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Two coumarin-triarylimidazole hybrid derivatives having a N,N-diethylamine at 7-position and triaryl-substituted imidazole at 3-position on the coumarin core, 3-(1-(4-(tert-butyl)phenyl)-4,5-diphenyl-1H-imidazol-2-yl)-7-(diethylamino)-2H-chromen-2-one (C-IM-Bu) and 3-(1-(4-cyanophenyl)-4,5-diphenyl-1H-imidazol-2-yl)-7-(diethylamino)-2H-chromen-2-one (C-IM-CN), were successfully synthesized for application in organic-light emitting. Their photophysical and electrochemical properties, thermal stability and electroluminescent properties were investigated. The results showed that these compounds have excellent thermal stability, and exhibit strong blue-green emission in dichloromethane solution and green emission in thin solid films. Further, the solution-processed doped devices based on the compounds were fabricated, in which the devices fabricated from C-IM-CN exhibited the best device performance with a turn-on voltage of 3.6 V, a maximum brightness of 6896 cd/m2, a maximum current efficiency of 6.39 cd/A and a maximum external quantum efficiency of 2.92%.

Three biscoumarin dyes bridged by polycyclic aromatic bridges (anthracen, pyrene and dibenzo[g,p]chrysene) were prepared as the emissive materials for the application of organic light-emitting devices. The relationship between their structures, photophysical properties, electrochemical properties and performances of organic light-emitting devices are described. The multilayered doped devices with a configuration of ITO/NPB (20 nm)/TBADN: biscoumarin compound (x wt%, 30 nm)/TPBi (30 nm)/Liq (2 nm)/Al (100 nm) have been successfully fabricated by vacuum-deposition method. All the devices showed green emission with high electroluminescent efficiencies. Especially, the device based on the compound containing pyrene as a bridge group at 7% doping concentration showed the best performance with a maximum brightness of 10552 cd/m2, maximum luminous efficiency of 5.39 cd/A and maximum external quantum efficiency (EQE) of 2.35%. Keywords: Biscoumarin derivative, Polycyclic aromatic bridge, Dibenzo[g,p]chrysene, Photoluminescence, Electroluminescence

Two new coumarin derivatives containing phenothiazine or phenoxazine moiety, 3-(benzo[d]oxazol-2-yl)-7-(10H-phenoxazin-10-yl)coumarin (PXZ-C) and 3-(benzo[d]oxazol-2-yl)-7-(10H-phenothiazin-10-yl)coumarin (PTZ-C), were synthesized and characterized by elemental analysis, NMR spectroscopy, and MS. Their photophysical and electrochemical properties and thermal stabilities were investigated systematically. The results showed that these compounds have good thermal stability. The compound PTZ-C exhibits weak blue–green emission upon ultraviolet light excitation, whereas the compound PXZ-C displays weak blue emission.

Two new cationic iridium(III) complexes were successfully synthesized as highly sensitive and selective phosphorescent sensors for detection of Cu2+ in MeOH/H2O (1:1) solution and in living cells. These cationic Ir(III) complexes were prepared by reactions of two different Ir(III) chloro-bridged dimers with 2,2′-dipyridine tethered DPA (di(2-picolyl)amine) moiety as the ancillary ligand. These phosphorescent sensors displayed significant reversible phosphorescence quenching upon binding to Cu2+ ions with a 10 ppb detection limit. They had strong binding ability with Cu2+ ions and the binding ratios were approximately 1:1, and also exhibited good cell permeability and good imaging characteristics in detecting Cu2+ ions in living cells. It is worth mentioning that one of the phosphorescent sensors is almost nontoxic to Hela cells, indicating that it greatly increases the possibility of application in biochemistry.

A 9,9′-bifluorenylidene derivative, 2,2′,2′′,2′′′-([9,9′-bifluorenylidene]-2,2′,7,7′-tetrayltetrakis(4-octylthiophene-5,2-diyl))tetrakis(methanylylidene)tetrakis(3-oxo-2,3-dihydro-1H-indene-2,1-diylidene)tetramalononitrile (BF-TDCI4), was synthesized as an electron acceptor for organic photovoltaic cells. Its photophysical and electrochemical properties and thermal stability were investigated systematically. The photovoltaic devices were fabricated using PTB7-Th as the electron donor and BF-TDCI4 as the electron acceptor at various composition ratios. The optimized device exhibited a maximum power conversion efficiency of 4.35% with an open-circuit voltage of 0.87 V.

Three novel fullerene derivatives containing a C60-fluorene core and thiophenyl, terthiophenyl and tetrathiophenyl groups grafted at the 2-position of the fluorene ring, respectively, were synthesized and characterized. Their photophysical and electrochemical properties were investigated systematically. The results showed that their UV-vis absorption bands in the range of 350–500 nm were much wider and stronger than that of the traditional fullerene derivative PC61BM, and the LUMO energy levels of the synthesized fullerene derivatives were gradually up-shifted by increasing of the number of thiophene rings in the oligothiophene units.

