DFT and TD‐DFT study of iridium complexes with low‐color‐temperature and low‐efficiency roll‐off properties

A series of heteroleptic cyclometalated Ir (III) complexes with low‐color‐temperature and low‐efficiency roll‐off properties, which cause a fast reduction in efficiency when the drive current increases, for organic light‐emitting devices are investigated theoretically to explore their electronic structures and spectroscopic properties. The geometries, electronic structures, lowest‐lying singlet absorptions and triplet emissions of (ptpy)₂Ir(acac), and the theoretically designed models (ptpy)₂Ir(tpip), (F‐ptpy)₂Ir(acac), (F‐ptpy)₂Ir(tpip), (F₂‐ptpy)₂Ir(acac) and (F₂‐ptpy)₂Ir(tpip), are investigated with density functional theory approaches, where ptpy denotes 4‐phenylthieno [3,2‐c] pyridine, acac denotes acetylacetonate, tpip denotes tetraphenylimido‐diphosphinate, F‐ptpy denotes 4‐(3‐fluorophenyl) thieno [3,2‐c] pyridine, and F₂‐ptpy denotes 4‐(2,4‐difluorophenyl) thieno [3,2‐c] pyridine.     

A theoretical study: Green phosphorescent iridium(III) complexes with low-efficiency roll-off

A series of heterocyclic Ir(III) complexes used in organic light-emitting diode (OLED) materials with low-efficiency roll-off performance have been studied theoretically. Their electronic structures, spectral properties, and their application value in OLEDs are discussed. The geometries, electronic structures, lowest-lying singlet absorptions, and triplet emissions of (dmdppr-dmp)₂Ir(dibm), and the theoretically designed models of (dmdppr-dmp)₂Ir(acac), (dmdppr-dmp)₂Ir(tpip), (dmdppr-Fdmp)₂Ir(dibm), (dmdppr-Fdmp)₂Ir(acac), and (dmdppr-Fdmp)₂Ir(tpip) were investigated with density-functional-theory-based approaches, where dibm denotes 2,6-dimethy-3,5-heptanedionato-κ₂-O,O′, acac denotes acetylacetonate, and tpip denotes tetraphenylimido-diphosphinate.     

Theoretical study on the electronic structures and optical properties of blue‐green and blue phosphorescent iridium(III) complexes with tetraphenylimidodiphosphinate ligand

The electronic structures and photophysical properties of five iridium(III) complexes Ir(tfmppy)₂(tpip) (1), Ir(dfppy)₂(tpip) (2), Ir(afCNppy)₂(tpip) (3), Ir(CNpyN₃)₂(tpip) (4), and Ir(2fphpta)₂(tpip) (5) [where tfmppy = 4‐trifluoromethylphenylpyridine; dfppy =4,6‐difluorophenylpyridine; afCNppy = 6‐fluoro‐4‐octyloxy‐5‐cyano‐phenylpyridine; CNpyN₃ = 2‐(4‐cyano‐phenyl)‐[1,2,3]‐triazole; 2fphpta=2‐(2,6‐difluoro‐phenyl‐[1,2,4]‐triazol‐3‐yl)‐pyridine; tpip=tetraphenylimido‐diphosphinate] have been investigated by using density functional theory (DFT) methods and time‐dependent DFT ones, aiming at elucidating the influences of different substituents and cyclometalated ligands on the emission properties and quantum yield. The calculated results revealed that the different substituents in 1 ‐ 3 have a great influence on the energy levels, in particular highest occupied molecular orbital. Meanwhile, we have also get a further insight into the reason for different phosphorescence quantum yields of the studied complexes. The higher quantum yield (Φ) reported for 1 was found to be closely related to both its smaller S₁–T₁ splitting energy ( ) and larger transition electric dipole moment ( ) upon the S₀ → S₁ transition. Complex 5 is expected to be a potential candidate for blue‐emitting material with good organic light‐emitting diodes performances. We propose that the optical properties of this class of materials can be tuned by the modifications of the cyclometalated ligands. © 2013 Wiley Periodicals, Inc.     

