Comprehensive studies of spiropyrrolidines towards spectroscopic characterization, X-ray diffraction, Hirshfeld surface and DFT computations

•Crystals of three spiropyrrolidines were grown by a slow solvent evaporation technique.•The structures were characterized by X-ray diffraction and UV-visible spectroscopy.•A combined experimental and DFT based study has been reported.•Hirshfeld surface analysis has been employed for intramolecular contact description. Three functionalized spiropyrrolidines have been studied in terms of spectroscopic analyses and single crystal X-ray crystallography. Prior synthesized spiropyrrolidines experimental FT-IR, NMR and UV-Vis spectral analyses and obtained findings correlated with density functional theory (DFT) calculations at B3LYP/6–311++G(d,p) basis set. The spectroscopic and electronic properties, frontier molecular orbitals (HOMO, LUMO), and molecular electrostatic potentials (MEPs) were simulated using the DFT. The calculated electronic transitions responsible for UV-Vis absorption, IR vibrational bands, and NMR chemical shifts were used to guide the experimental spectral assignments and to provide further insights into the spectroscopic properties. The single crystal X-ray outcomes exhibited that two compounds have one independent molecule in their unit cell, while the third compound has four independent molecules in its unit cell and correlated with Hirshfeld surface analysis, which were different intramolecular contacts described. The composition of HOMO, LUMO, and HOMO-LUMO energy gaps determines the possible intramolecular charge transfer between moieties. The MEPs show that the chloro, methoxy group and atoms (N–H groups) of the indole and azole moieties are susceptible sites for reactions that are electrophilic and nucleophilic, respectively in all three compounds. [Display omitted]