The cooperative effects of substituents and anions in Mn(III) spin crossover complexes with hexadentate Schiff-base ligands

In this paper, the syntheses, crystal structures and magnetic properties of spin crossover (SCO) salts of formula [Mn(4-OMe-sal-N-1,5,8,12)]SbF6.0 center dot 45H(2)O (1), [Mn(3-OMe-sal-N-1,5,8,12)]SbF6.H2O (2), [Mn(4-OMe-sal-N1,5,8,12)]ClO4.H2O (3) and [Mn(3-OMe-sal-N-1,5,8,12)]Br (4) have been reported. Magnetic susceptibility measurements demonstrate that complex 1 shows a gradual one-step SCO between the high-spin (HS, S = 2) and low-spin (LS, S = 1) states without thermal hysteresis. The transition temperatures T1/ 2 of the 4-OMe-SbF6 (1) salt estimated from the magnetic susceptibility measurement is 213 K. As for complex 2, pi center dot center dot center dot pi stacking interactions lead to more close stacking which hinder the flexibility of the whole ligand and it is stable in the HS state in the temperature range of 2-300 K. Both complexes 3 and 4 exhibit incomplete spin crossover behavior. These results are consistent with Hirshfeld analysis. Electrochemical analysis indicates that the change of methoxy-substituent position from 4 to 3 decreases the electron density on the metal center.