Study on photomagnetism of 2-D magnetic compounds coupled with photochromic diarylethene cations

Intercalation of an organic photochromic molecule into the magnetic system provides multifunctionalities such as photomagnetism. In order to build up a photosensitive multifunctional-material, we have synthesized an organic-inorganic hybrid system consisting of layered-perovskite-type copper halides and photochromic diarylethenes. By mixing the stoichiometric amounts of CuCl₂ and 2,2′-dimethyl-3,3′-(perfluorocyclopentene-1,2′-diyl) bis-(benzo-[b]thiophene-6-ammonium)(1) in aqueous hydrochloric acid and methanol solution, we obtained (1)CuCl₄. In the dark synthetic condition, the resulting compound with open-form 1a has an intralayer ferromagnetic interaction whose exchange coupling constant is estimated at J/k_B = 10.7 K. Additionally, this compound shows antiferromagnetic transition at T_N = 3 K because of the antiferromagnetic interaction between adjacent sheets. In UV irradiated synthetic condition, the resulting compound with close-form 1b has a weaker intralayer ferromagnetic interaction (J/k_B = 6.9 K) and shows no magnetic phase transition above 2 K. By the photo-irradiation, we can control the antiferromagnetic transition and the intralayer magnetic interaction.