Structural and spectroscopic study of 5-cyanomethyl chromeno[4, 3-b]pyridine-3-carbonitrile (CCPC) using DFT and Thermodynamic: Computational and experimental analysis

The reaction of 3-(6,8-dimethylchromonyl)acrylonitrile ( 1 ) with cyanoacetamide ( 2 ) under basic conditions afforded a novel heterocyclic system: 5-cyanomethylchromeno[4,3- b ]pyridine-3-carbonitrile ( CCPC , 3 ). The transformation proceeds via a cascade mechanism involving initial Michael addition, retro - Michael -induced γ-pyrone ring opening and subsequent double recyclization steps. The structure of compound 3 was confirmed by analytical and spectral data. Its optimized molecular geometry and electronic properties were investigated using density functional theory (DFT/B3LYP) with the 6-311 + + G(d,p) basis set. Key global reactivity descriptors including electronegativity (χ), chemical potential (µ), electrophilicity index (ω), softness (S), and hardness (η) were calculated. Molecular electrostatic potential (MEP) maps provided insight into reactive sites. The experimental IR and NMR spectra exhibited strong agreement with theoretical predictions, validating the computational model. Swiss ADME analysis confirmed that all evaluated physicochemical parameters conform to Lipinski’s and Veber’s rules, indicating favorable drug-likeness. Additionally, non-linear optical (NLO) properties and quantum chemical descriptors were examined. Natural bond orbital (NBO) analysis revealed intramolecular charge transfer characteristics. Thermo kinetic behavior of CCPC was evaluated using the KiSThelP package across the temperature range 250–400 K in the gas phase and in various solvents (water, ethanol, acetone, dioxane, and DMSO). Rate constants (k _uni ) were estimated via transition state theory (TST) and unimolecular Eckart tunneling corrections. UV–Vis spectra were simulated using TDDFT-CAM-B3LYP/6-311 + + G(d,p), revealing solvent-dependent shifts in absorption maxima (λ _max ) and transition intensities. The nature of the electronic excitations was analyzed based on molecular orbital contributions.