DFT and TD-DFT study a series of blue and green iridium complexes with mesityl-phenyl-imidazole ligand

Accepted Manuscript DFT and TD-DFT study a series of blue and green iridium complexes with mesitylphenyl-imidazole ligand Ming-Xing Song, Ke-Chuan He, Peng Lü, Li-Jun Wang, Ya-Qi Cao, Shu-Yan Song, Xiang-Wei Meng, Shi-Quan Lü, Zheng-Kun Qin, Fu-Quan Bai, Hong-Jie Zhang PII:

S1566-1199(18)30546-9

DOI:

https://doi.org/10.1016/j.orgel.2018.10.031

Reference:

ORGELE 4947

To appear in:

Organic Electronics

Received Date: 22 July 2018 Revised Date:

17 October 2018

Accepted Date: 20 October 2018

Please cite this article as: M.-X. Song, K.-C. He, P. Lü, L.-J. Wang, Y.-Q. Cao, S.-Y. Song, X.-W. Meng, S.-Q. Lü, Z.-K. Qin, F.-Q. Bai, H.-J. Zhang, DFT and TD-DFT study a series of blue and green iridium complexes with mesityl-phenyl-imidazole ligand, Organic Electronics (2018), doi: https://doi.org/10.1016/ j.orgel.2018.10.031. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Graphical abstract

A series of heteroleptic cyclometalated Ir (III) complexes, which are used for OLED application, were investigated by DFT and TD-DFT method. The frontier molecular orbital character and charge transfer character shown that they have the advantages of

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low efficiency roll-off properties, which is a “stumbling block” in the process of OLED solid-lighting’s development. Namely, means the materials will play an

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important role in the journey development of OLED.

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DFT and TD-DFT Study a series of Blue and Green Iridium Complexes with Mesityl-Phenyl-Imidazole Ligand Ming-Xing Song,a* Ke-Chuan He,a Peng Lü,a Li-Jun Wang,a Ya-Qi Cao,a Shu-Yan

Baid,** and Hong-Jie Zhang b a

College of Information Technology, Jilin Normal University, Siping 136000,

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People’s Republic of China.

State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute

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b

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Song,b Xiang-Wei Meng, c Shi-Quan Lü,c , Zheng-Kun Qin, a* Fu-Quan

of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China. c

College of physics, Jilin Normal University, Siping 136000, People’s Republic of

d

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China.

Institute of Theoretical Chemistry, Jilin University, Changchun 130023, People’s

Republic of China.

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*Correspondence author: Ming-Xing Song (E-mail: [email protected]) and

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Zheng-Kun Qin (E-mail: [email protected]) ** Also for correspondence: Fu-Quan Bai (E-mail: [email protected])

A series of blue and green-emitting phosphorescent heteroleptic cyclometalated Ir(III) complexes with mesityl-phenyl-imidazole Ligand for organic light-emitting devices are investigated theoretically to explore their electronic structures, spectroscopic properties and the application value for organic light emitting devices. The geometries, electronic structures, lowest-lying singlet absorptions, and triplet emissions of

ACCEPTED MANUSCRIPT Ir(mpim)3, and the theoretically designed models Ir(F-mpim)3, Ir(F2-mpim)3, (mpim)2Ir(acac),

(F-mpim)2Ir(acac),

(F2-mpim)2Ir(acac),

(mpim)2Ir(tpip),

(F-mpim)2Ir(tpip), (F2-mpim)2Ir(tpip), are investigated with Density Functional

F-mpim

denotes

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Theory (DFT) approaches, where mpim denotes 1-mesityl-2-phenyl-1H-imidazole, 2-(4-fluorophenyl)-1-mesityl-1H-imidazole,

F2-mpim

denotes

tpip denotes tetraphenylimido-diphosphinate.

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2-(2,4-difluorophenyl)-1-mesityl-1H-imidazole, acac denotes acetylacetonate, and

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KEYWORDS: Ir(III) complex; Blue and Green; TD-DFT; OLEDs; Efficiency roll-off. INTRODUCTION

Ir(III) complexes has drawn great attention in the past two decades due to their

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applications as organic light emitting diodes (OLEDs),[1] which were first reported by C. W. Tang et al. in 1987.[2] During the last two decades of gradual development, more and more Ir(III) complexes were discovered, Such as in red-emitting ( Ir(piq)3,

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piq denotes 1-phenylisoquinolato), green-emitting (Ir(ppy)3 and Ir(dfppy)2(acac), ppy