Three anthracen- or pyrene-based coumarin derivatives have been successfully synthesized and characterized by EA, IR and 1H NMR. The photophysical properties of all derivatives were investigated by UV-Vis and photoluminescence spectroscopic analysis. Their thermal stabilities were demonstrated by TGA. These compounds exhibit strong blue mission under ultraviolet light excitation and have potential possible to explore organic electroluminescent materials. The vacuum-processed doped devices with a configuration of ITO/TAPC (20 nm)/TBADN: b1 (x wt%, 30 nm)/TPBi (50 nm)/Liq (2 nm)/Al (150 nm) was fabricated, in which the devices based on b1 exhibited the best electroluminescence performance with a maximum brightness of 8165 cd/m2 and a maximum luminous efficiencies of 6.13 cd/A and a maximum external quantum efficiency (EQE) of 2.75%.

Three new imidazole-derived moiety/spiro[fluorene-9,9′-xanthene] hybrid compounds, 1-phenyl-2-(4-(spiro[fluorene-9,9′-xanthen]-2-yl)phenyl)-1H-benzo[d]imidazole (SFX-PBI), 1-(4-(tert-butyl)phenyl)-2-(4-(spiro[fluorene-9,9′-xanthen]-2-yl)phenyl)-1H-phenanthro[9,10-d]imidazole (SFX-PPI), and 1-(4-(tert-butyl)phenyl)-4,5-diphenyl-2-(4-(spiro[fluorene-9,9′-xanthen]-2-yl)phenyl)-1H-imidazole (SFX-PIM), were successfully synthesized for highly efficient blue light-emitting devices. The thermal stabilities, photophysical and electrochemical properties of the hybrid compounds were investigated. These hybrid compounds exhibited strong deep blue emission in solutions. Furthermore, the vacuum-processed nondoped devices based on these compounds were fabricated, in which the device based on the compound SFX-PPI exhibited the best electroluminescence performance with a maximum brightness of 4542 cd/m2, a maximum current efficiency of 4.51 cd/A and a maximum external quantum efficiency (EQE) of 5.03%.

A new Cu(II) selective phosphorescent sensor based on a cationic iridium(III) complex was synthesized and characterized. Compared with other commonly coexisting metal ions, the Ir(III) complex displayed significant phosphorescence quenching for detecting Cu2+ with a 1:1 stoichiometry in MeOH/H2O (1:1, v/v) solution. Upon addition of Cu2+, the rapid quenching of emission intensity provided a sensitive method for detection of Cu2+. The corresponding detection limit was determined to be 7.6 × 10−8 M and the association constant between the Ir(III) complex and Cu2+ was calculated to be 0.31 × 105 M−1. Luminescence imaging experiments demonstrated that this Ir(III) complex was cell permeable and suitable for monitoring intracellular Cu2+ in living Hela cells by confocal microscopy.

Two novel cationic Ir(III) complexes, [(nbt)2Ir(L)](PF6) and [(CF3-bt)2Ir(L)](PF6), where nbt = 2-(1-naphthyl)benzothiazole; CF3-bt = 2-phenyl-6-(trifluoromethyl)-benzothiazole and L = 1-(4-(tert-butyl)phenyl)-2-(5-(9-(p-tolyl)-9H-carbazol-3-yl)pyridin-2-yl)-1H-phenanthro [9,10-d]imidazole, were successfully synthesized and characterized. The structures of L and [(nbt)2Ir(L)](PF6) were confirmed by single crystal X-ray diffraction. Their photophysical, electrochemical properties and thermal stabilities were investigated systematically. The results showed that the Ir(III) complexes had higher thermal stabilities, and exhibited strong red emission and orange emission, respectively.

Four new carbazole-based coumarin derivatives comprising a carbazole core and one or two coumarin chromophores, 7-(diethylamino)-3-(4-(9-(p-tolyl)-9H-carbazol-3-yl)phenyl)coumarin (Cz-Ph-C) and 3,3'-((9-(p-tolyl)-9H-carbazole-3,6-diyl)bis(4,4′-phenyl))bis(7- (diethylamino)coumarin) (Cz-2(Ph-C)), 7-(diethylamino)-3-(5-(9-(p-tolyl)-9H-carbazol-3- yl)thiophen-2-yl)coumarin (Cz-Th-C) and 3,3'-((9-(p-tolyl)-9H-carbazole-3,6-diyl)bis(thiophene- 5,2-diyl))bis(7-(diethylamino)coumarin) (Cz-2(Th-C)), were successfully synthesized as the emissive materials for organic light-emitting devices. The photophysical, electrochemical properties and thermal stabilities of the compounds were systematically investigated. The results showed that these coumarin-carbazole hybrids exhibited excellent thermal stabilities and high photoluminescence quantum efficiencies in dichloromethane solutions, and they emitted strong green emissions. The vacuum-processed doped devices with a configuration of ITO/TAPC (20 nm)/TBADN: Coumarin-carbazole hybrid (x wt%, 30 nm)/TPBi (50 nm)/Liq (2 nm)/Al (150 nm) was fabricated, in which the devices based on Cz-Ph-C exhibited the best electroluminescence performance with a maximum brightness of 12910 cd/m2 and a maximum luminous efficiencies of 7.39 cd/A and a maximum external quantum efficiency (EQE) of 3.36%.

