Synthesis and the crystal and molecular structures of 4-(piperidyl-1)-2-phenylpyrido[2,3-a]anthraquinone-7,12 Mono- and dibromohydrates (HL)Br · 3H2O and (H2L)Br2 · 3H2O

4-(Piperidyl-1)-2-phenylpyrido[2,3-a]anthraquinone-7,12 monobromohydrate (HL)Br · 3H2O (I) and 4-(piperidyl-1)-2-phenylpyrido[2,3-a]anthraquinone-7,12 dibromohydrate (H2L)Br2 · 3H2O (II) are isolated in the crystalline state. The crystal structures of compounds I and II are determined using X-ray diffraction. It is established that the protonation of 4-(piperidyl-1)-2-phenylpyrido[2,3-a]anthraquinone-7,12 proceeds primarily through the pyridine atom at pH 2–3. The attachment of the second proton occurs through the piperidine nitrogen atom at pH ∼ 1.