Photoswitchable organic magnetic materials.

Controlling magnetism with molecular spin state using external stimuli has a wide range of applications in spintronics, information technology, data storage, and quantum computations. Due to their weak spin-orbit coupling and low hyperfine interactions, all organic bistable spin systems are advantageous over transition metal-based spin systems. However, controlling the molecular spin state using light as an external stimulus in all organic systems is difficult. Many of these difficulties and challenges have been discussed in this review. Although there have been a few recent reports, light-driven spin-state switching in all-organic systems is still in its early stages. Photochemical reactions have proven to be one of the most promising and successful methods for spin-state switching. Despite a few successes, accessing the magnetically active triplet state using this approach remains challenging. The singlet state is usually the ground state with a high singlet-triplet energy gap, leading to an inaccessible excited triplet state. This review focuses on insights into the development of the reported photochromic magnetic materials and the recommendations for new materials that can potentially be used for photonic switching of magnetism.