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denotes 2-phenylpyridine, dfppy denotes 4,6-difluorophenylpyridine, acac denotes acetylacetonate),

blue-emitting

(Ir(III)

bis[(4,6-difluoropheny)-pyridinato-N,C2]

picolinate, Firpic), and so on.[3] As the electroluminescent phosphors of OLEDs, the color of the Ir(III) complex

is very important, especially the three basic colors. For red-emitting phosphorescence, there are many efficient Ir(III) complexes can be used, but for blue and green-emitting phosphorescence are not, because of their requirement to exhibit the highest excitation

ACCEPTED MANUSCRIPT and emission energy with reasonable efficiency.[4] In addition, most of the blue and green-emitting Ir(III) complexes cannot satisfy to be used for applications in OLEDs, since the existing roll-off property.[5] Thus now, it is essential to find blue and green

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Ir(III) complexes with good performance. In this article, we use Ir(mpim)3 (mpim denotes 1-mesityl-2-phenyl-1H-imidazole) (labeled 1), which has been confirmed as a high-efficiency blue-color Ir(III) complex

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[6], as a reference, and theoretically designed a series of blue and green Ir(III)

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complexes by density functioanl theory (DFT) and time-dependent density fuctional theory (TDDFT) approaches:[7] Ir(F-mpim)3 (labeled 2), Ir(F2-mpim)3 (labeled 3), (mpim)2Ir(acac) (labeled 4), (F-mpim)2Ir(acac) (labeled 5), (F2-mpim)2Ir(acac) (labeled

6),

(mpim)2Ir(tpip) (labeled

9),

7),

(F-mpim)2Ir(tpip)

where

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(F2-mpim)2Ir(tpip)

(labeled

2-(4-fluorophenyl)-1-mesityl-1H-imidazole,

F-mpim

F2-mpim

(labeled

8),

denotes denotes

2-(2,4-difluorophenyl)-1-mesityl-1H-imidazole, acac denotes acetylacetonate, and

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tpip denotes tetraphenylimido-diphosphinate. From the main ligand and auxiliary

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ligand structures, substituents and side chain structure, our design idea is to use functional groups which are easy to synthesize and has been utilized commonly in transition metal complexes. To show the comprehensive properties of complexes 1–9 on computational area,

we

theoretically

investigated

the

molecular

structures,

the

absorption,

phosphorescence properties and the application prospect on OLED, etc. The methods we used in this article are shown in supporting information. Furthermore, we hope

ACCEPTED MANUSCRIPT that the materials designed can be synthesized in the future. RESULTS AND DISCUSSION 1. Geometries in the Ground State S0 and the lowest-lying Triplet State T1

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In order to verify the correctness of our approach, the maps of the complexes are shown in Figure 1, and the optimized ground-state geometrical structures for the complexes are shown in Figure 2 (complex 1) and Figure S1 (see Supporting

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Information). The main geometric structural parameters of the ground states (S0) are

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summarized in Table 1. In addition, the complexes 1, 2 and 3 have three same ligands, and the complexes 4, 5, and 6 have a same ancillary ligand, acac, while 7, 8, and 9 have the same ancillary ligand, tpip. For ease of discussion, we refer to these three groups of complexes as MPIMs, ACAC and TPIP, respectively. In a similar way, the

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MPIM group include complexes 1, 4, and 7, f-MPIM group include 2, 5, and 8, f2-MPIM group include 3, 6, and 9 respectively, based on the main ligands. As shown in Table 1, all the complexes maintain quasi-octahedral geometry

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around the metal centres, as is observed in other typical, six-coordinated Ir(III)

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complexes. The calculated cyclometallic Ir–N and Ir–C bond lengths, and Ir-O are in good agreement with experiment values and previous theoretical explorations of cyclometallic iridium complexes [8]. In addition, the structural distortions are slight. For MPIMs group, as the number of F atoms increased, the bond length of Ir-C becomes shorter, while the bond length Ir-N has no significant changes for the ground states (S0), because the atoms F replaced the hydrogen atom of the phenyl. And for ACAC and TPIP group, comparing complexes MPIM, f-MPIM, and f2-MPIM, we

ACCEPTED MANUSCRIPT found that as the number of F atoms increased, the Ir-O bond lengths became shorter, because the F atom has an electron-withdrawing ability, while the ancillary ligands that we used comprise an electron-donating group. Other than that, for the ground

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states (S0), compared to the ACAC complexes, the Ir-O bond length in TPIP complexes increases by 0.072–0.078 Å. This could be attributed to the phenyls, which cause the increased steric hindrance of the molecules connected to the atoms P.

