Reversible photomagnetism in a cobalt layered compound coupled with photochromic diarylethene

Photomagnetism is one of the most attractive topics in recent research oil Molecular solids. In order to produce a photocontrollable magnet. we have synthesized a novel organic-inorganic hybrid system Coupled with a photochromic diarylethene anion, 2.2'-dimethyl-3.3-(perfluorocyclopentene-1,2-diyl)bis(benzo[b]thiophene-6-sulfonate) (1a) and cobalt LDHs (layered double hydroxides). Based oil the elemental analysis, the title compound, which was synthesized by the anion exchange reaction between Co-2(OH)(3)(CH3COO)center dot H2O (2) and 1a, has the chemical composition, Co-4(OH)(7)(1a)(0.5)center dot 3H(2)O (3). Powder X-ray diffraction analysis revealed the interlayer distance of c=27.8 A. The magnetic Susceptibility measurements elucidated the ferromagnetic intra- and inter-layer interactions and the Curie temperature of T-c = 9 K. By UV irradiation of 313 nm, 3 shows the photo-isomerization of diarylethene anion from the open form to the closed one in solid state, which leads to the decreases in the coercive field and the remnant magnetization. Furthermore, the photo-excited state is returned to the initial state (open form) almost reversibly by visible irradiation of 550 nm. (c) 2005 Elsevier Ltd. All rights reserved.