Crystal Structure, Hirshfeld Surface Analysis, and Computational Study of Quinolin-8-yl 4-Chlorobenzoate: Insights from Spectroscopic, Thermal, and Antitumor Properties

We report the time-efficient synthesis of quinolin-8-yl 4-chlorobenzoate (3) via an O-acylation reaction between 8-hydroxyquinoline (1) and 4-chlorobenzoyl chloride (2) mediated by triethylamine in acetonitrile under heating at 80 °C for 20 min in the Monowave 50 reactor. This protocol is distinguished by its short reaction time, operational simplicity, and clean reaction profile. The structure of 3 was fully characterized through a combination of analytical techniques, including NMR, IR, and UV–Vis spectroscopy, MS spectrometry, differential scanning calorimetry (DSC), thermogravimetry (TG), and crystallographic studies. Interestingly, X-ray diffraction analyses of 3 show that the crystal structure is characterized by C-H···N, C-H···O, Cl···π, and π···π interactions. The molecular conformation presents an orthogonal orientation between aromatic rings in the solid state. The calculated interaction energies using the CE-B3LYP model show that dispersion forces act in a higher proportion to build the crystal, which is consistent with the few short hydrogen interactions detected. Electrostatic potential maps suggest the formation of σ-holes over the Cl atoms. Although they can behave as both Lewis acid and base sites, Cl··Cl interactions are absent due to the shallow depth of these σ-holes. Quantum chemical descriptors and global reactivity descriptors were examined using the B3LYP method with the 6-31G(d,p) basis set implemented in CrystalExplorer. Finally, compound 3 exhibited low activity against HOP-92 and EKVX non-Small-cell lung and UO-31 Renal cancer cell lines, with a growth inhibition percentage (GI%) ranging from 6.2% to 18.1%.