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The structure parameters of lowest-lying triplet states (T1) are also listed in Table

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1. Comparing the T1 and S0 states, the changes of the Ir-N, Ir-C and Ir-O bond lengths (0–0.037 Å) in the MPIMs and TPIP groups are very equably, this means the ligand-to-ligand charge-transfer transitions (3LLCT), which belong to long charge transitions, will occur between two relatively distant ligands, so the phosphorescence

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lifetime of the them will come longer.[9] But for ACAC group, the changes of the Ir-N and Ir-C bond lengths (0.001–0.033 Å) in the complex 4 is obvious, while the Ir-O bond length shows only a slight shift (0.008–0.012 Å), this means nearly no LLCT occur between two relatively distant ligands, so the complex 4, which we

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3

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theoretically designed, will exhibit the low-efficiency roll-off property since their shorter phosphorescence lifetime,[10] while for complexes 5 and 6, the changes of the Ir-O bond lengths (0.053–0.096 Å) are very obviously, this means the 3LLCT will be the main charge-transfer transition when they are working. 2. Frontier Molecular Orbital Properties In order to show the optical and chemical properties of these complexes, we theoretically analysed the frontier molecular orbital (FMO) properties. It is known

ACCEPTED MANUSCRIPT that the concept of emission colour tuning by grafting various substituents and use of the electron-withdrawing substituents at the cyclometalating ring relies on the fact that the lowest excited state is relatively well described as a highest occupied molecular

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orbital (HOMO) to lowest occupied molecular orbital (LUMO) transition in a given ligand.[11] Therefore, we will discuss in detail the ground-state electronic structure with the special emphasis on the HOMO and LUMO distribution, energy levels, and

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energy gaps. The FMO of the complexes are listed in Tables S1–S9 (see Supporting

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Information). The HOMO and LUMO distribution, energy levels, and energy gaps are plotted in Figure 3.

In MPIMs and TPIP groups, the HOMO mainly resides on the d orbital of the metal atom Ir and three ligands uniformly, while the LUMO just resides on three (HOMO: for Ir, 48%, 47%, 48%, 53%, 50%, and 51%; HOMO/LUMO:

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ligands,

for ligands(mpim-1-Ph and mpim-1-Im, or mpim-2-Ph and mpim-1-Im, or mpim-3-Ph and mpim-3-Im, or tpip), 52%/99%, 22%/25%, 40%/98%, 77%/96%, 46%/96%, and

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49%/97%). Thus, for the emission T1 → S0 (LUMO → HOMO) of them, the

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metal-to-ligand charge-transfer transition (3MLCT) will appear between the metal atom Ir and ligands, and the ligand-ligand charge-transfer transition (3LLCT) will appear between the ligands. In addition, for ACAC group, the HOMO mainly resides on the d orbital of the metal atom Ir and the main ligands (mpim-1-Ph and mpim-1-Im, or mpim-2-Ph and mpim-2-Im) (for Ir, 52%, 49%, and 50%; for main ligands, 42%, 46%, and 46%), while the LUMO is distributed on the main ligands (96%, 96%, and 94%), there is no contribution by auxiliary ligand acac. Thus in this part, we can

ACCEPTED MANUSCRIPT conjecture that the complexes of ACAC group all have a low-efficiency roll-off property, the accompanied reduced charge and exciton accumulation at the EML edges decreases the triplet-triplet annihilation and triplet polaron quenching. [11, 12].

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3. Absorption and Emission in CH2Cl2 Media The absorption spectra in CH2Cl2 solution and their associated oscillator strengths, assignment, and excitation energies are listed in Table 2, and the fitted Gaussian-type

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absorption curve is shown in Figure 4 and Figure S2 (shown in supporting

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information).

From the details obtained, the lowest absorption bands are at 375, 356, 349, 375, 359, 356, 358, 368, and 365 nm for complexes 1–9, respectively, and the HOMO→LUMO transition is the primary transition.

state 2m2

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The oscillator strength f12 of a transition from a lower state 1m1

to an upper

may be defined by

2 me ( E2 − E1 )∑ ∑ 1m1 | Rα | 2m2 3 h2 m2 α = x , y , z

2

(1)

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f12 =

Where me is the mass of an electron and h is the reduced Planck constant.

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The quantum states nmn , n = 1,2,…, are assumed to have several degenerate sub-states, which are labelled mn . "Degenerate" means that they all have the same energy En . The operator Rα is the sum of the x coordinates

ri ,α

of all N

electrons in the system, etc.: N

Rα = ∑ ri ,α i =1

The oscillator strength is the same for each sub-state 1m1 .