Three new coumarin derivatives containing biphenyl group have been successfully synthesized and characterized by EA, IR and NMR. The photophysical properties of all derivatives were investigated by UV–vis and photoluminescence spectroscopic analysis. Their thermal stabilities were demonstrated by TGA. The doped light-emitting devices using the coumarin derivatives as dopants were fabricated. The results show that one of coumarin derivatives with coumarin-biphenyl skeleton would serve as promising luminescent materials.

Two carbazole-substituted fullerene derivatives containing mono- and bi-C60 units, (9-butyl-9H-carbazole-3-yl)-C61-butyric acid methyl ester (Cz-C60) and (9-butyl-9H-carbazole-3,6-diyl)-bis(C61-butyric acid methyl ester) (Cz-2C60), were successfully synthesized and characterized by NMR, MS and FT-IR spectroscopy. The photophysical, electrochemical properties and thermal stabilities of the fullerene derivatives were systematically investigated. P3HT-based organic photovoltaic devices were fabricated using Cz-C60 and Cz-2C60 as electron acceptors. The highest power conversion efficiencies (PCEs) of the devices fabricated with Cz-C60 and Cz-2C60 were 3.88 and 3.59%, respectively.

Two new red-emitting Ir(III) complexes containing 2-(1-naphthyl)benzothiazole as cyclometalated ligands and the carrier transporting group-functionalized picolinate as ancillary ligands have been successfully synthesized and characterized. The Ir(III) complexes have good thermal stability with less than 2% weight-reduction occurring at 285 °C, and exhibit strong red emissions. The doped light-emitting devices using the Ir(III) complexes as dopants were fabricated. The result indicated that the light-emitting devices fabricated by the carbazole-functionalized complex and the diaryl-1,3,4-oxadiazole-functionalized complex exhibited red emissions with a maximum brightness of 3074 and 2520 cd/m2 at 10.7 V and a maximum current efficiency of 4.84 and 5.18 cd/A, respectively.

Three new organic bipolar molecules containing phenothiazine and phenanthoimidazole moieties, 10-butyl-3-(phenanthroimidazol-2-yl)phenothiazine (PI-PTZ), 10-butyl-3-((4-(tert-butyl)phenyl)phenanthroimidazol-2-yl)phenothiazine (PPI-PTZ) and 10-butyl-3,7-bis((4-(tert-butyl)phenyl)phenanthroimidazol-2-yl)phenothiazine (PPI-PTZ-PPI), were successfully synthesized for organic light-emitting devices. Their thermal stabilities, photophysical and electrochemical properties were investigated systematically. These compounds exhibited strong blue or blue-green emissions with photoluminescence quantum efficiency (Φf) of 41.48 %, 40.51 % and 61.52 % in chloroform solutions, while their Φf in the solid thin films decreased to 37.53 %, 34.05 % and 47.77 %, respectively. Furthermore, the vacuum-processed doped devices based on these compounds were fabricated, in which the devices based on the compound PPI-PTZ-PPI exhibited the best electroluminescence performance with a maximum brightness of 30,180 cd/m2, a maximum current efficiency of 10.65 cd/A and a maximum external quantum efficiency (EQE) of 4.0 %.

Three new asymmetric 9,9′-bifluorenylidene-based derivatives, 2,7-dibutoxyl-3′,6′-bis(5-methylenemalononitrile-3-octylthiophen-2-yl)-9,9′-bifluorenylidene (BF-TDCN2), 2,7-dibutoxyl-3′,6′-bis(5-(methylene-indene-1,3-dione)-3-octylthiophen-2-yl)-9,9′-bifluorenylidene (BF-TID2) and 2,7-dibutoxyl-3′,6′-bis(5-(2-methylene-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile)-3-octylthiophen-2-yl)-9,9′-bifluorenylidene (BF-TDCI2), were successfully synthesized by grafting different electron-withdrawing groups (malononitrile (DCN), 1H-indene-1,3(2H)-dione (ID) and 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (DCI)), which were used as the electron acceptors for organic photovoltaic cells. By changing the electron-withdrawing ability of the terminal group, the molecular energy level and band gap can be easily adjusted. The optical bandgaps of the three compounds in the thin films decreased with increasing the electron-withdrawing ability of the terminal group. Besides, the lateral chains of alkoxy groups located at the asymmetric end also play a certain influence on the solubility, molecular aggregation and the miscibility with polymer donor. Among these electron acceptors, the photovoltaic cell fabricated PBDB-T:BF-TDCI2 exhibited a maximum power conversion efficiency of 4.85% with an open-circuit voltage of 0.88 V and a low energy loss of 0.62 eV. By investigating different processing processes, the results showed that the power conversion efficiency can be improved by 20% with simple solvent annealing treatment. Through further study on the morphology and photophysical properties of the active layers, it was found that the processed device had better phase separation size and morphology, which was favorable to enhancing the intermolecular interaction, thus improving exciton separation and charge transfer in the active layer.

