A series of MnIII saltmen dimers, [Mn2(5-Rsaltmen)2(X)2](A)2n (saltmen2- = N,N′-(1,1,2,2-tetramethylethylene)bis(salicylideneiminate); R = H, Cl, Br, MeO, Me; X = H2O, ReO4 -, NO3 -, N3 -, NCS-, A- = ClO4 -, PF6 -, CF3SO3 - for X = H2O) were synthesized and structurally and magnetically investigated to understand the correlation between their intradimer ferromagnetic (FM) interaction and single-molecule magnet (SMM) behavior. All complexes had a similar di-μ-phenolate-bridged out-of-plane dimer structure but displayed different bridging Mn-Oph∗ distances depending on the R substituents of the saltmen ligand and axial X ligand. Magnetic susceptibility studies revealed intradimer FM coupling (JMn-Mn∗), resulting in an ST = 4 ground state for all dimers. However, the magnitude of FM coupling strongly depended on R and X. JMn-Mn∗ increased with decreasing Mn-Oph∗ distance but decreased with decreasing Mn-X distance with a relation of H2O ≈ ReO4 - > NO3 - > N3 - ≈ NCS- with a linear trend for R = H, Cl, Me but not for R = Br, MeO. Theoretical investigations revealed that a larger orbital overlap stabilized a FM spin configuration through competition between the orbital degeneracy and on-site Coulomb repulsion of out-of-phase and in-phase orbitals. Most dimers showed typical SMM behavior. The dimers with larger JMn-Mn∗ tended to have higher blocking temperatures.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films