D. A. Long

Internal rotation: A historical perspective

Abstract The histrorical evolution of the concept of restricted rotation about a single bond is presented. The essential features of a potential function association with restricted rotation are described and the parameters necessary for a complete description of the phenomenon of internal rotation in molecules are established. The many physical methods available for the characterisation of internal rotation are mentioned briefly and a more detailed account of the use of infra-red, Raman and hyper Raman spectroscopy for such studies is then given. The far-reaching importance for chemistry of the concept of internal rotation is discussed.

The tricyanomercurate(II) ion

Abstract The tricyanomercurate(II) ion, [Hg(CN) 3 ] − , is isolated in the form of its solid caesium salt from a 1:1:1 ethanolic solution of CsF, KCN and Hg(CN) 2 , and characterised by IR and Raman vibrational spectroscopy. Assignments are made for the CN and HgC stretching vibrations and the HgCN bending vibrations. The spectra are consistent with the [Hg(CN) 3 ] − ion occupying a site of C 1 symmetry.