Two isoquinoline-nucleated polycyclic aromatic compounds, 4,5-diphenyl-7H-dibenzo[de,g]quinolin-7-one (A) and 3,4-diphenyl-6H-phenanthro[3,4,5-defg]quinolin-6-one (B), were synthesized in high yields through three-component reaction of phenanthrene diketone or pyrene diketone, ammonium acetate and 1,2-diphenylethyne in one-pot. Their structures, thermal stabilities, photophysical properties and energy levels are investigated systematically. Both compounds emit very weak fluorescence in acetone, but their luminescence intensity increased significantly when the water content reaches 50% for A and 40% for B, exhibiting aggregation-induced emission (AIE) characteristics, and showing that the AIE effect of the compound A is stronger than that of the compound B. The vacuum-processed doped devices based on the compound B showed green emission with a maximum brightness of 2162 cd/m2, a maximum current efficiency of 2.97 cd/A and a maximum external quantum efficiency (EQE) of 2.23%.

Two new iridium(III) complexes containing the coumarin derivatives as cyclometalated ligands (L) and the carrier transporting group-functionalized dibenzoylmethane as ancillary ligands have been successfully synthesized and characterized. The X-ray crystal structure analyses of the free ligands and the complex containing a carbazole-functionalized dibenzoylmethane as ancillary ligand were described. The photophysical properties of the Ir(III) complexes were examined via ultraviolet-visible, photoluminescence spectroscopic spectra. The good thermal stability of the Ir(III) complexes was demonstrated by the thermogravimetric analysis. The doped light-emitting devices using the Ir(III) complexes as dopants were fabricated. The devices based on the complex containing a carbazole-functionalized dibenzoylmethane as ancillary ligand possess better performance as compared with the devices fabricated by the complex containing a 1,3,4-oxadiazole-functionalized dibenzoylmethane as ancillary ligand. The devices based on the former Ir(III) complex with a 15 wt% doping concentration exhibit a maximum efficiency of 13.8 cd/A and a maximum brightness of 4955.7 cd/m2.

A new iridium complex containing coumarin derivative as a cyclometalated ligand (1L) and a carbazole-functionalized β-diketonate (2L) as the ancillary ligand, namely, Ir(III)bis(3-(pyridin-2-yl)coumarinato-N,C4)(1-(9-butyl-9H-carbazol-3-yl)-4,4,4-trifluoro-butane-1,3-dionato-O,O) (Ir(1L)2(2L)), was synthesized. The crystal structure of Ir(1L)2(2L) was determined via combined wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM), which showed π–π the interactions of Ir(1L)2(2L) molecules stacking along the crystal axes. The doped light-emitting diodes using this novel Ir(1L)2(2L) complex as the phosphorescent dopant were fabricated. At a Ir(1L)2(2L) concentration of 6.0 wt%, a green-yellow emitting OLED was achieved with a maximum external quantum efficiency (EQE) of 6.11% and a maximum luminous efficiency of 22.55 cd A−1 at the current density of 6.06 mA cm−2, and a maximum luminance of 6653 cd m−2 at 10.7 V. Furthermore, two reference complexes Ir(1L)2(acac) and Ir(1L)2(TTA) were also used as emitters to fabricate OLED devices with the same device configuration. The maximum luminous efficiency of Ir(1L)2(acac) doped device was measured to be 20.04 cd A−1 at 2.15 mA cm−2 (10.0 wt%), while the doped device of Ir(1L)2(TTA) had a maximum luminous efficiency of 16.59 cd A−1 at 1.36 mA cm−2. The better performances of Ir(1L)2(2L) doped devices could be largely attributed to an improved hole-transporting property due to the introduction of the carbazole moiety.

Two new mononuclear Cu(I) complexes based on 2-(2′-pyridyl)benzimidazolyl derivative ligand containing hole-transporting carbazole (L), [Cu(L)(DPEphos)](BF4) and [Cu(L)(PPh3)2](BF4), where L = (4-(9H-carbazol-9-yl)phenyl)methyl-2-(2′-pyridyl)benzimidazole; DPEphos = bis[2-(diphenylphosphino)phenyl]ether and PPh3 = triphenylphosphine, have been synthesized and characterized on the basis of elemental analysis, 1H NMR and FT-IR spectra. The structures of the ligand L and the Cu(I) complexes were characterized by single crystal X-ray diffraction. The results reveal that in the Cu(I) complexes the central Cu(I) ions assume the irregular distorted tetrahedral geometry and are tetra-coordinated by the two nitrogen atoms from L ligand and two phosphorus atoms from ancillary ligands. The photophysical properties of the complexes were examined by using UV–vis, photoluminescence spectroscopic analysis. The complexes exhibit weak MLCT absorption bands ranging from 360 to 480 nm, and display strong orange phosphorescence in the solid states at room temperature, which is completely quenched in solutions.

