Modulation of Mn(3+) Spin State by Guest Molecule Inclusion

Spin state preferences for a cationic Mn(3+) chelate complex in four different crystal lattices are investigated by crystallography and SQUID magnetometry. The [MnL(1)](+) complex cation was prepared by complexation of Mn(3+) to the Schiff base chelate formed from condensation of 4-methoxysalicylaldehyde and 1,2-bis(3-aminopropylamino)ethane. The cation was crystallized separately with three polyatomic counterions and in one case was found to cocrystallize with a percentage of unreacted 4-methoxysalicylaldehyde starting material. The spin state preferences of the four resultant complexes [MnL(1)]CF(3)SO(3)·xH(2)O, (1), [MnL(1)]PF(6)·xH(2)O, (2), [MnL(1)]PF(6)·xsal·xH(2)O, (2b), and [MnL(1)]BPh(4), (3), were dependent on their ability to form strong intermolecular interactions. Complexes (1) and (2), which formed hydrogen bonds between [MnL(1)](+), lattice water and in one case also with counterion, showed an incomplete thermal spin crossover over the temperature range 5–300 K. In contrast, complex (3) with the BPh(4)(−), counterion and no lattice water, was locked into the high spin state over the same temperature range, as was complex (2b), where inclusion of the 4-methoxysalicylaldehyde guest blocked the H-bonding interaction.