Rh-Mediated Enantioselective Synthesis, Crystal Structures, and Photophysical/Chiroptical Properties of Phenanthrenol-Based [9]Helicene-like Molecules

Abstract

The enantioselective synthesis of phenanthrenol-based [9]helicene-like molecules has been achieved via the rhodium-mediated intramolecular [2 + 2 + 2] cycloadditions of 3-phenanthrenol-linked triynes. Crystal structures and photophysical/chiroptical properties of these [9]helicene-like molecules were compared with the corresponding [7]helicene-like molecules.

Rhodium‐Catalyzed Enantioselective Synthesis of Highly Fluorescent and CPL‐Active Dispiroindeno[2,1‐c]fluorenes

“…In this context, helicenes, [15–19] heterohelicenes [19,20] and helical compounds [19,21–30] as representatives of SOMs have enjoyed a surge of interest as their twisted molecular structures and inherent helical chirality has been proven as a valuable structural motive for examining CPL properties [31,32] …”

Quantifying the Overall Efficiency of Circularly Polarized Emitters

“…Given both the large number of reported CPL‐active [ n ]helicenes and also their quite diverse structural motifs (Scheme 4), we shall distinguish and base the discussion of the surveyed compounds on five main classes: 1) purely monomeric organic [ n ]helicenes (in turn divided into 6 subclasses according to n, with n being the number of aromatic units forming the helicene scaffold); [38–65] 2) dimeric systems; [48, 50, 66–68] 3) S‐shaped systems; [69, 70] 4) systems with semimetals (B and Si) in the [ n ]helicenes core or directly linked to it; [71–76] and 5) cationic systems [77–80] (Scheme 4 and Table 4).…”

“…Comprehensively, the [6]helicenes subclass presents a median B CPL value of 8.9 m −1 cm −1 which significantly differs from its average of 29.2 m −1 cm −1 . Concerning [7]helicenes, the quantum yields are in the range of 0.23–0.66, [51, 53, 55–61] with lower values of 0.1 and 0.06 associated to the phosphahelicene Hel‐26 [52] and to the carbohelicene Hel‐28 , [54] respectively. As for the [5] and [6]helicenes, the g lum factors are in the order of 10 −4 –10 −3 .…”

“…The median B CPL value is 12.9 m −1 cm −1 and the average 17.4 m −1 cm −1 . For larger [ n ]helicenes (with n= 8, 9 and 11), the quantum yields are generally low (<0.3) and the g lum factors are again in the order of 10 −4 –10 −3 [53, 60, 62–65] . For n= 8 and n= 11, the B CPL analysis could be performed only on two cases each, so the median/average values are 4.8 m −1 cm −1 for [8]helicenes and 1.35 m −1 cm −1 for [11]helicenes.…”

Recent Theoretical and Experimental Progress in Circularly Polarized Luminescence of Small Organic Molecules

“…Introduction of a fluorene substructure into a helicene framework would be the key for such a high fluorescence property and provide a promising molecular design for emissive helicenes and helicene-like compounds. Tanaka et al [99] achieved the phenanthrenol-based [9]helicene-like molecules ( H40 and H41 ) via the rhodium-mediated intramolecular [2 + 2 + 2] cycloadditions of 3-phenanthrenol-linked triynes.…”