Far-infrared and low-frequency Raman spectra and normal coordinate analysis of the CuNO₃⁺ complex

The far-infrared and low-frequency Raman spectra of copper(II) nitrate hydrate in acetone-d₀ and acetone-d₆ reveal four new signals that have been assigned to vibrations involving the copper and oxygen atoms of a CuNO₃⁺ complex. Normal coordinate analysis suggests that the structure of the complex is C_2v bidentate, and this finding is supported by the observation of four polarized Raman lines in the 1700-225-cm^-1 region. The calculation for the C_2v bidentate structure reproduces the observed frequencies with an average error of 4 cm^-1 and provides an accurate reproduction of the ¹⁵N isotopic shifts. The calculation also indicates that coupling between ring modes is occurring, and this is confirmed by the observation of ¹⁵N isotopic shifts for vibrational modes in portions of the ring well removed from the substituted nitrogen atom.