Asymmetric Coordination Toward a Photoinduced Single‐Chain Magnet Showing High Coercivity Values

The production of photo‐switchable molecular nanomagnets with substantial coercivity, which is indispensable for information storage and process applications, is challenging. Introducing photo‐responsive spin‐crossover units provides a feasible means of controlling the magnetic anisotropy, interactions, and overall nanomagnet properties. Herein, we report a cyanide‐bridged chain 1⋅12H 2 O ({[( Pz Tp)Fe III (CN) 3 ] 2 Fe II (Pmat) 2 } n ⋅12 H 2 O) generated by linking the Fe II ‐based spin‐crossover unit with the [( Pz Tp)Fe(CN) 3 ] − ( Pz Tp: tetrakis(pyrazolyl)borate) building block in the presence of asymmetric ditopic ligand Pmat ((4‐pyridine‐4‐yl)methyleneamino‐1,2,4‐triazole). Structural characterization revealed that the introduction of this asymmetric ligand led to a distorted coordination environment of Fe II ions, which were equatorially coordinated by four cyanide N atoms, and apically coordinated by one pyridine N atom and one triazole N atom. Upon 808‐nm light irradiation, 1⋅12H 2 O underwent photoinduced spin‐crossover and exhibited single‐chain magnet behavior with a coercive field of up to 1.3 T. This represents a 3d‐based photoinduced single‐chain magnet exhibiting pronounced hysteresis.