Synthesis and Porous Crystal Structure of a New Tetranuclear {Mn_2^IIMn_2^III} Cluster Based on a Calix[4]Arene Functionalized at the Upper Rim by Distal p-(4-Nitrophenyl)Diazenyl and p-tert-Butyl Groups

New crystalline {Mn_2^IIMn_2^III} tetranuclear cluster is prepared by the interaction of manganese(II) chloride with calix[4]arene 3 functionalized at the upper rim by distal p-(4-nitrophenyl)diazenyl and p-tert-butyl groups displaying different electronic effects and sizes. The structure of the cluster is studied by single-crystal XRD. Due to the presence of (4-nitrophenyl)diazenyl moieties at the upper rim of the macrocyclic ligand, the molecules of the tetranuclear {Mn_2^IIMn_2^III} clusters are involved in π-stacking interactions leading to the formation of 2D supramolecular layers affording a porous crystal packing.