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

We measured temperature dependences of ESR spectra and 1 H NMR spin-lattice relaxation time T 1 on recently prepared mixedvalence hetero-metal complexes [Pd(en) 2 ][PtX 2 (en) 2 ](ClO 2 ) 4 (en: ethylenediamine; X: Cl, Br) which consist of a 1-D structure of-X-Pd II -X-Pt IV -X-Pd II -X-Pt IV -X-chain giving a non-degenerated electronic ground state. The observed low-concentration of paramagnetic M III sites and also long 1 H NMR T 1 compared with those in homo-metal complexes [M II (en) 2 ][M IV X 2 (en) 2 ](ClO 4 ) 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.