Investigation of the Effects of Solvents on the Structural, Electronic and Thermodynamic Properties of Rosiglitazone Based on Density Functional Theory

Rosiglitazone ( C18H19N3O3S ) is an anti-diabetic drug that reduces insulin resistance in patients with type 2 diabetes. The parameters (bond lengths and bond angles), HOMO, LUMO, HOMO-LUMO energy gap, dipole moment, thermodynamic properties, total energy and vibrational frequencies and intensities of the Rosiglitazone molecule in gas phase and in solvents (Water, Ethanol, DMSO and Acetonitrile) were calculated based on Density Functional Theory (DFT) using standard basis sets: B3LYP/6-31G(d,p), B3LYP/6-31+G(d,p) and B3LYP/6-31++G(d,p). Windows version of Gaussian 09 was used for all the calculations. From the results obtained, the solvents have little influence on the optimized parameters of the molecule. The highest HOMO value of -5.433 eV was found in gas phase showing that the molecule will best donate electron in the gas phase, followed by ethanol in comparison with other solvents. The values of the HOMO were observed to increase with the decrease in dielectric constants of the solvents across all the basis sets used. The lowest LUMO energy of -1.448 eV was found to be in ethanol which shows that the molecule will best accept electron in ethanol compared to the gas phase and other solvents. The largest HOMO-LUMO gap of 4.285 eV was found in water which shows its higher kinetic stability and less chemical reactivity compared to other solvents and in the gas phase. The chemical softness of the molecule was found to decrease as the dielectric constants of the solvents increased namely from ethanol to water. The chemical hardness was found to slightly increase with the increase in dielectric constants of the solvents. The highest value of the dipole moment of 4.6874 D was found in water indicating that the molecule will have the strongest intermolecular interactions in water compared to other solvents and in the gas phase. The total energy increased as the dielectric constants of the solvents decreased from water to ethanol. The vibrational frequencies and intensities increased as the dielectric constants of the solvents increased from ethanol to water. The results confirmed the effects of solvents on the structural, electronic and thermodynamic properties of the studied molecule and will be useful in the design and development of rosiglitazone as an anti-diabetic drug.