Piperazine-1,4-diol (PipzDiol): synthesis, stereodynamics and assembly of supramolecular hydrogen-bonded 2D networks

Abstract

Piperazine (Pipz) is widely used as a building block for the self-assembly of supramolecular hydrogen-bonded crystalline networks. Here, piperazine-1,4-diol (PipzDiol) has been suggested as an analog of piperazine with an extended H-bond donor geometry. A convenient synthesis of PipzDiol has been developed and the compound has been fully characterized. Structural and stereodynamic studies showed that PipzDiol exists in solution as a dynamic mixture of conformers/invertomers. The formation of co-crystals with acids is accompanied by preferable selection of one stereoisomeric form depending on the nature of the co-former. Piperazine and PipzDiol were found to form distinct supramolecular H-bonded networks with topologically different H-bonded motifs. In crystalline adducts with sulfuric, oxalic, and para-aminobenzoic acids, piperazine forms 3D H-bonded networks, while 2D layers are assembled with PipzDiol.