Anatoly P. Pushkarev

Near-infrared electroluminescent lanthanide [Pr(III), Nd(III), Ho(III), Er(III), Tm(III), and Yb(III)] N,O-chelated complexes for organic light-emitting devices

New near-IR electroluminescent complexes of Pr3+, Nd3+, Ho3+, Er3+, Tm3+, Yb3+ with N,O-chelated ligands, Ln2(OON)6 (OON = 2-(2-benzoxyazol-2-yl)phenolate) and Ln2(SON)6 (SON = 2-(2-benzothiazol-2-yl)phenolate), were synthesized by the reaction of Ln[N(SiMe3)2]3 and the corresponding N,O-chelating ligand. X-Ray analysis for the Pr and Nd compounds reveals centrosymmetric dimeric structures of the complexes. The solid-state electronic absorption spectra and the electroluminescent spectra show long-wavelength 4f–4f transitions which provide potential use of the compounds as NIR emitting materials in organic light-emitting devices (OLEDs). When constructing OLEDs based on Ln2(OON)6 and Ln2(SON)6, the best results were achieved with the Nd3+ and Yb3+ complexes, where the NIR wall plug efficiency of the ITO/TPD/Ln-complex/BATH/Yb system is 0.82 and 1.22 mW W−1, respectively.

Electroluminescent properties of lanthanide pentafluorophenolates

Lanthanide pentafluorophenolates Ln(OC6F5)3(L)x (Ln = Pr, Nd, Sm, Eu, Dy, Ho, Er, Yb; L = 1,10-phenanthroline, 2,2′-bipyridine; x = 1 and 2) are used as emissive layers in organic light emitting devices (OLEDs). Single-layer ITO/Ln(OC6F5)3(L)x/Yb devices reveal no electroluminescence (EL) with the exception of Tb-derivative-based OLEDs. Bilayer ITO/TPD/Ln(OC6F5)3(L)x/Yb samples exhibit a broad band emission peaked at 580 nm assigned to an electroplex at the TPD/complex interface. Besides, the spectra of the devices based on Pr, Nd, Sm, Eu, Er, Tb and Yb derivatives contain the characteristic narrow bands of f–f transitions. Terbium-based bilayer OLEDs exhibit unusual changes in the EL spectra with increasing the applied voltage. The emission color of the devices tunes from orange towards green. The possible nature of the phenomenon is discussed.

Lanthanide complexes with substituted naphtholate ligands: extraordinary bright near-infrared luminescence of ytterbium

A series of Pr, Nd, Ho, Er, Tm, and Yb complexes with 3-(2-benzoxazol-2-yl)-2-naphtholate and 3-(2-benzothiazol-2-yl)-2-naphtholate ligands was synthesized. The structure, as well as the photo- and electroluminescent properties of these complexes were studied. An extraordinary bright emission of Yb3+ was detected. To explain the phenomenon, a novel excitation mechanism involving intramolecular electron transfer was proposed.

Lithium, zinc and scandium complexes of phosphorylated salicylaldimines: synthesis, structure, thermochemical and photophysical properties, and application in OLEDs

The reaction of phosphorylated salicylaldimines containing the PO group either directly attached to the central benzene core (1a) or connected with it via a methylene unit (1b) with lithium and scandium hexamethyldisilazides readily afforded [κ3-O,N,O-(L–H)Li]2 (2a,b) and [κ2-O,N-(L–H)3Sc] (3a,b) (L – ligand) complexes in high yields. The treatment of 1b with Et2Zn in the presence of 1,10-phenanthroline led to zinc(II) complex 4b of (L–H)2Zn(phen) composition featuring a bidentate coordination mode of both salicylaldiminate ligands without participation of the phosphoryl groups. The structures of the complexes obtained were confirmed by the IR spectroscopic data and, in some cases, X-ray diffraction analysis. The thermal behavior of compounds 1a,b and 4b was studied by DSC. The temperature dependences of saturated vapor pressures of ligands 1a,b and complexes 2a, 4b were measured by the Knudsen effusion method. The thermodynamic parameters characterizing crystal-to-gas phase transitions were calculated. The complexes obtained were shown to possess weak photoluminescence in THF solution at room temperature. The unoptimized three-layer OLEDs based on 2a,b and 3a,b emit green light of low and moderate intensity.

