Features of the Preparation and Luminescence of Langmuir-Blodgett Films Based on the Tb(III) Complex with 3-Methyl-1-phenyl-4-stearoylpyrazol-5-one and 2,2'-Bipyridine.

In this study, we investigated the effect of terbium ions (Tb3+) on the subphases of the limiting area of the molecule for the complex compound (CC) TbL3∙bipy (where HL is 3-methyl-1-phenyl-4-stearoylpyrazol-5-one and bipy is 2,2'-bipyridine). We examined the Langmuir monolayer and the change in the luminescence properties of TbL3∙bipy-based Langmuir-Blodgett films (LBFs). The analysis of the compression isotherms, infrared, and luminescence spectra of TbL3∙bipy LBFs was performed by varying the concentration of Tb3+ in the subphases. Our results demonstrate the partial dissociation of the CC at concentrations of C(Tb3+) < 5 × 10-4 M.

Copper(ii) self-assembled clusters of bis((pyridin-2-yl)-1,2,4-triazol-3-yl)alkanes. Unusual rearrangement of ligands under reaction conditions.

The reaction of two structurally related bridging ligands bis[5-(2-pyridyl)-1,2,4-triazole-3-yl]methane (H2L1) and bis[5-(2-pyridyl)-1,2,4-triazole-3-yl]ethane (H2L2) with copper(ii) salts resulted in a surprising wide variety of complex structures [Cu2(H2L1)Cl2]Cl2·4CH3OH (1), [Cu4(L1)4]·4H2O (2), [Cu(H2L2)(ClO4)2] (3) and [Cu3(OH)Na2(L')6](ClO4)·5H2O·C3H6O (4), where HL' is 3,5-bis-(pyridin-2-yl)-1,2,4-triazole, which were structurally characterized by the X-ray diffraction method. Complexes 1 and 2 were prepared on the H2L1 basis and have binuclear and tetranuclear structures, respectively, demonstrating strong impact of the type of counter anion on the coordination mode of the ligand. In contrast, the reaction between Cu(ClO4)2 6H2O and H2L2 led to the preparation of mononuclear complex 3. The reaction of H2L2 with Cu(ClO4)2 under alkaline conditions led to oxidative rearrangement of the ligand and the homoleptic pentanuclear complex 4 with anionic ligand L' was prepared. Magnetic properties were studied for compounds 1, 2 and 4 and for all of them the antiferromagnetic interactions between the Cu atoms were confirmed and analyzed by the spin Hamiltonian formalism. Furthermore, the occurrence of the antisymmetric exchange was confirmed in 4. The magnetic data analysis was supported by the X-band EPR measurements performed for complexes 1, 2 and 4.

Luminescent Properties of Zn and Mg Complexes on N-(2-Carboxyphenyl)salicylidenimine Basis.

New zinc and magnesium complexes of N-(2-carboxyphenyl)salicylidenimine) were synthesized and structurally characterized by elemental analysis, FT-IR, and X-ray single-crystal analysis. These complexes exhibit tuneable luminescence in the solid state from blue to green by varying by metal ion and composition. Moreover, the quantum yields range from 0.11 to 0.41, while lifetimes were determined to be in the nanosecond timescale. Thermal analysis shows that these complexes exhibit good thermal stability and can therefore well be used as electroluminescent materials.

Tetranuclear Lanthanide Complexes Containing a Hydrazone-type Ligand. Dysprosium [2 × 2] Gridlike Single-Molecule Magnet and Toroic.

A multidentate hydrazone-type ligand (Z,Z)-bis(1-(pyridin-2-yl)-1-amino-methylidene)oxalohydrazide (H2L) was utilized in the synthesis of three new isomorphous tetranuclear complexes of the general formula [Ln4(HL)4(H2L)2(NO3)4](NO3)4·4CH3OH (Ln = GdIII, 1, TbIII, 2, DyIII, 3) with the gridlike [2 × 2] topology. The analysis of the static magnetic data revealed weak anti-ferromagnetic interaction among lanthanide(III) atoms, whereas dynamic magnetic data led to the observation of the single-molecule magnet behavior in zero static magnetic field for the Dy4 compound 3 with Ueff = 42.6 K and τ0 = 1.50 × 10-5 s. The theoretical CASSCF calculations supported also the presence of the net toroidal magnetic moment, which classifies compound 3 also as a single-molecule toroic.

Spacer-armed copper(II) complexes with benzenecarboxylic acids and trifluoroacetylacetone aroylhydrazones.

New bi- and trinuclear copper(ii) complexes of aroylhydrazones of TFA and benzenecarboxylic acids were synthesized and characterized. Despite long range intramolecular CuCu distances of about 10 Å, exchange couplings between paramagnetic centres are observed with J values of 0.33 and 0.37 cm(-1) in binuclear complexes, and -0.33 cm(-1) in trinuclear complexes. Seven hyperfine peaks with a value of aCu = 37.0 × 10(-4) cm(-1) are observed in EPR spectra of binuclear complexes. The possible mechanisms responsible for the observed weak long range coupling via aromatic spacers are discussed.

