Double-stranded dimetallic helicates: assembling-disassembling driven by the Cu~I/Cu~(II) redox change and the principle of homochiral recognition

摘要

In the presence of d~(10) metal ions, prone to tetrahedral coordination, ligands containing two bidentate subunits will give rise to double-stranded helical complexes (helicates). Upon electrochemical oxidation of Cu~I to Cu~(II), the helicate complex tends to disassemble, thus giving rise to two mononuclear Cu~(II) complexes with tetragonal geometry. Upon subsequent Cu~(II)-to-Cu~I electrochemical reduction, two Cu~I complexes instantaneously re-assemble to give the helicate complex. A helicand containing a chiral subunit (e.g. 1,2-substituted cyclohexanediamine) contains a racemic mixture of the R,R and S,S enantiomers. The racemic helicand, reacting with Cu~I, forms dimetallic helicates, in which the two strands show the same chirality, whether R,R or S,S, thus obeying the principle of homochiral recognition.