Tetra-, tetradeca- and octadecametallic clusters of Mn.

Reaction of equimolar amounts of MnBr 2 ·4H 2 O and HL 1 ((3,5-dimethyl-1 H -pyrazol-1-yl)methanol) in a basic MeCN solution leads to the formation of [MnII4(L 1 ) 4 Br 4 (H 2 O) 4 ] (1), whose metallic skeleton is a [MnII4] tetrahedron and cluster core a [MnII4(μ 3 -O) 4 ] cubane. Replacing MnBr 2 ·4H 2 O with Mn(O 2 CMe) 2 ·4H 2 O affords [MnIII2MnII12O 2 (L 1 ) 4 (OAc) 22 ] (2) which is best described as a series of edge-sharing [Mn 4 ] tetrahedra that have self-assembled into a linear array in which each [Mn 2 ] pair is 'twisted' with respect to its neighbours in a corkscrew-like manner. Employment of the triangle [MnIII3O(OAc) 6 (py) 3 ](ClO 4 ) as a reactant instead of a Mn II salt results in the formation of [MnIII14MnII4O 14 (L 1 ) 4 (HL 1 ) 2 (OAc) 18 (H 2 O) 2 ] (3) whose core is comprised of three vertex-sharing [MnIII4] butterflies flanked on either side by one [MnIII4] cubane and one [MnIII2MnII2] tetrahedron. Dc magnetic susceptibility and magnetisation measurements of polycrystalline samples of 1-3 reveal the predominance of antiferromagnetic exchange interactions. For [Mn 4 ] (1) this leads to a diamagnetic ground state, while for [Mn 18 ] (3) competing exchange interactions result in Single-Molecule Magnet (SMM) behaviour with U eff = 22 K.