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.     

Creation of cationic iridium(III) complexes with aggregation-induced phosphorescent emission (AIPE) properties by increasing rotation groups on carbazole peripheries

Three cationic iridium complexes containing 4,7-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)-1,10-phenanthroline (L(1)) and 4,7-bis(3',6'-di-tert-butyl-6-(3,6-di-tert-butyl-9H-carbazol-9-yl)-3,9'-bi(9H-carbazol)-9-yl)-1,10-phenanthroline (L(2)) as the ancillary ligands, namely, [Ir(ppy)(2)(L(1))]PF(6) (1), [Ir(ppy)(2)(L(2))]PF(6) (2) and [Ir(oxd)(2)(L(2))]PF(6) (3) (ppy is 2-phenylpyridine, oxd is 2,5-diphenyl-1,3,4-oxadiazole), have been designed and prepared. With more intramolecular rotational units on the ancillary ligand (L(2)), 2 and 3 possess a unique aggregation-induced phosphorescent emission (AIPE) property. This phenomenon was unprecedentedly observed in the cationic iridium(III) complexes. In order to investigate the underlying mechanism of this AIPE behavior, their photophysical, temperature-dependent aggregation properties as well as theoretical calculations, were performed. The results suggest that restricted intramolecular rotation is responsible for the AIPE of cationic complexes. Moreover, photoluminescent quantum yields in the neat film, thermal stabilities and off/on luminescence switching of 2 were investigated, revealing its potential application as a candidate for LECs and organic vapor sensing.     

2,5-二[4-(2-芳基乙烯基)苯基]噁二唑的合成及发光特征

二乙烯联苯及其衍生物是一种可发射蓝光的小分子空穴型有机发光材料, 通过Wittig-Horner反应, 将电子传输型噁二唑环“嵌入”其中, 设计合成了6个2,5-二[4-(2-芳基乙烯基)苯基]-1,3,4-噁二唑化合物. 经光谱分析和元素分析等方法确认了它们的化学结构. IR和UV-vis分析数据表明标题化合物分子结构中的C＝C双键均为反式结构特征. 研究结果表明: 2,5-二[4-(2-对二甲氨基苯基乙烯基)苯基]-1,3,4-噁二唑具有良好的蓝色发光性能; 取代基对标题化合物的UV-vis吸收光谱和发光特性的影响显着.     

Carbazole-oxadiazole containing polyurethanes as phosphorescent host for organic light emitting diodes

New types of polyurethanes (PUs) were prepared from condensation polymerization of isophorone diisocyanate (IPDI) with various combination of 9-butyl-3,6-bis(4-hydroxyphenyl)carbazole (Cz) and 2,5-bis(4-hydroxyphenyl)-1,3,4-oxadiazole (OXD), and end-capped with 4-tert-butyl phenol. The Cz-OXD PUs can also be used as host for phosphorescent dye. Red EL emission was obtained when Ir(btp)₂(acac) or Ir(2-phq)₂(acac) was used as the phosphorescent dyes in Cz-OXD (3:1) PU. Maximum brightness of 394 cd/m² and EL efficiency of 1 cd/A were achieved for the Ir(2-phq)₂(acac) base device. In addition, white light PLED was demonstrated when co-dopant of Ir(btp)₂(acac) and Firpic were used.     

Sulfur-bridged early-late heterobimetallics synthesized by incorporation of titanium,vanadium, and molybdenum into bis(hydrosulfido) templates of group 9 metals

Reactions of the bis(hydrosulfido) complexes [Cp*Rh(SH)(2)(PMe(3))] (1a; Cp* = eta(5)-C(5)Me(5)) with [CpTiCl(3)] (Cp = eta(5)-C(5)H(5)) and [TiCl(4)(thf)(2)] in the presence of triethylamine led to the formation of the sulfido-bridged titanium-rhodium complexes [Cp*Rh(PMe(3))(micro(2)-S)(2)TiClCp] (2a) and [Cp*Rh(PMe(3))(micro2-S)(2)TiCl(2)] (3a), respectively. Complex 3a and its iridium analogue 3b were further converted into the bis(acetylacetonato) complexes [Cp*M(PMe(3))(micro(2)-S)(2)Ti(acac)(2)] (4a, M = Rh; 4b, M = Ir) upon treatment with acetylacetone. The hydrosulfido complexes 1a and [Cp*Ir(SH)(2)(PMe(3))] (1b) also reacted with [VCl(3)(thf)(3)] and [Mo(CO)(4)(nbd)] (nbd = 2,5-norbornadiene) to afford the cationic sulfido-bridged VM2 complexes [(Cp*M(PMe(3))(micro2-S)(2))2V](+) (5a(+), M = Rh; 5b(+), M = Ir) and the hydrosulfido-bridged MoM complexes [Cp*M(PMe(3))(micro2-SH)(2)Mo(CO)(4)] (6a, M = Rh; 6b, M = Ir), respectively.     

