dissymmetry factor (g PL) (defined as 2(I L − I R)/(I L + I R) where I is the emission intensity), which takes a value between −2 and +2. [3] In addition, good emission efficiency is clearly important, especially in the condensed state. Over the past decades, several strategies to realize efficient CPL-active materials have been developed [4] and much work has concentrated on determining the most efficient method of introducing a chiral center into the emissive material. [5] To date, various kinds of chiral materials, including polymers and small molecules, [6] have been developed for CPL. However, most of the reported CPLactive emitters are fluorescent materials which therefore have an intrinsic internal quantum efficiency (IQE) of 25%, [7] leading to a limitation in the device. To enhance the IQE of the CPL emitter, various complexes with different transition metals were explored recently as they offer the prospect of quantitative IQE. [8] For these circularly polarized organic light-emitting diodes (CP-OLEDs), device performance, and the luminescence dissymmetry factor (g EL) of circularly polarized electroluminescence (CPEL) were two main aspects to evaluate the level of device. [9] To date, few examples have been reported with both high emission efficiency in solution-processable CP-OLED and a large luminescence dissymmetry factor. For example, Di Bari et al. reported a CP-OLED based on chiral Eu-complexes and its Circularly polarized luminescence (CPL) is of interest due to its wide potential application in semiconductors. To balance the emission efficiency and luminescence dissymmetry factor (g PL) of a CPL emitter, in this context, two chiral, phosphorescent and liquid-crystalline cyclometalated platinum complexes, abbreviated R-Pt and S-Pt, are prepared. The complexes, which show an intense green emission at 504 nm both in solution and in the solid state, contain a simple, ortho-metalated 2-phenylpyridine unit functionalized with a chiral 2-octanol chain, with liquid crystallinity being induced by modifying the β-diketonato ligand with mesogenic groups. Interestingly, both the chiral smectic (SmA*) and nematic (N*) phases are found by a combination of polarized optical microscopy, differential scanning calorimetry, and small-angle X-ray scattering. By annealing, distinct CPL emission is achieved in the solid state with a g PL around 0.02. Employing the chiral platinum complexes as the dopant, solution-processable organic light-emitting diodes present an external quantum efficiency of 11.3% and strong, circularly polarized electroluminescence with an extremely high luminescence dissymmetry value (g EL) of 0.06 after annealing at 100 °C. This work opens an avenue for designing CPL-active emitters with high emission efficiency and high dissymmetry factor.

Ionic, tetracatenar liquid crystals containing an N-phenylpyridinum core are described; many of these compounds display a SmA phase, something extremely rare in tetracatenar materials.

Families of symmetric, ionic, tetracatenar mesogens are described based on a rigid, N-phenylpyridinium core, prepared as their triflimide, octyl sulfate and dodecyl sulfate salts for a range of terminal chain lengths. The mesomorphism of the individual series is described before a comparison is drawn between the different families and then more broadly with (i) neutral tetracatenar materials and (ii) related bis(3,4-dialkoxystilbazole)silver(I) salts. For the octyl and dodecyl sulfates and the related triflates reported earlier, a SmA phase is seen at shorter chain lengths, giving way to a Colh phase as the terminal chain lengthens. For the alkyl sulfate salts, an intermediate cubic phase is also seen and the terminal chain length required to cause the change from lamellar to columnar mesophase depends on the anion. Furthermore, there is an unexpected and sometime very large mesophase stabilisation seen on entering the columnar phase. All of the triflimide salts show a rectangular columnar (ribbon) phase.

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