Stable Synapse‐Like Memory Switching in N‐Heterocyclic Carbene Monolayers

ABSTRACT We report a robust redox‐active N‐heterocyclic carbene (NHC) monolayer that exhibits synapse‐like behavior driven by proton‐coupled electron transfer (PCET). Our quinone‐functionalized NHC (Rex–NHC) forms densely packed, upright self‐assembled monolayers (SAMs) on Au, confirmed by cyclic voltammetry, x‐ ray photoelectron spectroscopy, sum‐frequency generation spectroscopy, and infrared reflection absorption spectroscopy. Molecular junctions built as Au–Rex–NHC//Ga 2 O 3 /EGaIn operate over ± 2 V and can withstand electric fields up to 3.3 GV/m. Bias‐induced PCET toggles between quinone (off) and hydroquinone (on) states, yielding reversible hysteresis with on/off ratios up to 1.9 × 10 2 . The devices exhibit spike‐timing and spike‐rate‐dependent plasticity, demonstrating for the first time molecular‐level neuromorphic behavior using NHCs as anchoring groups.