Three new POM-based supramolecular hybrids containing flexible bis-pyridyl-bis-amide molecules: Syntheses, structures, and electrocatalysis

Abstract

Three new inorganic–organic hybrid supramolecular architectures constructed by polyoxometalates (POMs) and two flexible bis-pyridyl-bis-amide ligands with different spacer lengths (L1=N,N′-di(3-pyridyl)butanediamide, L2=N,N′-di(3-pyridyl)octanediamide): (L1)[H3PMo12O40] (1), (L1)2[H4Mo8O26] (2), and (3-C5H6N2)(L2)[H3PMo12O40] (3) (3-C5H6N2=aminopyridine), have been hydrothermally synthesized and characterized by IR, TG and single-crystal X-ray diffraction. All of the title compounds are supramolecular structures composed of discrete bis-pyridyl-bis-amide ligands and polyanions, which exhibit three different supramolecular frameworks directed by the different hydrogen bonding interactions. Compounds 1 and 2 show (5,5)- and (4,8)-connected 3D supramolecular frameworks, respectively. In the (4,5)-connected 3D supramolecular network of compound 3, the fascinating structural feature is the existence of supramolecular 1D double helix chains and 2D double layers. Both the POM anions and flexible bis-pyridyl-bis-amide molecules show great effect on the final structures of the title compounds. Additionally, the electrochemical behaviors and electrocatalytic activities of compounds 1–3 toward the reduction of H2O2, KBrO3 and NaNO2 are also investigated.