Discrete half-sandwich Ir, Rh-based organometallic molecular boxes: synthesis, characterization, and their properties

The treatment of binuclear complexes [Cp*(2)M(2)(μ-QA)Cl(2)] (M = Ir, 2a; M = Rh, 2b) (H(2)QA = 1,4-dihydroxyanthraquinone) with pyrazine or bifuncational pyridyl-based ligands (4,4'-dipyridine (bpy), E-1,2-bis(4-pyridyl)ethene (bpe), 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (bpo), and 2,5-bis(4-pyridyl)-1,3,4-thiadiazol (bpt)) in the presence of AgOTf (OTf = CF(3)SO(3)) in CH(3)OH, gave the corresponding tetra-nuclear complexes, with a general formula of [Cp*(4)M(4)(μ-QA)(2)(μ-L)(2)](OTf)(4) (M = Ir, 3a-7a; M = Rh, 3b-7b), respectively. The molecular structure of [Cp*(4)Ir(4)(μ-QA)(2)(μ-pyrazine)(2)](OTf)(4) (3a) has been determined by single-crystal X-ray analysis, revealing that the metal centers were connected by pyrazine and bis-bidentate QA(2-) ligands to construct a rectangular cavity with the dimension of 7.30 × 8.41 × 6.92 ?. Complexes 3a and 3b were found to exhibit selective trapping of halocarbons properties.     

Poly(1,3,4-oxadiazole-imide)s containing dimethylsilane groups

New poly(1,3,4-oxadiazole-imide)s containing dimethylsilane units have been prepared by solution polycondensation reaction of an aromatic dianhydride incorporating dimethylsilane group, namely bis(3,4-dicarboxyphenyl)dimethylsilane dianhydride, with different aromatic diamines having preformed 1,3,4-oxadiazole ring, such as 2,5-bis(p-aminophenyl)-1,3,4-oxadiazole, 2,5-bis[p-(4-aminophenoxy)phenyl]-1,3,4-oxadiazole, 2,5-bis[p-(3-aminophenoxy)phenyl]-1,3,4-oxadiazole, 2-(4-fluorophenyl)-5-(3,5-diaminophenyl)-1,3,4-oxadiazole, and 2-(4-dimethylaminophenyl)-5-(3,5-diaminophenyl)-1,3,4-oxadiazole. The polymers were easily soluble in polar organic solvents, such as N-methylpyrrolidinone, N,N-dimethylformamide, and pyridine, as well as in less polar organic solvents, such as tetrahydrofuran and chloroform. Very thin coatings deposited on silicon wafers exhibited smooth, pinhole-free surface in atomic force microscopy investigations. The polymers showed high thermal stability with decomposition temperature being above 415 °C.They exhibited a glass transition in the temperature range of 202-282 °C, with reasonable interval between glass transition and decomposition temperature. Solutions of the polymers in N,N-dimethylformamide exhibited fluorescence, having maximum emission wavelength in the range of 353-428 nm.     

Light-emitting conjugated molecule containing 1,3,4-oxadiazole, carbazole and naphthalene units

A novel pi-conjugated small molecule VNCO, 2,5-bis{3'-[3'-vinyl-9'-(alpha-naphthyl)carbazolyl]phenyl}-1,3,4-oxadiazole, containing hole-transporting carbazole moieties, electron-injecting 1,3,4-oxadiazole moieties and chromophore naphthalene was designed and synthesized by Wittig reaction of 2,5-bis(3-tolylene-triphenylphosphonium bromide)-1,3,4-oxadiazole and 3-formyl-9-(alpha-naphthyl)carbazole. The UV-vis absorption, fluorescence excitation and emission spectra have been obtained in solution for VNCO. The photoluminescence (PL) of VNCO were examined in different solvents and the luminescence quantum yield was 0.746 in chloroform. It emitted blue and blue-green light, with the band gap of 3.30 eV estimated from the onset absorption. In addition, the light-emitting can be quenched by both electron donor (N,N-dimethylaniline) and electron acceptor (dimethylterephalate). Furthermore, the molecular interactions of VNCO with fullerene (C60) or carbon nanotubes (CNTs) were also carefully investigated.     

