Stereoisomerism in Nanohoops with Heterogeneous Biaryl Linkages of E/Z- and R/S-Geometries

Abstract

The stereochemistry of cycloarylene nanohoops gives rise to unique cyclostereoisomerism originating from hoop-shaped molecular shapes. However, cyclostereoisomerism has not been well understood despite the ever-increasing number of structural variants. The present work clarifies the cyclostereoisomerism of a cyclophenanthrenylene nanohoop possessing both E/Z- and R/S-geometries at the biaryl linkages. Involvement of the R/S axial chirality in the nanohoop leads to the deviation of the structure from a coplanar belt shape and allows for structural variations with 51 stereoisomers with E/Z- and R/S-geometries. Experimental investigations of the dynamic behaviors of the cyclophenanthrenylene nanohoop revealed the presence of two-stage isomerization processes taking place separately at the E/Z- and R/S-linkages. Consequently, despite the presence of E/Z-fluctuations, the R/S axial chirality resulted in a separable pair of enantiomers. The structural information reported here, such as geometric descriptors and anomalous dynamics, may shed light on the common structures of various nanohoops.

An Obtuse‐angled Corner Unit for Fluctuating Carbon Nanohoops

“…Moreover, the anthracenylene–phenylene linkage preferred an orthogonal orientation at 89°, which matched well with the crystal structure as well as the global minimum of the calculations (Figure S7). We believe that this persistence of the anthracenylene–phenylene linkage at the orthogonal orientation may, most likely, be the structural origin that dismissed the D 5 h ‐ 4 structure from the 5000 low‐energy conformations …”

“…More precisely, the phenylene–phenylene angles spanned a range of 17–36°, and the anthracenylene–phenylene angles spanned a range of 61–89°. The wider dihedral angles at the anthracenylene–phenylene linkages should originate from the steric interactions, which deviated the anthracenylene panels from the potential cylinder surface of the molecule …”

“…More precisely,t he phenylene-phenylene angles spanned ar ange of 17-368,a nd the anthracenylene-phenylene angles spanned ar ange of 61-898.T he wider dihedrala ngles at the anthracenylene-phenylene linkages should originate from the steric interactions, whichd eviated the anthracenylene panels from the potential cylinder surfaceofthemolecule. [27,28] Finally,w ei nvestigated the solution-phase structure of 5mer 4 and, with the aid of theoretical calculations, disclosed the details of fluctuating structures. As pectrum from 1 HNMR spectroscopy showed four resonances that can be assigned to CH moieties of the phenylene and anthracenylene panels (Figure 3b).…”

[n]Cyclo‐3,6‐phenanthrenylenes: Synthesis, Structure, and Fluorescence

“…Owing to the inherent geometric constraint of cyclic structures with 3,6‐linkages, the molecule possesses a unique planar structure. Another congener with a non‐planar hoop shape was recently synthesized by connecting eight phenanthrenylene panels at the 3,9‐positions ([8]cyclo‐3,9‐phenanthrenylene; [8]CPhen 3,9 ), disclosing its unique stereoisomerism (Figure ) . Recently, we discovered the highly fluorescent nature of [3]CPhen 3,6 in the solid state and successfully fabricated an efficient fluorescent organic light‐emitting device (OLED) composed solely of hydrocarbon macrocycles .…”

Efficient Blue Electroluminescence from a Single‐layer Organic Device Composed Solely of Hydrocarbons

“…[10,11] For instance, recent DA molecules, NI-1-PhTPA and NI-2-PhTPA, achieved an anomalously high EQE of 6.1% and 4.4 %f or am ultilayer Fl OLED with ETL, HTL and electronblockinglayer (EBL) and for asingle-layer Fl OLED, respectively; these values are the rare, highest Fl OLED EQE values recorded to-date ( Figure 1). [13,14] With the [5]CMP hydrocarbon as an excellent base material, the [3]CPhen 3,6 hydrocarbon efficiently emitted fluorescence. In this study,w er evisited electronically unbiased hydrocarbons, the originalc omposition of Fl OLEDs, and found that an efficient blue Fl OLED with an EQE of 4.7 %c ould be realizedi n an emitter-doped single-layer architecture composed solely of hydrocarbons.…”