Efficient blue‐emitting Ir(III) complexes with phenyl‐methyl‐benzimidazolyl and picolinate ligands: A DFT and time‐dependent DFT study

The series of heteroleptic cyclometalated Ir(III) complexes for organic light‐emitting display application have been investigated theoretically to explore their electronic structures and spectroscopic properties. The geometries, electronic structures, and the lowest‐lying singlet absorptions and triplet emissions of Ir‐(pmb)₃ and theoretically designed models Ir‐(Rpmb)₂pic were investigated with density functional theory (DFT)‐based approaches, where pmb = phenyl‐methyl‐benzimidazolyl, pic = picolinate, and R = H/F. Their structures in the ground and excited states have been optimized at the DFT/B3LYP/LANL2DZ and TDDFT/B3LYP/LANL2DZ levels, and the lowest absorptions and emissions were evaluated at B3LYP and M062X level of theory, respectively. The mobility of holes and electrons were studied computationally based on the Marcus theory. Calculations of ionization potentials were used to evaluate the injection abilities of holes into these complexes. The reasons for the higher electroluminescence efficiency and phosphorescence quantum yields in Ir‐(Rpmb)₂pic than in Ir‐(pmb)₃ have been investigated. The designed moleculars are expected to be highly emissive in pure‐blue region. © 2013 Wiley Periodicals, Inc.     

Theoretical study on the influence of ancillary and cyclometalated ligands on the electronic structures and optoelectronic properties of heteroleptic iridium(III) complexes

We report a theoretical analysis of a series of heteroleptic iridium(III) complexes (dox)(2)Ir(acac) [dox = 2,5-diphenyl-1,3,4-oxadiazolato-N,C(2), acac = acetylacetonate] (1a), (fox)(2)Ir(acac) [fox = 2,5-bis(4-fluorophenyl)-1,3,4-oxadiazolato-N,C(2)] (1b), (fox)(2)Ir(Et(2)dtc) [Et(2)dtc = N,N'-diethyldithiocarbamate] (2), (fox)(2)Ir(Et(2)dtp) [Et(2)dtp = O,O'-diethyldithiophosphate] (3), (pypz)(2)Ir(acac) [pypz = 3,5-di(2-pyridyl)pyrazole] (4a), (O-pypz)(2)Ir(acac) (4b), (S-pypz)(2)Ir(acac) (4c) and (bptz)(2)Ir(acac) [bptz = 3-tert-butyl-5-(2-pyridyl)triazole] (5) by using the density functional theory (DFT) method to investigate their electronic structures and photophysical properties and obtain further insights into the phosphorescent efficiency mechanism. Meanwhile, we also investigate the influence of ancillary and cyclometalated ligands on the properties of the above complexes. The results reveal that the nature of the ancillary ligands can influence the electron density distributions of frontier molecular orbitals and their energies, resulting in change in transition character and emission color, while the different cyclometalated ligands have a large impact on the charge transfer performances of the studied complexes. The calculated absorption and luminescence properties of the four complexes 1a, 1b, 2 and 3 are compared with the available experimental data and a good agreement is obtained. Further, the assumed complexes 4a and 4b possess better charge transfer abilities and more balanced charge transfer rates, and they are potential candidates as blue-emitting materials.     

以苯基吡唑为主配体的Ir配合物电子结构和光谱性质的密度泛函理论研究

用密度泛函理论(DFT)和含时密度泛函理论(TD-DFT)的B3LYP方法对以苯基吡唑ppz为主配体的4种Ir配合物Ir(ppz)₃, Ir(ppz)₂(acac), Ir(ppz)₂(pic)和Ir(ppz)₂(dbm)的电子结构和光谱性质进行了理论研究. 计算结果表明, 辅助配体的改变对Ir配合物的最高占据轨道(HOMO)的影响不大, 但会显著的降低分子最低空轨道(LUMO)的能级, 从而调节Ir配合物的HOMO和LUMO间的能隙. 4种配合物对应的发射跃迁分别为Ir(ppz)₃:d(Ir)+π(ppz)→π*(ppz); Ir(ppz)₂(pic):d(Ir)+(ppz)→π*(pic); Ir(ppz)₂(acac), Ir(ppz)₂(dbm):d(Ir)+π(acacdbm)→π*(acacdbm). 金属配合物的发光颜色可以通过选择合适的辅助配体调节.     