The synthesis and structure of a new type of aromatic heterocyclic macrocycle. IV. Synthesis of a 1,3,4-oxadiazole-containing azomacrocycle

A novel azomacrocycle containing the 1,3,4-oxadiazole ring has been prepared from 2,5-bis[3-(4-hydroxyphenylazo)phenyl]-1,3,4-oxadiazole 5 and 2,5-bis(2-chloromethlylphenyl)-1,3,4-oxadiazole 8 . The coupling reaction between the diazonium salt 4 and bisphenol A has been reported.     

New oxadiazole derivatives as promising electron transport materials: synthesis and characterization of thermal, optical and electrochemical properties

2,5-bis-(4-biphenyl)-yl-1,3,4-oxadiazole (1a), 2,5-bis-(4-(6,8-difluoro)-biphenyl)-yl-1,3,4-oxadiazole (1b) and 2,5-bis-(4-(spiro-fluorenyl)-phenyl)-yl-1,3,4-oxadiazole (1c) were designed, synthesized and characterized. 1a–c were easily obtained from Suzuki reactions between 2,5-bis-(4-bromo-phynyl)-[1,3,4]oxadiazole (2) and aromatic boronic acids (3). They were characterized by ¹H-NMR, DSC, TGA, UV-Vis, photoluminescence (PL) spectrometry and CV. The melting temperatures (T _m ) of 1a–c are 237, 208 and 370 °C, respectively, much higher than that of 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole (PBD, T _m = 136 °C). The oxidation potentials of 1a–c are 1.86, 1.94 and 1.18 V, and their reduction potentials are −2.31, −2.22 and −2.27 V, respectively, indicating that the introduction of electronegative oxadiazole unit lowers the electron density in molecules and enhances their stabilities. The LUMO/HOMO energy levels of 1a–c are as low as −2.39/−6.56, −2.48/−6.69 and −2.43/−5.88 eV, respectively. The good thermal stabilities and low orbital levels of 1a–c make them promising electron-transporting or hole-blocking materials for organic optoelectronic devices.     

对称4-枝和8-枝噁二唑衍生物的合成与荧光性质

采用Wittig-Horner和Heck反应合成了3个对称多枝[1,3,4]-噁二唑衍生物2,5-双{4-{4-[N,N-二(4-溴苯基)-氨基] 苯乙烯基}苯基}-1,3,4-噁二唑(BrPASPO), 2,5-双{4-{4-{N,N-二{4-{4-[5-(4-叔丁基苯基)-1,3,4-噁二唑基-2-]苯乙烯基}苯基}氨基}苯乙烯基}苯基}-1,3,4-噁二唑(TPASPO)和2,5-双{4-{4-{N,N-二{4-{3,5-二[5-(4-叔丁基苯基)-1,3,4-噁二唑基-2]-苯乙烯基}苯基}氨基}苯乙烯基}苯基}-1,3,4-噁二唑(OPASPO). 目标化合物的结构经过红外光谱、核磁共振氢谱、质谱和熔点确认. 在CH2Cl2溶液中三者的最大吸收波长分别在403 (BrPASPO), 408 (TPASPO)和409 nm (OPASPO), 荧光发射峰分别为495 (BrPASPO), 509 (TPASPO)和506 nm (OPASPO). 化合物TPASPO和OPASPO在CH2Cl2溶液中的荧光量子产率分别为0.47和0.45. 8枝化合物的荧光寿命高于4枝化合物. 对称多枝化合物具有很强的分子内电荷转移能力和荧光发射能力.     

Acceptor (CF3)PCPH pincer reactivity with (PPh3)3Ir(CO)H

The syntheses of Ir(I) and Ir(III) complexes incorporating the electron-withdrawing pincer ligand (1,3-C(6)H(4)(CH(2)P(CF(3))(2))(2)) ((CF(3))PCPH) with (PPh(3))(3)Ir(CO)H and subsequent chemistry are reported. Under ambient conditions, reaction of 1 equiv. (CF(3))PCPH with (PPh(3))(3)Ir(CO)H gave the mono-bridged complex [Ir(CO)(PPh(3))(2)(H)](2)(μ-(CF(3))PCPH) (1). Reaction of (PPh(3))(3)Ir(CO)H with excess (CF(3))PCPH and MeI gave the doubly-bridged complex [Ir(CO)(PPh(3))(H)](2)(μ-(CF(3))PCPH)(2) (2), whereas the tetrameric oligomer [Ir(CO)(PPh(3))(H)](4)(μ-(CF(3))PCPH)(4) (2-sq) was obtained from a 1:1 ligand:metal mixture in benzene in the presence of excess MeI. At higher temperatures (165 °C) the reaction of (CF(3))PCPH with (PPh(3))(3)Ir(CO)H afforded the 5-coordinate Ir(I) complex ((CF(3))PCP)Ir(CO)(PPh(3)) (3). Complex 3 shows mild catalytic activity for the decarbonylation of 2-naphthaldehyde in refluxing diglyme (162 °C).     

