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

3,6-Diamino-7,8-dihydroisoquinoline-4-carbonitrile derivatives: unexpected facile synthesis, full-color-tunable solid-state emissions and mechanofluorochromic activities

A facile synthesis of novel 3,6-diamino-7,8-dihydroisoquinoline-4-carbonitrile derivatives and their solid-state emissions are presented.

Synthesis, Optical Investigation and Biological Properties of Europium(III) Complexes with 2-(4-Chlorophenyl)-1-(2-Hydroxy-4-Methoxyphenyl)Ethan-1-one and Ancillary Ligands

Synthesis and photoluminescence behaviour of six novel europium complexes with novel β-hydroxyketone ligand, 2-(4-chlorophenyl)-1-(2-hydroxy-4-methoxyphenyl)ethan-1-one (CHME) and 2,2'-bipyridine (bipy) or neocuproine (neo) or 1,10-phenanthroline (phen) or 5,6-dimethyl-1,10-phenanthroline (dmphen) or bathophenanthroline (bathophen) were reported in solid state. The free ligand CHME and europium complexes, Eu(CHME)₃.2H₂O [1] Eu(CHME)₃.bipy [2], Eu(CHME)₃.neo [3], Eu(CHME)₃.phen [4], Eu(CHME)₃.dmphen [5] and Eu(CHME)₃.bathophen [6]were characterized by elemental analysis, FT-IR and ¹H-NMR. The photoluminescence emission spectra exhibited four characteristic peaks arising from the ⁵D₀ → ⁷F_J (J = 1-4) transitions of the europium ion in the solid state on monitoring excitation at λ_ex = 395 nm. The luminescence decay curves of these europium complexes possess single exponential behaviour indicating the presence of a single luminescent species and having only one site symmetry in the complexes. The luminescence quantum efficiency (η) and the experimental intensity parameters, Ω ₂ and Ω ₄ of europium complexes have also been calculated on the basis of emission spectra and luminescence decay curves. In addition, the antimicrobial and antioxidant activities were also studied of the investigated complexes.

A europium complex with enhanced long-wavelength sensitized luminescent properties

We report a new complex Eu(tta)(3).bpt (tta = thenoyltrifluoroacetonate; bpt = 2-(N,N-di-ethylanilin-4-yl)-4,6-bis(pyrazol-1-yl)-1,3,5-triazine) with excellent long-wavelength sensitized luminescent properties, in which four hydrogen atoms replace the methyl groups at the 3,3'- and 5,5'-positions of the pyrazolyl rings in a previously reported complex Eu(tta)(3).dpbt. Upon visible-light excitation (lambda(ex) = 410 nm) at 295 K, the quantum yield (Phi(Ln)(L)) of Eu(3+) luminescence of Eu(tta)(3).bpt is higher by 23% than that of Eu(tta)(3).dpbt. Different from the case of Eu(tta)(3).dpbt, Phi(Ln)(L) of Eu(tta)(3).bpt increases linearly with the decrease in temperature. Because of the different coordination environments around Eu(3+) ion, the fine structure of the hypersensitive (5)D(0)-->(7)F(2) emission band of Eu(tta)(3).bpt is quite different from that of Eu(tta)(3).dpbt, with the strongest emission line locating at 620 nm rather than 613 nm where the strongest emission line of Eu(tta)(3).dpbt appears. The excitation window of Eu(tta)(3).bpt is much broader than that of Eu(tta)(3).dpbt with a red edge extending up to 450 nm in a dilute toluene solution (1.0 x 10(-5) M) and 500 nm in a toluene solution (1.0 x 10(-2) M). Eu(tta)(3).bpt also exhibits excellent two-photon-excitation luminescent properties.

Preparation, photo- and electro-luminescent properties of a novel complex of Tb (III) with a tripod ligand

A novel Tb(III) complex TbL (L=tris[2-(2-carboxyphenoxy)ethyl]amine, H3L) was synthesized and characterized by means of elemental analyses, IR spectra, thermal analyses, and molar conductivity measurement. The photoluminescent properties of the complex were investigated. In addition, PVK doping Tb(III) complex was fabricated as the emissive layer by spin-coating and its electroluminescent properties were studied, in which the structure of the device was ITO (indium tin oxide)/PVK (polyvinylcarbazole)/PVK: TbL/PBD (2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole)/LiF/Al. It was indicated that pure green and narrow bandwidth emission at 545nm from photoluminescence of TbL complex film and the organic electroluminescent device is the characteristic emission of Tb(III) ion, and the electroluminescence spectrum of the device was very similar to that of the photoluminescence of TbL complex film. The lowest triplet level of the ligand was calculated from the phosphorescence spectrum of GdL in N,N-dimethyl formamide (DMF) dilute solution determined at 77K, and the energy transfer mechanisms in TbL complex were discussed.

