Deciphering Three Beneficial Effects of 2,2 '-Bipyridine-N,N '-Dioxide on the Luminescence Sensitization of Lanthanide(III) Hexafluoroacetylacetonate Ternary Complexes

Lanthanide hexafluoroacetylacetonate ternary complexes with 2,2'-bipyridine-N,N'-dioxide, [Ln(hfa)3(bpyO2)], were synthesized for Ln = Eu, Gd, Tb, and Lu and fully characterized by elemental, thermal, and mass-spectrometric analyses. The X-ray crystal structure of [Eu(hfa) 3(bpyO2)].0.5C6H6 reveals an octa-coordinate metal ion lying in a severely distorted trigonal dodecahedron geometry; the Eu-O distances lie in the range 2.36-2.44 Å with no significant difference between hfa- and bpyO2. A detailed comparative photophysical investigation has been carried out to determine the exact influence of the introduction of bpyO2 in the inner coordination sphere of the metal ion in replacement of the two water molecules in [Ln(hfa)3(H2O)2]. While this replacement is detrimental for Tb, it leads to a 15-fold increase in the overall quantum yield for Eu. This large improvement originates from (i) a better sensitization efficiency, the ancillary ligand being responsible for 3/4 of the energy transfer, (ii) elimination of nonradiative deactivation pathways through harmonics of O-H vibrations, and (iii) reduction in the radiative lifetime. The latter influence is rarely documented, but it accounts here for ã25% increase in the intrinsic quantum yield, so that more attention should be given to this parameter when designing highly luminescent lanthanide complexes. © 2011 American Chemical Society

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

Heteroleptic complexes of terbium(III) phenylanthranilate (Tb(PA)(3)) with triphenylphosphine oxide (TPPO): A Tb(PA)(3)(TPPO)2-based electroluminescent device

International audienceHeteroleptic complexes of terbium(III) phenylanthranilate with triphenylphosphine oxide of composition Tb(PA)3(TPPO)n (n = 1 or 2) were synthesized and characterized by elemental analysis, IR and photoluminescence spectroscopy, and thermal analysis. The structures of Tb(PA)3(TPPO)2 and Tb(PA)3(Phen) in solution were studied by the MALDI TOF-MS method. The photoluminescence properties of the terbium(III) complex with phenylanthranilic acid were compared with those of the terbium(III) complex with salicylic acid. An electroluminescent device with the structure ITO/PEDOT : PSS/PVC/Tb(PA)3(TPPO)2 /Al was constructed. The possibility of using heteroleptic aromatic carboxylates as emission layers for the construction of electroluminescent devices was exemplified by the Tb(PA)3(TPPO)2 comple

Highly Luminescent and Triboluminescent Coordination Polymers Assembled from Lanthanide beta-Diketonates and Aromatic Bidentate O-Donor Ligands

The reaction of hydrated lanthanide hexafluoroacetylacetonates, [Ln(hfa)(3)(H2O)(2)], with 1,4-disubstituted benzenes afforded a new series of one-dimensional coordination polymers [Ln(hfa)(3)(Q)](infinity), where Ln = Eu, Gd, Tb, and Lu and Q = 1,4-diacetylbenzene (acbz), 1,4-diacetoxybenzene (acetbz), or 1,4-dimethyltherephtalate (dmtph). X-ray single crystal analyses reveal [Ln(hfa)(3)(acbz)](infinity) (Ln = Eu, Gd, Tb) consisting of zigzag polymeric chains with Ln Ln Ln angles equal to 128 degrees, while the arrays are more linear in [Eu(hfa)(3)(acetbz)infinity and [Eu(hfa)(3)(dmtph)](infinity), with Ln Ln Ln angles of 165 degrees and 180 degrees, respectively. In all structures, Ln(III) ions are 8-coordinate and lie in distorted square-antiprismatic environments. The coordination polymers are thermally stable up to 180-210 degrees C under a nitrogen atmosphere. Their volatility has been tested in vacuum sublimation experiments at 200-250 degrees C and 10(-2) Torr: the metal organic frameworks with acetbz and dmtph can be quantitatively sublimed, while [Ln(hfa)(3)(acbz)](infinity) undergoes thermal decomposition. The triplet state energies of the ancillary ligands, 21 600 (acetbz), 22 840 (acbz), and 24 500 (dmtph) cm(-1), lie in an ideal range for sensitizing the luminescence of Eu-III and/or Tb-III. As a result, all of the [Ln(hfa)(3)(Q)](infinity) polymers display bright red or green luminescence due to the characteristic D-5(0)-> F-7(J)(J=0-4) or D-5(4) -> F-7(J) (J=6-0) transitions, respectively. Absolute quantum yields reach 51(Eu) and 56(Tb) % for the frameworks built from dmtph. Thin films of [Eu(hfa)(3)(Q)](infinity) with 100-170 nm thickness can be obtained by thermal evaporation (P<3 x 10(-5) Torr, 200-250 degrees C). They are stable over a long period of time, and their photophysical parameters are similar to those of the bulk samples so that their use as active materials in luminescent devices can be envisaged. Mixtures of [Ln(hfa)(3)(dmpth)](infinity) with Ln = Eu and Tb yield color-tunable microcrystalline materials from red to green. Finally, the crystalline samples exhibit strong triboluminescence, which could be useful in the design of pressure and/or damage detection probes

Dimeric Complexes of Lanthanide(III) Hexafluoroacetylacetonates with 4-Cyanopyridine N-Oxide: Syn thesis, Crystal Structure, Magnetic and Photoluminescent Properties

