Electron spin carriers in halogen-bridged 1-d complexes with nondegenerate cdw ground state

We measured temperature dependences of ESR spectra and 1H NMR spin-lattice relaxation time T1 on recently prepared mixedvalence hetero-metal complexes [Pd(en)2][PtX2(en)2](ClO2)4 (en: ethylenediamine; X: Cl, Br) which consist of a 1-D structure of-X-PdII-X-PtIV-X-PdII-X-PtIV-X-chain giving a non-degenerated electronic ground state. The observed low-concentration of paramagnetic MIII sites and also long 1H NMR T1 compared with those in homo-metal complexes [MII(en)2][MIVX2(en)2](ClO4)4 (M: Pt, Pd; X: Cl, Br) having the degenerated ground state, can be explained well by the hindrance of the formation of domainwall type spin solitons in the hetero-metal complexes. This result supports our previous conclusion of the neutral soliton formation in the homo-metal halogen-bridged complexes.