Mononuclear Fe(iii) complexes with 2,4-dichloro-6-((quinoline-8-ylimino)methyl)phenolate: synthesis, structure, and magnetic behavior

초록

Three Fe(iii)-based coordination complexes [Fe(dqmp)(2)](NO3)<middle dot>H2O (1), [Fe(dqmp)(2)](BF4)<middle dot>2CH(3)COCH(3) (2), and [Fe(dqmp)(2)](ClO4) (3) were synthesized from Fe(NO3)(3)<middle dot>9H(2)O/Fe(ClO4)(3)<middle dot>xH(2)O, NaBF4, and 2,4-dichloro-6-((quinoline-8-ylimino)methyl)phenol (Hdqmp) in methanol/acetone and characterized. The structures of complexes 1-3 were determined via single-crystal X-ray crystallography at 100 K and room temperature, and their magnetic properties in the solid and solution forms were investigated. All complexes showed meridional structures with two tridentate dqmp(-) ligands coordinated with Fe(iii) cations. In the solid state, complex 1 showed an abrupt and complete spin crossover at 225 K, whereas complexes 2 and 3 exhibited an incomplete spin crossover at 135 and 150 K, respectively. In a dimethylformamide solution, the complexes showed counterion-dependent spin transitions. In contrast to the solid state, in solution, complex 1 did not exhibit complete spin crossover. However, complexes 2 and 3 showed more complete spin transitions in solutions than in the solid state. The relaxation times, T-1 and T-2, for 1 and 2 were determined and both increased with temperature from 220 to 380 K. The T-1 of 1 was larger than that of 2 at 380 K, and the T-1 values were larger than the T-2 values.

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