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

Abstract

The use of salicylaldehyde oxime (H 2salox) in manganese(III) carboxylate chemistry has yielded new members of the family of hexanuclear compounds presenting the [Mn 6(μ 3-O) 2(μ 2-OR) 2] 12+ core, complexes [Mn III 6(μ 3-O) 2(O 2CPh) 2(salox) 6(L 1) 2(L 2) 2] (L 1 = py, L 2 = H 2O ( 1); L 1 = Me 2CO, L 2 = H 2O ( 2); L 1 = L 2 = MeOH ( 3)). Addition of NaOMe to the acetonitrile reaction mixture, afforded the 1D complex [Mn III 3Na(μ 3-O)(O 2CPh) 2(salox) 3(MeCN)] n ( 4), whereas addition of NaClO 4 to the acetone reaction mixture afforded an analogous 1D complex [Mn III 3Na(μ 3-O)(O 2CPh) 2(salox) 3(Me 2CO)] n ( 5). The structures of 1–3 present the [Mn 6(μ 3-O) 2(μ 2-OR) 2] 12+ core and can be described as two [Mn 3(μ 3-O)] 7+ triangular subunits linked by two μ 2-oximato oxygen atoms of the salox 2− ligands, which show the less common μ 3-κ 2 O:κ O′:κ N coordination mode. The benzoato ligands are coordinated through the usual syn, syn-μ 2-κ O:κ O′ mode. The 1D polymeric structures of 4 and 5 consist of alternating [Mn 3(μ 3-O)] 7+ subunits and Na + atoms linked through two μ 3-κ 2 O:κ O′:κ N and one μ 4-κ 2 O:κ 2 O′:κ N salox 2− ligands as well as one syn, anti-μ 2-κ O:κ O′ 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 [Mn 3] subunit. Solid state 1H NMR data of 1 were used to probe the spin-lattice relaxation of the system.