Christian Slugovc

Phosphorescent Organic Light-Emitting Devices: Working Principle and Iridium Based Emitter Materials

Even though organic light-emitting device (OLED) technology has evolved to a point where it is now an important competitor to liquid crystal displays (LCDs), further scientific efforts devoted to the design, engineering and fabrication of OLEDs are required for complete commercialization of this technology. Along these lines, the present work reviews the essentials of OLED technology putting special focus on the general working principle of single and multilayer OLEDs, fluorescent and phosphorescent emitter materials as well as transfer processes in host materials doped with phosphorescent dyes. Moreover, as a prototypical example of phosphorescent emitter materials, a brief discussion of homo- and heteroleptic iridium(III) complexes is enclosed concentrating on their synthesis, photophysical properties and approaches for realizing iridium based phosphorescent polymers.

Hole transport in triphenylamine based OLED devices: from theoretical modeling to properties prediction.

For the series of para-substituted triphenylamines, optimized geometries, HOMO and LUMO energy levels, ionization potentials Ip, reorganization energies for hole transport λ(+), and frontier orbital contours have been calculated by means of ab initio computations. Relationships between them and the Hammett parameter are presented. According to calculations, electron releasing substituents increase the HOMO and LUMO energies of TPA, while electron withdrawing ones decrease it. This behavior is reflected in subsequent decreasing and increasing of ionization potentials of substituted TPAs. Calculations show that there exists also a strong substituent effect on the reorganization energy λ(+), which is a dominating factor of hole mobility. It is concluded that proper tuning of the HOMO and LUMO levels (and, as a result, ionization potential, Ip) and reorganization energy λ(+) (consequently, hole mobility) of the triphenylamine can be done by alteration of the TPA electronic structure by an appropriate substitution. It is demonstrated that the proper adjustment of the HOMO levels of HTM facilitates the reduction of an energy barrier at the interface of ITO/HTL and HTL/EL and ensure the high hole injection and hole transport rate. On the other hand, appropriate adjustment of the LUMO level prevents an electron leak from the EL into the HTM layer. Results of these calculations can be useful in the process of designing new HTM materials of desired properties (high efficiency, stability, and durability).

Inherently reactive polyHIPE material from dicyclopentadiene

A simple formulation of a stable high internal phase emulsion of dicyclopentadiene which is cured by using properly selected ring opening metathesis polymerization initiators yields highly porous monolithic materials with paramount mechanical properties and the possibility of easy functionalisation.

HYDRIDOTRIS(PYRAZOLYL)BORATE RUTHENIUM COMPLEXES : PROPERTIES AND APPLICATIONS

Abstract This review deals with ruthenium complexes of the hydrotris(pyrazolyl)borate (Tp) ligand and derivatives thereof. The period covered is from 1993 to 1998 (along with a few earlier references) including more than 40 new references, the majority of which have been published in the last 3 years. Among the co-ligands are hydride, dihydrogen, dinitrogen, CO, phosphines and amines. Particular emphasis is on complexes containing metal–carbon single and double bonds. Noteworthy is the synthesis of highly reactive vinylidene complexes and their involvement in stoichiometric CC coupling reactions with activated alkanes and olefines. Most recent developments include the application of RuTp complexes in catalytic transformations of organic molecules, such as the dimerization and polymerization of acetylenes, and the hydrogenation of ketones.

The Influence of Phosphane Ligands on the Versatility of Ruthenium–Indenylidene Complexes in Metathesis

The aim of the present study is to develop readily available and stable pre-catalysts that could be easily prepared on large scale from simple starting materials. Based on the hypothesis that substitution of classical PCy(3) with phosphanes of varying electron-donating properties could be a straightforward manner to improve catalytic activity, a methodical study dealing with the effect of phosphane fine-tuning in ruthenium-indenylidene catalysts was performed. Challenged to establish how the electronic properties of para-substituted phosphane ligands translate into catalyst activity, the versatile behaviour of these new ruthenium-indenylidene complexes was investigated for a number of metathesis reactions.

Ring opening metathesis polymerisation of emulsion templated dicyclopentadiene giving open porous materials with excellent mechanical properties

Surfactant stabilized emulsions of dicyclopentadiene and 50%, 60%, 70% or 80% of water were cured using ring opening metathesis polymerisation. All formulations gave open porous architectures featuring excellent mechanical properties which change upon oxidation.

WPLEDs prepared from main-chain fluorene–iridium(III) polymers

A novel heteroleptic iridium(III) complex containing 5,7-dibromoquinolinolate as co-ligand has been used to prepare main-chain iridium(III) polymers which produced white light emission when used as the active layer in polymeric light-emitting devices.

On the mechanical properties of HIPE templated macroporous poly(dicyclopentadiene) prepared with low surfactant amounts

Reducing the surfactant amount below generally accepted values in polyHIPE chemistry allowed for distinctly improving the mechanical properties of ROMP derived HIPE templated poly(dicyclopentadiene) without compromising the open cellular structure of the scaffold rendering the preparation of a ductile polymer foam with 80% porosity and a Youngs modulus of 110 MPa possible.

Ester type banana-shaped liquid crystalline monomers: synthesis and physical properties

New ester-type banana (bent-shaped) monomers, 1,3-phenylene bis[4′-(alken-1-yloxy)-biphenyl-4-carboxylate]s Ia–Vb, with different substituent(s) on the central phenyl ring (H, CH3, Cl or NO2) and alkenyl tails in the side arms (decenyl or undecenyl) were prepared. The analogues IIIa–IVb with 4-chloro- or 4,6-dichloro-substituents exhibited a nematic phase, while Va,Vb with 2-nitro-substituent showed a B7 phase at relatively low temperature. All the compounds were stable, no degradation or polymerization was observed under applied electric fields or heat treatments. Electro-hydrodynamic instabilities were observed in the nematic phase of each sample. In the B7 phase of Vb there was an electro-optical switching in the range 112–114.5 °C with a switching time of about 150 µs at 20 V µm−1 field. At lower temperatures no electro-optical switching occurred, but a ferroelectric-type spontaneous polarization of 22 nC cm−2 could be detected. The bend angle was calculated by the semiempirical CAChe/MOPAC/PM5 method.

C–H bond activation reactions by TpMe2Ir(III) centres. Generation of Fischer-type carbenes and development of a catalytic system for H/D exchange

The unsaturated [TpMe2Ir(C6H5)2] fragment, readily generated from [TpMe2Ir(C6H5)2(N2)], or from [TpMe2Ir(C2H4)2] and C6H6, is able to induce the regioselective cleavage of two sp3 C–H bonds of anisole, with formation of a Fischer-type carbene, 1. The process involves additionally ortho-metallation of the anisole aromatic ring, hence three C–H bonds are sequentially broken, the last one in the course of an α-H elimination reaction. Phenetole (ethyl phenyl ether) gives an analogous product, 3, despite the possibility of competitive α- or β-H eliminations in the last step. For C6H5NMe2, two hydride-carbenes, 5a and 5b, are produced. In the latter, the aniline phenyl ring is also metallated, but the former contains a C6H5 aryl group and a C6H5N(Me)CH carbene ligand. The same Ir(III) fragment, viz. [TpMe2Ir(C6H5)2], alternatively generated from C6H6 and [TpMe2Ir(η4-CH2C(Me)C(Me)CH2)], accomplishes the efficient, catalytic H/D exchange between C6D6 (used as the deuterium source) and a variety of organic and organometallic molecules that contain C–H bonds of different nature.