New layered organic-inorganic magnets incorporating azo dyes

Abstract

New hybrid organic/inorganic magnets have been synthesized by insertion of stilbazolium-carboxylate and/or -sulfonate dyes into cobalt and copper layered hydroxides. Co₂(OH)_3.57(MR)_0.43·1.88 H₂O (MR⊂Co (1)) (MRNa: Methyl Red sodium salt: sodium 2-[4-(Dimethylamino)phenylazo]benzoate), Co₂(OH)_3.27(MO)_0.73·2.94 H₂O (MO⊂Co (2)) (MONa: Methyl Orange sodium salt: sodium 4-[4-(Dimethylamino)phenylazo]benzenesulfonate), Co₂(OH)_3.45(OrangeIV)_0.55·2.92 H₂O (OrangeIV⊂Co (3)) (OrangeIVNa: OrangeIV sodium salt: sodium 4-[4-(Anilino)phenylazo]benzenesulfonate), and Co₂(OH)_3.46(MY10)_0.27·2.34 H₂O (MY10⊂Co (4)) (MY10Na₂: Mordant Yellow 10 disodium salt: sodium 3-[4-(sodium sulfonate)phenylazo]-6-hydroxybenzoate) have been synthesized by anionic exchange in alkaline media starting from Co₂(OH)₃(OAc)·H₂O. Cu₂(OH)_3.23(MR)_0.77·2.92 H₂O (MR⊂Cu (5)), Cu₂(OH)_3.29(MO)_0.71·2.31 H₂O (MO⊂Cu (6)), and Cu₂(OH)_3.39(OrangeIV)_0.61·1.80 H₂O (OrangeIV⊂Cu (7)) were obtained starting from the pre-intercalated copper hydroxide Cu₂(OH)₃(DS) (DS⁻: dodecylsulfate). This is the first time pre-intercalation is used for the insertion of molecules within the interlamellar space of simple layered hydroxides. The hybrid copper layered hydroxides show ferrimagnetic behaviour with ordering at very low temperature (below 1.8 K). The cobalt analogues are ferrimagnets with ordering temperatures ranging from 6.9 K to 18 K.