γ‐(Hydroxyalkyl)naphthalene‐tetracarboxdiimides: Organic White Pigments

Abstract

Keywords: Pigments / Naphthalene / Heterocycles / Aromatic compounds / Sun protection Naphthalene-1,8:4,5-tetracarboxdiimides were prepared from cyanoacetic acid and its alkylation, reduction and condensation with naphthalenetetracarboxylic dianhydride and exhibit strong light-scattering and opacifying properties. Applications are discussed.

Fluorescence and fluorescent dyes

“…Gaussian curves (Figure 2, solid curves) are much faster, exponentially damped than Lorentzian curves ( Figure 2, dotted curves) and cause for normal dispersion a spectral region where the index of refraction n is still comparably high, whereas the absorptivity κ is already damped to insignificantly small values; this is of special advantage for the generation of materials with high index of refraction for optical dispersing devices or light scattering. The latter is important for white pigment because strongly light scattering crystallites with micrometer dimensions (elastic light scattering) are required such as titanium dioxide (rutile) and zinc sulfide as well as organic pigments [11] such as the pteridines in wings of butterflies [12] or technical [13] organic white pigments. Their strong light absorption close to the visible region makes these substances also interesting as UV sun protectors [14].…”

“…The naphthalenecarboximides (10, n = 1) absorb in the UV [44] and may be applied as white pigment [45] or for sun protection [46]; see Figure 9. The fluorescence is comparably weak because the S 1 state is close to a further, non-fluorescent state [47] and looses energy of excitation by their interaction.…”

“…Förster [28,95] and Perrin [96,97] established eq. (11) for the quantitative description of FRET where the rate constant of energy transfer (k T ) corresponds to the inverse sixth power of the distance R between the centers of the transition dipoles.…”

Sexterrylenetetracarboxylic Bisimides: NIR Dyes

“…Dyes absorbing in the near-infrared (NIR) are receiving increasing interest both in research and in technology where the peri -arylenes (Chart ) (also shortened to rylenes in the literature) are attractive candidates for many applications because of their stability and interesting photophysical properties. Chemistry and applications of the lower homologues of 1 are well-established such as for the naphthalene derivatives with n = 1 as sun-protecting materials and organic white pigments, the perylenes with n = 2 as red pigments and fluorescent dyes, the terrylenes with n = 3 for fluorescent applications in the bathochromic visible, and the quaterrylenes reaching the NIR . Chemistry becomes more difficult for the higher homologues.…”

Laterally Extended Naphthalene Tetracarboxylic Bisimides

“…Naphthalene tetracarboxylic bisimides ( 1 ) with aliphatic N substituents are colorless materials and may be applied as white pigments . Many attempts were made to shift their absorption into the visible , such as the substitution of the aromatic core with a single or with several donor groups, preferently in the positions 2,7 and 2,6.…”