(2)

ACCEPTED MANUSCRIPT The emission details, which are obtained under the TDDFT/M062X/LanL2DZ; 6-311+G* level, are listed in Table 3, and the computations are carried out with CH2Cl2 media. The calculated low-lying emission of complexes 1–9 are at 502, 505,

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512, 503, 535, 476, 509, 510, and 514 nm, respectively, and the charge-transfer transition characters are mainly 3MLCT and 3ILCT for ACAC group, while 3MLCT and 3ILCT for MPIMs and TPIP groups. In 2014, complex 1 was used by Kazuo et

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al.[6] in an OLED, which showed emitting light colour at 510 nm, which

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demonstrates that the computational details are reliable. The calculated emission wavelength of complex 1 has a small deviation with experimental result. However, from qualitative analysis, complexes 2-9 keep almost the same emission wavelength with complex 1. While for complex 5 (535 nm), it has a relative large

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bathochromic-shift compared with complex 1 and the 6 present blue shift about 0.15 ev. The substitution of F has a greater effect on the excitation energy of ACAC series complexes. In addition, from the details we obtained, all the complexes in the ACAC

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group we theoretical designed will show blue/green and have the low-effective

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roll-off property when they are used in an OLED. Presented in Table 4 are the calculated radiative decay rate constants, kr

and three spin sublevels krα (α = x, y, z) of the Tm→S0 transition. For 1, the number (kr = 3.90×104 s-1) is underestimated compared to the experimental radiative rate constant (about 104), however, the deviation, which can be due to the oversimplifications of spin-orbit interaction and have the same magnitude. Thus, the present simplified analysis can be applicable in evaluating the kr

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conducive to increasing the radiation rate constant. The computational schemes we have adopted here are all described in literatures therein [8a, 8c, 13]. 4. The Application Prospect on OLED

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In order to conform the potential application value of the Ir(III) complexes we

complexes are shown in Figure 5.

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studied in this article, the OLED device configuration and energy levels for these

In general, the OLED devices with a three-layer structure were fabricated, the holes transition layer (HTL), the emitting layer (EML), and the electrons transition

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layer (ETL), together with the indium tin oxide (ITO), whose work function is 5.2 eV, as anode and lithium fluoride (LiF)/aluminium (Al) (LiF/Al) as cathode. HTL must be wide band gap p-type materials, and several inorganic materials such as V2O5 and

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MoO3 have been reported with NiO being the most effective. However, inorganic

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HTL are incompatible with solution-processable printable. Thus, the most commonly employed HTL is semiconducting PEDOT:PSS between the ITO anode and the active layer. PEDOT:PSS has the advantages that it is deposited from solution and serves to minimize the detrimental effects of ITO roughness as well as to align the work functions of P3HT and ITO for more efficient collection of holes. [6,6]-phenyl C61 butyric acid methyl ester (PCBM), C60 and their derivatives as n-type ETL. Nowadays, there are so many materials are used in HTL and ETL, such as TAPC

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cyclohexane)

and

TmPyPb

(1,3,5-tri[m-pyrid-3-yl-phenyl] benzene), in addition, mCP (1,3-bis(carbazol-9-yl) benzene) is used as host materials in EML usually.[5] So in this article, these three

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materials also be used for checking. From the Figure 5, we can find that the HOMO levels of the complexes 1–9 are higher than the host mCP, and their LUMO levels are lower than the host except

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complex 1, so for complexes 2-9, the dopants will behave as hole and electron traps so

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that both electron and hole mobility in the EML will be retarded by the doping, namely, the device structure we used on complexes 2-9 is compatibly. But for complex 1, the LUMO level is higher than mCP 0.16 eV, the carriers transfer are very unbalanced, not only the emission spectrum will red shift seriously, but also the

(4,4,4-tris

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luminous efficiency of the device will very low, maybe that is why the TCTA (N-carbazolyl)

triphenylamine

)

and

26DCzPPy

(2,6-bis(3-(carbazol-9-yl)phenyl)pyridine) were used on the device by Kazuo et al.[6]

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In addition, for complexes 2, 4 and 7, the LUMOs are very close to mCP, so we

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speculate that the blue shift will occur with the emission, since the effect of excimers. To sum up, we can confirm that the Ir(III) complexes we analysed in this article

are very suit for using in OLED. CONCLUSIONS

In order to find a series of low-efficiency roll-off blue and green Ir(III) cyclometalated complexes, we carried out DFT/B3LYP and TDDFT/B3LYP calculations

on

the

geometric

structures,

absorptions,

and

emissions

ACCEPTED MANUSCRIPT (TDDFT/M062X), using the LANL2DZ basis set on the metal atom Ir and the 6-311+G* basis set on the C, H, N, O, P, and F atoms in all the calculations. The emission details that we obtained for complex 1 are comparable to the experimental

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results. The calculated low-lying emission of complexes 1–9 are at 502, 505, 512, 503, 535, 476, 509, 510, and 514 nm respectively. Thus, we speculate that the emission of the complexes referred to in this article belong to the range of blue and green. And we

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confirm that the complexes of ACAC group will have low-efficient roll-off property

