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

Abstract

AbstractSmall perfluorocycloalkanes (hexafluorocyclopropane (c‐C3F6), octafluorocyclobutane (c‐C4F8) and decafluorocyclopentane (c‐C5F10) and cage‐shaped perfluoroalkanes (perfluoro tetrahedral alkane (C4F4), perfluoro prismane (C6F6) and perfluoro cubane (C8F8)) 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‐CnF2ns (n=3, 4, 5) and e@CnFn (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 NeJ‐coupling between two coupled F nuclei (NeJFF‐coupling) in perfluoroalkane systems through density functional theory calculations. We find unusual trans‐NeJFF‐couplings (two coupled F nuclei in trans‐position) in e@c‐CnF2n (n=3, 4, 5) and NeJFF‐couplings in e@CnFn (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 NeJFF‐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 NeJFF through cooperation and competition. Interestingly, the former plays a dominant role for long‐range NeJFF‐coupling (N=5), while the latter plays a role in the short‐range NeJFF‐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.