Shedding light on the photophysical properties of iridium(<scp>iii</scp>) complexes with a dicyclometalated phosphate ligand via N-substitution from a theoretical viewpoint

Shang, Xiaohong; Han, Deming; Zhou, Defeng; Zhang, Gang

doi:10.1039/c6nj03617a

Cited by 9 publications

(8 citation statements)

References 37 publications

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“…In addition, the use of nitrogen rich ligands promotes the blue‐emission and the decrease in the 3 MLCT character, resulting in a decreased value of k r , which agrees with the behavior of the proposed anionic complexes . Otherwise, it has been theoretically described that k r is inversely proportional to the splitting energy between the S 1 and T 1 states [Δ E (S 1 ‐T 1 )], and directly proportional to the transition electric dipole moment in the S 0 →S 1 transition (μ S1 ):

k_{normalr} \propto \frac{E_{normale normalm normali} {normalμ}_{normalS 1}^{2}}{{true({Δ E}_{normalS 1 - normalT 1} true)}^{2}}

where E emi is the emission energy in cm −1 . Accordingly, k r can be qualitatively characterized in terms of the values of [Δ E (S 1 ‐T 1 )] and μ S1 .…”

Section: Resultssupporting

confidence: 76%

“…It has been determined that a large 3 MLCT contribution in the emissive state increases the k r and quantum yield Φ p as observed in Os, Ir, and Pt complexes The % 3 MLCT for a given excited state is obtained as the sum of the single 3 MLCT contributions from each monoexcitations from i to j orbitals:

%^{3} normalM normalL normalC normalT = {false\sum}_{I}^{n} ([]|, C_{I} (|, i \to j)) ([]|, {% (|, M)}_{i} - {% (|, M)}_{j})

where C I is the configuration coefficient of each monoexcitation from i to j orbital in the excited state wavefunction, and %( M ) i and %( M ) j are the metal contributions to the occupied i and virtual j orbitals, respectively (more details in Section S7 of the Supporting Information). The 3 MLCT contribution in C1 ‐ C3 is of 22%‐30%, which decreases in systems C4 ‐ C6 by the fluorination of the ppy ligand.…”

Section: Resultsmentioning

confidence: 99%

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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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k_{normalr} \propto \frac{E_{normale normalm normali} {normalμ}_{normalS 1}^{2}}{{true({Δ E}_{normalS 1 - normalT 1} true)}^{2}}

where E emi is the emission energy in cm −1 . Accordingly, k r can be qualitatively characterized in terms of the values of [Δ E (S 1 ‐T 1 )] and μ S1 .…”

Section: Resultssupporting

confidence: 76%

%^{3} normalM normalL normalC normalT = {false\sum}_{I}^{n} ([]|, C_{I} (|, i \to j)) ([]|, {% (|, M)}_{i} - {% (|, M)}_{j})

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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“…Some factors related to the k r are the transition electric dipole moment in the S 0 → S 1 transition (

μ_{S_{1}}

) and the energy difference between S 1 and T n excited state (Δ E [ S 1 − T n ]; n = 1 or 2 depending of the complexes of this study). These parameters are important to evaluate since

μ_{S_{1}}

is directly proportional to k r , and Δ E ( S 1 − T n ) represent the efficiency of the ISC, therefore, a large

μ_{S_{1}}

and smaller Δ E ( S 1 − T n ) evidence a favored radiative deactivation . In addition, the Ir atom increases the spin‐orbital coupling (SOC) improving the intersystem crossing during the electronic transition, and the metallic contribution in the T n excited states (% 3 MLCT) can be quantified, since a large 3 MLCT percentage increases the k r .…”

Section: Resultsmentioning

confidence: 99%

“…The % 3 MLCT were calculated by a sum of the 3 MLCT contributions from each monoexcitations (according with their respective orbitals involved), considering the corresponding configuration coefficient as has been reported in literature …”

Section: Computational Detailsmentioning

confidence: 99%

Electron‐donor substituents on the dppz‐based ligands to control luminescence from dark to bright emissive state in Ir(III) complexes

Dreyse

Santander-Nelli

Zamorano

et al. 2020

Int J of Quantum Chemistry

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Dppz-based Ir(III) complexes show a competition between dark and bright excited states. Paulina Dreyse and colleagues in e26167 used DFT/TD-DFT to determine geometrical and photophysical properties, and the possible applicability of these systems as new luminescent materials in Light Emitting Electrochemical Cells (LECs). The study found an improved radiative decay (bright) in presence of electron-donor substituents.

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“…In OLEDs, researchers can control the emission color and photophysical properties of emitters by a modification of the chelating ligands [ 13 , 14 , 15 , 16 , 17 ]. The common approach in tuning the photophysical properties of FIrpic is to modify the chemical structures of 2-(2,4-difluorophenyl) pyridine (C ∧ N) ligands.…”

Section: Introductionmentioning

confidence: 99%

Tuning the Geometrical Structures and Optical Properties of Blue-Emitting Iridium(III) Complexes through Dimethylamine Substitutions: A Theoretical Study

2017

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The geometrical structures and photophysical properties of Ir(4,6-dFppy)2(pic) (FIrpic) and its derivative (o-FIr, m-FIr, p-FIr) with dimethylamine substituted at the picolinic acid (N∧O) ligand were fully investigated by density functional theory and time-dependent density functional theory. The simulated electronic structure, as well as absorption and emission spectra of FIrpic are in good agreement with the experimental observations. The introduction of dimethylamine at the N∧O ligand at different positions is beneficial to extend the π-electron delocalization, increase HOMO energy levels, and hence improve the hole injection and transfer ability compared with those of FIrpic. Furthermore, o-FIr, m-FIr, and p-FIr have large absorption intensity and participation of metal-to-ligand charge transfer (MLCT) contribution in the main absorption spectra, which would be useful to improve the intersystem crossing (ISC) from the singlet to triplet excited state. More importantly, the high quantum yield of o-FIr (which is explained based on the detailed analysis of triplet energy, ET1), participation of 3MLCT contribution in the phosphorescent spectra, and energy difference between 3MLCT and triplet metal centered (3MC) d-d excited state compared with m-FIr and p-FIr indicate that o-FIr is expected to be an excellent blue phosphorescence emitter with high efficiency.

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Shedding light on the photophysical properties of iridium(iii) complexes with a dicyclometalated phosphate ligand via N-substitution from a theoretical viewpoint

Abstract: The geometrical structures and phosphorescence efficiency of two series of iridium(iii) complexes with wide-range color tuning have been focused on in this work.

Cited by 9 publications

References 37 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

Electron‐donor substituents on the dppz‐based ligands to control luminescence from dark to bright emissive state in Ir(III) complexes

Tuning the Geometrical Structures and Optical Properties of Blue-Emitting Iridium(III) Complexes through Dimethylamine Substitutions: A Theoretical Study

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