Theoretical studies of blue-emitting iridium complexes with different ancillary ligands

The structural and electronic properties of two heteroleptic iridium complexes Ir(dfppy)2(pic) (FIrpic) and Ir(dfppy)2(acac) (FIracac) have been investigated theoretically, where dfppy = 2-(2,4-difluorophenyl) pyridine, pic = picolinic acid, and acac = acetoylacetonate. The geometries of ground and excited states are optimized at PBE0/LANL2DZ and CIS/LANL2DZ levels, respectively. Time-dependent density functional theory (TDDFT) method is employed to explore the absorption and emission properties. In the ground state, the highest-occupied molecular orbital has a significant mixture of metal Ir(d) and dfppy(pi), the lowest-unoccupied orbital locates primarily on pi* of pic for FIrpic and pi* of dfppy for FIracac. The luminescence of each complex originates from the lowest triplet excited state, which is assigned to the mixing of metal-to-ligand charge transfer and intraligand charge transfer characters. The effects of ancillary ligands pic and acac on absorption and emission spectra are observed by analysis of TDDFT results. The connection between the nature of excited states and the behavior of the complexes with different ancillary ligands is elucidated.     

Synthesis, Photophysical and Electrochemical Characterization of the Heteroleptic Iridium Complexes with Modified Ancillary Ligand by Carrier-transporting Groups

Two heteroleptic iridium complexes with a general formulation of (piq)₂Ir(G‐pic) were synthesized and characterized by ¹H NMR, ¹³C NMR and element analysis, in which piq is 1‐phenylisoquinoline, G‐pic is picolinic acid derivative containing carrier‐transporting group by a non‐conjugated connection of 1,6‐dioxyhexane. Both (piq)₂Ir(G‐pic) complexes exhibited an enhanced UV absorption band at 310–400 nm, an increased HOMO energy level and an identical red emission peaked at 612 nm with higher fluorescence quantum efficiency (ø_f), compared to (piq)₂Ir(pic) in dichloromethane solution. Interestingly, this iridium complex containing both hole‐transporting triphenylamine and electron‐transporting oxadiazole moieties exhibited the best Ф_f of 0.58 using Ru(bpy)₃(PF6)₂ as the reference (ø_f=0.062 in acetonitrile). This work indicates that incorporating carrier‐transporting groups into ancillary ligand by a non‐conjugated connection is available for improving the optophysical properties of their iridium complexes.     

Effect of substituents on the photoluminescence performance of Ir(III) complexes: Synthesis, electrochemistry and photophysical properties

We have prepared and characterized a series of substituted imidazole ligands namely dmmppi, dmmpfpi, dmdmppi and dmdmpfpi. These compounds will readily undergo cyclometalation with iridium trichloride and form di-irrido and the six coordinated iridium(III) dopants of the substituted imidazole ligands. They emit green colour both in solid and in solution phase. The peak emission wavelength of the dopants (λ_max = 428–497 nm) can be finely tuned depending upon the electronic properties of the phenyl, fluorophyenyl, methoxy phenyl and dimethoxyphenyl substituents as well as their positions in the imidazole ring. These iridium complexes namely Ir(dmmppi)₂(pic) 1a, Ir(dmmpfpi)₂(pic) 1b, Ir(dmdmppi)₂(pic) 1c and Ir(dmdmpfpi)₂(pic) 1d were characterized by ¹H NMR, MS and elemental analysis. All these iridium complexes 1a–1d show unusual high HOMO levels (E_HOMO = 5.21–5.41 eV) and high phosphorescence. These complexes emit green light with exceedingly high efficiency.     

Theoretical study of the electronic spectrum of binuclear gold(I) complexes

The electronic structure and the spectroscopic properties of [Au₂(CS₃)₂]^?2, [Au₂(pym‐2‐S)₂] (pym = pyrimidethiolate), [Au₂(dpm)₂]⁺² (dpm = bis(diphosphino)methane) were studied using density functional theory (DFT) at the B3LYP level. The absorption spectrum of these binuclear gold(I) complexes was calculated by single excitation time‐dependent (TD) method. All complexes showed a ¹(5dσ* → 6pσ) transition associated with a metal–metal charge transfer, which is strongly interrelated with the gold–gold distance. Furthermore, we have calculated the frequency of the gold–gold vibration (ν_Au2) on the above complexes. The values obtained are theoretically in agreement with experimental range. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Near‐IR Emitting Iridium(III) Complexes with Heteroaromatic β‐Diketonate Ancillary Ligands for Efficient Solution‐Processed OLEDs: Structure–Property Correlations

