Salt and co-crystal formation from the reaction of fumaric acid with different N-heterocyclic compounds: Experimental and DFT study

In this work, four fumaric acid adducts with different nitrogenous bases were synthesized and characterized with FT-IR, ¹H NMR, ¹³C NMR and UV-Vis. spectroscopies. The solid-state structures of the compounds were determined by X-ray diffraction analysis. In addition, quantum chemical calculations employing density functional theory (DFT/B3LYP) method with the 6 − 311++G(d,p) basis set were performed to study the structural and spectroscopic properties of the compounds, and the results were compared with the experimental findings. X-ray analysis suggests that the crystal structures is stabilized by O–H···O, N–H···O, O–H···N and C–H···O type hydrogen bonds and also π···π stacking interactions. The harmony between the experimental and theoretical structural and spectroscopic data is acceptable in general.