Solution-processible conjugated electrophosphorescent polymers

We report the synthesis and photophysical study of a series of solution-processible phosphorescent iridium complexes. These comprise bis-cyclometalated iridium units [Ir(ppy)(2)(acac)] or [Ir(btp)(2)(acac)] where ppy is 2-phenylpyridinato, btp is 2-(2'-benzo[b]thienyl)pyridinato, and acac is acetylacetonate. The iridium units are covalently attached to and in conjugation with oligo(9,9-dioctylfluorenyl-2,7-diyl) [(FO)(n)] to form complexes [Ir(ppy-(FO)(n))(2)(acac)] or [Ir(btp-(FO)(n))(2)(acac)], where the number of fluorene units, n, is 1, 2, 3, approximately 10, approximately 20, approximately 30, or approximately 40. All the complexes exhibit emission from a mixed triplet state in both photoluminescence and electroluminescence, with efficient quenching of the fluorene singlet emission. Short-chain complexes, 11-13, [Ir(ppy-(FO)(n)-FH)(2)(acac)] where n = 0, 1, or 2, show green light emission, red-shifted through the FO attachment by about 70 meV, but for longer chains there is quenching because of the lower energy triplet state associated with polyfluorene. In contrast, polymer complexes 18-21 [Ir(btp-(FO)(n))(2)(acac)] where n is 5-40 have better triplet energy level matching and can be used to provide efficient red phosphorescent polymer light-emitting diodes, with a red shift due to the fluorene attachment of about 50 meV. We contrast this small (50-70 meV) and short-range modification of the triplet energies through extended conjugation, with the much more substantial evolution of the pi-pi* singlet transitions, which saturate at about n = 10. These covalently bound materials show improvements in efficiency over simple blends and will form the basis of future investigations into energy-transfer processes occurring in light-emitting diodes.     

Phosphorescence vs fluorescence in cyclometalated platinum(II) and iridium(III) complexes of (oligo)thienylpyridines

Two newly prepared oligothienylpyridines, 5-(2-pyridyl)-5'-dodecyl-2,2'-bithiophene, HL(2), and 5-(2-pyridyl)-5'-dodecyl-2,2':5',2'-ter-thiophene, HL(3), bind to platinum(II) and iridium(III) as N∧C-coordinating ligands, cyclometallating at position C(4) in the thiophene ring adjacent to the pyridine, leaving a chain of either one or two pendent thiophenes. The synthesis of complexes of the form [PtL(n)(acac)] and [Ir(L(n))(2)(acac)] (n = 2 or 3) is described. The absorption and luminescence properties of these four new complexes are compared with the behavior of the known complexes [PtL(1)(acac)] and [Ir(L(1))(2)(acac)] {HL(1) = 2-(2-thienyl)pyridine}, and the profound differences in behavior are interpreted with the aid of time-dependent density functional theory (TD-DFT) calculations. Whereas [PtL(1)(acac)] displays solely intense phosphorescence from a triplet state of mixed ππ*/MLCT character, the phosphorescence of [PtL(2)(acac)] and [PtL(3)(acac)] is weak, strongly red shifted, and accompanied by higher-energy fluorescence. TD-DFT reveals that this difference is probably due to the metal character in the lowest-energy excited states being strongly attenuated upon introduction of the additional thienyl rings, such that the spin-orbit coupling effect of the metal in promoting intersystem crossing is reduced. A similar pattern of behavior is observed for the iridium complexes, except that the changeover to dual emission is delayed to the terthiophene complex [Ir(L(3))(2)(acac)], reflecting the higher degree of metal character in the frontier orbitals of the iridium complexes than their platinum counterparts.     

Photochemistry of heterocyclic compounds—II : The photochemical reaction of 2,5-disubstituted 1,3,4-oxadiazoles with furan

The photochemical reaction of 2,5-disubstituted 1,3,4-oxadiazoles with furan has been studied. With or without benzophenone as a sensitizer, irradiation of 2,5-diphenyl-1,3,4-oxadiazole with furan in benzene solution gives the 1 : 1 cycloadduct, tetrahydrofuro[2·3-b]azetidino[2·1-b]-1,3,4-oxadiazole. However in the presence of iodine 3-acylfurans and their acylhydrazones are formed. A reaction pathway of this novel photo-induced acylation has been suggested.     

