Synthesis and optical and redox properties of core-substituted naphthalene diimide dyes.

2,6-Dichloronaphthalene dianhydride has been synthesized by a modified procedure. The imidization of this dichlorinated anhydride with amines and subsequent stepwise nucleophilic exchange of the chlorine atoms by alkyl- or arylamines afforded a series of hitherto unknown monoamino- and diamino-substituted naphthalene diimides. An alternative route for the synthesis of diamino-substituted naphthalene diimides is also reported. Optical and electrochemical properties of the newly synthesized amino-functionalized naphthalene diimides were studied in detail. The absorption maxima (530-620 nm) of these dyes are appreciably bathochromically shifted compared to those of the corresponding core-unsubstituted compounds. At the naphthalene core alkylamino-substituted diimides exhibit fluorescence quantum yields up to 60%.