Theoretical study on the electronic structures and phosphorescent properties of a series of iridium(III) complexes with the different positional N-substitution in the pyridyl moiety

Han, Deming; Hao, Fengqi; Jian, Tian; Pang, Chunying; Li, Jingmei; Zhao, Lihui; Zhang, Gang

doi:10.1016/j.jlumin.2014.10.064

Cited by 10 publications

(16 citation statements)

References 48 publications

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“…To account for the formation of the doped regions, the ionization potential (IP) and electron affinity (EA) of the emitting compounds can be used as an approach of their charge injection abilities . IP and EA give information about the energy barrier for the hole and electron injection of Ir(III) complexes . In this way, a favored hole injection from the anode into the emitting compound is related to a small IP; while, a larger EA is related to the easy electron injection from the cathode into the emitter .…”

Section: Resultsmentioning

confidence: 99%

Insights into the luminescent properties of anionic cyclometalated iridium(III) complexes with ligands derived from natural products

Cortés‐Arriagada

Dreyse

Salas

et al. 2018

Int J of Quantum Chemistry

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In the search of remarkable anionic electroluminescent semiconductors to be applied in energy conversion devices such as Light Emitting Electrochemical Cells, we report the electronic, photophysical, and charge injection/transfer properties of a series of cyclometalated iridium(III) complexes through a DFT/TD-DFT procedure. The proposed semiconductors involve bidentated ligands based on natural products (salicylic acid and boldine), and phenylpyridine and phenylpyrazole as the cyclometalating units. The proposed compounds emit in the range of 446 to 571 nm, where the boldine based compounds have red-shifted emissions compared to their analogs with salicylic acid. Blue phosphors were obtained by the use of phenylpyrazole units; however, the ligand field is weak in these cases compared to the ligand field exerted by the phenylpyridine ligands. The latter allows the accessibility to the radiationless states for emitters below 495 nm as a result of the increased stability of the metal centered excited states; consequently, the luminescent quantum yield could be decreased. Conversely, the semiconductors with phenylpyridine units show a restricted accessibility to radiationless processes, which could result in emitters with a high luminescent quantum yield and low non-radiative constants. Finally, the proposed anionic semiconductors show a better balance between hole/electron transfer rate compared to related cationic Ir (III) complexes; while, the easier hole-electron injection is favored for semiconductors with salicylic acid and phenylpyridine units.anionic semiconductors, iridium complexes, LECs, luminescence, TD-DFTThe improvement of the lighting technologies is a challenge to reduce the consumption of electrical energy. Solid-state lighting (SSL) systems comprise LED (Light Emitting Diode), OLED (Organic Light Emitting Diode), and LEC (Light Emitting Electrochemical Cell) devices. [1,2] In particular, LECs consist of a layer of an ionic transition metal complex (iTMC) with luminescent properties, which is sandwiched between two electrodes; a cathode that consists of a metal layer, and a transparent conductive film that acts as the anode. [3][4][5] In addition, LECs require less stringent packaging procedures compared to OLEDs since the iTMC layers are processed from a solution, and also because the air-sensitive electron injection layers are not necessary. [3][4][5] The cationic Ir(III) cyclometalated complexes of general formula [Ir(C^N) 2 (N^N)] 1 (C^N: cyclometalating ligand and N^N: ancillary ligand) have been widely used as semiconductor iTMCs, due to their remarkable photophysical properties such as i) high ligand-field splitting energy; [6,7] ii) the strong spin-orbit coupling (SOC) exerted by Ir; [7,8] iii) and wider color tunability through chemical functionalization and its effects onto the energy of frontier molecular orbitals. [1,9] Despite the wide implementation of cationic Ir(III) complexes, anionic complexes have also emerged as semiconductors for use in LEC devices. [10][11][12] In this regard, t...

