DFT study of electron absorption and emission spectra of pyramidal LnPc(OAc) complexes of some lanthanide ions in the solid state.

The electron absorption and emission spectra were measured for the pyramidal LnPc(OAc) complexes in the solid state and co-doped in silica glass, where Ln=Er, Eu and Ho. The theoretical electron spectra were determined from the quantum chemical DFT calculation using four approximations CAM-B3LYP/LANL2DZ, CAM-B3LYP/CC-PVDZ, B3LYP/LANL2DZ and B3LYP/CC-PVDZ. It was shown that the best agreement between the calculated and experimental structural parameters and spectroscopic data was reached for the CAM-B3LYP/LANL2DZ model. The emission spectra were measured using the excitations both in the ligand and lanthanide absorption ranges. The possibility of energy transfer between the phthalocyanine ligand and excited states of lanthanide ions was discussed. It was shown that the back energy transfer from metal states to phthalocyanine state is responsible for the observed emission of the studied complexes both in the polycrystalline state and silica glass.

Optical spectroscopy of europium 3,5-dinitrosalicylates-Intense red luminophores.

It was found, that alkali metal-europium dinitrosalicylates of composition M(3)Eu(3,5-NO(2)-Sal)(3).nH(2)O (M=Li, Na, K, Cs) are intense red luminophores with wide excitation band. Using methods of optical spectroscopy we studied the influence of nitrogroups and alkali metal counterions on Eu(3+) luminescence efficiency and on processes of excitation energy transfer to Eu(3+) ion in compounds synthesized. The Eu(3+) luminescence and Eu(3+) luminescence excitation spectra, as well as vibrational IR and Raman spectra were investigated. Details of the structure of compounds were discussed. The network of hydrogen bonds in lanthanide dinitrosalicylates is weakening at introduction of large alkali metal ions in compounds and at the increase of the temperature. As a consequence, the long-wavelength shift of the intraligand charge transfer (ILCT) band in Eu(3+) excitation spectra arises at inclusion of Cs(+) cations instead of Li(+) in the crystal lattice of europium dinitrosalicylates and at heating of these compounds. To obtain the energy of the lowest excited triplet state the phosphorescence spectra of alkali metal-gadolinium compounds M(3)Gd(3,5-NO(2)-Sal)(3).nH(2)O, of alkali metal dinitrosalicylate and salicylate salts were measured with time delay. Change of the energies of ligand electronic states and ligand-metal charge transfer state (LM CTS) can give a two-three orders of magnitude enhancement of the Eu(3+) luminescence efficiency in dinitrosalicylates in comparison with salicylates and ten-fold enhancement at the substitution of Li(+) and Na(+) for Cs(+) in dinitrosalicylates.

On the determination of empirical absolute chiral structure: chiroptical spectrum correlations for D3 lanthanide (III) complexes.

Circularly polarized luminescence (CPL) from selected transitions of Eu(III) in resolved single crystals of Na3[Eu(ODA)3].2NaClO4.6H2O are compared to CPL results obtained from solutions containing perturbed racemic mixtures of Eu(2,6-pyridine-dicarboxylate)3 (3-) and enantiomerically pure d-f helicate LambdaLambda-(-)EuCr(L8)3] in order to determine an empirical relationship between helicity and CPL spectra. Comparison of the CPL results, even for the magnetic dipole allowed transitions of Eu(III) where one measures large chiral discrimination, shows that the signs and magnitudes do not correlate with the overall helicity of the Eu(III) site. It is concluded that the symmetry of the Eu(III) site in LambdaLambda-(-)EuCr(L8)3 is not close enough to D3 to allow for the confirmation of the presumed spectra:structure correlation.

Characterization of the electronic excited-state energetics and solution structure of lanthanide(III) complexes with the polypyridine ligand 6,6'-bis[bis(2-pyridylmethyl)aminomethyl]-2,2'-bipyridine.