Three NIR‐emitting neutral Ir^III complexes [Ir(iqbt)₂(dpm)] ( 1 ), [Ir(iqbt)₂(tta)] ( 2 ), and [Ir(iqbt)₂(dtdk)] ( 3 ) based on the 1‐(benzo[b]thiophen‐2‐yl)‐isoquinolinate (iqtb) were synthesized and characterized (dpm=2,2,6,6‐tetramethyl‐3,5‐heptanedionate; tta=2‐thienoyltrifluoroacetonate; dtdk=1,3‐di(thiophen‐2‐yl)propane‐1,3‐dionate). The compounds emit between λ=680 and 850 nm with high luminescence quantum yields (up to 16 %). By combining electrochemistry, photophysical measurements, and computational modelling, the relationship between the structure, energy levels, and properties were investigated. NIR‐emitting, solution‐processed phosphorescent organic light‐emitting devices (PHOLEDs) were fabricated using the complexes. The devices show remarkable external quantum efficiencies (above 3 % with 1 ) with negligible efficiency roll‐off values, exceeding the highest reported values for solution‐processible NIR emitters.     

A Series of Pure Orange-yellow Iridium Complexes with Low Efficiency Roll-off: a Computational Study

The electronic structures and spectroscopic properties of heteroleptic cyclometalated iridium(III) complexes were investigated. The geometries, electronic structures, and the lowest-lying excited states of (DBQ)₂Ir(acac) and (MDQ)₂Ir(acac) were investigated via density functional theory-based approaches. A series of designed models of (DBQ)₂Ir(dpis), (DBQ)₂Ir(tpip), (MDQ)₂Ir(dpis) and (MDQ)₂Ir(tpip) was also calculated for comparison. The structures in the ground and excited states were optimized via B3LYP method. The lowest absorptions and emissions spectra were evaluated via TD-B3LYP and TD-PBE1PBE methods. The computational results reveal that the emission peaks of the designed complexes are at around 585-640 nm, which belong to the orange-yellow wavelength. The frontier molecular orbital properties indicate that the Ir(III) complexes have low efficiency roll-off.     

Synthesis and photoluminescence of iridium complexes with benzothiazol-2-yl carbazole derivative ligand

Two new iridium(III) complexes containing benzothiazol-2-yl carbazole derivative as a cyclometalated ligand (L) and picolinate (pic) or acetylacetonate (acac) as the ancillary ligand, Ir(III) bis(3-(benzothiazol-2-yl)-9-butyl-carbazole)(picolinate) [Ir(L)₂(pic)] and Ir(III) bis(3-(benzothiazol-2-yl)-9-butyl-carbazole)(acetylacetonate) [Ir(L)₂(acac)], were synthesized and characterized by elemental analysis, ¹H NMR, FT-IR, and UV–Vis absorption spectra. Both the iridium(III) complexes emit intense green–yellow emissions, indicating that they are useful for the fabrication of organic light-emitting diodes.     

Synthesis and characterization of phosphorescent cyclometalated iridium complexes containing 2,5‐diphenylpyridine based ligands

A series of phosphorescent cyclometalated iridium complexes with 2,5‐diphenylpyridine‐based ligands has been synthesized and characterized to investigate the effect of the simple ligand modification on photophysics, thermostability and electrochemistry. The complexes have the general structure (C^∧N)₂Ir(acac), where C^∧N is a monoanionic cyclometalating ligand [e.g. 2,5‐diphenylpyridyl (dppy), 2,5‐di(4‐methoxyphenyl)pyridyl (dmoppy), 2,5‐di(4‐ethoxyphenyl)pyridyl (deoppy) and 2,5‐di(4‐ethylphenyl)pyridyl (deppy)]. The absorption, emission, cyclic voltammetry and thermostability of the complexes were systematically investigated. The (dppy)₂Ir(acac) has been characterized using X‐ray crystallography. Calculation on the electronic ground state of (dppy)₂Ir(acac) was carried out using B3LYP density functional theory. The highest occupied molecular orbital (HOMO) level is a mixture of Ir and ligand orbitals, while the lowest occupied molecular orbital (LUMO) is predominantly dppy ligand‐based. Electrochemical studies showed the oxidation potentials of (dmoppy)₂Ir(acac), (deoppy)₂Ir(acac), (deppy)₂Ir(acac) were smaller than that of (ppy)₂Ir(acac), while the oxidation potential of (dppy)₂Ir(acac) was larger relative to (ppy)₂Ir(acac). The 10% weight reduction temperatures of these complexes were above that of (ppy)₂Ir(acac). All complexes exhibited intense green photoluminescence, which has been attributed to MLCT triplet emission. The maximum emission wavelengths in CH₂Cl₂ at room temperature were in the range 531–544 nm, which is more red‐shifted than that of (ppy)₂Ir(acac). Copyright © 2005 John Wiley & Sons, Ltd.     

