Effects of Orthohalogen Substituents on Nitrate Binding in Urea-Based Silver(I) Coordination Polymers

The urea group is a widely used functional group in anion recognition, owing to its ability to interact effectively with anions via formation of chelate hydrogen bonds. Previous solution state study shows that the presence of halogen substituents at ortho-positions to the urea moiety strongly enhances intermolecular hydrogen bonding interactions. In order to investigate the effect of the presence of ortho-halogen substituents on hydrogen bonding of aromatic ureas in the context of metallosupramolecular chemistry, three Ag­(I) coordination polymers were synthesized and characterized by different techniques. The nitrate binding and the supramolecular organization in these compounds were studied by different geometrical and theoretical calculations. Based on this study, we can conclude that, as expected, the N–H···O hydrogen bond plays a key role in nitrate binding for this type of ligands, while weak C–X···O halogen bonds assist the anion binding to the receptor.