The synthesis and characterisation of europium terpyridine-N-oxide complexes

Europium complexes of a series of terpyridine-N-oxide ligands have been prepared and structurally characterised by crystallographic studies. While the addition of three equivalents of terpyridine-1-oxide or terpyridine-1,1'-bisoxide results in complexes with nine co-ordinate tricapped trigonal prismatic or monocapped square antiprismatic geometries, respectively, three equivalents of the terpyridine-1,1',1'-trisoxide yields an unexpected 8 co-ordinate geometry. Luminescence studies of the three complexes in acetonitrile show a typical europium emission spectra, dominated by the (5)D(0)-(7)F(2) transition. While no simple trend in the relative quantum yields could be ascertained, the terpyridine-1-oxide complex was observed to have the most intense luminescence for this set of complexes.

Cathodic electrochemiluminescence of acetonitrile, acetonitrile–1,10-phenanthroline and acetonitrile–ternary Eu(III) complexes at a gold electrode

Cathodic electrochemiluminescence (ECL) behaviours of the acetonitrile, acetonitrile-1,10-phenanthroline (phen) and acetonitrile-ternary Eu(III) complex systems at a gold electrode were studied. One very weak cathodic ECL-2 at -3.5 V was observed in 0.1 mol/L tetrabutylammonium tetrafluoroborate (TBABF(4)) acetonitrile solution. When 10 mmol/L tetrabutylammonium peroxydisulphate [(TBA)(2)S(2)O(8)] was added to 0.1 mol/L TBABF(4) acetonitrile solution, another cathodic ECL-1 at -2.7 V appeared and the potential for ECL-2 was shifted from -3.5 to -3.1 V. Furthermore, ECL-2 intensity was enhanced about 20-fold. When 1 x 10(-4) mol/L phen was added to 0.1 mol/L TBABF(4) + 10 mmol/L (TBA)(2)S(2)O(8) acetonitrile solution, the ECL intensities of ECL-1 and ECL-2 were enhanced about 20-fold compared with those of 0.1 mol/L TBABF(4) + 10 mmol/L (TBA)(2)S(2)O(8) acetonitrile solution. The maximum emission peaks of ECL-1 and ECL-2 in the three systems mentioned above appeared at about 530 nm. The products obtained by electrolysing 0.1 mol/L TBABF(4) acetonitrile solution at -3.5 V for 20 min were analysed by Fourier Transform Infrared (FTIR) spectra and gas chromatography-mass spectrometry (GC-MS) and the emitter of ECL-1 and ECL-2 was identified as excited state polyacetonitrile. When ternary Eu(III) complexes were presented in 0.1 mol/L TBABF(4) + 10 mmol/L (TBA)(2)S(2)O(8) acetonitrile solution, another maximum emission peak with a narrow band centred at about 610 nm appeared in ECL-1 in addition to the maximum emission peaks at about 530 nm for ECL-1 and ECL-2. The emitter of ECL emission at 610 nm was identified as the excited states Eu(III)*. The mechanisms for cathodic ECL behaviours of the acetonitrile, acetonitrile-phen and acetonitrile-ternary Eu(III) complex systems at a gold electrode have been proposed. The extremely sharp emission bands for ternary Eu(III) complexes may have analytical potential.

Spectroscopic characterization of Eu(III) complexes with new monophosphorus acid derivatives of H(4)dota

The luminescence lifetimes of europium(III) complexes with new monophosphorus acid derivatives of H(4)dota were measured by means of time-resolved laser-induced luminescence spectroscopy in H(2)O and D(2)O. The hydration numbers of these complexes were estimated using different empirical equations [Horrocks and Sudnick (1979) J. Am. Chem. Soc. 101 (1979) 334; Choppin and Barthelemy(1989) Inorg. Chem. 28, 3354-3357; Choppin and Bünzli Lanthanide probes in life, chemical and earth sciences. Theory and practice (1989); Kimura and Kato J. Alloys Comp. 275-277 (1998) 806; Parker (1999) J. Chem. Soc., Perkin Trans. 2, 493-503; Supkowski and Horroks (2002) Inorg. Chim. Acta. 340, 44-48]. It was shown that all the relationships gave similar results with a satisfactory precision. The hydration numbers of complexes of H(3)do3a and H(4)dota agreed with the literature values. One water molecule is coordinated in complexes of the new ligands. The results showed that the Choppin formula based on measurements only in H(2)O can be satisfactorily used for estimation of the hydration numbers.

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.

