Newly assigned microwave transitions and a global analysis of the combined microwave/millimeter wave rotational spectra of 9-fluorenone and benzophenone

•New microwave spectra have been observed for 9-fluorenone and benzophenone.•Highly accurate rotational constants were obtained from the data between 8 and 80GHz.•The 9-fluorenone data corresponds to a planar C2v ground state structure.•The benzophenone data corresponds to a paddle-wheel like C2 ground state structure.•The torsional angle of the paddle-wheel has been determined to be ∼32.9°.