Controlled Synthesis of Heterotrimetallic Single‐Chain Magnets from Anisotropic High‐Spin 3 d–4 f Nodes and Paramagnetic Spacers

By using the node‐and‐spacer approach in suitable solvents, four new heterotrimetallic 1D chain‐like compounds (that is, containing 3d–3d′–4f metal ions), {[Ni(L)Ln(NO 3 ) 2 (H 2 O)Fe(Tp*)(CN) 3 ] ⋅ 2 CH 3 CN ⋅ CH 3 OH} n (H 2 L= N , N ′‐bis(3‐methoxysalicylidene)‐1,3‐diaminopropane, Tp*=hydridotris(3,5‐dimethylpyrazol‐1‐yl)borate; Ln=Gd ( 1 ), Dy ( 2 ), Tb ( 3 ), Nd ( 4 )), have been synthesized and structurally characterized. All of these compounds are made up of a neutral cyanide‐ and phenolate‐bridged heterotrimetallic chain, with a {FeCNNi(OLn)NC} n repeat unit. Within these chains, each [(Tp*)Fe(CN) 3 ] − entity binds to the Ni II ion of the [Ni(L)Ln(NO 3 ) 2 (H 2 O)] + motif through two of its three cyanide groups in a cis mode, whereas each [Ni(L)Ln(NO 3 ) 2 (H 2 O)] + unit is linked to two [(Tp*)Fe(CN) 3 ] − ions through the Ni II ion in a trans mode. In the [Ni(L)Ln(NO 3 ) 2 (H 2 O)] + unit, the Ni II and Ln III ions are bridged to one other through two phenolic oxygen atoms of the ligand (L). Compounds 1 – 4 are rare examples of 1D cyanide‐ and phenolate‐bridged 3d–3d′–4f helical chain compounds. As expected, strong ferromagnetic interactions are observed between neighboring Fe III and Ni II ions through a cyanide bridge and between neighboring Ni II and Ln III (except for Nd III ) ions through two phenolate bridges. Further magnetic studies show that all of these compounds exhibit single‐chain magnetic behavior. Compound 2 exhibits the highest effective energy barrier (58.2 K) for the reversal of magnetization in 3d/4d/5d–4f heterotrimetallic single‐chain magnets.