Click reactions to prepare symmetrical and asymmetrical and broad-band near-infrared absorbing dyes

Abstract

The high-yield [2+2] click reaction and Sonogashira coupling reaction were used to synthesize several symmetric and asymmetric charge-transfer aniline compounds. Owing to the introduction of tetracyanoethylene (TCNE), 7,7,8,8-tetracyanoquinodimethane (TCNQ) and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), these compounds exhibited adjustable energy levels and excellent solubility, and were easily synthesized. The molecular structures of these compounds were characterized via¹H NMR, FT-IR, MS and elemental analysis. Via electrochemical studies, the cyclic voltammograms of these compounds exhibited a strong correlation with the spectroscopic results. Furthermore, electrochemical studies and UV-VIS-NIR spectroscopy showed that donor–acceptor chromophores were inserted into the compounds to give the molecules wider absorption and narrower optical and electrochemical band gaps in the near-infrared region. The Z-scan results also showed that the donor–acceptor chromophores could strongly enhance the third-order nonlinear optical properties. Moreover, the prospective nonlinear optical properties of these compounds were shown.