The effect of metal chelate complexation on the reactivity and absorption spectra of 1,2-naphthoquinones: new types of near-infrared-absorbing metal complex dyes

Abstract

The reaction of sodium 1,2-naphthoquinone-4-sulphonate with various arylamines and 1,1-bis[p-(dimethylamino)phenyl]ethylene were efficiently promoted by nickel(II) ion to give 4-aminated, 4-arylated, and 4-vinylated 1,2-naphthoquinones in good yield. The first absorption bands of the products with strongly electron-donating 4-substituents were drastically shifted to longer wavelength together with an increase in the absorption intensity by metal chelate complexation. The resulting metal chelate complexes have an intense absorption band in the near-IR region.