Tris-heteroleptic iridium complexes for white emission

Within the past decades, extensive research has been focusing on developing electroluminescent technologies (OLED and LEC). Especially, a lot of effort has been dedicated to the search a efficient phosphorescent materials with highly tuneable emission maxima bearing l a te transition metal atoms. Emitters such as cyclometalated idirium complexes have been proven to be very successful in this regards exhibiting colours from blue to red and being successfully applied in electroluminescent technologies. However, in order to decrease the manufacturing cost of these technologies, a single-centre white emitting material is highly desirable. In this context, this work investigates a new family of complexes bearing three different bidentate ligands known as tris-heteroleptic complexes to develop an emitter with a broad emission profile that would result in a white colour. Eighteen new tris-heteroleptic complexes with unprecedented ligand configurations have been synthesised by mixing different kind of ligand such as phenylpyridines (ppy), phenylpyrazo les (ppz) and phenylimidazoles (pim). This resulted in significant emission broadening with FWHM values up to nearly 6000 em- 1

Tris-heteroleptic iridium complexes based on cyclometalated ligands with different cores

A series of tris-heteroleptic iridium complexes of the form [Ir(C^N1)(C^N2)(acac)] combining 2-phenylpyridine (ppy), 2-(2,4-difluorophenyl)pyridine (dFppy), 1-phenylpyrazole (ppz), and 1-(2,4-difluorophenyl)pyrazole (dFppz) as the C^N ligands have been synthesized and fully characterized by NMR, X-ray crystallography, UV–vis absorption and emission spectroscopy, and electrochemical methods. It is shown that “static properties” (e.g., absorption and emission spectra and redox potentials) are primarily dictated by the overall architecture of the complex, while “dynamic properties” (e.g., excited-state lifetime and radiative and nonradiative rate constants) are, in addition, sensitive to the specific positioning of the substituents. As a result, the two complexes [Ir(dFppy)(ppz)(acac)] and [Ir(ppy)(dFppz)(acac)] have the same emission maxima and redox potentials, but their radiative and nonradiative rate constants differ significantly by a factor ∼2. Then acetylacetonate (acac) was replaced by picolinate (pic), and two pairs of diastereoisomers were obtained. As expected, the use of pic as the ancillary ligand results in blue-shifted emission, stabilization of the oxidation potential, and improvement of the photoluminescence quantum yield, and only minor differences in the optoelectronic properties are found between the two diastereoisomers of each pair

Teaching Story without Struggle: Using Graded Readers and Their Audio Packs in the EFL Classroom

In recent years the support for extensive reading (ER) in English as a second or foreign language (ESL/EFL) programs has been compelling. When practicing extensive reading, the learner reads a wide variety of texts for pleasure and achieves a general understanding of the content while deciphering unknown words through context. This approach contrasts with intensive reading, a more traditional approach based on a slow, careful reading of a text, with goals of complete comprehension and the identification of specific details and information

Synthesis of Trifluoromethyl-Substituted Cyclopropanes via Sequential Kharasch–Dehalogenation Reactions

A two-step process for the synthesis of trifluoromethyl-substituted cyclopropanes is described. Halothane, an anesthetic agent, is added to olefins in a ruthenium-catalyzed Kharasch reaction. The resulting 1,3-dihalides are converted into cyclopropanes by dehalogenation with magnesium. This procedure represents an alternative to metal-catalyzed cyclopropanations involving trifluoromethyl diazomethane

High performance optical oxygen sensors based on iridium complexes exhibiting interchromophore energy shuttling

A doubly pyrene-grafted bis-cyclometallated iridium complex with engineered electronically excited states demonstrates reversible electronic energy transfer between adjacent chromophores giving rise to extremely long-lived red luminescence in solution (τ = 480 μs). Time-resolved spectroscopic studies afforded determination of pertinent photophysical parameters including rates of energy transfer and energy distribution between constituent chromophores in the equilibrated excited molecule (ca. 98% on the organic chromophores). Incorporation into a nanostructured metal–oxide matrix (AP200/19) gave highly sensitive O 2 sensing films, as the detection sensitivity was 200–300% higher than with the commonly used PtTFPP and approaches the sensitivity of the best O 2-sensing dyes reported to date.Architectures à base de foldamères pour le transport d'electronsTris-heteroleptic cyclometalated iridium(III) complexes for white electroluminescenc