Copper(II)-terbium(III) single-molecule magnets linked by photochromic ligands.

Two assemblies composed of single-molecule magnets (SMMs) linked by photochromic ligands, [Cu(II)(2)Tb(III)(2)(L)(2)(NO(3))(2)(dae-o)(2)]·2(n-BuOH) (1) and {[Cu(II)Tb(III)(L)(n-BuOH)(0.5)](2)(dae-c)(3)}·5(DMF)·4(n-BuOH)·2(H(2)O) (2), were synthesized by reacting the SMM [Cu(II)Tb(III)(L)(NO(3))(3)] (H(2)L = 1,3-bis((3-methoxysalicylidene)amino)propane) and photochromic molecules, H(2)dae-o and H(2)dae-c, which are open- and closed-ring isomers of 1,2-bis(5-carboxyl-2-methyl-3-thienyl)perfluoropentene (H(2)dae), respectively. 1 has a tetranuclear ring-like structure comprised of two [CuTb] units and two dae-o(2-) ligands. On the other hand, 2 has a one-dimensional ladder-type structure involving the [CuTb] and dae-c(2-) units in a 3 : 2 ratio. Magnetic studies revealed that 1 and 2 had ferromagnetic interactions between the Cu(II) and Tb(III) ions and that both compounds exhibited frequency dependence of ac susceptibilities owing to freezing the magnetization of the [CuTb] SMM. Upon irradiation with ultraviolet light and visible light, an absorption band at ∼600 nm changed, indicating that photochromic reactions involving the dae(2-) ligands occurred. After irradiation, the magnetic behaviour of 1 did not change, whereas magnetic behaviour of 2 changed, due to the modification of intermolecular environment.