Design, Synthesis, and Modulation of Valence Tautomeric Binuclear Cobalt Compounds with Redox‐Active Bridged Ligands

Valence tautomeric (VT) compounds are a kind of bistable materials characterized by intramolecular electron transfer (ET). This study focuses on the controlled synthesis and performance modulation of compounds exhibiting VT behavior. Through the design of redox‐active ligands and the adoption of auxiliary ligands and counter‐anions, three compounds are successfully prepared, that is, [{Co(tpa)} 2 (L cat−cat )](PF 6 ) 2 ·8H 2 O·4CH 3 OH ( 1 ), [{Co(tpa)} 2 (L cat−cat )](BPh 4 ) 2 ·2CH 2 Cl 2 ( 2 ), and [{Co(dpa OMe )} 2 (L cat−cat )](BPh 4 ) 2 ·6CH 3 CN ( 3 ), respectively, where L cat−cat = 6,6 ′ ‐((1 E ,1 ′E )‐hydrazine‐1,2‐diylidenebis(methaneylylidene)) bis(3,5‐di‐ tert ‐butylbenzene‐1,2‐diol), tpa = tris(2‐pyridinylmethyl) amine, and dpa OMe = 2‐methoxy‐ N , N ‐bis(pyridine‐2‐ylmethyl)aniline. Structural, magnetic, and spectroscopic analyzes reveal that 1 and 2 remain in the {Co III ‐cat‐cat‐Co III } configuration, whereas 3 undergoes VT transition near 350 K. Comparative studies highlight that the modification of auxiliary ligand from tpa to dpa OMe significantly enhances the intramolecular ET capability. This finding provides valuable insights into how ligand engineering regulates VT behavior, offering a foundation for the design of advanced functional materials.