Linking Solvent Structure to Ionic Memory: AIMD/DFT of Crown-Ether Release Dynamics

Ion capture and release from crown ether hosts governs ionic retention in electrolyte‐gated and hybrid synaptic devices, yet the solvent–dependent molecular mechanisms remain incompletely resolved. Here we combine ab initio molecular dynamics (AIMD, CP2K) with electronic-structure calculations (DFT, ORCA) to quantify the release of Na⁺ from dibenzo-18-crown-6 in three different organic solvents: 1,4-dioxane (DOX), dimethyl carbonate (DMC), and dimethoxymethane (DME). Explicit-solvent AIMD with umbrella sampling yields potentials of mean force along the ion–crown separation coordinate, from which we extract binding free energies, release barriers, and dissociation rate constants via transition-state analyses. Cluster–continuum DFT (ωB97X-D/def2-TZVP with SMD/CPCM) provides complementary insights into first- and second-sphere coordination and dielectric stabilization. 

Explicit AIMD shows a solvent-dependent balance between Na⁺–crown coordination and solvent-separated ion–dipole states, consistent with experiment: DOX stabilizes contact complexes (↑ΔG‡, ↓k₋₁), DME favors separation (↓ΔG‡, ↑k₋₁), and DMC is intermediate. SMD-DFT also reproduces this ordering (DOX > DMC > DME). Mapping ΔG‡→k₋₁ gives DOX ≪ DMC ≪ DME, explaining solvent-tunable hysteresis and retention in crown-ether ion-trapping layers. 

These results establish a transferable simulation protocol for linking molecular complexation thermodynamics and solvent structure to mesoscale ionic memory.