Electron spin carriers in halogen-bridged 1-D complexes with non-degenerate CDW ground state

We measured temperature dependences of ESR spectra and H-1 NMR spin-lattice relaxation time T-1 on recently prepared mixed-valence hetero-metal comple xes [Pd(en)(2)][PtX2(en)(2)](ClO4)(4) (en: ethylenediamine; X: Cl, Br) whic h consist of a 1-D structure of -X-Pd-II-X-Pt-II-X-Pd-II-X-Pt-IV-X- chain g iving a non-degenerated electronic ground state. The observed low-concentra tion of paramagnetic M-III sites and also long H-1 NMR T-1 compared with th ose in home-metal complexes [M-II(en)(2)][(MX2)-X-IV(en)(2)](ClO4)(4) ( M: Pt, Pd; X: Cl, Br) having the degenerated ground state, can be explained we ll by the hindrance of the formation of domain-wall type spin solitons in t he hetero-metal complexes. This result supports our previous conclusion of the neutral soliton formation in the home-metal halogen-bridged complexes.