Supramolecular interaction-induced assemblies of polyanions and 2-aminopyridinium in two polyoxometalate-based hybrids

Abstract

Organic–inorganic hybrids consisting of organic cations and polyanions are promising functional materials due to their various compositions and structures. An important aspect of these materials is the interactions between the organic and inorganic components, which not only produce the final structures, but also influence the properties. Here, we investigated the interactions between organic cations and polyanions using protonated 2‐aminopyridinium (Hap) as the cation, and successfully obtained two polyoxometalate‐based hybrids, namely (C5H7N2)4[Mo8O26], (I), and (C5H7N2)2[NiMo6O16(OH)2{CH3C(CH2O)3}2]·4H2O, (II). In the crystal structure of (I), every Hap cation links with two polyanions by donating one or two N—H…O hydrogen bonds, and every polyanion is surrounded by eight Hap cations via terminal or bridging O atoms. Conversely, in compound (II), every Hap cation only links with one polyanion decorated by a triol ligand; this organic–inorganic component further assembles via uncoordinated water molecules. In the extended structures, Hap plays a key role, not only providing a counter charge, but also acting as `glue' linking polyanions in the role of hydrogen‐bond donors. In both compounds, as the nodes of the supramolecular network, the polyanions exhibit an ordered two‐dimensional arrangement due to strong hydrogen bonds and electrostatic interactions between the organic and inorganic parts. The electrochemistry of compound (I) shows that redox sourcing from polyanions is a surface‐controlled process. Conversely, the magnetic behaviour of compound (II) indicates dominant antiferromagnetic properties.

Crystal engineering of an adenine–decavanadate molecular device towards label-free chemical sensing and biological screening

“…A very important advancement in POM chemistry is the use of their oxo-enriched surfaces in enhancing the synergistic combination of properties of POMs and organic units towards the development of multifunctional hybrid materials (Duan et al, 2018;Ren et al, 2006;Wang et al, 2010;Yan et al, 2011). Hydrogen-bonding interactions play a crucial role in many biochemical processes and supramolecular chemistry, hence, one can tailor the organic and/or inorganic interactions towards high sensitivity and unique selectivity to specific molecular events, which can be the functional basis of numerous biosensors (Baaske et al, 2014;Park & Park, 2015;Wajs et al, 2016;Xia et al, 2006).…”