Spectroscopic investigation of 9-xanthenecarboxylic acid with DFT insights into reactivity and molecular interactions

9-Xanthenecarboxylic acid (9XCA) was investigated through a combined experimental and density functional theory (DFT) approach to understand its structural features, spectroscopic behavior, and potential biological relevance. The most stable molecular conformation was identified using Potential Energy Surface (PES) scan analysis and optimized at the B3LYP/6–311++G(d,p) level. The simulated geometry showed good agreement with experimental FT-IR and FT-Raman spectra, enabling reliable vibrational assignments. Calculated 1H and 13C nuclear magnetic resonance (NMR) chemical shifts obtained using the GIAO method closely matched the experimental observations, confirming the structural accuracy. Electronic absorption analysis interpreted the observed UV–Vis absorption bands, while frontier molecular orbital (FMO) and natural bond orbital (NBO) analyses revealed significant intramolecular charge transfer (ICT) and molecular stability. Electrostatic potential (ESP), electron localization function (ELF), localized orbital locator (LOL), reduced density gradient (RDG), and quantum theory of atoms in molecules (QTAIM) investigations provided additional insight into reactive regions, electron localization, weak intermolecular interactions, and bonding characteristics. Drug-likeness evaluation indicated favorable physicochemical and ADME characteristics. The stereochemical reliability of the protein-ligand complexes was supported by Ramachandran plot assessment. Molecular docking suggested stable binding of 9XCA with selected biological targets, supporting its potential as a bioactive scaffold. Overall, this integrated spectroscopic and computational study establishes a reliable structural model and highlights the molecule’s reactivity and possible pharmaceutical relevance.