Complexes of Zn(II)–Triazoles with CO2 and H2O: Structures, Energetics, and Applications

Abstract

Using a first-principle methodology, we investigate the stable structures of the nonreactive and reactive clusters formed between Zn2+–triazoles ([Zn2+-Tz]) clusters and CO2 and/or H2O. In sum, we characterized two modes of bonding of [Zn2+-Tz] with CO2/H2O: the interaction is established through (i) a covalent bond between Zn2+ of [Zn2+-Tz] and oxygen atoms of CO2 or H2O and (ii) hydrogen bonds through N–H or C–H of [Zn2+-Tz] and oxygen atoms of H2O or CO2, N–H···O. We also identified intramolecular proton transfer processes induced by complexation. Indeed, water drastically changes the shape of the energy profiles of the tautomeric phenomena through strong lowering of the potential barriers to tautomerism. The comparison to [Zn2+-Im] subunits formed with Zn2+ and imidazole shows that the efficiency of Tz-based compounds for CO2 capture and uptake is due to the incorporation of more accessible nitrogen donor sites in Tzs compared to imidazoles. Since [Zn2+-Tz] clusters are subunits of an organometallic nanoporous materials and Zn–proteins, our data are useful for deriving force fields for macromolecular simulations of these materials. Our work also suggests the consideration of traces of water to better model the CO2 sequestration and reactivity on macromolecular entities such as pores or active sites.