Two novel iridium-europium bimetallic complexes, {[(dfppy)2Ir(mu-phen5f)]3EuCl}Cl2 and (dfppy)2Ir(mu-phen5f)Eu(TFAcA)3 [dfppy represents 2-(4',6'-difluorophenyl)-pyridinato-N,C(2'), phen5f stands for 4,4,5,5,5-pentafluoro-1-(1',10'-phenanthrolin-2'-yl)-pentane-1,3-dionate and TFAcA represents trifluoroacetylacetonate], were successfully synthesized. The novel ligand Hphen5f with four coordination sites was designed as a bridge to link the Ir (III) center and the Eu (III) center. The X-ray diffraction data shows that the nonbonding distances for Eu...Ir are 6.028, 5.907, and 6.100 A in the bimetallic complex {[(dfppy)2Ir(mu-phen5f)]3EuCl}Cl2. Photophysical studies implied that the high efficient red luminescence from the Eu (III) ion was sensitized by the (3)MLCT (metal-to-ligand charge transfer) energy based on an Ir (III) complex-ligand in a d-f bimetallic assembly. The excitation window for the new bimetallic complex {[(dfppy)2Ir(mu-phen5f)]3EuCl}Cl2 extends up to 530 nm (1 x 10(-3) M in EtOH), indicating that this bimetallic complex can emit red light under the irradiation of sunlight.

A novel red phosphorescent iridium complex containing a carbazole‐functionalized β‐diketonate, Ir(DBQ)2(CBDK) (bis(dibenzo[f,h]quinoxalinato‐N,C2) iridium (1‐(carbazol‐9‐yl)‐5,5‐dimethylhexane‐2,4‐diketonate)) is designed, synthesized, and characterized. The electrophosphorescence properties of a nondoped device using the title complex as an emitter with a device configuration of indium tin oxide (ITO)/N,N′‐diphenyl‐N,N′‐bis(1‐naphthyl)‐1,1′‐diphenyl‐4,4′‐diamine (NPB; 20 nm)/iridium complex (20 nm)/2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline (BCP; 5 nm)/tris(8‐hydroxyquinoline) (AlQ; 30 nm)/Mg0.9Ag0.1 (200 nm)/Ag (80 nm) are examined. The results show that the nondoped device achieves a maximum lumen efficiency as high as 3.49 lm W–1. To understand this excellent result observed, two reference complexes Ir(DBQ)2(acac), where acac is the acetyl acetonate anion, and Ir(DBQ)2(FBDK), [bis(dibenzo[f,h]quinoxalinato‐N,C2) iridium (1‐(9‐methyl‐fluoren‐9‐yl)‐6,6‐dimethylheptane‐3,5‐diketonate)], have also been synthesized, and as emitters they were examined under the same device configuration. The maximum lumen efficiency of the former compound is found to be 0.26 lm W–1 while that for the latter is 0.37 lm W–1, suggesting that the excellent performance of Ir(DBQ)2(CBDK) can be attributed mainly to an improved hole‐transporting property that benefits the exciton transport. In addition, a bulky diketonate group separates the emitter centers from each other, which is also important for organic light‐emitting diodes.

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An iridium complex PIr(qnx) (iridium(III) bis(2-phenylpyridinato-N,C(2))(quinoxaline-2-carboxylate)) is reported for its unique and fast vapochromic and vapoluminescent behaviors. The emission of PIr(qnx) is governed by the whole crystal rather than the individual molecule. PIr(qnx) has been found to exist as both black and red forms in the solid state. The black form can be transformed into the red form upon its exposure to acetonitrile or propiononitrile vapor, whereas no response was observed when it was exposed to other volatile organic compounds. To understand the vapochromic and vapoluminescent behaviors, we determined crystal structures of both forms by X-ray diffraction. In addition, we employed density functional theory in investigating weak intermolecular interactions, such as hydrogen bonding and pi-pi interactions in the two forms.

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Two novel Eu 3+ complexes Eu(CDBM) 3 Á 2H 2 O and Eu(CCDBM) 3 Á 2H 2 O have been synthesizedshowed strong internal ligand charge transfer (ILCT) fluorescence and sensitized emission of Eu 3+ . Due to the charge transfer character, the fluorescence band of CDBM shifted from 403 nm in cyclohexane to 559 nm in acetonitrile. Photophysical studies demonstrated that no energy was migrated from the ILCT excited state of the ligands to Eu 3+ , and that Eu 3+ was sensitized by the triplet state which was localized in the 1,3-diphenyl-1,3-propanedione (DBM) part. The quantum efficiencies of Eu 3+ in the three complexes are in the order Eu(DBMin both solution and the solid state. The energy transfer pathways in the three Eu 3+ complexes were discussed in detail. Based on the systematic photophysical studies, a new guideline for the organo-lanthanide light emitting materials has been proposed: ILCT should be avoided during molecular modification.

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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 beta-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 beta-diketonate is higher than that of the Ir(C;N)(2) fragment and there is no superposition on the state density map, strong (3)LC or (3)MLCT-based phosphorescence can be obtained. Alternatively, if the state density map of the two parts are in superposition, the (3)LC or (3)MLCT-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 beta-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.