Synthesis of Helical Indolophenanthridines Showing Aggregation-Induced Emission

Abstract

Helical indolo[2,3-k]-and [3,2-a]phenanthridines were synthesized from amines by amide formation and Morgan− Walls cyclization. The synthetic routes offer the advantage of latestage derivatization and do not require protecting groups, which makes the compounds directly suitable for further functionalization. The compounds exhibit remarkable acid-dependent bathochromic shifts of the luminescence, solvatochromism, and aggregation-induced emission (AIE) behavior, which make them especially interesting candidates for studies toward optoelectronic applications.

Synthesis of 5,9‐Diaza Analogues of [5]‐ and [6]Helicene and their Chiroptic and Photophysical Characterization

“…Contribution of these orbitals to the low-energy band is 72 % for 11 and 87 % for 18. The small intensity is reflected by small oscillator strengths for these transitions: f � 0.06 (11) and f � 0.09 (18). Further details to measured and calculated UV/Vis spectra are given in the SI.…”

“…[14] Further methods for the synthesis of aza-and diazahelicenes are transition metal-catalyzed [2 + 2 + 2] cyclizations [15] and couplings of ortho,ortho'-dihalobiaryls [7b,16] or ortho-alkynylbiaryls. [15b] In the recent years we used ortho,ortho' fusions (Figure 1, bottom) in suitably substituted terphenyls I to synthesize diaza [5]helicenes C and D, [17] indolo [2,3-c]carbazoles E, [17b] indolophenanthridines, [18] thiahelicenes F, [19] and heliceneshaped cyclopenta-fused polyaromatic hydrocarbons G and H Figure 1. Top row: carbohelicenes, center: structures previously obtained in our group, bottom: general scheme for ortho,ortho' fusion of terphenyl derivatives to pentahelicenes.…”