Fourier transform infrared and Raman spectra of metal halide complexes of 3,5-lutidine in relation to their structures

Fourier transform infrared (4000-200 cm(-1)) and Raman (3500-50 cm(-1)) spectra are reported for metal(II) halide 3,5-lutidine (3,5-dimethylpyridine) complexes of the following stoichiometries: M(3,5L)(4)X(2) M=Co or Ni, X=Cl or Br; M=Mn or Cu, X=Br; M=Cd, X=I; M(3,5L)(3)X(2) M=Fe, X=Cl; M=Cu, X=Br; Hg(3,5L)X(2) X=Cl or Br. Vibrational assignments are given for all the observed bands. Some structure-spectra correlations are found. For a given series of isomorphous complexes the sum of the difference between the liquid and ligand values of the vibrational modes of 3,5-lutidine is found to increase in the order of the second ionization potentials of the metals. The frequency shifts are also found to depend on the halogen.