Experimental and Theoretical Study of the Photophysics and Structures of Europium Cryptates Incorporating 3,3?-Bi-isoquinoline-2,2?-dioxide

A detailed photophysical study of [Eu within (biqO2.2.2)(CF3SO3)](CF3SO3)2. CH3CN.H2O (Eu within 1) and two other types of cryptates incorporating three 3,3'-biisoquinoline-2,2'-dioxide units has been performed. Structural crystallographic data of Eu within 1, electronic structure calculations and theoretical models were used to obtain the intramolecular energy transfer rates and the appropriate set of rate equations, which was solved numerically. Quantum yields and decay lifetimes were obtained from these results and compared to the experimental data. The role of the ligand-to-metal charge transfer (LMCT) states was ascertained. A theoretical ligand field and intensity analysis was carried out and the results agree very well with the emission spectra. The molecular structures of the lanthanide cryptates were successfully modelled by the YIII ion using the restricted Hartree-Fock (RHF) method, with the advantage of dealing with closed-shell systems. These molecular structures were used to explain the drastic differences in the photophysics of the three EuIII cryptates.

Photoluminescence and raman studies of curium and americium complexes of 6-methyl 2-(2-pyridyl)-benzimidazole: evidence for an efficient intramolecular energy transfer

The 6-methyl-2-(2-pyridyl)-benzimidazole (biz) ligand coordinates with the actinide species in solution, and the complexes display efficient intramolecular energy-transfer processes. The energy transfer in the Cm(III)-biz system proceeds in a nonradiative mode, whereas a radiative mode is the principal mechanism in the Am(III)-biz system.

Sparkle Model for AM1 Calculation of Lanthanide Complexes: Improved Parameters for Europium

In the present work, we sought to improve our sparkle model for the calculation of lanthanide complexes, SMLC,in various ways: (i) inclusion of the europium atomic mass, (ii) reparametrization of the model within AM1 from a new response function including all distances of the coordination polyhedron for tris(acetylacetonate)(1,10-phenanthroline) europium(III), (iii) implementation of the model in the software package MOPAC93r2, and (iv) inclusion of spherical Gaussian functions in the expression which computes the core-core repulsion energy. The parametrization results indicate that SMLC II is superior to the previous version of the model because Gaussian functions proved essential if one requires a better description of the geometries of the complexes. In order to validate our parametrization, we carried out calculations on 96 europium(III) complexes, selected from Cambridge Structural Database 2003, and compared our predicted ground state geometries with the experimental ones. Our results show that this new parametrization of the SMLC model, with the inclusion of spherical Gaussian functions in the core-core repulsion energy, is better capable of predicting the Eu-ligand distances than the previous version. The unsigned mean error for all interatomic distances Eu-L, in all 96 complexes, which, for the original SMLC is 0.3564 A, is lowered to 0.1993 A when the model was parametrized with the inclusion of two Gaussian functions. Our results also indicate that this model is more applicable to europium complexes with beta-diketone ligands. As such, we conclude that this improved model can be considered a powerful tool for the study of lanthanide complexes and their applications, such as the modeling of light conversion molecular devices.

Lanthanide-transition heterometallic extended structures with novel orthogonal metalloligand as building block

One-dimensional lanthanide-transition heterometallic chains of squares, [LnNi(2)L(3)(HL)(DMF)(4)(ClO(4))(4).S]( infinity ) (Ln = Gd and Tb; HL is the Schiff base obtained by the condensation of 2-pyridylaldehyde with isonicotinic hydrazide N-oxide; S = solvent) and [LnNi(2)L(4)(DMF)(4)(ClO(4))(3).S]( infinity ) (Ln = Dy; S = solvent), were synthesized by self-assembly between well-designed orthogonal metalloligands [Ni(HL)L](+) and the Ln(III) ions, which act as the bridging units and nodes, respectively.

Assembly of hydrophobic shells and shields around lanthanides

Luminescent lanthanide complexes have been developed, based on the assembly of bulky ligands around the lanthanide ion, to provide shell-type protection of the ion from coordinated solvent molecules. Aryl-functionalised imidodiphosphinate ligands (tpip and Metpip) provide a bidentate anionic site that leads to hexa-coordinate lanthanide complexes in which the aryl groups surround the ion. There are twelve phenyl groups around the lanthanide that act as "remote" (from the binding site) sensitisers for the metal ion. It is shown that these ligands are suitable for sensitising luminescence for all the lanthanides that emit in the visible range, namely, SmIII, EuIII, TbIII, DyIII. A "builtin" shield on the ligand is designed to provide a complete block of the approach of water to the lanthanide ion. The synthesis of the ligands and their lanthanides complexes as well as detailed photophysical studies of the complexes in solution and in the solid-state are presented.