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Organic Electronics
journal homepage: www.elsevier.com/locate/orgel
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 Song
b
,
Xiang-Wei Meng
c
, Shi-Quan Lü
c
, Zheng-Kun Qin
a,∗∗
, Fu-Quan Bai
d,∗∗∗
, Hong-Jie Zhang
b
a
College of Information Technology, Jilin Normal University, Siping, 136000, PR China
b
State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, PR China
c
College of Physics, Jilin Normal University, Siping, 136000, PR China
d
Institute of Theoretical Chemistry, Jilin University, Changchun, 130023, PR China
ARTICLE INFO
Keywords:
Ir(III) complex
Blue and green
TD-DFT
OLEDs
Efficiency roll-off
ABSTRACT
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 elec-
tronic structures, spectroscopic properties and the application value for organic light emitting devices. The
geometries, electronic structures, lowest-lying singlet absorptions, and triplet emissions of Ir(mpim)
3
, and the
theoretically designed models Ir(F-mpim)
3
, Ir(F
2
-mpim)
3
, (mpim)
2
Ir(acac), (F-mpim)
2
Ir(acac), (F
2
-mpim)
2
Ir
(acac), (mpim)
2
Ir(tpip), (F-mpim)
2
Ir(tpip), (F
2
-mpim)
2
Ir(tpip), are investigated with Density Functional Theory
(DFT) approaches, where mpim denotes 1-mesityl-2-phenyl-1H-imidazole, F-mpim denotes 2-(4-fluorophenyl)-
1-mesityl-1H-imidazole, F
2
-mpim denotes 2-(2,4-difluorophenyl)-1-mesityl-1H-imidazole, acac denotes acet-
ylacetonate, and tpip denotes tetraphenylimido-diphosphinate.
1. Introduction
Ir(III) complexes has drawn great attention in the past two decades
due to their 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) com-
plexes were discovered, Such as in red-emitting (Ir(piq)
3
, piq denotes 1-
phenylisoquinolato), green-emitting (Ir(ppy)
3
and Ir(dfppy)
2
(acac), ppy
denotes 2-phenylpyridine, dfppy denotes 4,6-difluorophenylpyridine,
acac denotes acetylacetonate), blue-emitting (Ir(III) bis[(4,6-di-
fluoropheny)-pyridinato-N,C
2
] picolinate, Firpic), and so on [3].
As the electroluminescent phosphors of OLEDs, the colour of the Ir
(III) complex is very important, especially the three basic colors. For
red-emitting phosphorescence, there are many efficient Ir(III) com-
plexes can be used, but for blue and green-emitting phosphorescence
are not, because of their requirement to exhibit the highest excitation
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 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-effi-
ciency blue-colour Ir(III) complex [6], as a reference, and theoretically
designed a series of blue and green Ir(III) complexes by density func-
tioanl theory (DFT) and time-dependent density fuctional theory
(TDDFT) approaches [7]: Ir(F-mpim)
3
(labeled 2), Ir(F
2
-mpim)
3
(la-
beled 3), (mpim)
2
Ir(acac) (labeled 4), (F-mpim)
2
Ir(acac) (labeled 5),
(F
2
-mpim)
2
Ir(acac) (labeled 6), (mpim)
2
Ir(tpip) (labeled 7), (F-
mpim)
2
Ir(tpip) (labeled 8), (F
2
-mpim)
2
Ir(tpip) (labeled 9), where F-
mpim denotes 2-(4-fluorophenyl)-1-mesityl-1H-imidazole, F
2
-mpim
denotes 2-(2,4-difluorophenyl)-1-mesityl-1H-imidazole, acac denotes
acetylacetonate, and tpip denotes tetraphenylimido-diphosphinate.
From the main ligand and auxiliary 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
https://doi.org/10.1016/j.orgel.2018.10.031
Received 22 July 2018; Received in revised form 17 October 2018; Accepted 20 October 2018
Corresponding author.
∗∗
Corresponding author.
∗∗∗
Corresponding author.
E-mail addresses: MxSong@jlnu.edu.cn (M.-X. Song), qin_zhengkun@126.com (Z.-K. Qin), baifq@jlu.edu.cn (F.-Q. Bai).
Organic Electronics 64 (2019) 181–187
Available online 21 October 2018
1566-1199/ © 2018 Elsevier B.V. All rights reserved.
T