Constructing "Closed" and "Open" {Mn} Clusters.

Use of the 1,3,5-tri(2-hydroxyethyl)-1,3,5-triazacyclohexane ligand, LH, in manganese chemistry affords access to two structurally related {Mn} clusters: a "closed" {Mn Mn } puckered square wheel of formula [MnL(LH)O(OH)(MeO)Br(imH)(HO)](Br) (; imH = imidazole) and an "open" {Mn } rod of formula [Mn LO(aibH)(aib)(MeO)(MeOH)](NO) (, aibH = 2-amino-isobutyric acid). In each case the triaza ligands, L/LH, direct the formation of {Mn} triangles with their N atoms preferentially bonding to the Jahn-Teller axes of the Mn 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 {Mn} triangles fold up on themselves in , forming a wheel. However, the syn, syn-bridging carboxylates in 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 due to the presence of Mn ions.