Density Functional Theory Investigation of Eu(III) Complexes with β-Diketonates and Phosphine Oxides:  Model Complexes of Fluorescence Compounds for Ultraviolet LED Devices

Abstract

The density functional theory was employed to investigate Eu(III) complexes with three beta-diketonates and two phosphine oxides (complex M1: Eu(bdk)3(TPPO)2, complex M2: Eu(bdk)3(TMPO)2, and complex M3: Eu(bdk)3(TPPO)(TMPO)) deemed to be the model complexes of the fluorescence compounds for the ultraviolet LED devices we have recently developed. For each complex, two minimum energy points corresponding to two different optimized geometries (structures A and B) have been found, and the difference of the energy between two minimum energy points is found to be quite small (less than 1 kcal/mol). Vertical excitation energies and oscillator strengths for each complex at two optimized geometries have been obtained by the time-dependent density functional theory, and the character of the excited states has been investigated. For complex M3, the absorption edge is red-shifted, and the oscillator strengths are relatively large. The efficiency of intersystem crossing and energy transfer from the triplet excited state to the Eu(III) ion is considered by calculating DeltaE(ISC) (the energy difference between the first singlet excited state and the first triplet excited state) and DeltaE(ET) (the difference between the excitation energy of the complex for the first triplet excited state and the emission energy of the Eu(III) ion for 5D to 7F).

Effect of secondary ligands’ size on energy transfer and electroluminescent efficiencies for a series of europium(iii) complexes, a density functional theory study

“…E x_t can be obtained by the energy difference between the lowest triplet and singlet state at the optimized ground-state geometry. 26 While E ET can be obtained from two pathways previously reported by Aigo: 26,27 one is the energy difference between E x_t and emission energy of Eu 3+ from 5 D 0 to 7 F 2 (E ET1 ), and the other is the excitation energy difference between the first singlet excited state and the first triplet excited state calculated by TDDFT (E ET2 ). In addition, Aigo suggested that the singlet to triplet intersystem crossing energy (E ISC ) is calculated with the excitation energy difference between the first singlet excited state and the first triplet excited state by TDDFT calculation.…”

“…In addition, Aigo suggested that the singlet to triplet intersystem crossing energy (E ISC ) is calculated with the excitation energy difference between the first singlet excited state and the first triplet excited state by TDDFT calculation. 27 To have efficient sensitization, an empirical rule indicates that E ET must be larger than 0.43 and E ISC must be larger than 0.62 eV. 28 For E x_t values in Table 2, Eu-Phen, Eu-PyPhen and Eu-MPP have the similar values of about 2.5 eV, and they are about 2.3 eV for other complexes, with the exception of Eu-BDPz, which is especially small in comparison with others (1.51 eV).…”

Charge injection and transfer tuning of a series of Pt complexes through oligothiophenes: A theoretical study

“…In addition, the intersystem crossing energy (DE ISC ) is the energy difference between the first singlet excited state (S 1 ) and the first triplet excited state (T 1 ) [32]. The DE ISC can estimate the probability of intersystem conversion.…”

Emission Properties, Solubility, Thermodynamic Analysis and NMR Studies of Rare-Earth Complexes with Two Different Phosphine Oxides

“…Two minimum energy points corresponding to two different optimized geometries (structures A and B) have been found, and the difference between two minimum energy points is small (less than 1 kcal/mol). From these results, it is known that structures A and B can both exist in a solution or a polymer [33]. Time-dependent density functional theory (TDDFT) calculations suggest that the absorption coefficient of structure A is larger than that of structure B, resulting in a larger emission intensity.…”