Synthesis, structure and luminescence studies of Eu(III), Tb(III), Sm(III), Dy(III) cationic complexes with acetylacetone and bis(5-(pyridine-2-yl)-1,2,4-triazol-3-yl)propane.

Studies concerning synthesis, structure and luminescence of eight-coordinate Eu, Tb, Sm and Dy complexes of the type [Ln(acac)2(L)]Cl (Hacac = pentanedione-2,4 and L = bis(5-(pyridine-2-yl)-1,2,4-triazol-3-yl)propane) are reported in detail. The obtained complexes were investigated by various means including elemental- and thermogravimetric analysis, IR- and electron transition spectroscopy. The structure of the Tb complex was determined by single-crystal X-ray crystallography: Tb is eight-coordinate, and L acting only as a tetradentate chelate together with two bidentate acac ligands. Photophysical studies of the complexes were carried out. The Tb(III) and Eu(III) complexes show strong emissions both in solid state and solution. The intensity of the luminescence of Dy(III) and Sm(III) are relatively weak. The factors determining the intensity of the photoluminescence are discussed.

Anionic lanthanide complexes with 3-methyl-1-phenyl-4-formylpyrazole-5-one and hydroxonium as counter ion.

A series of [H3O]+[LnL4]-·nH2O complexes (n = 1-3, Ln = Nd, (1), Sm (2), Eu (3), Tb (4); HL = 3-methyl-1-phenyl-4-formylpyrazole-5-one) were synthesized and characterized. The structures of the SmIII and EuIII complexes were investigated by X-ray diffraction. The isostructutal crystalls 2 and 3 consist the tetrakis [LnL4]- anions which are linked by H-bonding with the hydroxonium counter-ion and water molecules. The lanthanide ion is situated in the center of distorted tetragonal antiprism formed by eight oxygen atoms of 4-formyl-5-hydroxypyrazolonate anions. The TbIII and SmIII complexes show strong luminescence in solid state, whereas the EuIII and NdIII complexes show low luminescence activity.

Photo- and electroluminescent properties europium complexes using bistriazole ligands.

Luminescent properties of two heteroleptic dibenzoylmethanate europium(III) complexes with 1,3-bis(5-pyridin-2-yl-1,2,4-triazol-3-yl)propane (H2L1) and 1,4-bis(5-pyridin-2-yl-1,2,4-triazol-3-yl)butane (H2L2) as ancillary ligands are described. The two double-layer-type electroluminescent cells with the structures: (1) ITO/NPB(40 nm)/Eu(DBM)2HL1 (40 nm)/LiF (1 nm)/Al (100 nm) and (2) ITO/NPB(40 nm)/Eu(DBM)2HL2 (40 nm)/LiF (1 nm)/Al (100 nm) emit red light originating from the europium complexes. The device 2 gives the maximum brightness of 455 cd/m2 at 19.2 V.

Ln(III) complexes of a bis(5-(pyridine-2-yl)-1,2,4-triazol-3-yl)methane ligand: synthesis, structure and fluorescent properties.

The new tetradentate ligand H2L bis(5-(pyridine-2-yl)-1,2,4-triazol-3-yl)methane ligand H2L has been used to prepare corresponding Ln(III) complexes [Ln(L)(HL)H2O]·6H2O where Ln(III) is Tb(III), Sm(III), Eu(III), Gd(III), Nd(III). The resulting complexes were investigated by various means including elemental- and thermogravimetric analysis and IR-, UV-, VIS spectroscopy. The complexes form an isostructural series in the solid state according to X-ray diffraction. The optimal value of triple state energy of the ligand sensitizes both fluorescent visible and near-IR emissions of the lanthanides. However, the overall emission is moderate as a result of the quenching action of coordinated water molecules. The displacement of water molecules from the inner coordination sphere both in solid samples and the solutions results in a significant increase of the efficiency of the luminescence. The best value of the quantum yield was obtained for the Tb(III) complex with 41%. Luminescence titrations demonstrate that [Tb(L)(HL)H2O] is a pH-sensitive emitter which is able to detect pH values in both near neutral pH and acidic pH ranges.

Structural and photophysical studies on ternary Sm(III), Nd(III), Yb(III), Er(III) complexes containing pyridyltriazole ligands.

Two bidentate pyridine-triazole ligands (3-(pyridine-2-yl)-5-phenyl-1,2,4-triazole (L1) and 5-phenyl-2-(2'-pyridyl)-7,8-benzo-6,5-dihydro-1,3,6-triazaindolizine (L2)), have been synthesized and used for Ln(Dbm)3 (Ln = Sm(III), Nd(III), Yb(III) and Er(III)) coordination. The structures of the ligands and resulting Sm(III) complex were determined in the solid state by X-ray diffraction. The title complexes were characterized by UV, fluorescent, IR-spectroscopy and thermogravimetric and elemental analyses. Photophysical studies on the Ln(III) complexes were carried out showing luminescence in the region typical for Ln(III). The effect of various factors on the enhancement luminescence of complexes is discussed.