Solvatomorphism and Anion Effects in Fluorinated MnIII Spin Crossover Complexes

Abstract

Eight new Mn^III salts of the [Mn^III(3,5-diF-sal₂323)]X complex are reported, of which four show thermal spin crossover (SCO): 1a [Mn^III(3,5-diF-sal₂323)]PF₆·0.33CH₃CN, 1b [Mn^III(3,5-diF-sal₂323)]PF₆·CH₃CN, 1c [Mn^III(3,5-diF-sal₂323)]PF₆, 2 [Mn^III(3,5-diF-sal₂323)]AsF₆, 3 [Mn^III(3,5-diF-sal₂323)]NO₃, 4 [Mn^III(3,5-diF-sal₂323)]Br, 5 [Mn^III(3,5-diF-sal₂323)]BF₄, and 6 [Mn^III(3,5-diF-sal₂323)]OTf·0.66H₂O. Solvatomorphism is observed in the PF₆⁻ salt, revealing one complex which undergoes gradual SCO (1a·0.33CH₃CN), one that is fully high spin (1b·CH₃CN); a third solvent-free solvatomorph 1c is also recovered where structural data indicate a spin triplet at 100 K. In 1a, three independent Mn^III sites with spin state ordering of HS:LS:LS at 100 K and HS:IS:IS at 293 K are observed, where HS = high spin (S = 2), LS = low spin (S = 1), and IS = intermediate spin (i.e., an equilibrium of S = 1 and S = 2). Structural data are presented for all complexes, and magnetic data for 1a, 1b, 2, and 3.