The effect of metal chelate complexation on the reactivity and absorption spectra of 1,2-naphthoquinones: the synthesis of new types of near i.r. absorbing dyes
nyl]ethylene were efficiently promoted by nickel(II) ions to give 4-aminated, 4-arylated, and 4-vinylated 1,2-naphthoquinones with absorptionbands at larger wavelengths and with increased intensities on metal complex formation, with absorption maxima in the neari.r. region.