Infrared spectra of Br−-(C2H2)n complexes

Mid-infrared spectra of Br−-(C2H2)n (1⩽n⩽8) complexes have been recorded using vibrational predissociation spectroscopy. Spectra of smaller clusters (n⩽6), feature a single relatively narrow ν3 absorption red shifted with respect to the free molecule absorption, and are consistent with interior solvation structures containing roughly equivalent C2H2 ligands bound end-on to the central Br−. Onset of the second solvation shell occurs at n=7 and is signalled by the appearance of an additional isolated band situated between the ν3 absorptions of acetylene molecules bound directly to the Br− core and the one of free acetylene.