Formation of a CO–CH4 complex in thin solid films below 50 K

We have investigated the physical and chemical behaviour of pure-, mixed-, layered-, and thin-solid films of CO and CH4 using Fourier Transform Infrared Spectroscopy. Very little difference exists between the sublimation behaviour of the films. In contrast, a significant spectral feature was observed at ∼2136 cm−1 only in the mixed CO:CH4 films, and was replicated by ab initio calculations on the gas-phase CO–CH4 complex. The complex is due to a ‘pseudo-double π-hydrogen bond’, with binding energy of around 14 kJ mol−1. To the best of our knowledge this is the first report of this complex.