We present the first vibrational study of isomers of the same fullerene; C-84{D-2(IV)} and C-84{D-2d(II)}. Owing to their lower symmetry, the spectra of these isomers exhibit many more lines than the previously studied fullerenes C-60, C-70, and C-76. The temperature dependence of the IR spectra indicates a structural phase change occurs, for both isomers, near 150 K.