Search

Abstract Two iridium(III) complexes with 1-(3,5- bis (trifluoromethyl)-pyridin-4-yl)isoquinoline (tntpiq) as main ligand, 2-(5-pyridin-4-yl)-1,3,4-oxadiazol-2-yl)phenol (pop) and 2-(5-pyridin-4-yl)-1,3,4-thiadiazol-2-yl)phenol (psp) as ancillary ligands were investigated. Both complexes emit orange red lights with different photoluminescence efficiencies (Ir(tntpiq) 2 (pop) : λ em = 585 nm, Φ = 0.41 and Ir(tntpiq) 2 (psp) : λ em = 590 nm, Φ = 0.59). Moreover, the electron mobility values of the two complexes are higher than that of the electron transport material Alq 3 (tris(8-hydroxyquinoline)aluminium), which are beneficial for their performances in organic light-emitting diodes (OLEDs). The devices with a structure of ITO/MoO 3 (3 nm)/TAPC (1,1- bis [4-[ N , N -di(p -tolyl)amino]pyridin-4-yl]cyclohexane, 30 nm)/Ir(III) complexes (2 wt%): 26DCzPPy (2,6- bis (3-(carbazol-9-yl)pyridin-4-yl)pyridine, 10 nm)/TmPyPB (1,3,5-tri(m -pyrid-3-yl-pyridin-4-yl)benzene, 40 nm)/LiF (1 nm)/Al (100 nm) displayed similar performances with a maximum current efficiency of 24.3 cd A−1 and a maximum external quantum efficiency of 11.6%, respectively, and the efficiency roll-off is very mild. Graphical abstract Image 1 Highlights • Two efficient orange red iridium(III) complexes were synthesized with the photoluminescence efficiency up to 0.59. • Both complexes have good electron mobility. • The OLEDs display a η c,max of 24.3 cd A–1 and an EQEmax of 11.6%, respectively. • The OLEDs show very low efficiency roll-off. [ABSTRACT FROM AUTHOR]

Using 2-(2,4-difluorophenyl)-4-(trifluoromethyl)pyrimidine as main ligand and tetraphenylimidodiphosphinate as ancillary ligand, one iridium complex was synthesized. This complex shows a green emission peaking at 543 nm with a quantum efficiency yield as 48% in deareated CH 2 Cl 2 solution. It also has good thermal stability with a decomposition temperature of 351 °C. Using this material as emitter, the organic light-emitting diode shows good performances with a maximum luminance 42 898 cd/m 2 , a maximum current efficiency up to 54.29 cd/A with low efficiency roll-off. At the luminance of 5000 and 10 000 cd/m 2 , the current efficiencies are still kept at 46.70 and 40.63 cd/A, respectively. [ABSTRACT FROM AUTHOR]

Abstract: A rhenium(I) complex ReL R,R (CO)3Cl (1) based on a chiral ligand, L R,R =(−)-4,5-pinene-2,2′-bipyridine [(6R)-5,6,7,8-tetrohedro-7,7-dimethyl-3-(2-pyridinyl)-6,8-methanoisoquinoline], was synthesized and characterized. The emission spectrum of 1 shows efficient dπ(Re)→π* (diimine) (MLCT) phosphorescence with a photoluminescence quantum efficiency of 0.035. The excited state lifetimes of Re(I) complex, measured in CH2Cl2 solution (1.82μs) and solid state (2.15μs) at room temperature, support the hypothesis of the MLCT character of the emitting state. Single crystal X-ray diffraction analyses show that complex 1 crystallizes in the chiral space group P21 of monoclinic system. The P–E hysteresis loop indicates its obvious ferroelectricity with the remnant polarization (P r) value of 0.17μC/cm2 at an applied field of 4.8kV/cm. To the best of our knowledge, complex 1 represents the first rhenium-based complex reported with ferroelectricity. [Copyright &y& Elsevier]

Four rhenium(I) complexes Rel.l ReL4 based on dipyrido[3,2-a:2',3'-c]phenazine (LI) and derivatives L2-L4 ligands (L2: 10,13-dibromodipyrido[3,2-a:2',3'-c]phenazine, L3: 10-bromo-13-carbazolyl-dipyrido[3,2-a:2',3'-c]phenazine, L4: 10,13-dicarbazolyldipyrido[3,2-a:2',3'-c]phenazine) were synthesized and characterized. The Re(I) complexes ReLl ReL4 show photoluminescent emissions at 556, 582, 637 and 662 nm, respectively, assigned to dn (Re)-->π* (diimine) MLCT phosphorescence in CH2CI2 solution. The carbazole containing complexes ReL3 and ReL4, as com-pared to ReLl, exhibit higher luminescence. These observations imply that modification of diimine rhenium(l) carbonyl complexes with carbazole moiety would lead to efficient phosphorescent properties. [ABSTRACT FROM AUTHOR]

