Abstract
The intermolecular charge-transfer (CT) interaction of 2-aminopyrimidine (2AP) (as an electron donor) with oxalic acid (OA) (as a typical a-electron acceptor) has been studied at multiple temperatures in methanol solvent. The stoichiometry of the generated CT complex (2AP-OA) was determined using the Benesi-Hildebrand method (BHM). The molecular interaction of 2AP donor with OA acceptor has been discussed as a function of temperature. The crystal structure and space group of the 1:1 adduct has been determined using the single-crystal X-ray crystallographic technique. The H-1 NMR spectrum of 2AP-OA indicates the formation of N+-H center dot center dot center dot O- intermolecular hydrogen bonding. The FTIR spectrum of 2AP-OA also well resolved the complex absorption bands in the region where 2AP and OA bands have been observed. The thermal stability and composition of 2AP-OA were analyzed to compare with 2AP donor and OA acceptor using thermogravimetric (TGA) and differential thermal analysis (DTA). The Van't Hoff equation was employed to calculate various important thermodynamic parameters (i.e., entropy; delta S, enthalpy; delta H, and Gibbs free energy; delta G). The reaction between 2AP and OA was spontaneous and exothermic in nature, as indicated by the negative values of delta G and delta H. (C) 2022 Elsevier B.V. All rights reserved.