Synthesis and Characterization of Novel Template Complexes

Novel neutral polynuclear Ni^II chelates of L ‐cysteine (L ‐cyst) or D ‐penicillamine (D ‐pen) with dicyandiamide (dcda) were synthesized and characterized using elemental analysis, UV, CD, reflectance, and IR spectroscopy and/or thermogravimetric and X‐ray analysis. The obtained dinuclear compounds add important information about the chemistry of nickel(II) ions, which form types of bonds that cannot be obtained with other metal ions such as Co^II. These dinuclear nickel compounds contain four‐membered rings with two sulfur and two nickel atoms. Electronic transitions were elucidated from reflectance, CD and absorbance spectroscopy and confirm a distorted square planar arrangement of the nickel ions. Because the same structure with Co^II ions could not be obtained directly, dimethylglyoxime was added to a suspension of the template complex with D ‐pen in water to separate the nickel ions. The separation of the ligand was confirmed by elemental analysis, IR, and ¹H NMR spectroscopy. It reacted with Co^II to give a different mononuclear crystalline complex that was studied by X‐ray single crystal diffraction. The crystals are orthorhombically with space group C222₁, a = 0.11769(4) pm, b = 0.13632(4) pm, c = 0.25239(8) pm, V = 0.0040490(2) pm³, and Z = 8.