Constructing “Closed” and “Open” {Mn8} Clusters

Published as part of a Crystal Growth and Design virtual special issue on Molecular Magnets and Switchable Magnetic Materials.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.C.J.M. and T.G.T. thank the Hellenic Foundation for Research and Innovation (HFRI) under the “First Call for HFRI Research Projects to support Faculty members and Researchers and the procurement of high-cost research equipment grant” (Project No. 400). E.K.B. thanks the EPSRC for financial support under Grant No. EP/V010573/1. M.E. thanks the Ministerio de Ciencia e Innovación (RTI2018-098537-B-C22) and Gobierno de Aragón (E11_20R). M.M. thanks the University of Glasgow for financial support.Peer reviewe