Singlet Tetra‐Radical Nickel(II) Complex Based Versatile Molecular Memristor with Adaptive Learning Capability

Abstract Molecular memristors have emerged as pivotal components in next‐generation electronics, combining redox‐active functionality at the nanoscale with cognitive behaviors. Synthesis, characterization, and redox‐induced interconversion of a new binuclear open‐shell singlet (S = 0) tetra‐radical nickel(II)‐complex, [Ni II 2 (L •–•– ) 2 ] ( 1 ) featuring two two‐electron reduced dianionic diradical scaffolds 2,9‐bis(phenyldiazenyl)‐1,10‐phenanthroline ( L ) as a robust resistive switching element is reported. The complex 1 upon one‐electron ligand‐centered oxidation forms a mono‐cationic tri‐radical species [Ni II 2 (L •–•– )(L •– )] + ([ 1 ] + ), which upon further oxidation transforms to a di‐cationic monometallic species [Ni II (L 0 ) 2 ] [ 2 ] 2+ . Controlled ligand‐centered reduction in the presence of excess Ni(II)‐sources such as NiCl 2 or Ni(ClO 4 ) 2 transforms the mono‐metallic species [ 2 ] 2+ to the binuclear tetra‐radical complex 1 . Complex 1 demonstrates exceptional performance as a molecular memristor, including high endurance over 750 cycles, 2‐h data retention, and ultrafast switching speeds of 55 ns. The consistent On/Off conductivity difference under varying environmental conditions makes it promising for robust data storage and data‐processing applications. Moreover, it supports advanced functionalities such as logic gate operations, 4‐bit edge computing, and adaptive learning behavior, positioning it as a versatile building block for next‐generation all‐in‐one electronic technologies.