Two new 7-N,N-diphenylamino-3-benzoheterocyclic coumarin derivatives containing electron-transporting benzotriazolyl or benzoxazolyl moiety, 3-(1-benzotriazole)-7-N,N-diphenylaminocoumarin (BTDC) and 3-(2-benzoxazole)-7-N,N-diphenylaminocoumarin (BODC), were synthesized and characterized by element analysis, 1H NMR and FT-IR spectra. The UV–vis and fluorescence spectra of these coumarin derivatives were investigated. The results show that BTDC and BODC exhibit strong blue and red emissions, respectively, under ultraviolet light excitation. The relationships between the chemical structure and the fluorescence characteristics of the 7-N,N-diphenylamino-3-benzoheterocyclic coumarin derivatives are discussed. It was found that the coumarin derivative will become a high-efficiency emitting material when an amino group is attached in 7-position of the coumarin ring, and 7- strong electron donors can improve the ability of the intramolecular charge transfer of the coumarin molecules.

Two mononuclear Cu (I) complexes based on a 2-(2-pyridyl)benzimidazolyl derivative ligand containing the hole-transporting ligand 1-[4-(9-carbazolyl)butyl]-2-(2-pyridyl)benzimidazole (L), [Cu(L)(PPh3)2](BF4) (1) and [Cu(L)(DPEphos)](BF4) (2), where DPEphos is bis[2-(diphenylphosphino)phenyl]ether, were synthesized and characterized by elemental analysis, 1H NMR and FT-IR spectra. The structure of complex 2 was determined by X-ray single crystal analysis. It was demonstrated that the central Cu (I) ion in the complex has a distorted tetrahedral geometry and is tetra-coordinated by the two nitrogen atoms from L ligand and two phosphorus atoms from DPEphos ancillary ligand. The photophysical properties of the complexes were examined by using UV–Vis, photoluminescence spectroscopic analysis. The complexes exhibit weak MLCT absorption bands at 410 and 490 nm, and display strong phosphorescence in the solid states at T = 298 K, which is completely quenched in solution.

Polymer solar cells (PSCs) made by poly(3-hexylthiophene) (P3HT) with multi-adducts fullerenes, [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM), PC61BM-bisadduct (bisPC61BM) and PC61BM-trisadduct (trisPC61BM), were reported. Electrochemistry studies indicated that PC61BM, bisPC61BM and trisPC61BM had step-up distributional lowest unoccupied molecular orbital (LUMO) energy. PSCs made by P3HT with above PC61BMs show a trend of enlarged open-circuit voltages, which is in good agreement with the energy difference between the LUMO of PC61BMs and the HOMO of P3HT. On the contrary, reduced short-circuit currents (J sc) were observed. The investigation of photo responsibility, dynamics analysis based on photo-induced absorption of composite films, P3HT:PC61BMs and n-channel thin film field-effect transistors of PC61BMs suggested that the short polaron lifetimes and low carrier mobilities were response for reduced J sc. All these results demonstrated that it was important to develop an electron acceptor which has both high carrier mobility, and good compatibility with the electron donor conjugated polymer for approaching high performance PSCs.

Three coumarin derivatives, 7-hydroxy-3-(2-pyridyl)coumarin (HPC), 7-(4-(5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl)benzyloxy)-3-(2-pyridyl)coumarin (Ox-PC), and 7-(4-(9H-carbazol-9-yl)butoxy)-3-(2-pyridyl)coumarin (Cz-PC), were synthesized and characterized by elemental analysis, 1H NMR, FT-IR, and UV–vis absorption spectra. The fluorescence behaviors of the compounds in methanol solutions and solid states were investigated. HPC exhibits weak green emission, whereas Cz-PC and Ox-PC show strong blue emissions in dilute solutions.

A new fluorescent chemosensor (A18C6-Ox) in which a monoaza-18-crown-6 is linked to a diaryl-1,3,4-oxadiazole fluorophore by a methylene spacer has been synthesized to evaluate binding interaction with the rare earth ions by means of absorption and emission spectrophotometry. Absorption spectra of A18C6-Ox showed a broad band at 289 nm and there was no significant change in the presence of Sc3+, La3+, Pr3+, Sm3+, Gd3+, Tb3+, Yb3+ and Lu3+ except for Ce3+ and Eu3+. From the emission spectral change of A18C6-Ox, interaction of the rare earth ions with A18C6-Ox is very strong. The formation of A18C6-Ox complexing with Sc3+, La3+, Pr3+, Sm3+, Gd3+, Tb3+, Yb3+ and Lu3+ leads to an increase in fluorescence intensity of A18C6-Ox, while Ce3+ and Eu3+ ions interact strongly causing fluorescence quenching of A18C6-Ox. In addition, the optimal complexation stoichiometry of the rare earth ions with A18C6-Ox was investigated by the fluorescent titration.

