Tackling environmental and health issues via crystal engineering of metal complexes

This highlight reports results obtained by the group of Molecular Crystal Engineering at the University of Bologna by applying crystal engineering strategies to tackle two fundamental contemporary challenges of mankind, namely the antimicrobial resistance developed by pathogens as a consequence of misuse/overuse of antibiotics and, from a relatively distant but connected area, the need to inhibit urea degradation by soil enzymes to improve agricultural produce while decreasing environmental pollution. These two targets have been pursued by preparing and characterizing a series of co-crystals obtained by combining active organic molecules (antimicrobials, fertilizers, enzyme inhibitors) with coordination compounds of metals such as Zn, Cu, Ga, Ag, and Bi. Most compounds described in the following have been obtained by mechanochemically activated reactions between organic active molecules and coordination compounds, a method that also eliminates or reduces significantly the use of solvents. The characterization of the products has been carried out with a combination of solid-state techniques like X-ray diffraction, calorimetry, and thermogravimetry. The properties of all compounds have also been tested via collaborative efforts with expert research groups in Canada, USA, Germany and Italy to verify if the co-crystals obtained could, respectively, improve the activity of known organic antimicrobial agents or inhibit the activity of soil enzymes such as urease and ammonia monooxygenase responsible for urea degradation.