Valentina V. Utochnikova

Lanthanide 9-anthracenate: solution processable emitters for efficient purely NIR emitting host-free OLEDs

Searching for new NIR emitting materials, lanthanide 9-anthracenates Ln(ant)3 were synthesized and thoroughly characterized. Ytterbium 9-anthracenate Yb(ant)3, that demonstrated the highest NIR luminescence efficiency, was successfully used as an emission layer of a host-free OLED and its electroluminescence quantum efficiency, corresponding to the sole band at 1000 nm, reached 0.21%. This performance could be achieved due to the high quantum yield of Yb(ant)3, which reached 1.5% and was increased up to 2.5% by partial Yb3+ substitution with Lu3+, as well as its high electron mobility due to the extended stacking in its crystal structure. The first gadolinium-based PHOLED was prepared based on Gd(ant)3.

Highly Luminescent, Water‐Soluble Lanthanide Fluorobenzoates: Syntheses, Structures and Photophysics, Part I: Lanthanide Pentafluorobenzoates

Highly luminescent, photostable, and soluble lanthanide pentafluorobenzoates have been synthesized and thoroughly characterized, with a focus on Eu(III) and Tb(III) complexes as visible emitters and Nd(III) , Er(III) , and Yb(III) complexes as infrared emitters. Investigation of the crystal structures of the complexes in powder form and as single crystals by using X-ray diffraction revealed five different structural types, including monomeric, dimeric, and polymeric. The local structure in different solutions was studied by using X-ray absorption spectroscopy. The photoluminescence quantum yields (PLQYs) of terbium and europium complexes were 39 and 15 %, respectively; the latter value was increased almost twice by using the heterometallic complex [Tb0.5 Eu0.5 (pfb)3 (H2 O)] (Hpfb=pentafluorobenzoic acid). Due to the effectively utilized sensitization strategy (pfb)(-) →Tb→Eu, a pure europium luminescence with a PLQY of 29 % was achieved.

Photoluminescence of lanthanide aromatic carboxylates

Energy transfer processes affecting the luminescence properties and methods of controlling them by a change in the compositions and structures of luminescent compounds are analyzed in the review on example of lanthanide aromatic carboxylates. The analysis demonstrates clearly how the understanding of the physical regularities of the processes leading to luminescence makes it possible to perform the purposeful design of organic ligands and their brightly luminescing complexes with lanthanides.

Gas-Phase Synthesis of Lanthanide(III) Benzoates Ln(Bz) 3 (Ln = La, Tb, Lu)

A new method for the synthesis and film deposition of nonvolatile aromatic lanthanide(III) carboxylates by ligand exchange reaction between the starting volatile components in the gas phase was proposed. The complexes Ln(Bz)3 (Ln = La3+, Tb3+, Lu3+, HBz = benzoic acid) were synthesized by gas-phase ligand exchange reaction between the volatile Ln(Thd)3 and HBz (HThd = 2,2,6,6-tetramethylheptane-3,5-dione). The composition of the complexes was confirmed by elemental, thermal, IR-spectroscopic, and photoluminescence analyses and, in the case of lanthanum and lutetium complexes, by 1H NMR.

Gas-phase synthesis of terbium and lutetium carboxylates

Gas-phase ligand exchange between volatile lanthanide dipivaloylmethanates (Ln(dpm)3; Hdpm is dipivaloylmethane, Ln = Tb, Lu) and o-substituted aromatic carboxylic acids (HCarb = Hsal is o-hydroxybenzoic acid, Habz is o-aminobenzoic acid, Hpobz is o-phenoxybenzoic acid, Hpa is o-anilinobenzoic acid). The gas-phase reaction involves the formation of the mixed-ligand complex Ln (dpm)3−n(Carb)n, which is subsequently converted into tris-carboxylate (Ln(Carb)3) on heating of the product in vacuum.

Reactive chemical vapour deposition (RCVD) of non-volatile terbium aromatic carboxylate thin films

In this work we report a new RCVD technique which allows the deposition of nonvolatile compounds from the gas phase into thin films. The technique developed is based on the metathesis reaction in the gas phase between the volatile reagents with the following deposition of the nonvolatile product. A novel RCVD reactor has been constructed and consists of two evaporation (T1, T2) zones connected to the reaction zone (T3). This approach has been successfully tested on terbium carboxylates (Tb(Carb)3; HCarb = Hbz (benzoic acid), Hpobz (o-phenoxybenzoic acid)) as nonvolatile but promising complexes for their application as thin film optical materials. We demonstrated that the construction of the reactor plays a crucial role in the controlling of the films composition, morphology and thickness. The optimal parameters have been found and Tb(Carb)3 thin films with roughness ∼2–4 nm and thickness in the range of ∼40–200 nm were obtained.

