Enantiopure Cycloiridiated Complexes Bearing a Pentahelicenic N‐Heterocyclic Carbene and Displaying Long‐Lived Circularly Polarized Phosphorescence

Abstract

A fused π-helical N-heterocyclic carbene (NHC) system was prepared and examined through its diastereoisomerically pure cycloiridiated complexes. The latter display light-green phosphorescence with unusually long lifetimes and circular polarization that depends on both the helical NHC P/M stereochemistry and the iridium Δ/Λ stereochemistry. These unprecedented features are attributed to extended π conjugation within the helical carbenic ligand and efficient helicene-NHC-Ir interaction.

Configurationally Stable Platinahelicene Enantiomers for Efficient Circularly Polarized Phosphorescent Organic Light‐Emitting Diodes

“…In light of this, these helicene derivatives are often used in solution‐processed devices, which makes them difficult to obtain high performances. For example, Autschbach and Crassous and co‐workers developed a series of chiral metallahelicenes featuring good CPPL signals, which provide efficient access to achieve chiral transition‐metal complexes –. Later, Fuchter group has reported a solution‐processed CP‐PhOLED based on one of their platinahelicenes (Scheme a, 1 ) with a very high | g EL | value of 0.38, but the device performances (maximum luminance of 222 cd m −2 with current efficiency of 0.25 cd A −1 ) are inadequate for practical application .…”

An Enantiopure Cyclometallated Iridium Complex Displaying Long‐Lived Phosphorescence both in Solution and in the Solid State

“…In this context, we have recently shown for the first time that helicene-based NHCs can be synthesized, giving access to enantiopure iridium complexes that display strong chiroptical properties, especially intense electronic circular dichroism (ECD) [28] and longlived circularly polarized luminescence (CPL). [29] More specifically, we have described the first synthesis of a diastereomerically pure π-conjugated ortho-fused [5]helicenic complex B, [29] having a cycloiridiated core with meridional geometry, as in the corresponding nonhelicenic model complex A [22] (Figure 1). Other helicenebased systems have been prepared for catalytic applications.…”

Long‐Persistent Circularly Polarized Phosphorescence from Chiral Organic Ionic Crystals

“…[5] However,c ompared with circularly polarized fluorescence (CPF), its long-lived counterpart, circularly polarized phosphorescence (CPP),isnot that common. [6] Since phosphorescencea rises from the forbidden radiative (triplet to singlet) relaxations of the triplet excitons, which is sensitive to the presence of triplet oxygen molecules in air and susceptible to non-radiative relaxation via vibration and rotation, the phosphorescence process is hard to observe in solution and liquid dispersants under ambientt emperature, which hinders the investigation of the CPP process. [7] To observe CPP,t here are two feasible approaches.…”

“…One is settingc hiral emitters in absolute deoxygenated and freezing conditions, where the structures of chiroptical molecules are lockedu pi ns olvents. [6,8] There are few reports about the utilization of luminophore solutions under lowt emperature to observe the CPP phenomenon, where the stiffened solvents could not only preventt he O 2 quenching, but also reducet he non-radiative relaxation.A nother way is to encapsulate ac hiral emitter into as olid matrix. [9] Recently,r oom-temperature phosphorescence (RTP) in pure organic systemss hows remarkable oxygen resistance and luminescent abilities, which resulted from the confined environment.…”