Initial Example of a Triangular Single-Molecule Magnet from Ligand-lnduced Structural Distortion of a [Mn~(III)_3O]~(7+) Complex

摘要

Single-molecule magnets (SMMs) are individual molecules that function as nanoscale magnetic particles.They derive their properties from the combination of a large ground-state spin (S) and a magnetoanisotropy of the Ising-type (negative zero-field splitting parameter,D).They also display quantum tunneling of magnetization (QTM) and quantum phase interference,properties of the microscale.SMMs of various types and metal topologies are now known,with most being Mn species.There are,however,no triangular SMMs; numerous oxide-centered triangular [M_3O(O_2-CR)_6L_3]~(n+) (n=0,1) complexes are known for many transition metals,but antiferromagnetic exchange interactions within the [M_3O] core lead to small 5 values,and they are therefore not SMMs.It is thus tempting to conclude that this common triangular [M_3O] structural topology can never lead to SMMs,but we show in the present work that relatively small,ligand-imposed structural distortions can alter the sign of the exchange interactions and "switch on" the SMM property.