In contrast, as found in Zn 2+ -Cl -CIPs , the Zn 2+ -F -CIPs should involve more covalent interaction due to the smaller ion radius of F -. This specific interaction causes that CIPs are energetically favorable in thermodynamics and need to overcome high barrier to convert to SSIPs or 2SSIPs in kinetics. As a consequence, once the certain amounts of CIPs in the path 1 solutions are formed initially, they are difficult to convert to outer-sphere complexes in some concentration conditions. Finally, these result in the NMR signal difference between the path 1 and path 2 solutions.