Helicenes as All‐in‐One Organic Materials for Application in OLEDs: Synthesis and Diverse Applications of Carbo‐ and Aza[5]helical Diamines

Abstract

A set of eight helical diamines were designed and synthesized to demonstrate their relevance as all-in-one materials for multifarious applications in organic light-emitting diodes (OLEDs), that is, as hole-transporting materials (HTMs), EMs, bifunctional hole transporting + emissive materials, and host materials. Azahelical diamines function very well as HTMs. Indeed, with high Tg values (127-214 °C), they are superior alternatives to popular N,N'-di(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (NPB). All the helical diamines exhibit emissive properties when employed in nondoped as well as doped devices, the performance characteristics being superior in the latter. One of the carbohelical diamines (CHTPA) serves the dual function of hole transport as well as emission in simple double-layer devices; the efficiencies observed were better by quite some margin than those of other emissive helicenes reported. The twisting endows helical diamines with significantly high triplet energies such that they also function as host materials for red and green phosphors, that is, [Ir(btp)2 acac] (btp=2-(2'-benzothienyl)pyridine; acac=acetylacetonate) and [Ir(ppy)3 ] (ppy=2-phenylpyridine), respectively. The results of device fabrications demonstrate how helicity/ helical scaffold may be diligently exploited to create molecular systems for maneuvering diverse applications in OLEDs.

Enantioenriched Helicenes and Helicenoids Containing Main-Group Elements (B, Si, N, P)

“…An ultimate "point-tohelical" chirality transfer during the cyclization of enantiopure triynes mediated by [Ni(CO) 2 (PPh 3 ) 2 ] afforded (M)-(-) or (P)-(+)-7,8-bis(p-tolyl)hexahelicen-2-amine 293b (>99% ee) as well as its benzoderivative 294b (>99% ee) together with their Boc-protected analogues (293a and 294a). 288 For other (non-resolved) amino-substituted penta-, hexa-and hepta-helicenes, see references 289,290,291,292,293,294. Chiralpak IA column, hexane-chloroform mixture.…”

Oxa[7]superhelicene: A π‐Extended Helical Chromophore Based on Hexa‐peri‐hexabenzocoronenes

“…[7] Their roles in lightemitting devices, [8] solar cell devices, [9] chiroptical switches, [10] organic field-effect transistors (OFETs), [11] and nonlinear optics [12] are also notable. [7] Their roles in lightemitting devices, [8] solar cell devices, [9] chiroptical switches, [10] organic field-effect transistors (OFETs), [11] and nonlinear optics [12] are also notable.…”

The influence of nitrogen position on charge carrier mobility in enantiopure aza[6]helicene crystals

“…7 Helicenes have been studied for application in asymmetric catalysis, liquid crystals, chemosensors and as stereoselective charge transfer complexes. [7][8][9] In the last decade, their use as organic semiconductors has been rather limited, [10][11][12][13][14][15][16][17][18] but is increasing and includes growing interest in extended twisted aromatic structures. 19 Potentially, chirality adds a further variable that can influence the properties of organic semiconductors.…”