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and good quantum efficiency when they are used for OLED device. Furthermore, we also found that the complexes we analysed in this article are very suit to use in OLED area. ACKNOWLEDGEMENTS

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The authors are grateful for financial support from the National Natural Science Foundation for Creative Research Group (Grant Nos. 21701047 and 61605059), the Thirteenth Five-Year Program for Science and Technology of the Education

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Department of Jilin Province (Grant No. JJKH20170372KJ), the Science and

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Technology Development of Jilin Province of China (Grant No. 20180520191JH, 20180414008GH and 20180520199JH), and the State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences (Grant No. RERU2017013). SUPPORTING INFORMATION The FMO of the ground state for the complexes under the DFT/B3LYP level obtained are listed in Tables S1–S9. The optimized ground-state geometric structures

ACCEPTED MANUSCRIPT for the complexes 1–9 are shown in Figure S1, and the Simulated absorption spectra of the complexes in CH2Cl2 media with calculated data is shown in Figure S2. REFERENCES

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Appl. Phys. Lett., 90 (2007) 223508-1-223508-3. [11] (a) N. Sun, Q. Wang, Y.B. Zhao, Y.H. Chen, D.Z. Yang, F.C. Zhao, J.S. Chen, D. Ma, Adv. Mater. 26 (2014) 1617–1621. (b) B.-Q. Liu, L. Wang, D.-Y. Gao, J.-H. Zou, H.-L. Ning, J.-B. Peng, Y. Cao, Light: Science & Applications, 5 (2016) e16137. [12] I. Avilov, P. Minoofar, J. Cornil, L. De Cola, J. Am. Chem. Soc., 129 (2007) 8247-8258.

ACCEPTED MANUSCRIPT [13] G. S. M. Tong, P. K. Chow, W.-P. To, W.-M. Kwok, C.-M. Che, Chem. Eur. J., 20

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(2014) 6433–6443.

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Table 1. Main optimized geometries (ground S0 and lowest-lying triplet states T1) of the complexes.

Table 2. Calculated the Absorption of the complexes 1-6 in CH2Cl2 Media.

experimental values.

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Table 3. Phosphorescent emissions of the complexes in CH2Cl2 solution, together with

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Figure 1. Structures of complexes.

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Figure 2. Optimized geometries of ground states of complexes 1 and 2.

Figure 3. Presentation of energy levels, energy gaps, and orbital composition distribution of HOMOs and LUMOs for complexes.

Figure 4. Simulated absorption spectra of the complexes in CH2Cl2 media with calculated data.

Figure 5. The organic light emitting device (OLED) structure we designed in this work.

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ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT

4

5 6 7 8 9

R4 2.057 2.066

R5 2.120 2.132

R6 2.185 2.198

Exp.[8a]

2.097

2.041

2.036

2.031

2.111

2.146

S0 T1 S0 T1 S0 T1

2.104 2.093 2.098 2.094 2.019 2.000

2.022 2.021 2.020 2.018 2.019 2.019

2.065 2.028 2.062 2.029 2.055 2.022

2.059 2.067 2.053 2.058 2.055 2.064

2.116 2.124 2.111 2.119 2.197 2.204

2.181 2.190 2.166 2.178 2.197 2.209

Exp.[8b]

2.012

2.012

S0 T1 S0 T1 S0 T1 S0 T1 S0 T1

2.017 2.041 2.012 2.023 2.010 2.012 2.008 2.009 2.004 1.998

2.017 2.034 2.012 2.023 2.010 1.992 2.008 1.997 2.004 2.004

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R3 2.064 2.028

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3

R2 2.024 2.020

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2

S0 T1

R1 2.108 2.086

2.060

2.062

2.176

2.181

2.056 2.070 2.049 2.043 2.055 2.063 2.056 2.063 2.050 2.013

2.056 2.035 2.049 2.043 2.055 2.017 2.055 2.017 2.050 2.056

2.190 2.094 2.185 2.133 2.274 2.284 2.265 2.273 2.257 2.263

2.190 2.108 2.185 2.133 2.275 2.278 2.265 2.270 2.257 2.269

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1

Selected Bond Distances (Å)

States

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Complex

RI PT

Table 1. Main optimized geometries (ground S0 and lowest-lying triplet states T1) of complexes.

