Influence of neutral auxiliary ligands on crystal structure and magnetic behaviour of new [Mn II2Mn III2] clusters supported by p-adamantylcalix[4]arene

Abstract

A series of new manganese complexes of general formula 3₂-Mn₄X_n, displaying a highly-reproducible [Mn^II₂Mn^III₂] cluster core formation, was observed when tetra-p-adamantylcalix[4]arene 3 was used in combination with N,N′-chelating auxiliary ligands, such as bipy (3₂-Mn₄(bipy)₂, bipy = 2,2′-bipyridyl) and phen (3₂-Mn₄(phen)₂, phen = 1,10-phenanthroline), as well as with DMF/H₂O solvent molecules (3₂-Mn₄(dmf)₄, 3₂-Mn₄(dmf)₂(H₂O)₂), acting as O-donor coligands, in the crystalline phase. Single-crystal X-ray diffraction revealed that the involvement of auxiliary ligands in coordination with Mn-ions results in the distortion of their coordination sphere and leads to the controlled compression of the {Mn₄}-cluster core of complexes. Moreover, the appearance of adamantyl groups at the upper rim of the macrocyclic backbone of 3 influences the crystalline self-assembly of obtained clusters, providing a preferable “side-to-head” orientation of the cluster molecules within the crystal, leading to the observation of relatively higher {Mn₄}⋯{Mn₄} distances than those revealed for the earlier reported calix[4]arene supported {Mn₄} clusters. All 3₂-Mn₄X_n clusters demonstrated ferromagnetic interactions between the metal atoms within the cluster core independent of the nature of the O-donor or N-donor auxiliary ligands.