Inclusion complexes of some thiourea derivatives in cyclodextrins

The formation of the inclusion complexes of five thioureea derivatives both with α- and β-cyclodextrins is studied. The most stable conformers of these thioureea derivatives are selected. The deformation, binding and stabilization energies are evaluated by DFT calculations considering the dispersion corrections at the level D3. Basis set superposition errors were computed by counterpoise procedure. It is proved that a thioureea derivative can be inserted both in the cavity of a single cyclodextrin and of a cyclodextrin dimer, forming in both cases a soluble supramolecular structure. In the latter case the stability of the inclusion complex is mainly due to interaction between the two cyclodextrins. The formation of a supramolecular structure composed by one thioureea derivative and two cyclodextrins is possible by the insertion of a thioureea derivative in a cyclodextrin dimer as well as by the addition of a second cyclodextrin to an inclusion complex formed by one thioureea derivative and one cyclodextrin.