Selected Bond Angles (deg)

A1 78.4 80.2

A2 95.4 95.6

A3 172.2 173.1

A4 95.0 94.5

A5 90.0 89.7

78.5 80.1 78.3 79.9 79.8 81.5

95.0 95.2 95.3 96.0 97.1 96.9

171.8 172.5 172.0 172.9 175.6 176.2

95.1 94.7 95.6 94.3 94.7 93.6

90.4 90.2 90.2 90.3 88.6 88.5

79.9 79.5 79.7 79.5 80.0 80.0 80.1 80.0 79.9 81.5

96.8 97.3 97.2 95.7 96.5 96.0 96.2 95.6 96.3 97.2

175.3 174.3 175.6 173.2 175.0 176.0 174.7 175.5 174.5 175.6

94.7 96.5 94.8 93.4 92.7 92.0 92.7 91.8 92.3 90.9

88.7 91.7 88.4 91.5 91.2 91.2 91.4 91.7 91.6 91.0

ACCEPTED MANUSCRIPT

R1=RIr-C1, R2=RIr-C2, R3=RIr-N1, R4=RIr-N2, R5=RIr-O1/RIr-C3, R6=RIr-O2/RIr-N3, A1=Angle N1-Ir-C1, A2=Angle N1-Ir-C2, A3=Angle N1-Ir-N2, A4=Angle N1-Ir-O1/Angle

RI PT

N1-Ir-C3, A5=Angle N1-Ir-O2/Angle N1-Ir-N3, .

Table 2. Calculated the absorption energies and transitions of the complexes 1-9 in CH2Cl2 Media.

S4

353/3.50

0.066

S30

275/4.50

0.141

S42

262/4.72

0.125

S45

260/4.75

0.131

S57

249/4.96

0.073

HOMO→LUMO(69% ) HOMO-1→LUMO(63 %) HOMO-4→LUMO+1 (44%) HOMO→LUMO+9(3 8%) HOMO-1→LUMO+9 (40%) HOMO-6→LUMO(22 %) HOMO→LUMO+11( 40%) HOMO-6→LUMO(26 %) HOMO-1→LUMO+1 1(39%) HOMO-2→LUMO+9

Assign

Ir/C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-2-Im→C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-1-Im/C^N-2-Im/ C^N-3-Im Ir/C^N-1-Ph/C^N-3-Ph/C^N-2-Im/C^N-3-Im→C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-1-Im/C^N-2-Im/ C^N-3-Im

M AN U

0.079

Ir/C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-2-Im/C^N-3-Im→C^N-1-Ph/C^N-3-Ph/C^N-1-Im/C^N-3-Im Ir/C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-2-Im→Ir/C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-1-Im/C^N-3-I m Ir/C^N-1-Ph/C^N-3-Ph/C^N-2-Im/C^N-3-Im→Ir/C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-1-Im/C^N-3-I m Ir/C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-1-Im/C^N-2-Im/C^N-3-Im→C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/ C^N-1-Im/C^N-2-Im/C^N-3-Im Ir/C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-2-Im→Ir/C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-2-Im/C^N-3-I m Ir/C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-1-Im/C^N-2-Im/C^N-3-Im→C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/ C^N-1-Im/C^N-2-Im/C^N-3-Im Ir/C^N-1-Ph/C^N-3-Ph/C^N-2-Im/C^N-3-Im→Ir/C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-2-Im/C^N-3-I m Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/C^N-3-Im/→Ir/C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-1-I

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375/3.30

EP

S1

AC C

1

SC

Compl Stat Energy(nm/ Oscilla Main configurations ex es eV) tor

ACCEPTED MANUSCRIPT

0.062

S43

259/4.47

0.187

S49

253/4.88

0.105

S1

349/3.54

0.074

S6

315/3.12

0.074

S32

260/4.75

0.158

S43

S58

250/4.94

240/5.16

0.166

0.066

HOMO→LUMO(69% ) HOMO-2→LUMO(62 %) HOMO-5→LUMO+2 (28%) HOMO-6→LUMO(27 %) HOMO-1→LUMO+1 0(44%) HOMO-5→LUMO+2 (17%) HOMO-4→LUMO+3 (26%) HOMO-2→LUMO+1

Ir/C^N-1-Ph/C^N-2-Ph/C^N-2-Im→C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-1-Im/C^N-2-Im/C^N-3-Im

RI PT

337/3.67

Ir/C^N-2-Ph/C^N-2-Im→C^N-2-Im/C^N-3-Im

Ir/C^N-1-Ph/C^N-3-Ph/C^N-2-Im/C^N-3-Im→C^N-2-Im/C^N-3-Im Ir/C^N-1-Ph/C^N-3-Ph/C^N-2-Im/C^N-3-Im→Ir/C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-2-Im

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S4

HOMO→LUMO(69% ) HOMO-1→LUMO(69 %) HOMO-1→LUMO+1 1(25%) HOMO-5→LUMO(24 %) HOMO-5→LUMO+2 (52%)

Ir/C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-1-Im/C^N-2-Im/C^N-3-Im→C^N-2-Im/C^N-3-Im