Theoretical studies of ground and excited electronic states in a series of heteroleptic iridium complexes using density functional theory

A series of new heteroleptic iridium(III) complexes [Ir(C^?N)₂(N^?N)]PF₆ ( 1 ‐ 6 ) (each with two cyclometalating C^?N ligands and one neutral N^?N ancillary ligand, where C^?N = 2‐phenylpyridine (ppy), 5‐methyl‐2‐(4‐fluoro)phenylpyridine (F‐mppy), and N^?N = 2,2′‐dipyridyl (bpy), 1,10‐phenanthroline (phen), 4,4′‐diphenyl‐2,2′‐dipyridy (dphphen) were found to have rich photophysical properties. Theoretical calculations are employed for studying the photophysical and electrochemical properties. All complexes are investigated using density functional theory. Excited singlet and triplet states are examined using time‐dependent density functional theory. The low‐lying excited‐state geometries are optimized at the ab initio configuration interaction singles level. Then, the excited‐state properties are investigated in detail, including absorption and emission properties, photoactivation processes. The excited state of complexes is complicated and contains triplet metal‐to‐ligand charge transfer, triplet ligand‐to‐ligand charge transfer simultaneously. Importantly, the absorption spectra and emission maxima can be tuned significantly by changing the N^?N ligands and C^?N ligands. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Synthesis, opto-physics, and electroluminescence of cyclometalated iridium (III) complex with alkyltrifluorene picolinic acid

To improve the opto-physics, electroluminescence, and dispersibility of iridium (III) complexes in polymer light-emitting devices, we synthesized and characterized two red-emitting heteroleptic cyclometalated iridium (III) complexes of (Piq)₂Ir(Tfl-pic) and (Piq)₂Ir(Brfl-pic), in which Piq is 1-phenylisoquinoline, Tfl-pic and Brfl-pic are alkyltrifluorene- and dibromoalkylfluorene-containing picolinic acid derivatives bridged with alkoxy chain, respectively. Compared to (Piq)₂Ir(pic) and (Piq)₂Ir(Brfl-pic), (Piq)₂Ir(Tfl-pic) exhibited higher thermal stability, better dispersibility and excellent quantum efficiency. High-efficiency red emission with a maximum current efficiency of 6.28 cdA⁻¹ and a maximum EL peak at 608 nm was obtained in the (Piq)₂Ir(Tfl-pic)-doped devices using a blend of poly(9,9-dioctylfluorene) and 2-(4-biphenyl)-5-(4-tert -butylphenyl)-1,3,4-oxadiazole as a host matrix.     

A New Phosphorescent Cyclometalated Iridium(III) Complex for the Selective Detection of Silver(I) Ion

A new cyclometalated iridium(III) complex, Ir(ppz)₂(dtp) (Ir1) (ppzH = 4-phenylphthalazinone, dtp = diethyl dithiophosphate), has been synthesized and characterized by single-crystal X-ray diffraction. The photoluminescence spectrum of Ir1 shows an emission maximum at 597 nm and its quantum yield is ca. 0.072. Complex Ir1 exhibits a strong and fast decrease of emission upon addition of Ag⁺ in aqueous media. The ratio of Ir1 responding to Ag⁺ was determined to be 1:1 by UV?CVis absorption and phosphorescent emission measurements. Complex Ir1 is a highly selective chemosensor for Ag⁺ over other transition metal ions.     

