Manipulating Selective Metal‐to‐Metal Electron Transfer to Achieve Multi‐Phase Transitions in an Asymmetric [Fe2Co]‐Assembled Mixed‐Valence Chain.

Manipulation of multi‐functions in molecular materials is promising for future switching and memory devices, although it is currently difficult. Herein, we assembled the asymmetric {Fe2Co} unit into a cyanide‐bridged mixed‐valence chain {[(Tp)Fe(CN)3]2Co(BIT)} ⋅ 2CH3OH (1) (Tp=hydrotris(pyrazolyl)borate and BIT=3,4‐bis‐(1H‐imidazol‐1‐yl)thiophene), which showed reversible multi‐phase transitions accompanied by photo‐switchable single‐chain magnet properties and a dielectric anomaly. Variable‐temperature X‐ray structural studies revealed thermo‐ and photo‐induced selective electron transfer (ET) between the Co and one of the Fe ions. Alternating‐current magnetic susceptibility studies revealed that 1 displayed on and off single‐chain magnet behavior by alternating 946‐nm and 532‐nm light irradiation. A substantial anomaly in the dielectric constant was discovered during the electron transfer process, which is uncommon in similar ET complexes. These findings illustrate that 1 provided a new platform for multi‐phase transitions and multi‐switches adjusted by selective metal‐to‐metal ET. [ABSTRACT FROM AUTHOR]