Absorption, emission, and excitation spectra for solid-state and solution of Tb(III), Dy(III), and Gd(III) complexes with the polypyridine ligand 6,6'-bis[bis(2-pyridylmethyl)-aminomethyl]-2,2'-bipyridine (C36H34N8) are presented. Measurements of excited-state lifetimes and quantum yields in various solvents at room temperature and 77 K are also reported and used to characterize the excited-state energetics of this system. Special attention is given to the characterization of metal-to-ligand energy transfer efficiency and mechanisms. The measurement of circularly polarized luminescence (CPL) from the solution of the Dy(III) complex following circularly polarized excitation confirms the chiral structure of the complexes under study. No CPL is present in the luminescence from the Eu(III) or Tb(III) complex because of efficient racemization. The variation of the magnitude of the CPL as a function of temperature from an aqueous solution of DyL is used for the first time to characterize the solution equilibria between different chiral species.

Effect of ligand radicals on vibrational IR, Raman and vibronic spectra of europium beta-diketonates.

Vibrational IR, Raman spectra and vibronic sidebands of Eu(3+) electronic transitions of europium tris-beta-diketonates Eu(beta)(3).Ph (beta-dipyvaloylmethane (DPM), acetylacetone (AA), benzoylacetone (BA), thenoyltrifluoroacetone (TTFA) and other beta-diketones; Ph-methyl-, phenyl-, and nitro-derivatives of 1,10-phenanthroline (Phen)) as well as Eu(beta)(3).Bpy and Eu(beta)(3).D-Bpy (Bpy- and D-Bpy-H- and D-2,2'-bipyridine) were studied. Effect of ligand radical properties on spectra and manifestation of the reciprocal influence of non-equivalent ligands in spectra are discussed. Dependence of the spectra on electronic density distribution in both ligands as well as on the strength of M-O and M-N bonds at the variation of radicals of one of the ligands, beta or Ph, was examined. Shape of vibronic sidebands was analysed. Behaviour of bands in the middle and far regions of IR spectra of the series Eu(beta)(3).Phen and Eu(TTFA)(3).Ph was investigated. Increase of the polarising influence of Eu(3+) ions on Phen and Bpy molecules and strengthening the Eu-N bonds in TTFA compounds in comparison with DPM compounds were disclosed from the Raman spectra of Eu(beta)(3).Phen and Eu(beta)(3).Bpy, that is in accordance with properties of beta-diketone radicals. Conclusion about weaker Eu-N bonds in europium beta-diketonates with heterocyclic diimines in comparison with corresponding nitrates was derived from the spectra. Spectral data concerning the relative strength of Eu-ligand bonds are in agreement with available X-ray data.

Photophysics and crystal structure of a europium(III) cryptate incorporating 3,3'-biisoquinoline-2,2'-dioxide.

Increased interest in the emission properties of lanthanide(III) (Eu and Tb) complexes containing ultraviolet and visible sensitizers is being driven by the desire to produce efficient and selective luminescent probes of biological structure. Of special interest are cryptates and other macrocyclic chelating ligands that efficiently encapsulate the lanthanide ions. These species also form relatively stable systems and in some cases are well protected from penetration of the first coordination sphere by solvent molecules and counterions. This work describes the X-ray structure and various spectroscopic measurements on a europium cryptate containing 3,3'-biisoquinoline-2,2'-dioxide (biqO2). This cryptate has been previously recognized for special stability and luminescence efficiency. The compound, (Eu:biqO2.2.2)(CF3SO3)3.CH3CN.H2O, forms rhombic crystals with the space group Pbca. Absorption, emission, and excitation spectra at 293, 77, and 4 K as well as luminescence decay time measurements are used to characterize the solid state and solutions. The ligand-to-metal energy-transfer mechanism and thermally activated back-energy-transfer processes are analyzed and compared to previously published results on related Eu(III) cryptate systems. Preliminary results on the use of high liquid pressure to perturb ligand singlet and triplet states and, as a consequence, probe the ligand-metal orbital interactions are also presented.