Thin Films of Tb(pobz)3 (Hpobz = 2-phenoxybenzoic acid): Reactive CVD and Optical Properties

Thin films of aromatic terbium carboxylates are promising materials for application in different optical devices. However, thin films deposition of these compounds by common methods is almost impossible due to their low solubility in most common organic solvents and nonvolatility. In our previous work it was shown that thin films of one of the simplest aromatic terbium carboxylate Tb(bz)3 (Hbz - benzoic acid) can be obtained by the original approach based on the exchange reaction between volatile precursors - reactive CVD (RCVD). Herein we improved this approach and demonstrated its possibilities and advantages on deposition of thin films of new emissive material - Tb(pobz)3 (Hpobz - phenoxybenzoic acid). The bulk products and thin films of Tb(pobz)3, obtained by RCVD method were characterized by elemental analysis, IR-, Raman and photoluminescent spectroscopy as well as thin films were studied by AFM and SEM techniques.

Reactive Chemical Vapor Deposition Method as New Approach for Obtaining Electroluminescent Thin Film Materials

The new reactive chemical vapor deposition (RCVD) method has been proposed for thin film deposition of luminescent nonvolatile lanthanide aromatic carboxylates. This method is based on metathesis reaction between the vapors of volatile lanthanide dipivaloylmethanate (Ln(dpm)3) and carboxylic acid (HCarb orH2Carb′) and was successfully used in case of HCarb. Advantages of the method were demonstrated on example of terbium benzoate (Tb(bz)3) and o-phenoxybenzoate thin films, and Tb(bz)3 thin films were successfully examined in the OLED with the following structure glass/ITO/PEDOT:PSS/TPD/Tb(bz)3/Ca/Al. Electroluminescence spectra of Tb(bz)3 showed only typical luminescent bands, originated from transitions of the terbium ion. Method peculiarities for deposition of compounds of dibasic acids H2Carb′ are established on example of terbium and europium terephtalates and europium 2,6-naphtalenedicarboxylate.

From Isolated Anions to Polymer Structures through Linking with I2: Synthesis, Structure, and Properties of Two Complex Bismuth(III) Iodine Iodides

We report the synthesis, crystal structures, and optical properties of two new compounds, K18Bi8I42(I2)0.5·14H2O (1) and (NH4)7Bi3I16(I2)0.5·4.5H2O (2), as well as the electronic structure of the latter. They crystallize in tetragonal space group P4/ mmm with the unit cell parameters a = 12.974(1) and c = 20.821(3) Å for 1 and a = 13.061(3) and c = 15.162(7) Å for 2. Though 1 and 2 are not isomorphous, their crystal structures display the same structural organization; namely, the BiI6 octahedra are linked by I2 units to form disordered layers in 1 and perfectly ordered chains in 2. The I-I bond distances in the thus formed I-I-I-I linear links are not uniform; the central bond is only slightly longer than in a standalone I2 molecule, whereas the peripheral bonds are significantly shorter than longer bonds typical for various polyiodides, which is confirmed by Raman spectroscopy. The analysis of the electronic structure shows that the atoms forming the I-I-I-I subunits transfer electron density from their occupied 5p orbitals onto their vacant states as well as onto 6s orbitals of bismuth atoms that center the BiI6 octahedra. This leads to low direct band gaps that were found to be 1.57 and 1.27 eV for 1 and 2, respectively, by optical absorption spectroscopy. Luminescent radiative relaxation was observed in the near-IR region with emission maxima of 1.39 and 1.24 eV for 1 and 2, respectively, in good agreement with the band structure, despite the strong quenching propensity of I2 moieties.

New rare-earth metal acyl pyrazolonates: Synthesis, crystals structures, and luminescence properties

Ligand 3-methyl-1-phenyl-4-stearoylpyrazol-5-one (HQ) is synthesized and used to obtain new complexes of rare-earth metals (Eu, Gd, and Tb) of the composition [Ln(Q)3(H2O)(EtOH)]. The crystal structure of the terbium complex is determined by X-ray diffraction analysis (CIF file CCDC 975286). In a molecule of the complex, three aliphatic fragments n-C17H35 are codirected, which results in the formation of layers bound according to the fastener-sticker principle. The molecules of the complex are joined by a hydrogen bond network involving the pyrazolone rings and oxygen atoms of the inner-sphere solvent molecules (H2O and EtOH). The terbium complex is luminescent at room temperature, whereas the luminescence of the europium complex is very weak at room temperature and increases by 60 times at lowered temperatures. This makes it possible to consider these compounds as a new class of “luminescent thermometers.”