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

Yan, Zhi‐Ping; Luo, Xu‐Feng; Liu, Weiqiang; Wu, Zheng‐Guang; Liang, Xiao; Liao, Kang; Wang, Yi; Zheng, You‐Xuan; Zhou, Liang; Zuo, Jing‐Lin; Pan, Yi; Zhang, Hongjie

doi:10.1002/chem.201900955

Cited by 111 publications

(62 citation statements)

References 47 publications

(27 reference statements)

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“…In fine, the literature on enantioenriched helicenic derivatives with maingroup elements is constantly growing; this review addresses the results before the end of 2018 but many references on the topics have appeared in early 2019; they have not been detailed in the present review. 395,396,397,398,399,400 List…”

Section: Discussionmentioning

confidence: 99%

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

2019

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In this review, we discuss the rich chemistry of helicenes and helicenoids containing maingroup elements. Enantioenriched helicenic derivatives containing main-group elements B, Si, N and P, either incorporated within the helical backbone or grafted to it, will be thoroughly presented. We will describe their synthesis, resolution, and asymmetric synthesis, their structural features, electronic and chiroptical properties, emission, together with other photochemical properties and applications. OUTLINE 14 The absorption spectrum of 19c recorded in CH 2 Cl 2 solutions exhibited a maximum at 376 nm which is significantly red shifted compared with that of double [5]helicene 19a (310 nm) due to the more extended π-conjugation in 19c. According to TD-DFT calculations, the low-energy absorption band from 400 to 500 nm is assignable to the HOMO→LUMO transition corresponding to a π−π* transition of the fully conjugated bis-helical system. DFT calculations revealed a very high theoretical isomerization barrier of 45.1 kcal/mol for the (P,P)/(M,M)-19c stereoisomer, i.e. 4.4 kcal/mol higher than the (P,M) stereoisomer (not observed experimentally). The high configurational stability of 19c enabled to obtain the pure (P,P)and (M,M)-19c by chiral HPLC (Daicel Chiralcel IE column; EtOAc/MeOH = 9:1 as eluent) and to study their chiroptical properties. The ECD spectrum of (P,P)-19c in CH 2 Cl 2 displayed two strong positive bands at 275 and 320 nm, a strong negative one at 375 nm and a broad and less intense one between 425-475 nm. 52 Note that the isomerization barrier of the OBO-fused double [7]helicene is much higher than for oxabora[6]helicene 9 (vide supra) and higher than carbo[7]helicene (42.0 kcal/ mol), indicating the advantage of double helicenes over monohelicenes in terms of conformational stability. Indeed no racemization was observed upon heating enantiomer (P,P) and (M,M)-19c for 24 h up to 200 °C. 52 Note that in 2017 a longer double OBO-helicene analogue was deposited on a Au(111) under UHV conditions and its surface-assisted cyclodehydrogenation into a planar OBO-perihexacene was observed by STM. 54 Similarly to 6 and 9, the strong bond alternation found in the BOC4 rings of 19a 51 may account for the small NICS value of 1.3 while the surrounding C6 rings, including the distorted central benzene ring, show large negative NICS values (Scheme 3c). For comparison, in the all-carbon analogue tetrabenzo-[a,f,j,o]perylene shown in Scheme 3c, the central C6 ring shows a positive NICS value, indicating substantial antiaromatic character. Notably, molecular orbital calculations of 19a indicate that the HOMO and LUMO are spread over the C6 rings rather than on the boron and oxygen atoms, accounting for the substantial stability of 19a (Scheme 3c). Borahelicenes are efficient blue fluorophores. Indeed, azabora[6]helicene 6 displays blue fluorescence at 447 nm (Table 2), while smaller achiral [4]helicenic systems were successfully used as host materials in phosphorescent OLEDs with efficiencies better than the classical 4,4'...

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Section: Discussionmentioning

confidence: 99%

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

2019

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“…Since several years, our group has been investigating the preparation of chiral organometallic complexes bearing helicenic ligands . These compounds display attractivity for many applications, such as in optoelectronic devices, chiroptical switches, and asymmetric catalysis . The interest of these helicenic organometallic derivatives originates from the association of the inherent properties of the helicene with those of the transition metals (controlled coordination geometry, redox activity, strong spin‐orbit coupling, strong emission and absorption, reactivity), giving access to original chiral multifunctional molecules.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and chiroptical properties of organometallic complexes of helicenic N‐heterocyclic carbenes

et al. 2019

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Novel [4, 6]helicenes (4a,b) bearing a fused imidazolium unit have been prepared from [4, 6]helicene‐2,3‐di‐n‐propyl‐amines 3a,b. The in situ formation of N‐heterocyclic carbene (NHC) derivatives followed by their complexation to iridium(I) or rhodium(I) gave access to complexes 1a, 1′a, and 1b, containing mono‐coordinated helicene‐NHC, chloro and COD (COD = 1,5‐cyclooctadiene) ligands. Ir and Rh complexes 1a and 1′a were characterized by X‐ray crystallography. HPLC and NMR analyses showed that Ir(I) complex 1b existed as a mixture of two diastereomeric complexes corresponding to enantiomeric pairs M‐(−)/P‐(+)‐1b1 and M‐(−)/P‐(+)‐1b2 which differ by the position of COD through space. The chiroptical properties (electronic circular dichroism and optical rotation) of the four stereoisomers were measured. These complexes were also tested as catalysts in a transfer hydrogenation reaction.

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“…Chiral functional materials with circularly polarized luminescence (CPL) have risen to prominence in recent years due to their fascinating properties with wide potential applications in chiral sensors [1,2], photoelectric devices [3][4][5], 3D optical displays [6,7], encrypted storage of information [8,9], and even dissymmetric synthesis [10][11][12]. The general approach to fabricate CPL-active materials is through a covalent bonding of luminophore with a chiral moiety [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Dual-Mode Induction of Tunable Circularly Polarized Luminescence from Chiral Metal-Organic Frameworks

et al. 2020

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The general approach for fabricating solid-state materials showing circularly polarized luminescence (CPL) is still in its challenge. In this work, chiral metal-organic frameworks (MOFs) with full-color and white-color circularly polarized light emission are firstly achieved through a host-guest emitter-loading strategy. Chiral zeolitic imidazolate frameworks (ZIFs, a class of MOFs) are fabricated by a facile and simple mixed-ligand coassembly pathway. Meantime, achiral dyes, quantum dots (QDs), and upconversion nanoparticles (UCNPs) are easily loaded into the chiral ZIFs during the synthetic process. Size-matched dyes can be solely encapsulated into the chiral cages of ZIF, resulting in induced CPL and enhanced luminescence efficiency in solid-state ZIF⊃dye composites. Large-sized QDs, after embedding into the gap of the ZIF particles, also exhibited intense CPL activity. Furthermore, through modulating the blending ratio of colored dyes or QDs in chiral ZIFs, white light-emitting ZIFs with circular polarization could be constructed in a solid state. In addition, through loading rare earth element-based upconversion nanoparticles (UCNPs) into chiral ZIFs, upconverted CPL (UC-CPL) could be achieved with a high dissymmetry factor (glum). Thus, various achiral luminophores were endowed with CPL upon coupling with chiral ZIFs, which significantly deepened and enlarged the research scope of the chiroptical materials in a solid state.

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

Cited by 111 publications

References 47 publications

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

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

Synthesis and chiroptical properties of organometallic complexes of helicenic N‐heterocyclic carbenes

Dual-Mode Induction of Tunable Circularly Polarized Luminescence from Chiral Metal-Organic Frameworks

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