The effects of Li(+) and Mg(2+) on the electrochemical behaviour and photoreduction of N,N'-bis(2,6-diisopropylphenyl)naphthalene diimide (Dipp2NDI) have been investigated using cyclic voltammetry and UV-vis spectroscopy. Strong cation-anion interactions between Li(+) or Mg(2+) and [Dipp2NDI](2-) result in solvent-dependent anodic shifts of the NDI˙(-/2-) redox couple. In organic solvents of moderate dielectric constant and donor ability, the two, one-electron redox processes typically observed for Dipp2NDI merge into a single, two-electron process. This strong metal cation effect has been leveraged for the photoreduction of Dipp2NDI to [Dipp2NDI](2-)via a disproportionation process. Chemical reduction of Dipp2NDI with iPrMgCl has allowed the isolation of Mg(2+) complexes of [Dipp2NDI](2-). Single crystal X-ray diffraction was used to determine the structure of a dimeric complex, [(Dipp2NDI)Mg2(THF)3]2, that features strong coordination of Mg(2+) by the oxygen atoms of the reduced NDI.