Study On H–bond Directed Supramolecular Structure Based On Hexamethylenediamine–tetrakis(Methylenephosphonate)

Phosphonic acid is a diprotic acid,which can be viewed as a derivative of phosphoric acid,with one hydroxyl of?HO?₃PO being replaced by an organic group.Genarally,phosphonic acids not only have strong coordination ability,but also can form hydrogen-bond interaction in acidic environment.Compared with mono-phosphonic ligands,multi-phosphonic ligands have multiple oxygen atoms or hydroxyl groups,which are apt to form complex,variable coordination modes and hydrogen-bond interactions.As a typicalmulti-phosphonic acid,the hexamethylenediamine–tetrakis?methylenephosphonate??H₈L?have been intensively investigated as a diverse ligand in recent years.However,the studies on its hydrogen-bond interactions are rare.In this dissertation,we choose H₈L as the basic buliding block to study the related hydrogen-bond interactions,and six new tetraphosphonic compounds with rich hydrogen-bond interactions were obtained,which were characterized by single-crystal X–ray diffraction,IR spectroscopy and thermogravimetric analysis.The six new tetraphosphonic compounds are listed as follow:H₈L?1?,[(C₃H₁₀N)₂?H₆L?]·4H₂O,[?NBu₄??H₇L?]?3?,[Li₂?H₆L??H2O?₄]?4?,[Na₃?H₆L?₂?H₂O?₈]Na?H₂O?₆]·8H₂O?5?,[Na₃?H₅L??H₂O?₈]?6?.Compounds 1,2 and 3 feature zero-dimensional discrete structures.Compounds4,5 feature one-dimensional chain structures.Compound 6 exhibits a two-dimensional layer structure.The structural analysis reveals that the hydrogen-bond-directed supramolecular self-assemblies in the six compounds lead to compact three-dimensional supramolecular structures.Through the study of the supramolecular structure and hydrogen-bond interaction of the above complexes,we get a better understanding on the supramolecular self-assembly of the multi-phosphonic compounds.