A theoretical study of the energy-transfer process in [Eu⊂bpy.bpy.bpy]3+ cryptates: a ligand-to-metal charge-transfer state?

Longo, Ricardo L.; Silva, Fabiana R. Gonçalves e; Malta, O.L.

doi:10.1016/s0009-2614(00)00898-8

Cited by 50 publications

(31 citation statements)

References 19 publications

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“…The rate equations associated with the energy-level diagram in Fig. 3 were solved numerically by a fourth-order Runge-Kutta method with an adaptive integration step, where the initial populations of the ground states (F-centre and benzoate) were set to 1/2 and zero for the other states 61 . These equations were propagated up to 0.1 s and the steadystate populations were used as the starting populations for a new propagation to determine the lifetimes 56 .…”

Section: Methodsmentioning

confidence: 99%

Efficient and tuneable photoluminescent boehmite hybrid nanoplates lacking metal activator centres for single-phase white LEDs

et al. 2014

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White light-emitting diodes (WLEDs) are candidates to revolutionize the lighting industry towards energy efficient and environmental friendly lighting and displays. The current challenges in WLEDs encompass high luminous efficiency, chromatic stability, high colourrending index and price competitiveness. Recently, the development of efficient and low-cost downconverting photoluminescent phosphors for ultraviolet/blue to white light conversion was highly investigated. Here we report a simple route to design high-efficient WLEDs by combining a commercial ultraviolet LED chip (InGaAsN, 390 nm) and boehmite (g-AlOOH) hybrid nanoplates. Unusually high quantum yields (Z yield ¼ 38-58%) result from a synergic energy transfer between the boehmite-related states and the triplet states of the benzoate ligands bound to the surface of the nanoplates. The nanoplates with Z yield ¼ 38% are able to emit white light with Commission International de l'Eclairage coordinates, colour-rendering index and correlated colour temperature values of (0.32, 0.33), 85.5 and 6,111 K, respectively; overwhelming state-of-the-art single-phase ultraviolet-pumped WLEDs phosphors.

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Section: Methodsmentioning

confidence: 99%

Efficient and tuneable photoluminescent boehmite hybrid nanoplates lacking metal activator centres for single-phase white LEDs

et al. 2014

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“…A theoretical model to describe the energy transfer processes between the ligands and a lanthanide ion has been developed by Malta and coworkers [11][12][13][14]. From Fermi's golden rule and the Born-Oppenheimer approximation, the energy transfer rate, W ET , can be expressed by…”

Section: Energy Transfer Ratesmentioning

confidence: 99%

“…The temperature-dependent F factor contains a sum over the Franck-Condon factors as described in Refs. [11][12][13][14]20]. It is approximately given by…”

Section: Energy Transfer Ratesmentioning

confidence: 99%

“…Our theoretical methodology uses three types of calculations for these molecules. First, we use the "sparkle" model SMLC/AM1 [5][6][7][8][9] to predict the geometries of adducts; second, we use the INDO/S-CI method [10] to predict the energy levels of the coordinated organic ligands; and finally, we use the method recently developed by Malta and coworkers [11][12][13][14] to compute the rates of energy transfer and finally to obtain the quantum yields for the emitted radiation. Our ultimate goal is to be able to use these calculations to predict, and therefore design, complexes of high luminescence yields.…”

Section: Introduction Rmentioning

confidence: 99%

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Theoretical and experimental luminescence quantum yields of coordination compounds of trivalent europium

Faustino

Severino

Thompson

et al. 2005

Int J of Quantum Chemistry

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An appraisal of a semiempirical methodology recently introduced by us for the theoretical calculation of luminescence quantum yields is presented. Six coordination compounds of Eu 3ϩ were considered, possessing either benzoylacetonate or benzoyltrifluoroacetonate, together with either water, 2,2Ј-bipyridine, or 1,10-phenanthroline as ligands. Their geometries were calculated using the SMLC/AM1 method. The ligand-Eu 3ϩ energy transfer rates were calculated in terms of a model of intramolecular energy transfer processes in lanthanide coordination compounds developed earlier by our group. The luminescence quantum yields of the complexes were calculated by solving numerically a system of rate equations for each compound, and by comparing them with the quantum yields determined spectroscopically. Finally, we show that the theoretical quantum yields correlate linearly with the experimental yields, within their error bars. Such linear correlation indicates that the theoretical approach can be useful for the a priori design of highly luminescent lanthanide coordination compounds.

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“…[31] From a theoretical study, the presence of low energy ligand-to-metal charge-transfer excited state (LMCT) resulting in the depopulation of lanthanide excited states has also been proposed to explain the low luminescence quantum yield. [32] Herein, calculations were first performed on these two model compounds employing slightly different theoretical approaches to determine the most suitable model for the systems of interest and to test its reliability. Excited states calculations were done on compound 1b using two types of atomic basis set, the limited 6-31G basis set and the larger 6-31 + G* basis set, and small-core (SC) and large-core (LC) relativistic pseudopotential on europium.…”

Section: Resultsmentioning

confidence: 99%

Luminescent Eu(III) and Gd(III) Trisbipyridine Cryptates: Experimental and Theoretical Study of the Substituent Effects

Guillaumont

Bazin²,

Benech³

et al. 2007

ChemPhysChem

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Synthesis, absorption spectra and luminescebce properties of a series of lanthanide trisbipyridine cryptates Ln within R-Bpy x R-Bpy x R-Bpy, where Ln = Eu, Gd and R = H, COOH, COOCH3, CONH(CH2)2NH2 are described. Comparison of the unsubstituted parent compound with the substituted compounds shows that bipyridine substitution doesn't alter significantly the photophysical properties of the lanthanide cryptate. The absorption maximum is slightly red-shifted when three bipyridines are substituted, whereas substituting one bipyridines has a negligible effect on the absorption spectra. The experimental triplet state energy is between 21600 and 22 100 cm(-1) for the series of compounds and the luminescence lifetimes at 77 K are between 0.5 and 0.8 ms in HO2 and equal to 1.7 ms in D2O. The experimental characterizations are completed by DFT and TD-DFT calculations to assess the ability of these approaches to predict absorption maxima, triplet state energies and structural parameters of lanthanide cryptates and to characterize the electronic structure of the excited states. The calculations on the unsubstituted parent and substituted compounds show that absorption maxima and lowest 3pipi* triplet state energies can be accurately determined from density functional theory (DFT) and time-dependent (TD) DFT calculations.

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A theoretical study of the energy-transfer process in [Eu⊂bpy.bpy.bpy]3+ cryptates: a ligand-to-metal charge-transfer state?

Cited by 50 publications

References 19 publications

Efficient and tuneable photoluminescent boehmite hybrid nanoplates lacking metal activator centres for single-phase white LEDs

Efficient and tuneable photoluminescent boehmite hybrid nanoplates lacking metal activator centres for single-phase white LEDs

Theoretical and experimental luminescence quantum yields of coordination compounds of trivalent europium

Luminescent Eu(III) and Gd(III) Trisbipyridine Cryptates: Experimental and Theoretical Study of the Substituent Effects

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