Color Tunable Organic Light‐Emitting Diodes Using Pentafluorophenyl‐Substituted Iridium Complexes

Abstract

ordered and aligned lamellar phase structure of the synthesized monolithic silica. The SAXS pattern demonstrates that the order lamellar nanostructure of the prepared super-microporous silica does not collapse after removal of the template. Further work will be undertaken to employ the high robustness of the RTIL liquid-crystals for the generation of other mesoporous materials. ExperimentalPreparation of 1: The synthetic procedure of 1 followed a route reported in the literature [10]. 1-Chlorohexadecane (0.25 mol, 65.22 g) was mixed with 1-methylimidazole (0.25 mol, 20.53 g). The mixture was put into a 200 mL flask, refluxed at 90 C for 24 h, and then cooled down to room temperature. A white waxy solid was obtained. The product was dispersed into 200 mL THF, in which 1 was crystallized. After washing several times with THF, the crystalline powder of 1 was collected by centrifugation, and dried in vacuum at room temperature.Preparation of Monolithic Ordered Super-microporous Lamellar Silica with 1 as Template: In a typical synthesis, TMOS was used as the sol±gel precursor. 0.36 g of 1 was mixed with 1.0 mL of TMOS under mild magnetic stirring. After homogenization of the mixture, 0.5 mL of an aqueous solution of 0.01 M HCl, acting as an acid catalyst, was added dropwise. The resulting mixture was stirred at 40 C for 30 min, allowing pre-condensation of the silica, followed by mild vacuum exposure at 40 C for removal of the methanol formed due to the hydrolysis of TMOS. Complete gelation was accomplished by leaving the sample in an open flask at 40 C for 48 h. A transparent colorless silica monolith was obtained with no visible cracks and very high mechanical stability. The transparency of the hybrid materials strongly suggests the homogeneity of 1 in the silica matrix and the absence of phase separation between the RTIL and silica. 1 was removed from the silica by calcination of the sample at 550 C for 3 h at with a temperature ramp of 20 C min ±1 from room temperature to 250 C and from 350 C to 550 C, and 2 C min ±1 from 250 C to 350 C. The final product was ground into a powder for further characterization.Characterization: The TEM image was recorded on a Zeiss EM 912 X apparatus at an acceleration voltage of 120 kV. The sample was prepared by applying a drop of a diluted suspension of silica powder on a carbon-covered copper grid. The phase behavior of 1 in the reaction medium was studied by POM with a Leica DMR optical microscope. TGA was taken on a Netzsch 209. The sample was examined at a heating rate of 10 C min ±1 in an oxygen atmosphere. The powder SAXS curve was recorded on a rotating-anode instrument with pinhole collimation. A Nonius rotating anode device (P = 4 kW, Cu Ka) and an imageplate detector system were used. With the image plates placed at a distance of 40 cm from the sample, a scattering vector range from s = 0.05 to 1.0 nm ±1 was available [s = (2 sinh)/k, 2h scattering angle, k = 0.154 nm]. Nitrogen sorption data was obtained with a Micromeritics Tristar 3000 automated gas adsorption analyz...

New Trends in the Use of Transition Metal–Ligand Complexes for Applications in Electroluminescent Devices

“…Tsuzuki et al reported other examples involving perfluorophenyl-substituted phenylpyridines. [14] Lin, Tao, and co-workers produced new benzoimidazoles and their bis-cyclometalated iridium(III) complexes in good yields following the described Nonoyama method. [157] These iridium complexes revealed strong phosphorescence at ambient conditions.…”

“…Here we will discuss the synthetic routes employed for the preparation of iridium(III) complexes utilized in phosphorescent LEDs. Currently, neutral cyclometalated complexes with modified and unmodified phenylpyridines [22,49] or acetylacetonate derivatives are very promising candidates for phosphorescent LEDs, [14] while mixed-ligand cyclometalated systems with diimines [146] resulting in charged species find applications in LECs. Regarding the synthesis of 2,2¢-bipyridine-containing ruthenium(II) complexes, the reader is referred to recent review articles.…”

“…OLEDs prepared with heavy-metal complexes, such as Ir III or Pt II complexes, are the most efficient OLEDs reported to date, with theoretical internal quantum efficiencies of 100 % [50] due to the harvest of both singlet and triplet excitons. [14,17,19,50,51] Detailed studies of exciton-spin statistics for SMOLEDs as well as the determination of important device parameters can be found in the specialized literature. [5,6,39,52±57] The progress towards higher efficiencies raises the possibility for OLEDs to find new additional applications in many pocket electronic devices, such as mobile phones, portable electronic games, and personal digital assistants.…”

Recent Developments in the Application of Phosphorescent Iridium(III) Complex Systems

“…[6,7,31] However, much milder reaction conditions have proved to work out as well, reducing the formation of side products, simplifying the purification procedure, and providing the opportunity to include more sensitive functionalities. Tsuzuki et al successfully synthesized a number of bis-cyclometallated iridium(III) acetoacetonate complexes by reacting the respective precursor and acetoacetone in a mixture with ethanol and Na 2 CO 3 at 50 8C for 2-6 h. [32] By replacing 2-ethoxyethanol with a non-alcoholic solvent in the coordination reactions of 2,7-dibromo-fluorene-functionalized acetoactone derivatives, Evans et al were able to avoid undesired hydrodebromination side reactions. Performing the reactions in acetonitrile at 80 8C in the presence of Na 2 CO 3 , the desired functionalized bis-cyclometallated acetoacetonate complexes were obtained in 74-81% yield after purification.…”

High Efficiency Red Phosphorescent Organic Light-Emitting Diodes with Simple Structure

“…In phosphorescent devices, theoretically 100% internal quantum efficiency (IQE) is achieved by harvesting both singlet and triplet excitons generated by electrical injection which is four www.intechopen.com times that of fluorescent organic light-emitting devices (OLEDs) (Gong et al, 2002;Tsuzuki et al, 2003;Adachi et al, 2000). Förster and/or Dexter energy transfer processes (Tanaka and Tokito, 2008) between host and guest molecules play an important role in confining the triplet energy excitons in the phosphorescent guest.…”