Anion Modified Spin Crossover in [Fe(qsal-4-F)] Complexes with a 4-Position Substituted Qsal Ligand.

Four iron(III) complexes, [Fe(qsal-4-F)]Y·sol (Hqsal-4-F = 4-fluoro--(8-quinolyl)salicylaldimine; Y = NO, sol = 0.91MeOH·0.57HO (); Y = PF (); Y = BF (); Y = OTf, sol =1.5MeOH ()), with a new 4-position substituted qsal type ligand Hqsal-4-F have been synthesized and structurally and magnetically characterized. Complexes - consist of 1D chains formed by the [Fe(qsal-4-F)] cations connected by π-π and C-H···O interactions, which are further linked by more weak interactions to form 2D layers and 3D networks. On the other hand, complex has a structure of nearly isolated 1D column where the [Fe(qsal-4-F)] cations are connected by π-π, C-H···π, and C-F···π interactions. Magnetic studies revealed the occurrence of two-step symmetry-breaking SCO in and two-step gradual SCO in . Complex undergoes a gradual SCO, whereas remains almost high-spin. The smaller anions tend to stabilize the low-spin state, while larger anions tend to stabilize the high-spin state. In addition, the intermediate spin state of could be thermally trapped by quenching from the high temperature, thereby kinetically suppressing the spin transition to the full low-spin state. This work represents a good example that the position of the substituent and the anions plays critical roles in the preparation of SCO materials with tunable properties.