Abstract: The photoluminescence properties of one europium complex Eu(TFNB)3Phen (TFNB = 4,4,4-trifluoro-1-(naphthyl)-1,3-butanedione, Phen = 1,10-phenanthroline) doped in a hole-transporting material CBP (4,4′-N,N′-dicarbazole-biphenyl) films were studied. A series of organic light-emitting devices (OLEDs) using Eu(TFNB)3Phen as the emitter were fabricated with a multilayer structure of indium tin oxide, 250Ω/square)/TPD (N,N′-diphenyl-N,N′-bis(3-methyllphenyl)-(1,1′-biphenyl)-4,4′-diamine, 50nm)/Eu(TFNB)3phen (x): CBP (4,4′-N,N′-dicarbazole-biphenyl, 45nm)/BCP (2,9-dimethyl-4,7-diphenyl-l,10 phenanthroline, 20nm)/AlQ (tris(8-hydroxy-quinoline) aluminium, 30nm)/LiF (1nm)/Al (100nm), where x is the weight percentage of Eu(TFNB)3phen doped in the CBP matrix (1–6%). A red emission at 612nm with a half bandwidth of 3nm, characteristic of Eu(III) ion, was observed with all devices. The device with a 3% dopant concentration shows the maximum luminance up to 1169cd/m2 (18V) and the device with a 5% dopant concentration exhibits a current efficiency of 4.46cd/A and power efficiency of 2.03lm/W. The mechanism of the electroluminescence was also discussed. [Copyright &y& Elsevier]

Three N,N-bidentate ligands, 5,5′-dibromo-2,2′-bipyridine (L1) and two carbazole containing ligands of 5-bromo-5′-carbazolyl-2,2′-bipyridine (L2), 5,5′-dicarbazolyl-2,2′-bipyridine (L3), and their corresponding rhenium Re(CO)3Cl(L) complexes (ReL1–ReL3) have been successfully synthesized and characterized by elemental analysis, 1H NMR and IR spectra. Their photophysical properties and thermal analysis, along with the X-ray crystal structure analysis of L3and complexes ReL1and ReL3are also described. In CH2Cl2solution at room temperature, all complexes display intense absorption bands at ca.220–350 nm, which can be assigned to spin-allowed intraligand (π→π*) transitions, and the low energy broad bands in the 360–480 nm region are attributed to the metal to ligand charge-transfer dπ(Re)→π* (diimine) (MLCT). The introduction of carbazole moieties improves the MLCT absorption and molar extinction coefficient of these complexes. Upon excitation at the peak maxima, all complexes show strong emissions around 620 nm, which are assigned to dπ(Re)→π* (diimine) MLCT phosphorescence. The photoluminescence lifetime decay of Re(I) complexes were measured and the quantum efficiencies of the rhenium(I) complexes were calculated by using air-equilibrated [Ru(bpy)3]2+·2Cl−aqueous solution as standard (Φstd= 0.028). The complexes with appended carbazole moieties exhibit enhanced luminescence performances relative to ReL1. [ABSTRACT FROM AUTHOR]

Abstract: A series of homodinuclear lanthanide complexes Ln2(HTH)6Bpm (where Ln=Eu, Sm, Er, Yb, Pr; HTH=4,4,5,5,6,6,6-heptafluroro-1-(2-thienyl)hexane-1,3-dione; Bpm=2,2′-bipyrimidine) were synthesized and the photoluminescence properties of these complexes are described. After ligand-mediated excitation of the complexes, they all show the characteristic luminescence of the corresponding Ln3+ ions in the visible and NIR regions attributed to efficient energy transfer from the ligands to the metal centres. For the Eu2(HTH)6Bpm complex a lifetime of 738.8μs (100%, χ 2 =1.362) is found in solid and two lifetimes of 455.4μs (12.88%) and 618.5μs (87.12%) (χ 2 =1.652) are found in CH2Cl2 solution, respectively. Its quantum efficiency in air-equilibrated CH2Cl2 solution is found to be 28.4%, by using air-equilibrated aqueous [Ru(bpy)3]2+·2Cl− solution as reference sample (Φ std =2.8%). [Copyright &y& Elsevier]