Adsorption of thioindole as a biologically active anti-cancer to C 20 fullerene in different reaction media using density functional theory

Abstract

Abstract The reaction media effects on interaction of commercially available asymmetric thioindole; (E)-3-(1H-pyrrole-2-yl)methylene-indoline-2-thione (I) as a selective and potent inhibitor of tyrosine kinase; to C20 nanocage are studied at DFT. We have tackled this inter-molecular adsorption using the PCM-SCRF method in the gas phase, cyclohexane, CHCl3, MeOH, H2O, acetonitrile and DMSO. We completely optimized the scrutinized initial structures, transition states (TSs) and product (Ia) in the different reaction media and then compared and contrasted their properties. Stability of I solute and Ia complex depends on the dielectric constant of the used solvent (ε), the possibility of the hydrogen bonding (HB) and dipole–dipole interaction 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 liquid phase and gas phase i.e. │∆El-g│ obtained for Ia product. Moreover, the highest │∆El-g│ is measured for Ia in water, whereas the lowest value is associated in cyclohexane. Because of capability of HB, Ia 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 (∆EL-H) is observed in the opposite direction with ε. The π-π aromatic stacking between I and C20 leads to destabilization of endo TS. Dipole-pole interaction between I and more polar solvent, leads to more stability of exo TS and Ia in water solvent. The activation energy of exo and endo TSs (Eexo≠ and Eendo≠) in the studied reaction media is followed as H2O > DMSO > acetonitrile > MeOH > CHCl3 > cyclohexane > gas phase. The highest Eexo≠ and Eendo≠ is found in water. Evidently, the most and the least kinetically stable exo and endo TS is suggested for adsorption in water and gas phase, respectively.