σ- and π-hole interactions of iodotrifluoroethylene (C2F3I) with tertiary amines characterized by matrix isolation IR spectroscopy.

A), for which only C-I⋯N and C-I⋯π complexes could be identified. The origin of the characteristic shifts of the CC stretching mode is discussed. Furthermore, it is shown that the matrix environment plays a key role in the complex formation process, that is, it blocks π-surfaces for secondary interactions after formation of stronger σ-hole contacts.