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

Abstract

In this paper, a quantum chemistry method was used to investigate the effect of different sizes of substituted phenanthrolines on absorption, energy transfer, and the electroluminescent performance of a series of Eu(TTA)(3)L (L = [1,10] phenanthroline (Phen), Pyrazino[2,3-f][1,10]phenanthroline (PyPhen), 2-methylprrazino[2,3-f][1,10]phenanthroline(MPP), dipyrido[3,2-a:2',3'-c]phenazine(DPPz), 11-methyldipyrido[3,2-a:2',3'-c]phenazine(MDPz), 11.12-dimethyldipyrido[3,2-a:2',3'-c]phenazine(DDPz), and benzo[i]dipyrido[3,2-a:2',3'-c]phenazine (BDPz)) complexes. Absorption spectra calculations show that different sizes of secondary ligands have different effects on transition characters, intensities, and absorption peak positions. The larger secondary ligands DPPz, MDPz, DDPz and BDPz lead to incomplete energy transfer from the triplet states of ligands to the (5)D(0) of the Eu(3+) ion compared with smaller ones (PyPhen and MPP) due to their lower S(1) or T(1) state energy levels than that of TTA or (5)D(0) of Eu(3+). "Small polaron" stabilization energy (SPE) results reveal that electron trapping is the dominant electroluminescence (EL) mechanism in these materials due to their lower LUMO energies than 4,4'-N,N'-dicarbazolebiphenyl (CBP). Reorganization energy (l) values show that these materials have better electron than hole transporting properties. In addition, the reasons for the origin of the 500 nm emission in Eu-PyPhen- and Eu-MPP-based OLED devices were investigated, and we suppose this emission may result from 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), not from Alq(3).

DFT and Time-dependant DFT Investigation of eLectronic Structure, Phosphorescence and Electroluminescence Properties of Iridium (III) Quinoxaline Complexes

“…7 This can be rationalized by different conditions: in experiment, the measurement is influenced by many factors, such as temperature, solvent, and intermolecular π-π stacking, all of which can influence the HOMO energy levels as observed in previous theoretical reports. 21 The calculated LUMO energies are consistent with the experimental trend in the order 1<2<3, and we noticed that the stronger π-electron accepting ability of ancillary ligand can lead to the lower LUMO energy. As expected, the calculated LUMO energies for 1-3 are much stabilized than other Ir(C^N) 2 L complexes, 16 because of the stronger accepting ability of fpmqx ligand.…”

Metabolism and function of phenazines in bacteria: impacts on the behavior of bacteria in the environment and biotechnological processes

“…OLEDs are organic semiconductors containing an emissive layer placed between a transparent anode (e.g., transparent indium tin oxide) and a metal cathode (e.g., Mg, Al, Ag). When a bias is applied across the electrodes, the ‘holes’ (areas lacking electrons) and electrons combine in the emissive layer resulting in light emission (Li et al 2009). …”

Synthesis, photophysical and oxygen-sensing properties of a novel Eu3+ complex incorporated in mesoporous MCM-41

“…3. As for pure Eu(DPIQ)(TTA) 3 , two absorption bands located around 225 and 279 nm are observed, corresponding to the p-p n electronic transitions of DPIQ [27,28]. The band at 336 nm is assigned to the absorption of TTA electronic transitions.…”