Electrochemical and structural investigation of the interactions between naphthalene diimides and metal cations.

The effects of Li and Mg on the electrochemical behaviour and photoreduction of N,N'-bis(2,6-diisopropylphenyl)naphthalene diimide (DippNDI) have been investigated using cyclic voltammetry and UV-vis spectroscopy. Strong cation-anion interactions between Li or Mg and [DippNDI] result in solvent-dependent anodic shifts of the NDI˙ redox couple. In organic solvents of moderate dielectric constant and donor ability, the two, one-electron redox processes typically observed for DippNDI merge into a single, two-electron process. This strong metal cation effect has been leveraged for the photoreduction of DippNDI to [DippNDI]via a disproportionation process. Chemical reduction of DippNDI with iPrMgCl has allowed the isolation of Mg complexes of [DippNDI]. Single crystal X-ray diffraction was used to determine the structure of a dimeric complex, [(DippNDI)Mg(THF)], that features strong coordination of Mg by the oxygen atoms of the reduced NDI.