M AN U

0.078

Ir/C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-1-Im/C^N-2-Im/C^N-3-Im→C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/ C^N-1-Im/C^N-2-Im/C^N-3-Im

Ir/C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-1-Im/C^N-2-Im/C^N-3-Im→C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/ C^N-1-Im/C^N-2-Im/C^N-3-Im Ir/C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-1-Im/C^N-3-Im→C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-1-Im/ C^N-2-Im/C^N-3-Im

TE D

356/3.46

Ir/C^N-1-Ph/C^N-2-Ph→C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-1-Im/C^N-2-Im/C^N-3-Im

EP

3

S1

m/C^N-3-Im

Ir/C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-2-Im/C^N-3-Im→C^N-1-Ph/C^N-3-Ph

AC C

2

(31%)

Ir/C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-1-Im/C^N-3-Im→C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-1-Im/ C^N-2-Im/C^N-3-Im Ir/C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-1-Im/C^N-2-Im→C^N-1-Im/ C^N-2-Im

Ir/C^N-1-Ph/C^N-2-Ph/C^N-3-Ph/C^N-1-Im/C^N-2-Im/C^N-3-Im→C^N-1-Ph/C^N-3-Ph

ACCEPTED MANUSCRIPT

0(18%) 0.103

S10

306/4.05

0.066

S16

248/4.36

0.103

HOMO-3→LUMO+1 C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/acac→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/acac (59%)

S28

262/4.72

0.193

HOMO-4→LUMO(35 Ir/C^N-1-Ph/C^N -2-Ph/C^N-1-Im/C^N-2-Im→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im %)

S31

291/4.25

0.147

HOMO-3→LUMO+2 C^N-1-Ph/C^N-2-Ph C^N-1-Im/C^N-2-Im/acac→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/acac (46%) HOMO-9→LUMO(36 ^ C N-1-Im/C^N-2-Im→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im %) HOMO-6→LUMO+1 Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/acac→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/acac (34%) HOMO-3→LUMO+6 C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/acac→C^N-1-Im/C^N-2-Im (21%)

244/5.07

0.102

S1

359/3.44

0.102

S5

327/3.78

0.038

S12

289/4.28

0.101

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TE D

S44

RI PT

375/3.29

HOMO→LUMO(69% ) HOMO-1→LUMO+1 (68%) HOMO→LUMO+7(4 4%) HOMO-2→LUMO+2 (13%)

EP

5

HOMO→LUMO(69% Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im ) HOMO-2→LUMO+1 Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/acac→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/acac (68%)

S1

Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/acac→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/acac

AC C

4

Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im→Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/acac→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/acac

ACCEPTED MANUSCRIPT

S1

356/3.48

0.101

S11

283/4.37

0.089

S20

256/4.66

0.265

S41

S53

7

244/5.07

234/528

0.159

0.047

S1

358/3.22

0.075

S7

324/3.81

0.077

RI PT

0.072

HOMO→LUMO(69% ) HOMO-3→LUMO+1 (55%) HOMO-4→LUMO(47 %) HOMO-2→LUMO(19 %) HOMO→LUMO+9(4 0%) HOMO→LUMO+7(2 2%) HOMO-11→LUMO+ 1(41%) HOMO-11→LUMO+ 2(41%)

SC

230/5.37

Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-3-Im

M AN U

S59

HOMO-4→LUMO(57 Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im %) HOMO-2→LUMO+7 C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/acac→Ir/ C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im (41%) HOMO-6→LUMO(16 Ir/C^N-1-Ph/C^N-2-Ph/acac→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im %)

C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-3-Im/acac→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/acac Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-3-Im Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/acac→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-3-Im

TE D

0.302

Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im→C^N-1-Im/C^N-2-Im Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im→Ir/C^N-1-Ph/C^N-2-Ph

EP

263/4.70

C^N-1-Ph/C^N-2-Ph/acac→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/acac C^N-1-Ph/C^N-2-Ph/acac→C^N-1-Ph/C^N -2-Ph/C^N-1-Im/C^N-2-Im/acac

AC C

6

S25

HOMO→LUMO(66% Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip ) HOMO-2→LUMO(52 Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip %)

ACCEPTED MANUSCRIPT

9

S38

266/4.65

0.093

S1

368/3.36

0.072

S7

316/3.92

0.064

S30

269/4.59

0.197

S37

264/4.68

0.097

S40

260/4.75

0.065

S1

365/3.39

0.07

S6

317/3.91

0.085

S11

288/4.29

0.034

HOMO→LUMO(65% ) HOMO-2→LUMO(58 %) HOMO-4→LUMO(45 %) HOMO-3→LUMO+2 (29%) HOMO-3→LUMO+3 (54%) HOMO-2→LUMO+6 (48%)

Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip

RI PT

0.071

Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip→C^N-1-Ph/C^N-1-Im Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N -2-Im/tpip→C^N-1-Im/C^N-2-Im

SC

269/4.60

Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip

Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip→C^N-1-Ph/C^N-1-Im

M AN U

S34

HOMO-3→LUMO+2 (49%) HOMO-3→LUMO+3 (25%) HOMO-2→LUMO+5 (56%) HOMO-3→LUMO+3 (59%)

Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip

TE D

0.085

Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip→C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip

EP

8

277/4.46

Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip→tpip

HOMO→LUMO(68% Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip ) HOMO-2→LUMO(60 Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip %) HOMO→LUMO+9(5 Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip→C^N-1-Im/C^N-2-Im/tpip 1%)

AC C

S26

ACCEPTED MANUSCRIPT

247/5.01

0.394

0.074

HOMO-3→LUMO+1 (46%) HOMO-4→LUMO(40 %) HOMO-6→LUMO+1 (34%) HOMO-1→LUMO+1 0(22%)

Ir/C^N -1-Ph/C^N -2-Ph/C^N -1-Im/C^N -2-Im/tpip→Ir/C^N -1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip

RI PT

S54

270/4.58

Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip→C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip C^N-1-Ph/C^N-2-Ph/C^N -1-Im/C^N-2-Im→Ir/C^N-1-Ph/C^N-2-Ph/C^N -1-Im/C^N-2-Im/tpip

SC

S21

Ir/C^N-1-Ph/C^N-2-Ph/C^N-1-Im/C^N-2-Im/tpip→C^N-1-Im/C^N-2-Im/tpip

AC C

EP

TE D

M AN U

C^N: mpim, F-mpim and F2-mpim

ACCEPTED MANUSCRIPT Table 3. Phosphorescent emissions and assignments of the complexes in CH2Cl2 solution, together with experimental values. Emissions(nm/eV)

1

502/2.47/510a

L→H(54%)

3

MLCT/3LLCT

2

505/2.46

L→H(63%)

3

MLCT/3LLCT

3

512/2.42

L→H(66%)

3

MLCT/3LLCT

4

503/2.47

L→H(63%)

5

535/2.32

6

Character

MLCT/3ILCT

L→H(43%); L→H-2(38%)

3

MLCT/3ILCT

476/2.60

L→H-1(51%); L→H-2(41%)

3

MLCT/3ILCT

7

509/2.44

L→H(63%)

3

MLCT/3LLCT

8

510/2.43

L→H(65%)

3

MLCT/3LLCT

9

514/2.41

L→H(67%)

3

MLCT/3LLCT

EP

TE D

M AN U

: Ref: [6]

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3

AC C

a

Major contribution

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Complex

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kry/s-1

krz/s-1

kr/s-1

1

0.19

2.87×104

8.83×104

3.90×104

2

1.26

1.34×103

3.25×103

3.59×103

3

8.49×103

5.55×103

1.08×105

4.07×104

4

1.11×104

1.16×104

0.00

5

2.03×104

9.41×105

5.0×104

6

9.25×102

5.24×105

1.50×103

1.75×105

7

11.2

1.34×103

4.49×102

6.01×102

8

11.83

2.71×103

9

3.4×102

9.09×103

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krx/s-1

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Table 4 Radiative rate constants of 1-9 calculated at the triplet excited state geometry obtained at TDDFT/M062X level.

3.37×105

1.35

9.07×102

1.09×103

3.51×103

M AN U TE D EP AC C

7.56×103

EP

TE D

M AN U

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Figure 1. Structures of complexes.

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AC C

Figure 2. Optimized geometries of ground states of complexes 1 and 2.

Figure 3. Presentation of energy levels, energy gaps, and orbital composition distribution of HOMOs and LUMOs for complexes.

M AN U

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Figure 4. Simulated absorption spectra of the complexes in CH2Cl2 media with

AC C

EP

TE D

calculated data.

Figure 5. The organic light emitting device (OLED) structure we designed in this work.

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Highlights Cyclometalated iridium (III) complexes have received special attention as dopants for harvesting the otherwise nonemissive triplet states formed in OLEDs, but now, most of

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them cannot satisfy to be used for the applications, especially for blue and green, since that a fast reduction in efficiency known as roll-off, however, occurs when the drive current increases, this leads to a much lower luminance and more power consumption. Thus in this paper, in order to find a series of blue and green OLED materials with low

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efficiency roll-off properties, we theoretical design and investigate a series of Iridium complexes. The geometries, electronic structures, the lowest-lying singlet absorptions,

M AN U

triplet emissions properties and the application value for organic light emitting devices

AC C

EP

TE D

were all analyzed by theory in this article.