, dy were investigated.
Nine novel lanthanide complexes with 2-chlorobenzoic acid and 2,2′:6,2′'-terpyridine was synthesized in the ethanol solution. The structural formulae are Ln (2-ClBA)3(terpy)(H2O)2, Ln = La(1), Pr(2), Nd(3) and Ln (2-ClBA)3(terpy)(H2O), Ln = Sm(4), Eu(5), Gd(6), Tb(7), Dy(8), Ho(9), 2-ClBA= 2-chlorobenzoate, terpy= 2,2′:6′2’’-terpyridine. X-ray diffraction shows that these compounds form two types of structures: mononuclear and dimeric. Surprisingly, the complexes 4–9 have pseudo-dimeric supramolecular structures. The complexes were characterized by infrared and Raman spectroscopy. The thermal decomposition mechanism of nine complexes was studied by TG-DTG-DSC/FTIR coupling technique. Finally, the fluorescence of solid complexes 4, 5, 7, and 8 was tested, and the fluorescence lifetimes of complexes 5 and 7 are 637(6) and 331(5) μs, respectively. The fluorescence quantum yield of complex 5 is 14.3(8)%. The luminescence mechanism in terms of energy transfer is discussed.
Nine novel lanthanide complexes with 2-chlorobenzoic acid and 2,2′:6,2′'-terpyridine was synthesized in the ethanol solution. The structural formulae are Ln (2-ClBA)3(terpy)(H2O)2, Ln = La (1), Pr (2), Nd (3) and Ln (2-ClBA)3(terpy)(H2O), Ln = Sm (4), Eu (5), Gd (6), Tb (7), Dy (8), Ho (9), 2-ClBA = 2-chlorobenzoate, terpy = 2,2′:6′2’’-terpyridine. X-ray diffraction shows that these compounds form two types of structures: mononuclear and dimeric. Surprisingly, the complexes 4–9 have pseudo-dimeric supramolecular structures. The complexes were characterized by infrared and Raman spectroscopy. The thermal decomposition mechanism of nine complexes was studied by TG-DTG-DSC/FTIR coupling technique. Finally, the fluorescence of solid complexes 4, 5, 7, and 8 was tested, and the fluorescence lifetimes of complexes 5 and 7 are 637 (6) and 331 (5)μ s, respectively. The fluorescence quantum yield of complex 5 is 14.3 (8)%. The luminescence mechanism in terms of energy transfer is discussed.
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Two-dimensional faceted supramolecular structure of complex 1.
A series of Ln2(Salphen)3(H2O) compounds (1-Ln; Ln=Pr, Nd, Sm, Eu, Gd, Tb and Dy) was obtained and structurally characterized. Compound 1-Eu displays characteristic Eu3+ photoluminescence at 77K in ...the solid state and in frozen DMF/MeOH solution. A systematic analysis of magnetic properties of complexes 1-Ln revealed that the effect of coordination geometry or spin–orbit coupling in most cases is actually more significant than the exchange interactions between lanthanides.
•A series of lanthanide complexes with Schiff base was structurally characterized.•The Eu-compound displays characteristic Eu3+ photoluminescence at 77K.•A systematic analysis of the magnetic properties of studied complexes was performed.•The effects of coordination geometry or SOC on magnetic properties were discussed.
The series of compounds Ln2(Salphen)3(H2O) (1-Ln; Ln=Pr, Nd, Sm, Eu, Gd, Tb and Dy) was obtained. The crystal structure of 1-Nd was determined, and its isomorphism with the others was shown by powder XRD. These compounds possess dinuclear molecules with Ln–Ln distances of 3.965(30)Å (for 1-Nd). A systematic analysis of the magnetic properties of the complexes 1-Ln was performed in terms of the temperature dependences of the magnetic susceptibilities, revealing weak or, in the cases of the Eu and Dy complexes, negligible exchange interactions between the lanthanide ions. Compound 1-Eu displays characteristic Eu3+ photoluminescence at 77K both in the solid state and in DMF/MeOH solution.
The luminescence of silica aerogel-like composites, containing 1,10 – phenanthroline complexes of Tb(III) and Eu(III) as a model system for red-green-blue (RGB) sensor applications is described. The ...composites are obtained using an improved two-step colloidal approach, allowing the in situ formation of optical centers in the pores of the silica matrix. Quantum yield measurements, luminescence and excitation spectra suggest a dependence of the luminescence on the degree of hydrophobicity of the initial aerogel powders. A structural disorder, taking place during the in situ formation of the lanthanide complexes is detected using X-ray diffraction and a luminescence spectra – structure symmetry analysis.
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•The dependence of the optical properties of hybrid composites based on aerogels is studied.•It was confirmed that the quantum yield of the samples increases with the degree of hydrophobicity.•Thus, a potential for the development of RGB – sensors, based on hybrid aerogel composites with a tunable luminescence is opened.•Tracking the formation of the composites by XRD provided evidence for a structural disorder and morphological changes.
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