Thioindole adsorption as a biologically active anticancer over C20 fullerene in different reaction media using density functional theory

The adsorption of the pyrrole-thioindole (1) and C20 cage (2) are studied at B3LYP/6-311+G*, B3LYP/6-311++G** and B3LYP/AUG-cc-pVTZ. Stability of solute and complex (3) depends on the dielectric constant of the used solvent (ε), the possibility of the hydrogen bonding (H…B) and dipolar–dipolar interaction (D.-D.I.) between them. In going from the gas phase to less polar solvent, then in turn to more polar solvent, a good consistency appears between ε and the absolute value of adsorption energy difference among solvent phase and gas phase i.e. │∆Eads. of s-g│ obtained for product (3). Moreover, the highest │∆Eads. of s-g│ is measured for (3) in water, whereas the lowest value is associated in cyclohexane. Because of capability of (H…B), (3) is stabilized in the most polar solvent (water) more than gas phase and other solvents. The kinetic stability and energy difference between the frontier orbitals (Eg or ∆EL-H) is observed in the opposite direction with ε. A red shift is monitored when adsorption is taken in polar solvents as ∆EL-H is reduced.