Structural, magnetic, and optical studies of new mixed-valence copper(II)–platinum(IV) complexes with one-dimensional chain structures
Abstract
The crystal structures of halogen-bridged one-dimensional copper(II)–platinum(IV) complexes [Cu(en)2][PtX2(en)2][ClO4]4(en = ethylenediamine, X = Cl or Br) have been determined by X-ray structure analyses. The chloro-bridged complex (1) crystallizes in the orthorhombic space group Icma with unit-cell dimensions a= 13.645(1), b= 10.787(1), c= 9.645(1)Å, and Z= 2. The bromo-bridged complex crystallizes as two different non-stoicheiometric compounds (2a) and (2b) depending on the preparation conditions. Both compounds crystallize in the orthorhombic space group Icma with a= 13.599(1), b= 10.917(1), c= 9.657(1)Å, and Z= 2 for (2a) and a= 13.625(2), b= 10.905(2), c= 9.651 (1)Å, and Z= 2 for (2b). In (1), (2a), and (2b), the copper(II) and platinum(IV) complexes which are bridged by a halogen atom are stacked alternately, leading to a one-dimensional chain structure. The X-ray structure analyses using a full-matrix least-squares method revealed the non-stoicheiometric structures, in which the CuII and PtIV are partially replaced by PtII. The temperature dependence of the magnetic susceptibilities and e.s.r. measurements show no strong magnetic interaction between the copper atoms. Single-crystal reflectance spectra of complex (1) show a polarized band (parallel to the chain direction) at 2.7–2.8 eV corresponding to CuII→ PtIV charge transfer. A progression of peaks (313, 625, and 940 cm–1) due to the totally symmetric stretching mode of Cl–PtIV–Cl was observed in the resonance-Raman spectrum of complex (1).