Asymmetric Coordination Toward a Photoinduced Single-Chain Magnet Showing Large Coercivity.

The production of photoswitchable molecular nanomagnets with substantial coercivity, which is indispensable for information storage and process applications, is quite 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 ·12H 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 magnets exhibiting pronounced hysteresis.