  We analyze numerically the ground-state and spectral properties of the
three-quarter filled Peierls-Hubbard Hamiltonian. Various charge- and
spin-ordered states are identified. In the strong-coupling regime, we find
clear signatures of local lattice distortions accompanied by intrinsic
multi-phonon localization. The results are discussed in relation to recent
experiments on MX chain [-PtCl-] complexes. In particular we are able to
reproduce the observed red shift of the overtone resonance Raman spectrum.
