Indirect Nuclear Spin-Spin Exchange Coupling through Solvated Electron in Small Sizes of Cyclic and Cage-Shaped...

Small perfluorocycloalkanes (hexafluorocyclopropane (c-C₃ F₆ ), octafluorocyclobutane (c-C₄ F₈ ) and decafluorocyclopentane (c-C₅ F₁₀ ) and cage-shaped perfluoroalkanes (perfluoro tetrahedral alkane (C₄ F₄ ), perfluoro prismane (C₆ F₆ ) and perfluoro cubane (C₈ F₈ )) are better electron scavengers. The captured excess electrons are weakly bound inside their backbone voids or over their backbones, forming the solvated electron ( $$ ) systems (e@c-C_n F_2n s (n=3, 4, 5) and e@C_n F_n (n=4, 6, 8)). There have been many studies on the structures and properties of such $$ systems. However, the effect of $$ on the indirect nuclear spin-spin coupling (J-coupling) is unknown. In this work, we explore how $$ affects ^Ne J-coupling between two coupled F nuclei (^Ne J_FF -coupling) in perfluoroalkane $$ systems through density functional theory calculations. We find unusual trans-^Ne J_FF -couplings (two coupled F nuclei in trans-position) in e@c-C_n F_2n (n=3, 4, 5) and ^Ne J_FF -couplings in e@C_n F_n (n=4, 6, 8). One excess electron not only changes the molecular structures, but also enforces unique distributions and properties, depending on the structural characteristics. We also confirm that such unusual ^Ne J_FF -couplings are realized by through- $$ (T-SE) transmission mechanism, rather than the conventional through-bonds (T-B)/through-space (T-S) ones. The novel transmission mechanism consists of the T-SE coupling path (path 1) and $$ -enhanced T-B $$ T-S coupling path (path 2), and the two paths jointly control ^Ne J_FF through cooperation and competition. Interestingly, the former plays a dominant role for long-range ^Ne J_FF -coupling (N=5), while the latter plays a role in the short-range ^Ne J_FF -coupling (N=3, 4). Path bending angle mainly influences path 1, while path 2 is mainly influenced by the path length. This work not only provides novel insights into the mediating role of $$ in the coupling information exchange, but also proposes a new $$ -based coupling mechanism, possibly opening up potential applications for the $$ -based indirect nuclear spin couplings.