A new coumarin derivative, 3-(4-(anthracen-10-yl)phenyl)-7-(N,N′-diethylamino)coumarin, was synthesized and characterized by FT-IR, 1H NMR, element analysis and single crystal X-ray crystallography. The dihedral angle of coumarin ring and phenyl group is 30.83°, and the dihedral angle of phenyl group and anthracene skeleton is 76.99°. The photoluminescent (PL) and electroluminescent (EL) properties of the compound were investigated. The results show that the compound exhibits high fluorescence quantum yield (0.83), large Stokes shift and strong blue emission (466 nm). The electroluminescence devices comprised of vacuum vapor-deposited films using the compound as dopant were fabricated, showing blue emission that is identical to its photoluminescent spectrum in chloroform solutions. The electroluminescence device of indium tin oxide (ITO)/4,4′,4″-tris[2-naphthyl (phenyl)-amino]triphenylamine (2-TNATA) (5 nm)/N,N-bis-(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB) (40 nm)/4,4-N,N-dicarbazole-biphenyl (CBP): dopant (1.0 wt%, 30 nm)/2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole (PBD) (30 nm)/LiF (1 nm)/Al (100 nm) gives a maximum luminous efficiency of 3.3 cd/A at the current density of 20 mA/cm2, and maximum luminance of 5070 cd/m2 at 16 V.

Two new coumarin derivatives, 7-(diethylamino)-3-(pyridin-2-yl)coumarin (DAPC) and 3-(pyridin-2-yl)-benzo[5,6]coumarin (PBC), were synthesized and characterized by elemental analysis, 1H NMR, FT-IR and UV–vis absorption spectra. Their structures were determined by X-ray crystallography single crystal analysis. The fluorescence behaviors of the compounds in dichloromethane solutions were observed. The results show that the compound DAPC exhibits high fluorescence quantum yield (0.84) and they exhibit strong blue emissions under ultraviolet light excitation. The energy levels of the HOMO and LUMO of the compounds have been calculated with density functional theory (DFT) and time-dependent density functional theory (TD-DFT) at B3LYP/6-31G(d) level.

Two new coumarin derivatives containing an electron-transporting moiety (benzotriazole), 7-N,N-diethylamino-3-(benzotriazol-1-yl)coumarin (DABTC-1) and 7-N,N-diethylamino-3-(benzotriazol-2-yl)coumarin (DABTC-2), were synthesized and characterized by element analysis, 1H NMR, FT-IR and UV–vis absorption spectra. Their structures were determined by X-ray crystallography single crystal analysis. The photoluminescent behaviors of the compounds in both solution and solid states were observed, they exhibit strong blue and blue–green emissions under ultraviolet light excitation, respectively. The energy levels of the HOMO and LUMO of the compounds have been calculated with density functional theory (DFT) and time-dependent density functional theory (TD-DFT) at B3LYP/6-31G(d) level. The electroluminescent devices with the compounds as the emitters were fabricated.

A novel Tb(III) complex TbL (L = tris[2-(2-carboxyphenoxy)ethyl]amine, H3L) was synthesized and characterized by means of elemental analyses, IR spectra, thermal analyses, and molar conductivity measurement. The photoluminescent properties of the complex were investigated. In addition, PVK doping Tb(III) complex was fabricated as the emissive layer by spin-coating and its electroluminescent properties were studied, in which the structure of the device was ITO (indium tin oxide)/PVK (polyvinylcarbazole)/PVK: TbL/PBD (2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole)/LiF/Al. It was indicated that pure green and narrow bandwidth emission at 545 nm from photoluminescence of TbL complex film and the organic electroluminescent device is the characteristic emission of Tb(III) ion, and the electroluminescence spectrum of the device was very similar to that of the photoluminescence of TbL complex film. The lowest triplet level of the ligand was calculated from the phosphorescence spectrum of GdL in N,N-dimethyl formamide (DMF) dilute solution determined at 77 K, and the energy transfer mechanisms in TbL complex were discussed.

An aromatic bridged Schiff base ligand, N,n′-bis((4,4′-diethylamino)salicylidene)-1,2-phenylenediamine (H2L3), and its trinuclear Zinc(II) complex, Zn 3 L 2 3 ( CH 3 COO ) 2 , were synthesized and characterized by means of elemental analyses, FT-IR and UV–Vis absorption spectra, and single crystal X-ray crystallography. The X-ray crystal structure of the complex reveals that the zinc ion (Zn1 or Zn1A) is coordinated by two oxygen atoms in phenolate and two nitrogen atoms in imines of the ligand and one oxygen atom of the acetate, the zinc ion (Zn2) is coordinated by four oxygen atoms in phenolate of the ligands and two oxygen atoms of the acetates. Two acetates coordinate to three zinc ions through Zn–O–C–O–Zn bridges. The complex exhibits blue-green emission as the result of the fluorescence from the intraligand emission excited state. In addition, the ground-state geometries, the lowest energy transition and the UV–Vis spectrum of the ligand have been studied with density functional theory (DFT) and time-dependent density functional theory (TD-DFT) at B3LYP/6-31G(d) level, showing that the calculation outcomes are in good agreement with experimental data.

