Design, synthesis, structural analysis and quantum chemical insight into the molecular structure of coumarin derivatives

The aim of the current research article is to present the supramolecular features in the crystal structure of seven novel coumarin derivatives, their structural modification due to the addition of various functional groups and the results of spectroscopic investigations as well as theoretical calculations. The compounds were characterized by NMR, FTIR, UV-vis, mass spectroscopy, and single crystal X-ray diffraction studies. The structural analysis revealed that the coumarin moiety exhibits planarity in all the compounds with average dihedral angles of 1.71(2)degrees between the pyran and fused benzene rings and 9.40(9)degrees between the benzopyran and terminal benzene rings. Various supramolecular architectures formed due to the intermolecular interactions significantly contribute to the crystal packing of the molecules. The intermolecular interactions and their contributions were quantified using 2D fingerprint plots. The structural aspects of the compounds were examined based on their optimized geometry, intramolecular hydrogen bonding and chemical reactivity using density functional theory. Theoretical FTIR calculations were performed using VEDA4 software and the TD-DFT method was used to study the electronic transitions of the compounds. The theoretical FTIR and UV data were compared with the experimental data. Natural bond orbital (NBO) analysis revealed the presence and the importance of non-covalent and hyperconjugative interactions for the stability of the molecules in their solid state. The charge distribution and nucleophilic and electrophilic regions of the molecules were identified by molecular electrostatic potential (MEP) mapping. A quantum theory of atoms in molecules (QTAIM) study was carried out to investigate the nature and strength of the hydrogen bonding interactions.