Anhydrous mono- and dinuclear tris(quinolinolate) complexes of scandium: the missing structures of rare earth metal 8-quinolinolates

The first monomeric anhydrous scandium tris(8-quinolinolate) complex 1 with the 2-amino-8-quinolinolate ligands and the Sc(2)Q(6) dinuclear complex 2 with the unsubstituted 8-quinolinolate ligands have been synthesized and characterized by X-ray analysis and DFT calculations. The intramolecular hydrogen bonds appear to be responsible for the unique monomeric structure of complex 1. The DFT-based analysis of the electron density topology reveals the (3,-1) critical points corresponding to the O···H and N···H bonds. The two scandium atoms in compound 2 are inequivalent due to different ligand surroundings. They are coordinated by seven (5O, 2N) and eight (4O, 4N) ligand atoms. The increase in the coordination number is accompanied by a decrease in the positive charge of the metal atom as evidenced by the DFT calculations.

Cyclometallated iridium(III) complex with 1-phenylisoquinoline and norbornene-substituted pyrazolonate ligands and related electroluminescent polymers

A new cyclometallated iridium(III) complex NBEpzIr(Piq)2 (I) (NBEpzH is 1-phenyl-3-methyl- 4-(5-bicyclo[2.2.1]hept-5-en-2-yl)-5-pyrazolone, PiqH is 1-phenylisoquinoline) is synthesized. The structure of the compound is determined by X-ray diffraction analysis (СIF file CCDC no. 1521037). Copolymers with the carbazole and iridium-containing fragments in the side chains (P1–P3) are prepared from monomer I by the ring-opening metathesis polymerization method. Their photoluminescence and electroluminescence properties are studied. Copolymers P1–P3 exhibit an intense photoluminescence and electroluminesce of red color. The maximum luminance (3010 cd/m2) and current efficiency (15.1 cd/A) are achieved for emitter P2.

Synthesis and luminescence of some rare earth metal complexes

Abstract In the present paper the synthesis, photoand electroluminescent properties of new rare earth metal complexes prepared and studied at the Razuvaev Institute of Organometallic Chemistry during the last decade are reviewed. The obtained compounds give luminescence in UV, visible and NIR regions. The substituted phenolates, naphtholates, mercaptobenzothiazolate, 8-oxyquinolinolate, polyfluorinated alcoholates and chalcogenophosphinates were used as ligands. The synthesis and structure of unusual three–nuclear sulfidenitride clusters of Nd and Dy are described. The new excitation mechanism of ytterbium phenolates and naphtholates, which includes the stage of reversible reduction of Yb to divalent state and oxidation of the ligands in the excitation process, is discussed.

A Hybrid CuI/Fullerene Heterojunction in Transparent Flexible Photovoltaic Cells

We report on the fabrication and testing of multilayer thin-film photovoltaic cells based on a hybrid cuprous iodide/fullerene (CuI/C60) heterojunction. The cells were prepared by thermal evaporation of components on flexible polyethylene terephthalate (PET) substrates. The 0.4-V open circuit voltage (Uoc) arising at the junction does not depend on the thickness of the fullerene layer and on the introduction of a blocking layer at cathode. However, these changes strongly affect the short circuit current. A distinctive feature of such cells is high transparency in the entire visible range, which makes them potentially interesting for application in tandem (or multijunction) photovoltaic structures in order to enhance Uoc.

Substituted naphtholates of rare earth metals as emissive materials

The synthesis, characterization, photoluminescent (PL) and electroluminescent (EL) behavior of trivalent Sc, Nd, Gd, Er, Tm and Yb complexes with 3-(5-methylbenzoxazol-2-yl)naphthol (L-5Me) and 3-(6-methylbenzoxazol-2-yl)naphthol (L-6Me) ligands are reported. An X-ray analysis of Sc(L-5Me)3, Sc(L-6Me)3 as well as the non-methylated analogue Sc(L)3 has shown the monomeric structure of the complexes whereas the lanthanide naphtholates according to LDI-TOF data are dimers Ln2(L-5Me)6 and Ln2(L-6Me)6. The scandium complexes under photo- and electroexcitation revealed intense ligand-centered luminescence peaked at 522 nm. The PL and EL spectra of Nd, Tm and Yb compounds displayed moderate ligand-centered emission along with narrow bands of corresponding f–f transitions.

ate complexes of lanthanides with aryloxide ligands: Synthesis, structures, and luminescence properties

Abstract(2-Benzox(thi)azol-2-yl)phenolate and -naphtholate ate complexes of Sc, Y, La, Sm, Tb, and Yb are synthesized. The structure of (benzoxazolyl)phenolate complexes of La, Sm, and Yb are determined by X-ray diffraction analysis. All synthesized compounds manifest ligand-centered photo- and electroluminescence in a range of 510–540 nm. In addition, the spectra of the samarium and terbium complexes exhibit narrow bands of f-f transitions characteristic of Sm3+ and Tb3+ ions.