Cerium-dicyclohexano-18-crown-6 complex, Ce-DC-18·C·6, was prepared and used to fabricate organic light-emitting diode (OLEDs) with structure of ITO (indium tin oxide)/CuPc (copper-phthalocyanine)/Ce-DC-18·C·6: CBP (4,4′-bis(9-carbazolyl)biphenyl)/Bu-PBD (2-(4-biphenylyl)-5-(4- tert -butylphenyl)-1,3,4-oxadiazole)/LiF/Al. In the device the emitter layer consists of Ce(III)-complex as a dopant and CBP as a host. Adopting this doping Ce(III)-complex film, the device exhibits ultraviolet (UV) emission at 376 nm and maximum UV radiance power 13 μW/cm 2 at 3 wt% Ce(III)-complex doped device is obtained, which has been improved by about two times in comparison with no Ce(III)-complex layer UV device. In terms of photoluminescence (PL) of Ce(III) ion and CBP film, we demonstrated that the two UV emissions should be assigned to be from electron transitions of 5d → 4f of the Ce(III) ion and of S 1 → S 0 of CBP molecule, respectively. Increasing in UV radiation at shorter UV wavelength is more valuable and interesting for solid lighting application because the shorter UV emission would much match with excitation bands of more organic or inorganic phosphors. The mechanism on the electroluminescence (EL) processes of Ce(III) ion was also discussed.

Two novel iridium organometallic compounds, Ir(III)bis(3-(pyridin-2-yl)coumarinato N,C4)(thenoyltrifluoroacetonate) and Ir(III) bis(3-(pyridin-2-yl)coumarinato N,C4)(acetylacetonate) [Ir(L)2(TTA) and Ir(L)2(acac)], were synthesized and characterized by elemental analysis, 1H NMR, FT-IR and UV–vis absorption spectra. X-ray crystallography demonstrated that Ir atom is six coordinated in Ir(III)bis(3-(pyridin-2-yl)coumarinato N,C4)(thenoyltrifluoroacetonate). Both the iridium organometallic compounds emit intense green emissions, indicating that they are useful for the fabrication of organic light-emitting diodes.

Two novel triethylene-glycol dicoumarin-3-carboxylates were synthesized and characterized by element analysis, (1)H NMR, FT-IR and UV-vis absorption spectra. The photoluminescent behaviors of triethylene-glycol dibenzo[5,6]coumarin-3-carboxylate doped in PMMA were discussed. These compounds exhibit strong blue emission under ultraviolet light excitation. Compared to coumarin-3-triethylene glycol diester, the absorption and emission spectra of benzo[5,6]coumarin-3-triethylene glycol diester was bathochromically shifted due to the larger conjugation of benzene moiety. These derivatives have potential possible to explore organic electroluminescent materials.

In this paper a new cyclometalated iridium(III) coumarin complex, Ir(III)bis(3-(2-benzothiazolyl)coumarinato N,C(4))(acetylacetonate) (Ir(L)2(acac)), was synthesized and characterized. X-ray crystallography demonstrated that the iridium(III) ion is hexacoordinated by two C atoms and two N atoms from 3-(2-benzothiazolyl)coumarinato ligands and two O atoms from acac ligand, displaying distorted octahedral coordination geometry. The Ir(L)2(acac) complex has good thermal stability with less than 2 % weight-reduction occurring at 300 °C, and exhibits strong reddish orange emission. The results shown that Ir(L)2(acac) is useful for fabrication organic light-emitting diodes.

Red organic light-emitting diodes using a rhenium(I) bipyridyl complex, fac-[ClRe(CO)3(trans-4-methyl-4′-(2-4-octadecyloxylphenyl)vinyl)-2,2′-bipyridine] (Re-mopvb), as an emitter were fabricated. The optimized device has a bilayer structure of indium-tin oxide∕poly(N-vinylcarbazole): 2 wt. % Re-mopvb (80 nm)∕2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (50 nm)∕LiF (1 nm)∕Al (150 nm). Although no photoluminescence from Re-mopvb in the room-temperature solution appeared due to photoinduced isomerization, a bright red electrophosphorescence from an intraligand excited state of Re-mopvb was observed at room temperature, indicating the promising future of such a class of electroluminescent materials. The maximum luminance exceeding 120cd∕m2 at 11 V and maximum efficiency of 0.75 cd∕A at 7.5 V were obtained.

