Geometry and electron density of phenothazines

A systematic theoretical analysis of the structural parameters of 9,10-dihydroanthracene, 9H-thioxanthene and phenothiazine was performed at DFT B3LYP/6-311++G**-GD3 level. The main structural parameter determining the conformation and the electron density at the ring-critical point of the central ring is the angle between the aromatic rings. Although the axial orientation of the substituent at the central ring is preferred, both directions of the substituent are characterized by similar energy and can be realized in the solid state.