Solvent Effects on Structural and Electronic Properties of Lomustine Combined With DFT Method

The objective of this work is to examine the solute-solvent interactions by using optimised conformations of lomustine in various solvents and UV-Vis spectra by DFT calculations. The adjusted geometry of lomustine in the gas phase and in chloroform, acetone, ethanol, and water was estimated. A theoretical investigation of the potential stable formation of lomustine was conducted in various solvents using DFT/B3LYP with the 6-311G+(d) basis set. The findings indicate that the structural bonds vary with the solvent's polarity and solvation energy.  The effects of solvents on lomustine were investigated using the conductor-like polarisable continuum model (CPCM) technique. The electronic absorption spectra of the molecule was assessed using the time-dependent density functional theory (TD/DFT) approach at the same level of analysis. In this work, the energy gap (HOMO–LUMO) was determined by quantum chemical calculations. The Frontier Molecular Orbital (FMO) investigation examined the highest occupied molecular orbital (HOMO) values of the molecule in several solvents, yielding -7.2530 eV for chloroform, -7.2533 eV for acetone, -7.2533 eV for ethanol, and -7.2533 eV for water. Their lowest unoccupied molecular orbital (LUMO) values were -2.4947 eV, -2.4882 eV, -2.4877 eV, and -2.4866 eV, resulting in corresponding band gaps of 4.7583 eV, 4.7651 eV, 4.7656 eV, and 4.7667 eV. Notably, water solvent had the largest energy gap (4.7667 eV) among the solvents used, indicating elevated kinetic energy and substantial chemical reactivity.