The electroluminescent (EL) properties of a new coumarin derivative, 3-(4-(anthracen-10-yl)phenyl)-benzo[5,6]coumarin (APBC), were investigated. The results show that the EL devices comprised of vacuum vapor-deposited films using the derivative as dopant exhibited blue emission that is identical to the photoluminescence of the thin film. The electroluminescence device of ITO/2-TNATA (5 nm)/NPB (40 nm)/CBP : APBC (1.0 wt%, 30 nm)/PBD (30 nm)/LiF (1 nm)/Al (100 nm) gives a maximum luminous efficiency of 2.3 cd/A at the current density of 20 mA/cm(2), and maximum luminance of 5169 cd/m(2) at 16 V. The external quantum efficiency of the device is 1.85 %.

Two coumarin derivatives containing electron-transporting benzoxazolyl moiety, 7-(diethylamino)-3-(benzoxazol-2-yl)coumarin (DABOC) and 3-(benzoxazol-2-yl)benzo[5,6]coumarin (BOBC), were synthesized and characterized. The photoluminescence and electroluminescence of the compounds were investigated detailedly. The compounds exhibited strong blue-green emissions in both solution and solid states, but the devices with DABOC as the emitting layer exhibited orange emission and maximum luminous efficiency of 2.8 cd/A and maximum luminance of 8,800 cd/m(2), and the devices with BOBC displayed orange-white emission and maximum luminous efficiency of 0.13 cd/A and maximum luminance of 540 cd/m(2).

A new coumarin derivative, 3-(4-(anthracen-10-yl)phenyl)-benzo[5,6]coumarin, was synthesized and characterized by FT-IR, (1)H NMR, element analysis and single crystal X-ray crystallography. The dihedral angle of benzo[5,6]coumarin ring and phenyl group is 36.15 degrees, and the dihedral angle of phenyl group and anthracene skeleton is 89.37 degrees. The UV-vis absorption and photoluminescence of the compound were discussed. The result shown that the compound exhibits high fluorescence quantum yield (Phi(F)), large Stokes shift and green emission (508 nm). The molecular structure of the compound was optimized using density functional theory (DFT) at B3LYP/6-31G(d) level, and the HOMO and LUMO levels of the compound were deduced.

Two novel tripodal compounds, tris[2-(7-diethylamino-coumarin-3-carboxamide)ethyl]amine (Tren-C1) and tris[2-(benzo[5,6]coumarin-3-carboxamide)ethyl]amine (Tren-C2), were synthesized and characterized. The UV-vis and fluorescence properties of Tren-C1 and Tren-C2 in solutions were investigated. These two compounds exhibited strong blue emission under ultraviolet light excitation. The maximal fluorescence emission occurred at about the level of 10(-5) mol/L. The chromophore units in the tripodal compounds shown a little interaction in the ground state, while the interactions in the excited state was notable and which leads to a broad and bathochromic shift of the emission bands.

A novel 3-(1H-4-methyl-benzotriazol-1-yl)-4-methyl-benzo[7,8]coumarin(MBMBC) containing an electron-transporting moiety (benzotriazole) was characterized single crystal X-ray crystallography and UV-vis absorption spectra. The compound exhibits strong blue emission and may prove to be important class of OLED material.

A new complex, ZnL, was synthesized and characterized by spectral data (infrared, UV-vis, fluorescence), in which the ligand compound is N1,N2-bis (pyridine-2-ylonethylene) benzene-1,2-diamine (L). ZnL exhibits a strong emission peak at 414 nm.

Triethylene-glycol di (7-(N, N'-diethylamino))-coumarin-3-carboxylate was synthesized and the photoluminescent behavior was discussed. This compound exhibits a strong blue emission peak at 464 nm and has potential possible to explore organic electroluminescent materials.

A novel tripodal compound, tris[2-(7-diethylamino-coumarin-3-carboxamide)ethyl]amine (Tren-C), was synthesized and characterized by elemental analysis, infrared and 1H-NMR spectra. The photoluminescent (PL) and electroluminescent properties of Tren-C were investigated. Tren-C exhibits different colour emissions in solid states and solutions. The electroluminescence devices comprising vacuum vapour-deposited films using the compound as a dopant were fabricated, showing blue emissions that are identical to its PL spectrum in chloroform solutions. With the device structure of indium tin oxide (ITO)/4, 4', 4''-tris-N-naphthyl-N-phenylamino-triphenylamine (2-TNATA) (5 nm)/N, N'-bis-(naphthyl)-N, N'-diphenyl-1, 1'-biphenyl-4, 4'-diamine (NPB) (40 nm)/4, 4'-bis(9-carbazolyl) biphenyl (CBP) : Tren-C (0.5 wt%, 30 nm)/2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1, 3, 4-oxadiazole (Bu-PBD) (30 nm)/LiF (1 nm)/Al (100 nm), a maximum external quantum efficiency of 2.85%, a maximum luminous efficiency of 3.85 cd A−1 and a maximum luminance of 1450 cd m−2 are realized.