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Section: Resultsmentioning

confidence: 99%

Insights into the luminescent properties of anionic cyclometalated iridium(III) complexes with ligands derived from natural products

Cortés‐Arriagada

Dreyse

Salas

et al. 2018

Int J of Quantum Chemistry

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“…In the n-doped region the electrons are added from cathode, and holes are injected in the p-doped zone from anode. According to some studies, the performance of Ir III complexes in emitting devices can be related to several electronic properties evaluating the charge transport and electron (hole) injection 30,32 . According to some studies, the performance of Ir III complexes in emitting devices can be related to several electronic properties evaluating the charge transport and electron (hole) injection 30,32 .…”

Section: Electron Affinity and Ionization Potentialmentioning

confidence: 99%

“…According to some studies, the performance of Ir III complexes in emitting devices can be related to several electronic properties evaluating the charge transport and electron (hole) injection 30,32 . Theoretical studies have related the easier hole injection from the anode into the emissive compound to a small IP, while a larger EA is related to the easy electron injection from the cathode 30,32,58 . In this context, the thermodynamic parameters relating to the ionization potential (IP) and electron affinity (EA), account for the energy barrier for the hole and electron injection, respectively.…”

Section: Electron Affinity and Ionization Potentialmentioning

confidence: 99%

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About the electronic and photophysical properties of iridium(iii)-pyrazino[2,3-f][1,10]-phenanthroline based complexes for use in electroluminescent devices

Cortés‐Arriagada

Sanhueza

González

et al. 2016

Phys. Chem. Chem. Phys.

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A family of cyclometalated Ir(III) complexes was studied through quantum chemistry calculations to get insights into their applicability in light electrochemical cells (LECs). The complexes are described as [Ir(R-C^N)2(ppl)](+), where ppl is the pyrazino[2,3-f][1,10]-phenanthroline ancillary ligand. The modification of the HOMO energy in all the complexes was achieved by means of different R-C^N cyclometalating ligands, with R-ppy (phenylpyridine), R-pyz (1-phenylpyrazole) or R-pypy (2,3'-bipyridine); in addition, inductive effects were taken into account by substitution with the R groups (R = H, F or CF3). Then, compounds with HOMO-LUMO energy gaps from 2.76 to 3.54 eV were obtained, in addition to emission energies in the range of 438 to 597 nm. The emission deactivation pathways confirm the presence of metal-to-ligand transitions in all the complexes, which allow the strong spin-orbit coupling effects, and then improving the luminescence performance. However, the coupling with ligand and metal centered excited states was observed for the blue-shifted emitters, which could result in a decrease of the luminescence efficiencies. Furthermore, ionization potentials, electron affinities and reorganization energies (for holes and electrons) were obtained to account for the injection and transport properties of all the complexes in electroluminescent devices.

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“…The ground state geometry for each molecule was optimised by the DFT method with Becke's three parameter hybrid method combined with the Lee-Yang-Parr correlation functional (denoted as B3LYP) [24][25][26], which has been extensively used to deal with such complexes in many articles by our groups and others [27][28][29]. The geometry optimisations of the lowest triplet states (T 1 ) were performed by unrestricted B3LYP approach.…”

Section: Computational Detailsmentioning

confidence: 99%

A theoretical investigation on the electronic structures and phosphorescent properties of three heteroleptic iridium(III) complexes with different substituted ancillary groups

et al. 2016

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Three heteroleptic iridium(III) complexes 1, 2 and 3 bearing two cyclometalating 2 ,6 -difluoro-2,3 -bipyridyl (dfpypy) chelates and one pyridyl pyrazolate ligand have been investigated by using the density functional theory/time-dependent density functional theory method to study the influence of the different substituent groups (-CF 3 and -N(CH 3 ) 2 moiety on the electronic structures, phosphorescent properties and the organic light-emitting diode performance. The lowest energy absorption wavelength calculated is in good agreement with the experimental value. The lowest energy emissions of complexes 1, 2 and 3 are localised at 454, 534 and 821 nm, respectively. Ionisation potential and electron affinity have been calculated to evaluate the injection abilities of holes and electrons into these complexes. The calculated results show that the different substitute groups affect the charge transfer rate and balance. Finally, we hope that this study can provide a good guide to the future design and synthesis of novel phosphorescent materials for use in the organic light-emitting diodes.

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Theoretical study on the electronic structures and phosphorescent properties of a series of iridium(III) complexes with the different positional N-substitution in the pyridyl moiety

Cited by 10 publications

References 48 publications

Insights into the luminescent properties of anionic cyclometalated iridium(III) complexes with ligands derived from natural products

Insights into the luminescent properties of anionic cyclometalated iridium(III) complexes with ligands derived from natural products

About the electronic and photophysical properties of iridium(iii)-pyrazino[2,3-f][1,10]-phenanthroline based complexes for use in electroluminescent devices

A theoretical investigation on the electronic structures and phosphorescent properties of three heteroleptic iridium(III) complexes with different substituted ancillary groups

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