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

Abstract

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⋅12H2O ({[(PzTp)FeIII(CN)3]2FeII(Pmat)2}n⋅12 H2O) generated by linking the FeII‐based spin‐crossover unit with the [(PzTp)Fe(CN)3]− (PzTp: 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 FeII 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⋅12H2O 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.

Light actuated single-chain magnet with magnetic coercivity

“…showing high coercivity values. 58 The results showed that the asymmetric coordination environment of the metal ion can effectively improve singleion magnetic anisotropy and enhance the global uniaxial anisotropy. In this respect, we decided to focus our attention on new cyanide-bridged {FeCo}-based assemblies by applying the asymmetric coordination strategy.…”

Photoinduced magnetic hysteresis in a cyanide-bridged two-dimensional [Mn2W] coordination polymer

“…To date, one of the most widely studied photomagnetic effects is light-induced spin-state trapping (LIESST) in spin crossover (SCO) complexes, in which, for example, the spin states of Fe II ions can be switched between the low (S = 0) and high spin (S = 2) states by light irradiation. [15][16][17] However, most of these molecular systems, especially, photomagnets that exhibit light-induced magnetic ordering with hysteresis loops, 18,19 are operated at relatively lower temperatures. This is mainly because these photomagnets lack strong magnetic interactions and the photoexcited phase cannot survive at high temperatures.…”