One‐Dimensional 3d–3d–4f Trimetallic Assemblies Consisting of Cu II 2 Ln III Trinuclear Complexes and Hexacyanometallate

A series of one‐dimensional heterotrimetallic assemblies, [Cu 2 Ln(L) 2 (H 2 O) 4 ][M(CN) 6 ] · n H 2 O [Ln = Gd, M = Co ( 1 ), Fe ( 2 ), Cr ( 3 ), and Ln = La, M = Co ( 4 ), Fe ( 5 ), Cr ( 6 )], were prepared by the reaction of a Cu 2 Ln precursor complex, [Cu 2 Ln(L) 2 (NO 3 ) 3 ], with K 3 [M(CN) 6 ] in water. All of the assemblies were isomorphous and formed a 1D zigzag chain, in which the [Cu 2 Ln(L) 2 (H 2 O) 4 ] 3+ and [M(CN) 6 ] 3– units were alternately positioned and were linked in a Cu–NC–M–CN–Cu manner. Compound 1 showed magnetic behaviour similar to that of the discrete precursor complex, [Cu 2 Gd(L) 2 (NO 3 ) 3 ], owing to the diamagnetic nature of the [Co III (CN) 6 ] 3– unit. In the case of 2 , a simple summation of the magnetic behaviour of the [Cu 2 Gd(L) 2 (H 2 O) 4 ] 3+ and [Fe(CN) 6 ] 3– units was observed, whereas ferromagnetic interactions were found to be operative between the Cu 2+ and Cr 3+ ions in compound 3 . The same magnetic interactions between Cu 2+ and M 3+ were confirmed in compounds 4 to 6 , which included the diamagnetic La 3+ ion. The differences in the magnetic behaviours of 2 and 3 can be explained by the overlap of the d   z   2(Cu)–pπ(CN) orbitals in the bent Cu–N≡C linkage and the spin‐density on the cyanide nitrogen of the [Cr(CN) 6 ] 3– unit.