Synthesis, Structural Characterization, and Magnetic Properties of Two Iron(II) Complexes With Triazole- and Imidazole-Related Ligands

Two new mononuclear iron (II) coordination complexes: Fe(L1)2(SCN)2 (1, L1:5-dimethylether-4-(4-methylphenyl)-3-(2-pyridinyl)-1,2,4-triazole) and Fe(L2)3(ClO4)2 (2, L2 :1-ethyl acetate-2-(2-pyridinyl)-imidazole), for the exploration of spin-crossover compounds have been synthesized and characterized. Structural analysis revealed that the framework of complex 1 is featured with 1-D chain structure connected by weak π···π interactions between the adjacent L1 ligands, while complex 2 featured with various kinds of weak intermolecular hydrogen bonding interactions between Fe(L2)32+ cation and ClO4− anion, which lead to a close crystal packing. The intermolecular interactions have shown a significant influence on the physical properties, and magnetic measurements of complexes 1 and 2 in the solid state at the room temperature revealed that the weak intermolecular interactions in 1 resulted in HS (high-spin) state, while the strong interactions in 2 lead to LS (low-spin) state over the whole temperature range.