VIBRATIONAL ANALYSIS AND MOLECULAR-STRUCTURE OF 2,2'-BIPYRIMIDINE

A complete vibrational analysis of 2,2′-bipyrimidine is presented, based on infrared and Raman data and on the predictions of a valence force field transferred from parent molecules. Infrared and Raman solution spectra gave no evidence of a non-planar molecular conformation which is, however, possible in non-polar solvents, as suggested by the ultraviolet spectra. A D2h point group symmetry was assumed to interpret the vibrational spectra of the isolated molecule. The vibrational assignment was used as a refinement of the zero-order force constants, to account for the presence of four nitrogen atoms characteristic of the molecule under consideration. Addition of an intermolecular potential of the Buckingham type allowed a complete description of the normal modes of the corresponding crystal for k=0. The results are discussed in connection with the observed splittings and shifts produced by the crystal field. © 1990.