Crystal Structure, Hydrogen bonding interactions, Hirshfeld surfaces, Energy frameworks, and DFT calculation of Diethyl 3-(4-substitutedbenzoyl)indolizine-1,2-dicarboxylates

The diethyl 3-(4-substitutedbenzoyl)indolizine-1,2-dicarboxylates have been synthesized by reacting the electron-deficient diethyl but-2-ynedioate with 1-(2-(4-substitutedphenyl)-2-oxoethyl)pyridin-1-ium bromide, the intermediates obtained from the reaction of pyridine and 4-substituted phenacyl bromides. The synthesized compounds were investigated by FT-IR, NMR (1H and 13C), LC-MS, and elemental analysis spectroscopic methods along with PXRD. The molecular structures were determined using the single crystal X-ray diffraction technique which revealed that 5a and 5c crystallize in triclinic space group P1¯. The crystal structures of 5a and 5c preferred the C-H···O hydrogen-bonded dimeric ring motifs, resembling those observed in the earlier reported 5b. Furthermore, various computational analyses such as Hirshfeld surface, Energy framework, and MEP analysis predicted the interaction site and inter-molecular interactions in these molecules. The FMOs analysis was carried out to obtain global reactivity parameters for the synthesized compounds (5a-c). The NCI and QTAIM studies revealed the nature as well as qualitative and quantitative description of intra and inter-molecular hydrogen bonding interactions present in these molecules and their crystal packing.