Creations of solitons and polarons in MX-chain compounds, {[Pt(en)2][PtX2(en)2]}3(CuX4)4(X = Cl and Br)

The creations of solitons and polarons in the {[Pt(en)(2)][PtX2(en)(2)]}(3)(CuX4)(4) (X=Cl and Br) which consist of the double linear chain structures of the main one-dimensional halogen-bridged Pt(II)-Pt(IV) mixed-valence units and one-dimensional counteranions of trigonal bipyramidal Cu(I) ions, have been investigated by the absorption spectra, photo-induced absorption spectra, and ESR spectra. The ESR signals of the Pt(III) and Cu(II) species, which were introduced during the synthetic process, are observed in these compounds. The relative intensities of d-d transitions and ESR spectra of Cu(II) species in counteranions are consistent with each other in the Cl-bridged compounds obtained by pH control. The photo-induced absorption of the Cl-bridged compound is observed in the mid-gap region, which is attributable to the soliton. The doping effect by Br, was investigated for the Br-bridged compounds. The relative intensities of d-d transition and ESR spectra in Cu(II) increase with increasing exposure time, However, the electrical conductivities do not increase. Therefore, the induced Pt(III) species are attributable to neutral solitons.