A great deal of attention has been paid recently to the fullerene based complex systems for their possible applications as drug delivery vehicles and sensor applications. In the framework of this research, Si and Al-doped C20 fullerenes and physical interaction mechanisms of doped fullerenes with ortho, meta and para chlorophenylpiperazines were examined based on the computational density functional methods. Energetically stable complexes were searched with M06-2X and B3LYP functionals with 6-31G(d) basis set and some important geometrical structures including interatomic distances and dihedral angles were reported. All calculations were carried out in the gas phase and water media. It was observed that stabilities of the investigated systems were enhanced in the water phase calculations and upon adsorption besides the changes in NH stretching values, nuclear magnetic shielding tensors of 27A1 and 29Si nuclei were considerably changed. In order to further analyse the electronic, physical and chemical properties, binding and band gap energies, electrophilicity indexes and chemical hardness values were also calculated. (C) 2017 Elsevier B.V. All rights reserved.