One-dimensional electron systems in condensed matter are an important subject in material science, where charge, lattice, and spin are dominant factors for non-linear physical properties. Here, I introduced the fundamental knowledge of the quasi-one-dimensional halogen-bridged metal (MX) complexes and the charge-density-wave-to-Motto-Hubbard (CDW-to-MH) charge transfer phase transition and its mechanism of the Pd complex with alkyl chain. Then, unique CDW-to-MH charge transfer phase transition and CDW-MH phase separation and its mechanism of the Pd complex with weak in-plane ligand field, where the hydrogen bond network induced the perturbation and propagation of the phase transition and separation. In addition, the CDW-MH phase separation was observed in the macro and nano scale by optical and scanning tunneling microscopies.