Structural insights into coordination polymers based on 6s2 Pb(II) and Bi(III) centres connected via heteroaromatic carboxylate linkers and their potential applications

Abstract

Studies on coordination chemistry published over the last 20 years, have led to increased interest in coordination polymers (CPs). This interest has been generated not only by the intriguing structures of metal–organic hybrid materials but also by their potential applications in many fields such as luminescence, nonlinear optics, gas adsorption, catalysis, magnetism, and bioimaging. To appropriately design new materials for the chosen applications we identified the main goal of the published literature research, which was to understand the relationship between the composition and structure on the molecular and crystal levels and the properties of coordination polymers. Overall, in this review we focused on the three main topics concerning Pb(II) and Bi(III) polymers: i) coordination modes of linkers, ii) central ion lone electron pair stereoactivity, iii) topology, and potential applications. Given a comprehensive review of the literature, we examined the differences and similarities of polymers composed of i) 5- and 6-membered N-, S-, and O-heteroaromatic carboxylates, ii) linkers with mono- or dicarboxylate functional groups, and iii) isomers as linkers (e.g., the effect of the carboxylate group position). Such versatility of ligands plays a crucial role in modulating structure and topology, which directly influencing the potential application of the designed coordination polymers (e.g., as fluorescence materials). Other important structural components of CPs discussed in this review are the Pb(II) and Bi(III) ions. Both have several advantages: i) a large ionic radius, ii) a wide range of coordination numbers, and iii) the effect of 6s2 lone electron pair stereoactivity (holo- or hemidirected geometry). Moreover, there will be emphasized the significant role of noncovalent interactions (e.g. tetrel and pnictogen bonds), which simultaneously stabilized structure, expanded dimensionality, and finally, influenced physicochemical properties.