Constructing “closed” and “open” {Mn8} clusters

  • Home/
  • Constructing “closed” and “open” {Mn8} clusters

Constructing “closed” and “open” {Mn8} clusters

 

Use of the 1,3,5-tri(2-hydroxyethyl)-1,3,5-triazacyclohexane ligand, LH3, in manganese chemistry affords access to two structurally related {Mn8} clusters: a “closed” {MnIII6MnII2} puckered square wheel of formula [Mn8L2(LH)O3(OH)2(MeO)2Br(imH)(H2O)3](Br)3 (1; imH = imidazole) and an “open” {MnIII8} rod of formula [MnΙΙΙ8L2O4(aibH)2(aib)2(MeO)6(MeOH)2](NO3)2 (2, aibH = 2-amino-isobutyric acid). In each case the triaza ligands, L/LH, direct the formation of {Mn3} triangles with their N atoms preferentially bonding to the Jahn–Teller axes of the MnIII ions. Subsequent self-assembly is dependent on the anion of the Mn salt and the identity of the organic coligand employed─the terminally bonded imidazole and the chelating/bridging amino acid. The {Mn3} triangles fold up on themselves in 1, forming a wheel. However, the syn, syn-bridging carboxylates in 2 prevent this from happening, instead directing the formation of a linear rod. Magnetic susceptibility and magnetization measurements reveal competing ferro- and antiferromagnetic interactions in both complexes, the exchange being somewhat weaker in 1 due to the presence of MnII ions.