Salicylaldoxime in manganese(III) carboxylate chemistry: Synthesis, structural characterization and physical studies of hexanuclear and polymeric complexes

The use of salicylaldehyde oxime (H2salox) in manganese(III) carboxylate chemistry has yielded new members of the family of hexanuclear compounds presenting the [Mn6(μ3-O)2(μ2-OR)2]12+ core, complexes [MnIII6(μ3-O)2(O2CPh)2(salox)6(L1)2(L2)2] (L1 = py, L2 = H2O (1); L1 = Me2CO, L2 = H2O (2); L1 = L2 = MeOH (3)). Addition of NaOMe to the acetonitrile reaction mixture, afforded the 1D complex [MnIII3Na(μ3-O)(O2CPh)2(salox)3(MeCN)]n (4), whereas addition of NaClO4 to the acetone reaction mixture afforded an analogous 1D complex [MnIII3Na(μ3-O)(O2CPh)2(salox)3(Me2CO)]n (5). The structures of 1–3 present the [Mn6(μ3-O)2(μ2-OR)2]12+ core and can be described as two [Mn3(μ3-O)]7+ triangular subunits linked by two μ2-oximato oxygen atoms of the salox2− ligands, which show the less common μ3-κ2O:κO′:κN coordination mode. The benzoato ligands are coordinated through the usual syn,syn-μ2-κO:κO′ mode. The 1D polymeric structures of 4 and 5 consist of alternating [Mn3(μ3-O)]7+ subunits and Na+ atoms linked through two μ3-κ2O:κO′:κN and one μ4-κ2O:κ2O′:κN salox2− ligands as well as one syn,anti-μ2-κO:κO′ benzoato ligand. DC and AC magnetic susceptibility studies on 1 revealed the stabilization of an S = 4 ground state, and indications of single-molecule magnetism behavior, whereas the DC experimental data from polycrystalline sample of 5 are indicative of antiferromagnetic interactions within the [Mn3] subunit. Solid state 1H NMR data of 1 were used to probe the spin-lattice relaxation of the system.

Reactions of oligonuclear manganese clusters with salicylaldoxime in various solvents afforded hexanuclear and polymeric complexes. Slow magnetic relaxation phenomena have been observed for a hexanuclear complex as evidenced by dc and ac magnetic susceptibility measurements.Figure optionsDownload as PowerPoint slide