Counter-ion radius dependence of the mixed-valence state in MX chain platinum complexes

We have investigated the size effect of the counter anion influencing to the mixed-valence state in MX chain platinum complexes. In order to study the counter-ion radius dependence of the mixed-valence state, we have measured the polarized reflectance spectra of [Pt(en)2][PtCl2(en)2]Y4 (en=ethylenediamine, Y=PF6, HSO4, BF4) in single crystals, and analyzed the crystal structure of [Pt(en)2][PtCl2(en)2](BF4)4 by X-ray diffraction method. From comparing the tetrafluoroborate, the perchlorate, the hydrogensulfate and the hexafluorophosphate in the series of the chloro-bridged complex, we found that the mixed-valence gap of platinum decreases with decreasing the counter-anion radius.