Controlling the mixed-valence state of halogen-bridged one-dimensional platinum complexes by the substitution of counter ions

Abstract

The mixed-valence states of halogen-bridged one dimensional platinum complexes have been investigated by the substitution of counter ions. The crystal structures of [Pt(en) 2][PtCl 2(en) 2](PF 6) 4 (ClPF 6), [Pt(en) 2][PtCl 2(en) 2](HSO 4) 4 (ClHSO 4) and [Pt(en) 2][PtBr 2(en) 2](H 2PO 4) 4 · 6H 2O (BrH 2PO 4) (en=ethylenediamine) have been determined by single-crystal X-ray diffraction, and their absorption edges have been measured at room temperature. The crystal data are: for ClPF 6, monoclinic, P2/m, a=9.204(3), b=5.506(2), c=8.185(2) A ̊ , β=107.29(2)° and Z= 1 2 ; for ClHSO 4, orthorhombic, Ibam, a=9.261(1), b=14.422(2), c=10.929(1) A ̊ , and Z=2; for BrH 2PO 4, monoclinic, P2/a, a=19.463(2), b=5.722(1), c=8.325(1) A ̊ , ß=101.59(1)° and Z=1. The absorption edegs of the intervalence charge-transfer bands are c.a. 17,500cm −1 for ClPF 6, c.a. 16,500cm −1 for ClHSO 4 and c.a. 14,800cm −1 for BrH 2PO 4. These results show that the counter ion size and the hydrogen atom of the counter ion influence the mixed-valence state. A mid-gap absorption band below the absorption edge is found at c.a. 14,700cm −1 in ClHSO 4.