The dynamic interplay between intramolecular and intermolecular interactions in mononuclear manganese() 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)]PF 6 ( 1 ), [Mn(5-F-sal-N-1,5,8,12)]AsF 6 ( 2 ) and [Mn(5-F-sal-N-1,5,8,12)]SbF 6 ( 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)]BF 4 ( 4 ) exhibits a gradual and incomplete spin conversion. Complex [Mn(5-F-sal-N-1,5,8,12)] ClO 4 ( 5 ) shows a nearly complete SCO with T 1/2 = 100 K. The remaining salts with spherical anions form N am -H X (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)] Cl 0.28 Br 0.72 ( 7 ) feature gradual SCO behaviors with T 1/2 = 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 χ M T value of 1.89 cm 3 mol −1 K at 400 K. Spin crossover in Mn( iii ) ions is the most rare event. Changing the size of the anions from PF 6 − , AsF 6 − , SbF 6 − to BF 4 − , ClO 4 − , Cl − , Br − , and I − led to a significant change of the overall crystal packing and furthermore the Mn( iii ) spin state.