Supramolecular interactions in itaconic acid-2-amino-4,6-dimethylpyrimidine molecular adduct: Physicochemical characterisation and quantum chemical calculations for the molecular adduct

Abstract Quantum chemical calculations of an organic molecular adduct, itaconic acid: 2-amino-4,6-dimethylpyrimidine (IADAP) were carried out using B3LYP/6-311G(d,p), Cam-B3LYP/6-311G(d,p) and B3LYP/aug-cc-pVDZ levels of theory. The calculated geometric parameters were in good agreement with experimental values. The molecular structure was optimised and the microscopic optical properties were analysed. TD-DFT method was used to analyse the electronic transitions in the molecule. An electrostatic potential study revealed the nature of reactive sites based on the electron density of different sites. Experimental FT-IR, Raman and NMR spectroscopic analyses of IADAP ascertained the chemical composition and formation of the product. To correlate the molecular structure with optical properties, static and frequency-dependent hyperpolarisabilities, calculations were done using three different levels of theory. The results reveal that the charge-transfer and hydrogen-bonding interactions are responsible for optical properties. The compound belongs to the soft-material category. The compound is stable up to 160 °C. The intermolecular interaction between the heterocyclic pyrimidine moiety and carboxylic acid of IADAP induces photoluminescence at 450 nm.