Intense near-infrared luminescence of a mesomorphic ionic liquid doped with lanthanide b-diketonate ternary complexes

The ionic liquid 1-dodecyl-3-methylimidazole chloride ([C12- mim]Cl) is doped with 1 mol-% of the lanthanide ternary complexes [Ln(tta)3(phen)] (tta = thenoyltrifluoroacetonate, phen = 1,10-phenanthroline, Ln = Nd, Eu, Er, Yb), resulting in luminescent mesogenic phases at room temperature. According to DSC and SAXS measurements, the temperature of the crystal liquid crystal transition is below 10 °C. Analysis of vibrational and luminescence data points to the inner co-ordination sphere of the EuIII ion being very similar in both the mesomorphic sample and the parent β-diketonate complex. The mesomorphic samples containing NdIII, ErIII, or YbIII display relatively intense near-infrared luminescence. This emission is enhanced in the liquid crystalline phases with respect to the initial compounds, as demonstrated for instance by the quantum yield of the [Yb(tta)3(phen)]-containing mesogenic sample which amounts to 2.1%, as compared to 1.6 and 1.1%for the powdered ternary complex and its solution in toluene, respectively. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005

Intermolecular Interactions as Actors in Energy-Transfer Processes in Lanthanide Complexes with 2,2′-Bipyridine

A series of lanthanide complexes [LnClx(bpy)y(H2O)z]Cl3-x(H2O)n(EtOH)m (Ln ) Eu, Gd, Tb; x ) 1, 2; y ) 1, 2; z ) 2-4) with different numbers of 2,2′-bipyridine (bpy), chloride ions, and water molecules in the inner coordination sphere were synthesized and investigated with the aim of relating their molecular geometry and crystal packing to the efficiency of ligand-to-metal energy transfer. In conjunction to the rotation of the pyridine rings upon coordination to the Ln ion, the high flexibility displayed by bpy ligands leads to rather unexpected bending of these rings with respect to the central bond, owing to intermolecular interactions such as Cl · · ·π and π-stacking ones. Deciphering the luminescence properties of the Eu and Tb complexes needs to take into account both the composition of the inner coordination sphere and the peculiarities of the crystal packing. For instance, in addition to the classical ligand f Eu charge-transfer state (LMCT), another chargetransfer state induced by π-stacking interactions (SICT) could be identified. These two states, located between the singlet and triplet states of the bpy ligand(s), provide relays facilitating the energy migration from the singlet to the triplet states and eventually to the excited Eu states, improving the overall ligand-to-Eu energy transfer. Another point is the involvement of the inner-sphere water molecules in H-bonding with chloride ions, which considerably lowers their luminescence quenching ability, so that the adducts remain highly luminescent. For instance, the terbium chloride with two bpy ligands is an efficient near-UV to green light converter, with an overall quantum yield equal to 37% despite the coordinated water molecules. The interpretations given are substantiated by DFT and TD-DFT theoretical calculations of the complexes and ligand assemblies

Bis(3,4-diphenyl)(2-methythienyl)cyclopentadienyl Terbium Chloride

A new terbium(III) complex with a (3,4-diphenyl)(2-methylthienyl)cyclopentadienyl ligand was synthesized. Single-crystal X-ray analysis revealed a binuclear biscyclopentadienyl complex with a [TbCl2K]2 core. Luminescence properties of the terbium complex were analyzed

Bis(3,4-diphenyl)(2-methythienyl)cyclopentadienyl Terbium Chloride

A new terbium(III) complex with a (3,4-diphenyl)(2-methylthienyl)cyclopentadienyl ligand was synthesized. Single-crystal X-ray analysis revealed a binuclear biscyclopentadienyl complex with a [TbCl2K]2 core. Luminescence properties of the terbium complex were analyzed

Coordination Polymers of Polyphenyl-Substituted Potassium Cyclopentadienides

A series of potassium salts of di- and tri-arylsubstituted cyclopentadienes has been obtained by the metalation of the corresponding cyclopentadienes with benzylpotassium in THF media. Crystals of all compounds, afforded by recrystallization from THF/hexane, diglyme-THF/hexane and toluene/hexane mixtures, have been studied by X-ray diffraction. All studied potassium cyclopentadienides exhibit the luminescence at room temperature and overall quantum yield of photoluminescence for potassium salt of diarylsubstituted cyclopentadiene is 18%

Polyphenylcyclopentadienyl Ligands as an Effective Light-Harvesting π‑Bonded Antenna for Lanthanide +3 Ions

A new approach to design “antenna-ligands” to enhance the photoluminescence of lanthanide coordination compounds has been developed based on a π-type ligandthe polyphenyl-substituted cyclopentadienyl. The complexes of di-, tri-, and tetraphenyl cyclopentadienyl ligands with Tb and Gd have been synthesized and all the possible structural types from mononuclear to di- and tetranuclear complexes, as well as a coordination polymer were obtained. All types of the complexes have been studied by single-crystal X-ray diffraction and optical spectroscopy. All terbium complexes are luminescent at ambient temperature and two of them have relatively high quantum yields (50 and 60%). Analysis of energy transfer process has been performed and supported by quantum chemical calculations. The role of a low-lying intraligand charge transfer state formed by extra coordination with K⁺ in the Tb³⁺ ion luminescence sensitization is discussed. New aspects for design of lanthanide complexes containing π-type ligands with desired luminescence properties have been proposed