Catalytic asymmetric sulfoxidation by chiral manganese complexes: acetylacetonate anions as chirality switches

Three manganese(II) complexes, namely [Mn(1)(ClO(4))(2)] (3), [Mn(1)(acac)(2)] (4), and [Mn(2)(1)(acac)(4)] (5), were isolated from solutions of Mn(ClO(4))(2) or Mn(acac)(2), and an easily accessible diimine ligand (1S,2S)-N,N'-bis-pyridin-2-ylmethylene-cyclohexane-1,2-diamine (1). Their structure was determined by X-ray crystallography, and these complexes proved to be catalysts for asymmetric sulfide oxidation by H(2)O(2). Enantiomeric excesses ranging from 5% to 62% were obtained with a variety of aryl alkyl sulfides. We also observed an interesting "chirality switch" effect by the achiral acac anion reversing the enantioselectivity of the complex [Mn(1)(ClO(4))(2)] from the S to the R sulfoxide enantiomer.     

Conformational analysis and assignments of relative stereocenter configurations in fluoroalkyl-iridium complexes using 19F[1H] HOESY experiments. Comparison with solid-state X-ray structural results

Solution conformations about the metal-carbon bond of the secondary fluoroalkyl ligands in iridium complexes [IrCp(PMe(3))(R(F))X] [Cp* = C(5)Me(5); R(F) = CF(CF(3))(2), X = I (1), CH(3) (2); R(F) = CF(CF(3))(CF(2)CF(3)), X = I (4), CH(3) (5)] have been determined using (19)F[(1)H] HOESY techniques. The molecules adopt the staggered conformation with the tertiary fluorine in the more hindered sector between the PMe(3) and X ligands, with CF(3) (and CF(2)CF(3)) substituents lying in the less hindered regions between PMe(3) and Cp or X and Cp. In molecules containing the CF(CF(3))(2) ligand, these conformations are identical to those adopted in the solid state. For compound 4, containing the CF(CF(3))(CF(2)CF(3)) ligand, two diastereomers are observed in solution. Solution conformations and relative stereocenter configuration assignments have been obtained using (19)F[(1)H] HOESY and correlated with the X-ray structure for the major diastereomer of 4, which has the (S(Ir), S(C)) or (R(Ir), R(C)) configuration. Relative stereocenter configurations of analogue 5, for which no suitable crystals could be obtained, were assigned using (19)F[(1)H] HOESY and proved to be different from 4, with 5 preferring the (S(Ir), R(C)) or (R(Ir), S(C)) configuration.     

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.     

2,5-双取代-1,3,4-噁二唑类化合物的合成与表征

以3-( 4-氟苯基) -1H-吡唑-5-甲酸乙酯为原料,与H2NNH2?H2O发生肼解生成3-( 4-氟苯基) -1H-吡唑-5-甲酰肼,再与CS2环化生成2-巯基噁二唑中间体,最后在巯基上进行烷基化反应合成了一系列新型的2-硫醚-5-吡唑基-1,3,4-噁二唑类化合物,并利用IR、1H NMR、HRMS等波谱技术对目标化合物结构进行了表征。该合成方法具有原料易得,后处理简便,收率较高的优点。     

Synthesis and Luminescent Properties of Iridium Complexes with Reduced Concentration Quenching Effect

Three novel cyclometalated ligands 1-benzyl-2-phenyl-1H-benzoimidazole(BPBM), 1-(4-methoxy-benzyl)-2-(4-methoxy-phenyl)-1H-benzoimidazole(MBMPB) and 4-[2-(4-dimethylamino-phenyl)-benzoinidazol-1-ylmethyl]-phenyl-dimethyl-amine(DBPA) were designed and synthesized, and the corresponding highly efficiency green-emitting phosphorescent iridium complexes Ir(BPBM)₂(acac)(1), Ir(MBMPB)₂(acac)(2) and Ir(DPBA)₂(acac) (3) with acetylacetone(acac) as auxiliary ligand were also synthesized. The ligands are functionalized by bulky non-planarity substituents, thus the phosphorescent concentration quenching is substantially suppressed, and all the complexes exhibit bright photoluminescence(PL) in solid state. The photo-physical properties of the three iridium complexes were researched in detail. The results indicate that they have potential application in fabricating non-doped electrophosphorescence device.