Influence of Water Molecules on Properties of Binuclear or Bridged Structures for Chiral CuII-NiII, CuII-PdII, and CuII-PtII Tetracyano- Bimetallic Assemblies

ABSTRACT

We have prepared new chiral bimetallic assemblies of discrete binuclear [CuL₂][Ni(CN)₄]·2H₂O or onedimensional cyanide-bridged [CuL₂][Pd(CN)₄] (and [CuL₂][Pt(CN)₄]) (L = (1S,2S)-(+)-N,N'-dimethyl-cyclohexane-1,2- diamine). The numbers of co-crystallized water molecules contained are different from each other and their compositions are easy to vary due to co-crystallized water molecules. As far as we studied on the related [Cu(diamine)₂]a [M(CN)_b]_c·dH₂O compounds, actually such a feature has been found for the first time. According to crystal structures, the elongated axial bond distances of [CuL₂]²⁺ moieties are Cu-N = 2.195(7) Å for [CuL₂][Ni(CN)₄]·2H₂O, Cu-N = 2.443(4)and 2.519(2) Å for [CuL₂][Pd(CN)₄]. Single crystal structure analyses, variable low temperature XRD, measurements of electronic, CD, emission, and XPS spectra and magnetic properties have been carried out. We compared their structural preference between Ni^II and Pd^II (or Pt^II) metal ions. Novel emission band of [CuL₂][Pt(CN)₄] appeared at 410 nm (λ_ex = 360 nm) in the solid state regardless of quenching by cyanide-bridged CuL₂]²⁺ moieties.