Syntheses, Crystal Structures, and Magnetic Properties of Four New Cyano-Bridged Bimetallic Complexes Based on the mer-[Fe^III(qcq)(CN)₃]⁻ Building Block

Four new cyano-bridged bimetallic complexes, [{Mn^III(salen)}₂­{Fe^III(qcq)­(CN)₃}₂]_n·3nCH₃CN·nH₂O (1) [salen = N,N′-ethylenebis­(salicylideneiminato) dianion; qcq^– = 8-(2-quinoline-2-carboxamido)­quinoline anion], [{Mn^III(salpn)}₂­{Fe^III(qcq)­(CN)₃}₂]_n·4nH₂O (2) [salpn = N,N′-1,2-propylenebis­(salicylideneiminato)­dianion], [{Mn^II(bipy)­(CH₃OH)}­{Fe^III(qcq)­(CN)₃}₂]₂·2H₂O·2CH₃OH (3) (bipy = 2,2′-bipyridine), and [{Mn^II(phen)₂}­{Fe^III(qcq)­(CN)₃}₂]·CH₃CN·2H₂O (4) (phen = 1,10-phenanthroline) have been synthesized and characterized both structurally and magnetically. The structures of 1 and 2 are both unique 1-D linear branch chains with additional structural units of {Mn^III(salen/salpn)}­{Fe^III(qcq)­(CN)₃} dangling on the sides. In contrast, 3 and 4 are cyano-bridged bimetallic hexanuclear and trinuclear clusters, respectively. The intermolecular short contacts such as π–π interactions and hydrogen bonds extend 1–4 into high dimensional supermolecular networks. Magnetic investigation reveals the dominant intramolecular antiferromagnetic interactions in 1, 3, and 4, while ferromagnetic and antiferromagnetic interactions coexist in 2. Alternating current measurement at low temperature indicates the existence of slow magnetic relaxation in 1 and 2, which should be due to the single ion anisotropy of Mn^III.