Insights Into the Gas-Phase Structure and Internal Dynamics of Diphenylsilane: A Broadband Rotational Spectroscopy Study

The rotational spectrum of diphenylsilane was investigated using chirped-pulse Fourier transform microwave spectroscopy in the frequency range of 2-8 GHz. The lowest energy structure of diphenylsilane has C 2 ${_2 }$ point group symmetry with the C 2 ${_2 }$ symmetry axis coinciding with the b ${b}$ -inertial axis of the molecule. Through the assignment of the main isotopologue as well as singly substituted heavy-atom isotopologues, including 13 ${<^>{13} }$ C, 29 ${<^>{29} }$ Si, and 30 ${<^>{30} }$ Si, we were able to obtain a comprehensive gas-phase structure of diphenylsilane. The structure of diphenylsilane was compared with its oxygen analogue, diphenylether, including a discussion of the barrier height to the large-amplitude motion of the phenyl rings. Furthermore, the structural comparison was extended to include a range of C-Si bond lengths and bond angles from other organosilicon molecules where the silicon atom is bonded to aliphatic and/or aromatic moieties.