Photo-switched magnetic coupling in spin-crossover complexes

Photo-switched spin-crossover (SCO) complexes, especially iron( ii )-based ones, have been widely studied in the past few decades owing to their promising applications in high density information storage, optical memory materials, magneto-optical devices and light-responsive switches. In particular, photo-induced spin-crossover involves not only the changing of the spin state and magnetic anisotropy of metal centers, but also the magnetic coupling interactions between neighbouring metal centers, which is also of vital importance to the overall magnetic properties. The exchange interactions can be reversibly switched on and off via light-induced excited spin-state trapping (LIESST) and reverse processes, leading to an abrupt changing of the magnetization value, spontaneous magnetization, and even molecular nanomagnet properties, depending on their dimensionalities and topologies. In this feature article, we will discuss the recent progress on the photoswitchable magnetic coupling in spin-crossover complexes reported by both our group and other groups and highlight the role of magnetic coupling in determining their magnetic properties. The design strategy of magnetically coupled photo-switched SCO complexes will be discussed. Finally, a perspective with respect to the remaining challenges and growing trends in this field will be given. This feature article summarizes the recent progress in the magnetically coupled spin-crossover (SCO) complexes. The photo-switched molecular nanomagnet property, long range magnetic ordering, and the perspectives of SCO complexes are also presented.