High-resolution infrared studies of the ν10, ν11, ν14, and ν18 levels of [1.1.1]propellane

► High resolution infrared spectra of propellane (C5H6). ► A rovibrational analysis that accounts for effects of strong Coriolis interactions. ► Comparisons with results from quantum calculations at the anharmonic level. ► A determination of the C0 rotational constant from spectral perturbations. ► A value of 1.586 Ǻ for the length of the novel axial CC bond in propellane.