Density Functional Theory-Based Investigation on Thermodynamic and Electronic Properties of a Spiro-Indoline Pyranopyrazole Derivative Under External Electric Fields
Abstract
In this work, we present a density functional theory (DFT) study on the thermodynamic and electronic properties of 6'-amino-5-fluoro-2-oxo-3'-propyl-2'H-spiro[indoline-3,4'-pyrano[2,3-c]pyrazole]-5'-carbonitrile, a spiro-indolinepyranopyrazole derivative of growing importance in organic and pharmaceutical chemistry. Geometry optimisation and electronic-structure analyses were performed to evaluate frontier molecular orbitals and key electronic parameters. Emphasis was placed on understanding the influence of externally applied electric fields on orbital energies, the HOMO–LUMO gap, and molecular dipole behaviour. The applied field induced a clear modulation of the electronic structure, with the HOMO–LUMO gap varying from 4.9707 to 4.8422 eV across the studied field range, while the dipole moment increased from 5.0632 to 7.8219 Debye, indicating enhanced charge asymmetry under stronger fields. Furthermore, thermodynamic parameters including enthalpy, Gibbs’ free energy, entropy, and heat capacity were computed over a wide temperature range (100-700 K), revealing the molecule’s thermal stability and predictable energetic trends. Overall, this study provides quantitative insights into the structure–property relationships of the title compound and demonstrates how external electric fields can be used to tune its electronic characteristics, thereby offering guidance for the rational design of functional organic materials.