A series of new mixed-ligand lanthanide complexes [Ln(hfa)3(4-cpyNO)]2 (Ln = SmIII-HoIII and TmIII; hfa- = hexafluoroacetylacetonate; 4-cpyNO = 4-cyanopyridine N-oxide) have been synthesised by treating the corresponding lanthanide hexafluoroacetylacetonates with 4-cpyNO (molar ratio 1:1) in chloroform. Single-crystal X-ray analysis revealed that [Tb(hfa)3(4-cpyNO)]2 and [Ho(hfa)3(4-cpyNO)]2 are isostructural and are comprised of two types of symmetrically independent dimetallic molecules. Within a dimer, the eightfold-coordinated metal atoms are bridged by two 4-cpyNO ligands through the oxygen atoms of the N-oxide groups. The magnetic susceptibility data for the GdIII and TbIII complexes indicate the presence of weak antiferromagnetic interactions within the dimetallic Ln2O2 units. The thermal stability of the [Ln(hfa)3(4-cpyNO)]2 adducts was studied by thermogravimetric analysis and their volatility estimated from sublimation experiments under reduced pressure. The photoluminescent properties were measured for solid samples upon excitation at 330-360 nm. The mixed-ligand complexes of SmIII, EuIII, TbIII, DyIII and TmIII exhibit metal-centred luminescence in the entire visible spectral range with characteristic pink, red, green, yellow and blue emission, respectively. The introduction of ancillary 4-cpyNO molecules into the coordination sphere of the lanthanide(III) ions was found to significantly affect their luminescence quantum yields. [Eu(hfa)3(4-cpyNO)]2 thin films on quartz substrates were obtained by the vacuum evaporation technique and their photoluminescent properties were found to be enhanced when compared with those of the bulk samples. This suggests that these dimers could be good candidates for the fabrication of emitting layers for light-emitting diodes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006

Role of the Ancillary Ligand N,N-Dimethylaminoethanol in the Sensitization of EuIII and TbIII Luminescence in Dimeric β-Diketonates

Two types of dimeric complexes [Ln2(hfa)6(í2-O(CH2)2NHMe2)2] and [Ln(thd)2(í2,è2-O(CH2)2NMe2)]2 (Ln ) YIII, EuIII, GdIII, TbIII, TmIII, LuIII; hfa- ) hexafluoroacetylacetonato, thd- ) dipivaloylmethanato) are obtained by reacting [Ln(hfa)3(H2O)2] and [Ln(thd)3], respectively, with N,N-dimethylaminoethanol in toluene and are fully characterized. X-ray single crystal analysis performed for the TbIII compounds confirms their dimeric structure. The coordination mode of N,N-dimethylaminoethanol depends on the nature of the â-diketonate. In [Tb2(hfa)6(í2-O(CH2)2NHMe2)2], eight-coordinate TbIII ions adopt distorted square antiprismatic coordination environments and are O-bridged by two zwitterionic N,N-dimethylaminoethanol ligands with a Tb1âââTb2 separation of 3.684(1) Å. In [Tb(thd)2(í2,è2-O(CH2)2NMe2)]2, the N,N-dimethylaminoethanol acts as chelating-bridging O,N-donor anion and the TbIII ions are seven-coordinate; the Tb1âââTb1A separation amounts to 3.735(2) Å within centrosymmetric dimers. The dimeric complexes are thermally stable up to 180 °C, as shown by thermogravimetric analysis, and their volatility is sufficient for quantitative sublimation under reduced pressure. The EuIII and TbIII dimers display metal-centered luminescence, particularly [Eu2(hfa)6(O(CH2)2NHMe2)2] (quantum yield QLn L ) 58%) and [Tb(thd)2(O(CH2)2NMe2)]2 (32%). Consideration of energy migration paths within the dimers, based on the study of both pure and EuIII- or TbIII-doped (0.01-0.1 mol %) LuIII analogues, leads to the conclusion that both the â-diketone and N,N-dimethylaminoethanol ligands contribute significantly to the sensitization process of the EuIII luminescence. The ancillary ligand increases considerably the luminescence of [Eu2(hfa)6(O(CH2)2NHMe2)2], compared to [Ln(hfa)3(H2O)2], through the formation of intra-ligand states while it is detrimental to TbIII luminescence in both â-diketonates. Thin films of the most luminescent compound [Eu2(hfa)6(O(CH2)2NHMe2)2] obtained by vacuum sublimation display photophysical properties analogous to those of the solid-state sample, thus opening perspectives for applications in electroluminescent devices

Controlled Reduction of Sn⁴⁺ in the Complex Iodide Cs₂SnI₆ with Metallic Gallium

Metal gallium as a low-melting solid was applied in a mixture with elemental iodine to substitute tin(IV) in a promising light-harvesting phase of Cs2SnI6 by a reactive sintering method. The reducing power of gallium was applied to influence the optoelectronic properties of the Cs2SnI6 phase via partial reduction of tin(IV) and, very likely, substitute partially Sn4+ by Ga3+. The reduction of Sn4+ to Sn2+ in the Cs2SnI6 phase contributes to the switching from p-type conductivity to n-type, thereby improving the total concentration and mobility of negative-charge carriers. The phase composition of the samples obtained was studied by X-ray diffraction (XRD) and 119Sn Mössbauer spectroscopy (MS). It is shown that the excess of metal gallium in a reaction melt leads to the two-phase product containing Cs2SnI6 with Sn4+ and β-CsSnI3 with Sn2+. UV–visible absorption spectroscopy shows a high absorption coefficient of the composite material