Molecular modeling of the weakly bounded dimers of some phenothiazine derivatives

The intermolecular π-π stacking interaction between some phenothiazine derivatives has been investigated using the Hartree-Fock (HF) and the local second order Møller-Plesset perturbation theory (LMP2) methods. Two different conformations (parallel and antiparallel stacking) of ethyl-phenothiazine and the parallel stacking of thio-methyl-phenothiazine were investigated. In all three cases the HF results show nearly unbounded dimers, while at LMP2 level they become stable structures, mainly due to the presence of large dispersion forces. The intermolecular optimal distances were also calculated by both methods the values obtained by HF being significantly larger as compared with those obtained by LMP2. Considering the LMP2 geometry, the HF contribution in the intermolecular interaction energy gives positive values acting as a repulsion forces and slacking the dimer interaction. This effect is compensated by the large contribution of the dispersion component which finally keeps together the binary stacking structures. These results show the major role of the dispersion effects in stabilizing stacking structures of the aromatic rings and the feasibility of selfassembling in molecular two-dimensional supra-structures.