Spin Switching via Targeted Structural Distortion

The deliberate “stepwise” structural distortion of the [MnIII6O2(sao)6(O2CR)2L4] (S = 4, Ueff = 28
K) family of SMMs (where sao2- is the dianion of salicylaldoxime or 2-hydroxybenzaldeyhyde oxime and
L = MeOH, EtOH) via the use of derivatized oxime ligands and bulky carboxylates leads to a family of
single-molecule magnets with larger spin ground states and enhanced blocking temperatures. Replacing
sao2- and HCO2- in the molecule [MnIII6O2(sao)6(O2CH)2(MeOH)4] (1), with Et-sao2- (Et-saoH2 =
2-hydroxypropiophenone oxime) and Me3CCO2- (pivalate), produces the complex [MnIII6O2(Et-sao)6(O2CCMe3)2(EtOH)5] (2) that displays an S = 7 ground state with Ueff = 30 K. Replacing Me3CCO2- with
PhCO2- produces the complex [MnIII6O2(Et-sao)6(O2CPh)2(EtOH)4(H2O)2] (3) that displays an S = 12 ground
state with Ueff = 53 K. The ligand substitution invokes a subtle structural distortion to the core of the molecule
evidenced by an increased “twisting” of the oxime moiety (Mn−N−O−Mn) and a change in carboxylate
ligation, which, in turn, invokes a dramatic change in the observed magnetic properties by switching weak
antiferromagnetic exchange to weak ferromagnetic exchange.