Theoretical design of phosphorescence parameters for organic electro-luminescence devices based on iridium complexes

Time-dependent density functional theory with quadratic response methodology is used in order to calculate and compare spin–orbit coupling effects and the main mechanism of phosphorescence of the neutral Ir(ppy)₃ and cationic [Ir(bpy)₃]³⁺ tris-iridium compounds, [Ir(ppy)₂(bpy)]⁺ and [Ir(2-phenylpyridine)₂(4,4′-tert-butyl-2,2′-bipyridine]⁺ complexes, including also the recently synthesised [Ir(2-phenylpyridine)₂(4,4′-dimethylamino-2,2′-bipyridine]⁺ and [Ir(2,4-difluorophenylpyridine)₂(4,4′-dimethylamino-2,2′-bipyridine]⁺ dyes, where ppy = 2-phenylpyridine and bpy = 2,2′-bipyridine ligands. Comparison with the symmetric, lighter and more studied [Ru(bpy)₃]²⁺ and [Rh(bpy)₃]³⁺ complexes is also presented. Variations in phosphorescence lifetimes for Ir(ppy)₃ and [Ir(bpy)₃]³⁺ dyes as well as for the mixed cationic complexes are well reproduced by the quadratic response method. All the ortho-metalated iridium compounds exhibit strong phosphorescence, which is used in organic light-emitting diodes (OLEDs) to overcome the efficiency limit imposed by the formation of triplet excitons. The results from the first principle theoretical analysis of phosphorescence have helped to clarify the connections between the main features of electronic structure and the photo-physical properties of the studied heavy organometallic OLED materials.     

Polyfluorene derivatives pending iridium complexes: Improved optoelectronic properties by introducing D‐A units and altering pendent mode

To study influence of the donor(D)‐acceptor(A) units and pendent mode of phosphorescent moiety on the opto‐electronic properties for its resulting copolymers, two D‐A‐based polyfluorene derivatives ( P 1 and P 2) pending the red‐emitting iridium bi(phenylisoquilonato) (picolinato) [Ir(Piq)₂(pic)] unit and a polyfluorene derivative ( P 3) only pending Ir(Piq)₂(pic) unit were synthesized and characterized, in which the donor of carbazole, the acceptor of oxadiazole are grafted into the C‐9 position of fluorene, the Ir(Piq)₂(pic) unit is pended into either the C‐9 position for P 1 and P 3 or the end for P 2 of fluorene by unconjugated linkage, respectively. Their opto‐electronic properties were significantly influenced by the D‐A units and pendent mode of the Ir(Piq)₂(pic) unit. In the polymer light‐emitting devices with a configuration of ITO/PEDOT/polymers/LiF/Al, the P 1 showed best electroluminescent properties than the P 2 and P 3. The maximum current efficiency of 0.72 cd/A and the highest luminance of 1398 cd/m 2 were obtained in the P 1‐based device, which are 1.3 and 1.5 times higher than those in the P 2‐based device, respectively. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Photophysical Properties of Heteroleptic Iridium Complexes Containing Carbazole‐Functionalized β‐Diketonates

Twelve iridium complexes with general formula of Ir(C^N)₂(LX) [C^N represents the cyclometalated ligand, i.e. 2‐(2,4‐difluorophenyl) pyridine (dfppy), 2‐phenylpyridine (ppy), dibenzo{f, h}quinoxaline (DBQ); LX stands for β‐diketonate, i.e. acetyl acetonate (acac), 1‐(carbazol‐9‐yl)‐5,5‐dimethylhexane‐2,4‐diketonate (CBDK), 1‐(carbazol‐9‐yl)‐5,5,6,6,7,7,7‐heptafluoroheptane‐2,4‐diketonate (CHFDK), 1‐(N‐ethyl‐carbazol‐3‐yl)‐4,4,5,5,6,6,6‐heptafluorohexane‐1,3‐diketonate (ECHFDK)] are synthesized, characterized and their photophysical properties are systemically studied. In addition, crystals of Ir(DBQ)₂(CHFDK) and Ir(DBQ)₂(acac) are obtained and characterized by single crystal X‐ray diffraction. The choice of these iridium complexes provides an opportunity for tracing the effect of the triplet energy level of ancillary ligands on the photophysical and electrochemical behaviors. Data show that if the triplet energy level of the β‐diketonate is higher than that of the Ir(C^N)₂ fragment and there is no superposition on the state density map, strong ³LC or ³MLCT‐based phosphorescence can be obtained. Alternatively, if the state density map of the two parts are in superposition, the ³LC or ³MLCT‐based transition will be quenched at room temperature. Density functional theory calculations show that these complexes can be divided into two categories. The lowest excited state is mainly determined by C^N but not β‐diketonate when the difference between the triplet energy levels of the two parts is large. However, when this difference is very small, the lowest excited state will be determined by both sides. This provides a satisfactory explanation for the experimental observations.