Structural and Computational Analysis of H-bond mediated anion··· anion interactions in new salts of Fumaric and Maleic Acids

Abstract

We report the synthesis and the combined crystallographic/computational analysis of a series of ammonium salts of fumaric and maleic acids. In the solid state, the structures form a variety of non-covalent interactions including N-H⋯O, O-H⋯O and C-H···O H-bonds, supported additionally by other aromatic interactions such as π···π and C-H···π. They have been investigated through quantum chemical calculations, such as molecular electrostatic potential (MEP) surface analysis, quantum theory of atoms in molecules (QTAIM), and noncovalent interaction plot (NCIPlot) methodologies, specially focused on the formation of anion···anion interactions facilitated by hydrogen bonds. Our findings show that specific hydrogen bonds, can establish attractive forces between like-charged anionic units in the presence of counterions or within high-dielectric environments such as water, highlighting that cooperative noncovalent assemblies can overcome Coulombic repulsion driving the formation of organized anionic networks in the solid state.