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Oxadiazole Derivatives (oxadiazole + derivative)
Selected AbstractsFormation of Highly Luminescent Supramolecular Architectures Possessing Columnar Order from Octupolar Oxadiazole Derivatives: Hierarchical Self-Assembly from Nanospheres to Fibrous Gels,ADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Shinto Varghese Abstract The synthesis and study of the liquid crystalline, photophysical, and aggregation behavior of novel octupolar oxadiazole derivatives are reported. These molecules formed columnar mesophases at elevated temperatures which transformed into a glassy state at ambient temperatures wherein the columnar order was retained. Their spontaneous concentration dependent hierarchical self-assembly from spheres to fibrous gels has been investigated using TEM, SEM, and XRD. Retention of the hexagonal columnar (Colh) order was also observed in the fibrous aggregates. Concentration dependent luminescence spectral studies indicated that the change in morphology from spheres to fibrous aggregates was associated with a shift in chromophore packing from predominantly H -type to J -type aggregates. Time resolved anisotropic investigations revealed that the columnar stacking of molecules in the aggregated state provided a pathway for excitation energy migration to the lower energy J -traps. [source] Novel Light Emitting Diode Using Organic Electroluminescence MicrocapsulesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2003Jae-Seok Heo Abstract Novel light emitting diodes (LEDs) were prepared using electroluminescence (EL) material/polymer microcapsules (ELC). N-vinylcarbazole as a hole-transporting component and methyl methacrylate (MMA) were copolymerized for producing the seed particles using dispersion polymerization. An oxadiazole derivative, synthesized as a electron-transporting component, and tris(8-hydroxyquinolinato) aluminium(III) (Alq3) were incorporated into the polymer particles by using the solute co-diffusion method (SCM). The LEDs for the EL characterization were fabricated in a thin sandwich configuration: Al anode/ELC/ITO cathode. The surface imaging of the LED prepared using ELC was performed by atomic force microscopy (AFM). The EL characteristics of the ELC were investigated by UV, photoelectron and luminescence spectroscopy, and the current-voltage and the light-voltage characteristics for the LED were determined. Encapsulation procedure using solute co-diffusion method (SCM). [source] Tuning the Optoelectronic Properties of Carbazole/Oxadiazole Hybrids through Linkage Modes: Hosts for Highly Efficient Green ElectrophosphorescenceADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Youtian Tao Abstract A series of bipolar transport host materials: 2,5-bis(2-(9H -carbazol-9-yl)phenyl)-1,3,4-oxadiazole (o -CzOXD) (1), 2,5-bis(4-(9H -carbazol-9-yl)phenyl)-1,3,4-oxadiazole (p -CzOXD) (2), 2,5-bis(3-(9H -carbazol-9-yl)phenyl)-1,3,4-oxadiazole (m -CzOXD) (3) and 2-(2-(9H -carbazol-9-yl)phenyl)-5-(4-(9H-carbazol-9-yl)phenyl)-1,3,4-oxadiazole (op -CzOXD) (4) are synthesized through simple aromatic nucleophilic substitution reactions. The incorporation of the oxadiazole moiety greatly improves their morphological stability, with Td and Tg in the range of 428,464,°C and 97,133,°C, respectively. The ortho and meta positions of the 2,5-diphenyl-1,3,4-oxadiazole linked hybrids (1 and 3) show less intramolecular charge transfer and a higher triplet energy compared to the para-position linked analogue (2). The four compounds exhibit similar LUMO levels (2.55,2.59,eV) to other oxadiazole derivatives, whereas the HOMO levels vary in a range from 5.55,eV to 5.69,eV, depending on the linkage modes. DFT-calculation results indicate that 1, 3, and 4 have almost complete separation of their HOMO and LUMO levels at the hole- and electron-transporting moieties, while 2 exhibits only partial separation of the HOMO and LUMO levels possibly due to intramolecular charge transfer. Phosphorescent organic light-emitting devices fabricated using 1,4 as hosts and a green emitter, Ir(ppy)3 or (ppy)2Ir(acac), as the guest exhibit good to excellent performance. Devices hosted by o -CzOXD (1) achieve maximum current efficiencies (,c) as high as 77.9,cd A,1 for Ir(ppy)3 and 64.2,cd A,1 for (ppy)2Ir(acac). The excellent device performance may be attributed to the well-matched energy levels between the host and hole-transport layers, the high triplet energy of the host and the complete spatial separation of HOMO and LUMO energy levels. [source] Formation of Highly Luminescent Supramolecular Architectures Possessing Columnar Order from Octupolar Oxadiazole Derivatives: Hierarchical Self-Assembly from Nanospheres to Fibrous Gels,ADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Shinto Varghese Abstract The synthesis and study of the liquid crystalline, photophysical, and aggregation behavior of novel octupolar oxadiazole derivatives are reported. These molecules formed columnar mesophases at elevated temperatures which transformed into a glassy state at ambient temperatures wherein the columnar order was retained. Their spontaneous concentration dependent hierarchical self-assembly from spheres to fibrous gels has been investigated using TEM, SEM, and XRD. Retention of the hexagonal columnar (Colh) order was also observed in the fibrous aggregates. Concentration dependent luminescence spectral studies indicated that the change in morphology from spheres to fibrous aggregates was associated with a shift in chromophore packing from predominantly H -type to J -type aggregates. Time resolved anisotropic investigations revealed that the columnar stacking of molecules in the aggregated state provided a pathway for excitation energy migration to the lower energy J -traps. [source] | ||||||||||