Derivation of an accurate geometry of 2-fluoroaniline from rotational spectroscopy and computational chemistry

Abstract

The ground state rotational spectrum of 2-fluoroaniline was investigated using Fourier transform microwave spectroscopy in the 6-19 GHz range. The spectrum reveals hyperfine structure due to the 14N quadrupole moment and additional transitions due to the six 13C and one 15N minor isotopologues which were detected in natural abundance. The rotational constants derived from analysis of the observed spectral patterns for the eight isotopologues were used to derive accurate experimental geometries including the substitution (rs), ground state effective (r0) and mass dependence (rm(1)) structures of 2-fluoroaniline. These show excellent agreement with the equilibrium (re) geometry derived from quantum chemical calculations at the B3LYP/aug-cc-pVTZ level of theory. The geometry of the heavy atom backbone of 2-fluoroaniline, in comparison to the parent aniline, is consistent with effects from the electron withdrawing fluorine atom and from the presence of a weak non-covalent interaction between the neighbouring NH2 and F groups as supported by natural bond orbital and non-covalent interaction analyses, respectively.