Synthesis and Crystal Structure of New Heteroleptic Mononuclear Cobalt(III) Complexes Supported by 2,2'-Bipyrimidine and Lower-Rim 1,3-Disubstituted Calix[4]Arene Derivatives with Salicylideneamine Moieties

Heteroleptic mononuclear cobalt(III) complexes of the [L–Co^III(bipyr)]⁺ cation type are obtained for the first time by coordinating lower-rim 1,3-disubstituted calix[4]arene derivatives 2-3 (L) with coordinating salicylideneamine sites, 2,2′-bipyrimidine (bipyr), and cobalt(II) cations. Their structures are determined by single crystal X-ray diffraction. It is shown that regardless of the presence of an azophenyl substituent at the para-position of the coordinating fragment, a similar structural motif is observed that is featured by the cobalt(III) atom coordinated to two chelate N,O-coordinating centers of the macrocyclic ligand and two bipyr nitrogen atoms, forming a distorted octahedral trans-N₄O₂ coordination sphere. For the complex based on 3, containing azophenyl moieties, the 2D porous supramolecular architecture is obtained that is formed by numerous intermolecular CH/π- and π-stacking interactions.