The Dynamic Interplay between Intramolecular and Intermolecular Interactions in Mononuclear Manganese(III) SCO Complexes

The effect of counter anions on thermally induced manganese(iii)-based SCO within the [Mn(5-F-sal-N-1,5,8,12)]Y family has been investigated. All the complexes are crystallized without any lattice solvents. Crystal packing and intermolecular forces influence the spin-state stabilization and spin-transition profiles. Magnetic measurements indicate that salts with octahedral anions, [Mn(5-F-sal-N-1,5,8,12)]PF6 (1), [Mn(5-F-sal-N-1,5,8,12)]AsF6 (2) and [Mn(5-F-sal-N-1,5,8,12)]SbF6 (3), show HS electronic configurations between 2 and 300 K, and there exist π-π stackings between the phenyl groups from the neighboring [Mn(5-F-sal-N-1,5,8,12)]+ cations. As for the tetrahedral anions, complex [Mn(5-F-sal-N-1,5,8,12)]BF4 (4) exhibits a gradual and incomplete spin conversion. Complex [Mn(5-F-sal-N-1,5,8,12)] ClO4 (5) shows a nearly complete SCO with T1/2 = 100 K. The remaining salts with spherical anions form Nam-HX (X = Cl, Br, I) hydrogen bonds between Mn(iii) cations and counterions. Complexes [Mn(5-F-sal-N-1,5,8,12)]Cl (6) and [Mn(5-F-sal-N-1,5,8,12)] Cl0.28Br0.72 (7) feature gradual SCO behaviors with T1/2 = 220 K and 235 K, respectively. Complex [Mn(5-F-sal-N-1,5,8,12)]I (8) exhibits a more gradual spin conversion and is far from a complete HS state with a χMT value of 1.89 cm3 mol-1 K at 400 K.