DFT Simulation for Properties Determination of Chelating Spironaphthoxazine Derivatives

This work focuses on the investigation of ten newly synthesized spironaphthoxazines using DFT to elucidate how substituents control physicochemical behavior. Frontier-orbital analyses show substituent changes primarily shift the LUMO, controlling HOMO–LUMO gaps and electrophilicity; the open forms (MC) structures exhibit smaller gaps than closed spiro forms (SP) due to extended conjugation. Simulated IR/Raman spectra provide diagnostic markers for structural assignment. Thermodynamic parameters (S, Cp, H, G; 200–500 K) reveal higher S and Cp for MC and for longer alkyl chains, yielding lower G at elevated temperatures. Transition-state calculations indicate accessible SP↔MC isomerization barriers, confirming accessible switching. These results offer a predictive framework to position functional groups and tailor optical response, switching kinetics, and stability for responsive materials.