Crystal and molecular structures of benzoylpyrenes and acetylpyrenes. E-, Z-, M- & P-stereodescriptors

Abstract The crystal and molecular structures of the following acetylpyrenes ( AcPYs ), and benzoylpyrenes ( BzPYs ) have been determined by X-ray crystallography: 1-acetylpyrene, 2-acetylpyrene, 1,3-diacetylpyrene, 1,6-diacetylpyrene, 1,8-diacetylpyrene, 2,7-diacetylpyrene, 1-benzoylpyrene (1-BzPY) , 1,3-dibenzoylpyrene, 1,6-dibenzoylpyrene, 1,8-dibenzoylpyrene ( 1 , 8-Bz 2 PY ), 1-(4-fluorobenzoyl)pyrene, and 1,6-bis(4’-fluorobenzoyl)pyrene . Special attention was drawn to the stereodescriptors E , Z , P and M in the conformations of AcPYs and BzPYs . Geometrical parameters of the molecular structures of the AcPYs and BzPYs . and of previously reported crystal structures, including 1,3,6-tribenzoylpyrene and 1,3,6,8-tetrabenzoylpyrene are provided. Two cases of crystal dynamic isomerism, as distinct from polymorphism, have been revealed: 1 E -BzPY / 1 / Z -BzPY and 1 Z 8 E -Bz 2 PY / 1 Z 8 Z -Bz 2 PY . Most of the crystal structures of AcPYs and BzPYs under study adopt the more stable Z -conformations of the acetyl and benzoyl groups vis-à-vis the pyrene ring. The deviation from planarity of the carbonyl groups from the plane of the pyrene ring system is higher in AcPYs , as compared with BzPYs. The rich stereochemistry of the crystal structures of acetylpyrenes and benzoylpyrenes, as manifested in the E -, Z -, M - and P -stereodescriptors is noted.