A brief review of structural concepts of novel supramolecular proton transfer compounds and their metal complexes (part II)

In continuation of our previous brief review of structural concepts of novel supramolecular proton transfer compounds and their metal complexes by Aghabozorg et al. [1], we briefly surveyed the current research in the field of proton transfer compounds supramolecular synthons and their self-assembled metallic complexes from the points of view of Crystal Engineering and Density Functional Theory (DFT) since 2008. Our research groups have recently focused on the proton delivery from acids, which are considered to be suitable proton donors, to amines as proton acceptors. The results were the production of several proton transfer ion pairs possessing some remaining donor sites applied for coordination to metal centers in the preparation of metal-organic compounds. Some of the complexes showed contributions of both cationic and anionic fragments of the starting ion pair, while some others contained only one of these species as ligand. Our review and investigation of compounds revealed that they mainly focused on the concept of supramolecular systems, co-crystallization, stereochemically active lone pairs, coordination polyhedron, mainly on the various interactions involved, including van der Waals, ion pairing, hydrogen bondings, face to face ν-β stackings and edge to face C-H⃛π, C-O⃛π, N-H3π and S⃛S. These interactions were the most commonly used strategies in the extension of supramolecular structures.