Stable Crystalline Nanohoop Radical and Its Self‐Association Promoted by van der Waals Interactions

Abstract

A stable nanohoop radical (OR3) combining the structures of cycloparaphenylene and an olympicenyl radical is synthesized and isolated in the crystalline state. X-ray crystallographic analysis reveals that OR3 forms a unique head-to-tail dimer that further aggregates into a one-dimensional chain in the solid state. Variable-temperature NMR and concentration-dependent absorption measurements indicate that the π-dimer is not formed in solution. An energy decomposition analysis indicates that van der Waals interactions are the driving force for the self-association process, in contrast with other olympicenyl derivatives that favor π-dimerization. The physical properties in solution phase have been studied, and the stable cationic species obtained by one-electron chemical oxidation. This study offers a new molecular design to modulate the self-association of organic radicals for overcoming the spin-Peierls transition, and to prepare novel nanohoop compounds with spin-related properties.

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

“…The electrochemical property of OR4 was investigated with cyclic voltammogram and differential pulse voltammogram measurements in dry DCM (Figure 5c). The reversible oxidation wave at 0.05 V vs. Fc/Fc + and reduction wave at −1.24 V vs. Fc/Fc + was found, and the more positive oxidation potential of OR4 compared with OR derivatives substituted by triisopropylsilylethynyl group [ 13‐14 ] was attributed to the electron‐withdrawing effect of PFP group. [ 23 ]…”

“…In our previous work, olympicenyl radical (OR) was stabilized by putting triisopropylsilylethynyl group at the most spin‐residing site (6‐position), producing three stable and isolable OR derivatives, OR1 , OR2 [ 13 ] and OR3 . [ 14 ] Benefiting from further protection of 3,5‐di‐ tert ‐butylphenyl group at 4,8‐positions, OR2 possesses a high stability. A head‐to‐tail 20‐center‐2‐electron π‐dimer was disclosed in the single crystal structure of OR2 , which deepens the understanding for pancake bond.…”

Extremely Stable Perylene Bisimide‐Bridged Regioisomeric Diradicals and Their Redox Properties

“…The authors have cited additional references within the Supporting Information. [28][29][30][31][32][33][34]…”

Density Functional Theory Studies of B/N-Doped Phenalenyl Nanorings with C60 for Tuning Second-Order Nonlinear Optical Properties

“…7,14−18 CPP-based nanorings are curved aromatic molecules where planar curvature induces a radially oriented π system. In addition, research interest has been focused on novel carbon nanorings containing different polycyclic aromatic hydrocarbons (PAHs), such as PLY, 13 olympicenyl, 19 chrysene, 20 pyrene, 21 and hexa-peri-hexabenzocoronene. 22 In these aromatic systems, the synthesis of πconjugated macrocycles has introduced carbon nanorings with unique structural and electronic properties, which have enormous potential in various applications.…”

“…CPP represents the shortest cross section and the simplest structure of armchair CNTs, with the successful synthesis of various [ n ]­CPPs and CPP-based nanorings extensively reported since 2008. ,– CPP-based nanorings are curved aromatic molecules where planar curvature induces a radially oriented π system. In addition, research interest has been focused on novel carbon nanorings containing different polycyclic aromatic hydrocarbons (PAHs), such as PLY, olympicenyl, chrysene, pyrene, and hexa- peri -hexabenzocoronene . In these aromatic systems, the synthesis of π-conjugated macrocycles has introduced carbon nanorings with unique structural and electronic properties, which have enormous potential in various applications. – The development of novel CPP-based nanorings and PAHs containing carbon nanorings has become a field of great research interest, providing an opportunity for further exploration and development of functional carbon nanomaterials.…”