DFT investigation of host-guest interactions between α-Terpineol and β-cyclodextrin

Two models A and B of inclusion complex of alpha-Terpineol (alpha-Terp) into beta-cyclodextrin (beta-CD) were investigated by M06-2X/6-311G(d,p) and omega B97X-D/6-311G(d,p) levels of theory in vacuum and in water. EDA, TD-DFT, NBO, AIM and NCI analyses were also done to give more information about the nature of interaction between alpha-Terp and beta-CD. The calculated complexation energy gives that A model with partial encapsulation of alpha-Terp in beta-CD is more favored than B one where guest molecule is totally embedded into beta-CD cavity. EDA calculation shows that dispersion and electrostatic energies contribute greatly on total bonding energy of alpha-Terp @ beta-CD inclusion complexes. Also, electronic transitions obtained by TD-DFT method suggest the charge transfer between alpha-Terp and beta-CD. Finally, NBO and AIM analyses demonstrate the establishment of conventional H-bond interaction and NCI analysis illustrate H-bonds, van der Waals and steric repulsion during inclusion complex formation.