Formation of Slipped Dimer in 6‐Pentafluorophenyl‐substituted Olympicenyl Radical

Abstract

Comprehensive SummaryIntroduction of substituents to organic radical is important to increase the stability and realize its applications as multifunctional materials. In this work, pentafluorophenyl group was introduced to 6‐position of olympicenyl radical (OR) via a newly designed synthetic strategy to afford the fourth OR derivative, OR4. Due to the combined electro‐withdrawing effect and steric hindrance of pentafluorophenyl, OR4 was stable and isolable in crystalline state. A slipped dimer was found in single crystal structure dominated by C–H···F interaction. SQUID measurements revealed a singlet–triplet energy gap of −0.47 kcal mol−1 for the slipped dimer, suggesting weak SOMO–SOMO interaction. Moreover, electro‐withdrawing effect of pentafluorophenyl leads to a positive shift (0.15 V) of oxidative wave for OR4 compared with 6‐triisopropylsilylethynyl protected OR derivatives.This article is protected by copyright. All rights reserved.

The Olympicenyl Radical and Its Derivatives

“…So far, three OR derivatives (OR1-OR3) [32] [33] have been prepared from the reductive strategy and OR4 has been prepared from the oxidative strategy (Figure 3c). [24] The introduction of substituents at the strategic positions have rendered these OR derivatives soluble and stable, which allowed for purification by common lab techniques, such as silica gel column chromatography, without special cautions. The stability of OR1-OR4 in air-saturated toluene solution was quantitatively evaluated by tracking the absorption spectral decay.…”

“…[23] In 2023, our group synthesized 6-pentafluorophenyl-olympicene 7 by treatment of lithiated [4]helicene with pentafluorophenyl-aldehyde followed by BF 3 * Et 2 O mediated Friedel-Crafts-type cyclization. [24] The energies of olympicene isomers [25] and materials applications of olympicene [26] were also studied theoretically.…”

“…Recently, Wu and coworkers designed and synthesized a series of di-substituted olympicenyl ketones and their dimers (19-23, Scheme 3), which are key precursors for covalently linked olympicenyl diradicals and polyradicals. Combination of the building blocks through oxidative homocoupling reaction or Suzuki coupling reaction produced olympicenone dimer (24), trimer (25) and tetramer (26), which were transformed into the corresponding diradical (27), triradical (28) and tetraradical (29) using the reductive strategy. Interestingly, these open-shell species could further undergo radical-mediated intramolecular cyclization followed by dehydrogenation to afford giant πextended systems 30, 31 and 32.…”

“…In 2021, Akhmetov and coworkers synthesized olympicene 1 by Al 2 O 3 ‐mediated C−F bond activation of compound 5 followed by intramolecular C−H bond insertion [23] . In 2023, our group synthesized 6‐pentafluorophenyl‐olympicene 7 by treatment of lithiated [4]helicene with pentafluorophenyl‐aldehyde followed by BF 3 •Et 2 O mediated Friedel‐Crafts‐type cyclization [24] . The energies of olympicene isomers [25] and materials applications of olympicene [26] were also studied theoretically.…”

“…So far, three OR derivatives ( OR1 ‐ OR3 ) [32][33] have been prepared from the reductive strategy and OR4 has been prepared from the oxidative strategy (Figure 3c). [24] …”